Provided by: bpftrace_0.20.2-1ubuntu4_amd64 bug

NAME

       bpftrace - a high-level tracing language

SYNOPSIS

       bpftrace [OPTIONS] FILENAME
       bpftrace [OPTIONS] -e 'program code'

DESCRIPTION

       bpftrace is a high-level tracing language and runtime for Linux based on BPF. It supports
       static and dynamic tracing for both the kernel and user-space.

       When FILENAME is "-", read from stdin.

EXAMPLES

       List all probes with "sleep" in their name

             # bpftrace -l '*sleep*'

       Trace processes calling sleep

             # bpftrace -e 'kprobe:do_nanosleep { printf("%d sleeping\n", pid); }'

       Trace processes calling sleep while spawning sleep 5 as a child process

             # bpftrace -e 'kprobe:do_nanosleep { printf("%d sleeping\n", pid); }' -c 'sleep 5'

SUPPORTED ARCHITECTURES

       x86_64, arm64 and s390x

OPTIONS

   Output format
       -B MODE, Set the buffer mode for stdout. Valid values are
           none No buffering. Each I/O is written as soon as possible
           line Data is written on the first newline or when the buffer is full. This is the
           default mode.
           full Data is written once the buffer is full.

       -f FORMAT, Set the output format. Valid values are
           json
           text

       -o FILENAME
           Write bpftrace tracing output to FILENAME instead of stdout. This doesn’t include
           child process (-c option) output. Errors are still written to stderr.

       --no-warnings
           Suppress all warning messages created by bpftrace.

   Tracing
       -e PROGRAM
           Execute PROGRAM instead of reading the program from a file

       -I DIR
           Add the directory DIR to the search path for C headers. This option can be used
           multiple times.

       --include FILENAME
           Add FILENAME as an include for the pre-processor. This is equal to adding '#include
           FILENAME' to the start bpftrace program. This option can be used multiple times.

       -l [SEARCH]
           List all probes that match the SEARCH pattern. If the pattern is omitted all probes
           will be listed. This pattern supports wildcards in the same way that probes do. E.g.
           '-l kprobe:*file*' to list all 'kprobes' with 'file' in the name. For more details see
           the LISTING PROBES section.

       --unsafe
           Some calls, like 'system', are marked as unsafe as they can have dangerous side
           effects ('system("rm -rf")') and are disabled by default. This flag allows their use.

       -k
           Errors from bpf-helpers(7) are silently ignored by default which can lead to strange
           results. This flag enables the detection of errors (except for errors from
           'probe_read_*'). When errors occurs bpftrace will log an error containing the source
           location and the error code:

           stdin:48-57: WARNING: Failed to probe_read_user_str: Bad address (-14)
           u:lib.so:"fn(char const*)" { printf("arg0:%s\n", str(arg0));}
                                                            ~~~~~~~~~

       -kk
           Same as '-k' but also includes the errors from 'probe_read_*' helpers.

   Process management
       -p PID
           Attach to the process with PID. If the process terminates, bpftrace will also
           terminate. When using USDT probes, uprobes, and uretprobes they will be attached to
           only this process. For listing uprobes/uretprobes if you set the target to '*' the
           process’s address space will be searched for the symbols.

       -c COMMAND
           Run COMMAND as a child process. When the child terminates bpftrace stops as well, as
           if 'exit()' has been called. If bpftrace terminates before the child process does the
           child process will be terminated with a SIGTERM. If used, 'USDT' probes these will
           only be attached to the child process. To avoid a race condition when using 'USDTs'
           the child is stopped after 'execve' using 'ptrace(2)' and continued when all 'USDT'
           probes are attached.
           The child PID is available to programs as the 'cpid' builtin.
           The child process runs with the same privileges as bpftrace itself (usually root).

       --usdt-file-activation
           activate usdt semaphores based on file path

   Miscellaneous
       --info
           Print detailed information about features supported by the kernel and the bpftrace
           build.

       --no-feature feature,feature,..., Disable detected features, valid values are
           uprobe_multi to disable uprobe_multi link
           kprobe_multi to disable kprobe_multi link

       -h, --help
           Print the help summary

       -V, --version
           Print bpftrace version information

       -v
           verbose messages

       -d
           debug mode

       -dd
           verbose debug mode

ENVIRONMENT VARIABLES

       Some behavior can only be controlled through environment variables. Most of these can also
       be set via the config block directly in a script (before any probes). This section lists
       all those variables.

   BPFTRACE_BTF
       Default: None

       The path to a BTF file. By default, bpftrace searches several locations to find a BTF
       file. See src/btf.cpp for the details.

   BPFTRACE_CACHE_USER_SYMBOLS
       Default: PER_PROGRAM if ASLR disabled or -c option given, PER_PID otherwise.

       -* PER_PROGRAM - each program has its own cache. If there are more processes with enabled
       ASLR for a single program, this might produce incorrect results. -* PER_PID - each process
       has its own cache. This is accurate for processes with ASLR enabled, and enables bpftrace
       to preload caches for processes running at probe attachment ti me. If there are many
       processes running, it will consume a lot of a memory. -* NONE - caching disabled. This
       saves the most memory, but at the cost of speed.

   BPFTRACE_CPP_DEMANGLE
       Default: 1

       C++ symbol demangling in userspace stack traces is enabled by default.

       This feature can be turned off by setting the value of this environment variable to 0.

   BPFTRACE_DEBUG_OUTPUT
       Default: 0

       Outputs bpftrace’s runtime debug messages to the trace_pipe. This feature can be turned on
       by setting the value of this environment variable to 1.

   BPFTRACE_KERNEL_BUILD
       Default: /lib/modules/$(uname -r)

       Only used with BPFTRACE_KERNEL_SOURCE if it is out-of-tree Linux kernel build.

   BPFTRACE_KERNEL_SOURCE
       Default: /lib/modules/$(uname -r)

       bpftrace requires kernel headers for certain features, which are searched for in this
       directory.

   BPFTRACE_LOG_SIZE
       Default: 1000000

       Log size in bytes.

   BPFTRACE_MAX_BPF_PROGS
       Default: 512

       This is the maximum number of BPF programs (functions) that bpftrace can generate. The
       main purpose of this limit is to prevent bpftrace from hanging since generating a lot of
       probes takes a lot of resources (and it should not happen often).

   BPFTRACE_MAX_CAT_BYTES
       Default: 10k

       Maximum bytes read by cat builtin.

   BPFTRACE_MAX_MAP_KEYS
       Default: 4096

       This is the maximum number of keys that can be stored in a map. Increasing the value will
       consume more memory and increase startup times. There are some cases where you will want
       to: for example, sampling stack traces, recording timestamps for each page, etc.

   BPFTRACE_MAX_PROBES
       Default: 512

       This is the maximum number of probes that bpftrace can attach to. Increasing the value
       will consume more memory, increase startup times and can incur high performance overhead
       or even freeze or crash the system.

   BPFTRACE_MAX_STRLEN
       Default: 64

       Number of bytes allocated on the BPF stack for the string returned by str().

       Make this larger if you wish to read bigger strings with str().

       Beware that the BPF stack is small (512 bytes), and that you pay the toll again inside
       printf() (whilst it composes a perf event output buffer). So in practice you can only grow
       this to about 200 bytes.

       Support for even larger strings is [being
       discussed](https://github.com/iovisor/bpftrace/issues/305).

   BPFTRACE_MAX_TYPE_RES_ITERATIONS
       Default: 0

       Maximum should be the number of levels of nested field accesses for tracepoint args. 0 is
       unlimited.

   BPFTRACE_PERF_RB_PAGES
       Default: 64

       Number of pages to allocate per CPU for perf ring buffer. The value must be a power of 2.

       If you’re getting a lot of dropped events bpftrace may not be processing events in the
       ring buffer fast enough. It may be useful to bump the value higher so more events can be
       queued up. The tradeoff is that bpftrace will use more memory.

   BPFTRACE_STACK_MODE
       Default: bpftrace

       Output format for ustack and kstack builtins. Available modes/formats: bpftrace, perf, and
       raw. This can be overwritten at the call site.

   BPFTRACE_STR_TRUNC_TRAILER
       Default: ..

       Trailer to add to strings that were truncated. Set to empty string to disable truncation
       trailers.

   BPFTRACE_VMLINUX
       Default: None

       This specifies the vmlinux path used for kernel symbol resolution when attaching kprobe to
       offset. If this value is not given, bpftrace searches vmlinux from pre defined locations.
       See src/attached_probe.cpp:find_vmlinux() for details.

BPFTRACE LANGUAGE

   Overview
       The bpftrace (bt) language is inspired by the D language used by dtrace and uses the same
       program structure. Each script consists of an preamble and one or more action blocks.

           preamble

           actionblock1
           actionblock2

       Preprocessor and type definitions take place in the preamble:

           #include <linux/socket.h>
           #define RED "\033[31m"

           struct S {
             int x;
           }

       Each action block consists of three parts:

           probe[,probe]
           /predicate/ {
             action
           }

       Probes
           A probe specifies the event and event type to attach too.

       Predicate
           The predicate is optional condition that must be met for the action to be executed.

       Action
             Actions are the programs that run when an event fires (and the predicate is met). An
           action is a semicolon (;) separated list of statements and always enclosed by brackets
           {}

       A basic script that traces the open(2) and openat(2) system calls can be written as
       follows:

           BEGIN
           {
                   printf("Tracing open syscalls... Hit Ctrl-C to end.\n");
           }

           tracepoint:syscalls:sys_enter_open,
           tracepoint:syscalls:sys_enter_openat
           {
                   printf("%-6d %-16s %s\n", pid, comm, str(args.filename));
           }

       This script has two action blocks and a total of 3 probes. The first action block uses the
       special BEGIN probe, which fires once during bpftrace startup. This probe is used to print
       a header, indicating that the tracing has started.

       The second action block uses two probes, one for open and one for openat, and defines an
       action that prints the file being open ed as well as the pid and comm of the process that
       execute the syscall. See the PROBES section for details on the available probe types.

   Identifiers
       Identifiers must match the following regular expression: [_a-zA-Z][_a-zA-Z0-9]*

   Comments
       Both single line and multi line comments are supported.

           // A single line comment
           i:s:1 { // can also be used to comment inline
           /*
            a multi line comment

           */
             print(/* inline comment block */ 1);
           }

   Config Block
       To improve script portability, you can set bpftrace configs via the config block, which
       can only be placed at the top of the script before any probes (even BEGIN).

           config = {
               stack_mode=perf;
               max_map_keys=2
           }

           BEGIN { ... }

           uprobe:./testprogs/uprobe_test:uprobeFunction1 { ... }

       The names of the config variables can be in the format of environment variables or their
       lowercase equivalent without the BPFTRACE_ prefix. For example, BPFTRACE_STACK_MODE,
       STACK_MODE, and stack_mode are equivalent.

       Note: Environment variables for the same config take precedence over those set inside a
       script config block.

   Data Types
       The following fundamental integer types are provided by the language.

       ┌───────┬─────────────────────────┐
       │       │                         │
       │TypeDescription             │
       ├───────┼─────────────────────────┤
       │       │                         │
       │uint8  │ Unsigned 8 bit integer  │
       ├───────┼─────────────────────────┤
       │       │                         │
       │int8   │ Signed 8 bit integer    │
       ├───────┼─────────────────────────┤
       │       │                         │
       │uint16 │ Unsigned 16 bit integer │
       ├───────┼─────────────────────────┤
       │       │                         │
       │int16  │ Signed 16 bit integer   │
       ├───────┼─────────────────────────┤
       │       │                         │
       │uint32 │ Unsigned 32 bit integer │
       ├───────┼─────────────────────────┤
       │       │                         │
       │int32  │ Signed 32 bit integer   │
       ├───────┼─────────────────────────┤
       │       │                         │
       │uint64 │ Unsigned 64 bit integer │
       ├───────┼─────────────────────────┤
       │       │                         │
       │int64  │ Signed 64 bit integer   │
       └───────┴─────────────────────────┘

   Floating-point
       Floating-point numbers are not supported by BPF and therefore not by bpftrace.

   Constants
       Integers constants can be defined in the following formats:

       •   decimal (base 10)

       •   octal (base 8)

       •   hexadecimal (base 16)

       •   scientific (base 10)

       Octal constants have to be prefixed with a 0, e.g. 0123. Hexadecimal constants start with
       either 0x or 0X, e.g. 0x10. Scientific are written in the <m>e<n> format which is a
       shorthand for m*10^n, e.g. $i = 2e3;. Note that scientific literals are integer only due
       to the lack of floating point support, 1e-3 is not valid.

       To improve the readability of big literals a underscore _ can be used as field separator,
       e.g. 1_000_123_000.

       Integer suffixes as found in the C language are parsed by bpftrace to ensure compatibility
       with C headers/definitions but they’re not used as size specifiers. 123UL, 123U and 123LL
       all result in the same integer type with a value of 123.

       Character constants can be defined by enclosing the character in single quotes, e.g. $c =
       'c';.

       String constants can be defined by enclosing the character string in double quotes, e.g.
       $str = "Hello world";.

       Characters and strings support the following escape sequences:

       ┌─────┬──────────────────────┐
       │     │                      │
       │\n   │ Newline              │
       ├─────┼──────────────────────┤
       │     │                      │
       │\t   │ Tab                  │
       ├─────┼──────────────────────┤
       │     │                      │
       │\0nn │ Octal value nn       │
       ├─────┼──────────────────────┤
       │     │                      │
       │\xnn │ Hexadecimal value nn │
       └─────┴──────────────────────┘

   Type conversion
       Integer and pointer types can be converted using explicit type conversion with an
       expression like:

           $y = (uint32) $z;
           $py = (int16 *) $pz;

       Integer casts to a higher rank are sign extended. Conversion to a lower rank is done by
       zeroing leading bits.

       It is also possible to cast between integers and integer arrays using the same syntax:

           $a = (uint8[8]) 12345;
           $x = (uint64) $a;

       Both the cast and the destination type must have the same size. When casting to an array,
       it is possible to omit the size which will be determined automatically from the size of
       the cast value.

   Operators and Expressions
   Arithmetic Operators
       The following operators are available for integer arithmetic:

       ┌──┬────────────────────────┐
       │  │                        │
       │+ │ integer addition       │
       ├──┼────────────────────────┤
       │  │                        │
       │- │ integer subtraction    │
       ├──┼────────────────────────┤
       │  │                        │
       │* │ integer multiplication │
       ├──┼────────────────────────┤
       │  │                        │
       │/ │ integer division       │
       ├──┼────────────────────────┤
       │  │                        │
       │% │ integer modulo         │
       └──┴────────────────────────┘

   Logical Operators
       ┌───┬─────────────┐
       │   │             │
       │&& │ Logical AND │
       ├───┼─────────────┤
       │   │             │
       │|| │ Logical OR  │
       ├───┼─────────────┤
       │   │             │
       │!  │ Logical NOT │
       └───┴─────────────┘

   Bitwise Operators
       ┌───┬──────────────────────────────────┐
       │   │                                  │
       │&  │ AND                              │
       ├───┼──────────────────────────────────┤
       │   │                                  │
       │|  │ OR                               │
       ├───┼──────────────────────────────────┤
       │   │                                  │
       │^  │ XOR                              │
       ├───┼──────────────────────────────────┤
       │   │                                  │
       │<< │ Left shift the left-hand operand │
       │   │ by the number of bits specified  │
       │   │ by the right-hand expression     │
       │   │ value                            │
       ├───┼──────────────────────────────────┤
       │   │                                  │
       │>> │ Right shift the left-hand        │
       │   │ operand by the number of bits    │
       │   │ specified by the right-hand      │
       │   │ expression value                 │
       └───┴──────────────────────────────────┘

   Relational Operators
       The following relational operators are defined for integers and pointers.

       ┌───┬────────────────────────────────┐
       │   │                                │
       │<  │ left-hand expression is less   │
       │   │ than right-hand                │
       ├───┼────────────────────────────────┤
       │   │                                │
       │<= │ left-hand expression is less   │
       │   │ than or equal to right-hand    │
       ├───┼────────────────────────────────┤
       │   │                                │
       │>  │ left-hand expression is bigger │
       │   │ than right-hand                │
       ├───┼────────────────────────────────┤
       │   │                                │
       │>= │ left-hand expression is bigger │
       │   │ or equal to than right-hand    │
       ├───┼────────────────────────────────┤
       │   │                                │
       │== │ left-hand expression equal to  │
       │   │ right-hand                     │
       ├───┼────────────────────────────────┤
       │   │                                │
       │!= │ left-hand expression not equal │
       │   │ to right-hand                  │
       └───┴────────────────────────────────┘

       The following relation operators are available for comparing strings and integer arrays.

       ┌───┬───────────────────────────────┐
       │   │                               │
       │== │ left-hand string equal to     │
       │   │ right-hand                    │
       ├───┼───────────────────────────────┤
       │   │                               │
       │!= │ left-hand string not equal to │
       │   │ right-hand                    │
       └───┴───────────────────────────────┘

   Assignment Operators
       The following assignment operators can be used on both map and scratch variables:

       ┌────┬──────────────────────────────────┐
       │    │                                  │
       │=   │ Assignment, assign the           │
       │    │ right-hand expression to the     │
       │    │ left-hand variable               │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │<<= │ Update the variable with its     │
       │    │ value left shifted by the number │
       │    │ of bits specified by the         │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │>>= │ Update the variable with its     │
       │    │ value right shifted by the       │
       │    │ number of bits specified by the  │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │+=  │ Increment the variable by the    │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │-=  │ Decrement the variable by the    │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │*=  │ Multiple the variable by the     │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │/=  │ Divide the variable by the       │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │%=  │ Modulo the variable by the       │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │&=  │ Bitwise AND the variable by the  │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │|=  │ Bitwise OR the variable by the   │
       │    │ right-hand expression value      │
       ├────┼──────────────────────────────────┤
       │    │                                  │
       │^=  │ Bitwise XOR the variable by the  │
       │    │ right-hand expression value      │
       └────┴──────────────────────────────────┘

       All these operators are syntactic sugar for combining assignment with the specified
       operator. @ -= 5 is equal to @ = @ - 5.

   Increment and Decrement Operators
       The increment (+`) and decrement (`--`) operators can be used on integer and pointer
       variables to increment their value by one. They can only be used on variables and can
       either be applied as prefix or suffix. The difference is that the expression `x+ returns
       the original value of x, before it got incremented while ++x returns the value of x post
       increment. E.g.

           $x = 10;
           $y = $x--; // y = 10; x = 9
           $a = 10;
           $b = --$a; // a = 9; b = 9

       Note that maps will be implicitly declared and initialized to 0 if not already declared or
       defined. Scratch variables must be initialized before using these operators.

   Variables and Maps
       bpftrace knows two types of variables, scratch and map.

       'scratch' variables are kept on the BPF stack and only exists during the execution of the
       action block and cannot be accessed outside of the program. Scratch variable names always
       start with a $, e.g. $myvar.

       'map' variables use BPF 'maps'. These exist for the lifetime of bpftrace itself and can be
       accessed from all action blocks and user-space. Map names always start with a @, e.g.
       @mymap.

       All valid identifiers can be used as name.

       The data type of a variable is automatically determined during first assignment and cannot
       be changed afterwards.

   Associative Arrays
       Associative arrays are a collection of elements indexed by a key, similar to the hash
       tables found in languages like C++ (std::map) and Python (dict). They’re a variant of
       'map' variables.

           @name[key] = expression
           @name[key1,key2] = expression

       Just like with any variable the type is determined on first use and cannot be modified
       afterwards. This applies to both the key(s) and the value type.

       The following snippet creates a map with key signature [int64, string[16]] and a value
       type of int64:

           @[pid, comm]++

   Variable scoping
   Pointers
       Pointers in bpftrace are similar to those found in C.

   Tuples
       bpftrace has support for immutable N-tuples (n > 1). A tuple is a sequence type (like an
       array) where, unlike an array, every element can have a different type.

       Tuples are a comma separated list of expressions, enclosed in brackets, (1,2) Individual
       fields can be accessed with the . operator. Tuples are zero indexed like arrays are.

           i:s:1 {
             $a = (1,2);
             $b = (3,4, $a);
             print($a);
             print($b);
             print($b.0);
           }

       Prints:

           (1, 2)
           (3, 4, (1, 2))
           3

   Arrays
       bpftrace supports accessing one-dimensional arrays like those found in C.

       Constructing arrays from scratch, like int a[] = {1,2,3} in C, is not supported. They can
       only be read into a variable from a pointer.

       The [] operator is used to access elements.

           struct MyStruct {
             int y[4];
           }

           kprobe:dummy {
             $s = (struct MyStruct *) arg0;
             print($s->y[0]);
           }

   Structs
       C like structs are supported by bpftrace. Fields are accessed with the . operator. Fields
       of a pointer to a struct can be accessed with the -> operator.

       Custom struct can be defined in the preamble

       Constructing structs from scratch, like struct X var = {.f1 = 1} in C, is not supported.
       They can only be read into a variable from a pointer.

           struct MyStruct {
             int a;
           }

           kprobe:dummy {
             $ptr = (struct MyStruct *) arg0;
             $st = *$ptr;
             print($st.a);
             print($ptr->a);
           }

   Conditionals
       Conditional expressions are supported in the form of if/else statements and the ternary
       operator.

       The ternary operator consists of three operands: a condition followed by a ?, the
       expression to execute when the condition is true followed by a : and the expression to
       execute if the condition is false.

           condition ? ifTrue : ifFalse

       Both the ifTrue and ifFalse expressions must be of the same type, mixing types is not
       allowed.

       The ternary operator can be used as part of an assignment.

           $a == 1 ? print("true") : print("false");
           $b = $a > 0 ? $a : -1;

       If/else statements, like the one in C, are supported.

           if (condition) {
             ifblock
           } else if (condition) {
             if2block
           } else {
             elseblock
           }

   Loops
       Since kernel 5.3 BPF supports loops as long as the verifier can prove they’re bounded and
       fit within the instruction limit.

       In bpftrace loops are available through the while statement.

           while (condition) {
             block;
           }

       Within a while-loop the following control flow statements can be used:

       ┌─────────┬────────────────────────────────┐
       │         │                                │
       │continue │ skip processing of the rest of │
       │         │ the block and jump back to the │
       │         │ evaluation of the conditional  │
       ├─────────┼────────────────────────────────┤
       │         │                                │
       │break    │ Terminate the loop             │
       └─────────┴────────────────────────────────┘

           i:s:1 {
             $i = 0;
             while ($i <= 100) {
               printf("%d ", $i);
               if ($i > 5) {
                 break;
               }
               $i++
             }
             printf("\n");
           }

       Loop unrolling is also supported with the unroll statement.

           unroll(n) {
             block;
           }

       The compiler will evaluate the block n times and generate the BPF code for the block n
       times. As this happens at compile time n must be a constant greater than 0 (n > 0).

       The following two probes compile into the same code:

           i:s:1 {
             unroll(3) {
               print("Unrolled")
             }
           }

           i:s:1 {
             print("Unrolled")
             print("Unrolled")
             print("Unrolled")
           }

INVOCATION MODE

       There are three invocation modes for bpftrace built-in functions.

       ┌─────────────┬──────────────────────────┬──────────────────────┐
       │             │                          │                      │
       │Mode         │ Description              │ Example functions    │
       ├─────────────┼──────────────────────────┼──────────────────────┤
       │             │                          │                      │
       │Synchronous  │ The value/effect of the  │ reg(), str(), ntop() │
       │             │ built-in function is     │                      │
       │             │ determined/handled right │                      │
       │             │ away by the bpf program  │                      │
       │             │ in the kernel space.     │                      │
       ├─────────────┼──────────────────────────┼──────────────────────┤
       │             │                          │                      │
       │Asynchronous │ The value/effect of the  │ printf(), clear(),   │
       │             │ built-in function is     │ exit()               │
       │             │ determined/handled later │                      │
       │             │ by the bpftrace process  │                      │
       │             │ in the user space.       │                      │
       ├─────────────┼──────────────────────────┼──────────────────────┤
       │             │                          │                      │
       │Compile-time │ The value of the         │ kaddr(), cgroupid(), │
       │             │ built-in function is     │ offsetof()           │
       │             │ determined before bpf    │                      │
       │             │ programs are running.    │                      │
       └─────────────┴──────────────────────────┴──────────────────────┘

       While BPF in the kernel can do a lot there are still things that can only be done from
       user space, like the outputting (printing) of data. The way bpftrace handles this is by
       sending events from the BPF program which user-space will pick up some time in the future
       (usually in milliseconds). Operations that happen in the kernel are 'synchronous' ('sync')
       and those that are handled in user space are 'asynchronous' ('async')

       The asynchronous behaviour can lead to some unexpected behavior as updates can happen
       before user space had time to process the event. The following situations may occur:

       •   event loss: when using printf(), the amount of data printed may be less than the
           actual number of events generated by the kernel during BPF program’s execution.

       •   delayed exit: when using the exit() to terminate the program, bpftrace needs to handle
           the exit signal asynchronously causing the BPF program may continue to run for some
           additional time.

       One example is updating a map value in a tight loop:

           BEGIN {
               @=0;
               unroll(10) {
                 print(@);
                 @++;
               }
               exit()
           }

       Maps are printed by reference not by value and as the value gets updated right after the
       print user-space will likely only see the final value once it processes the event:

           @: 10
           @: 10
           @: 10
           @: 10
           @: 10
           @: 10
           @: 10
           @: 10
           @: 10
           @: 10

       Therefore, when you need precise event statistics, it is recommended to use synchronous
       functions (e.g. count() and hist()) to ensure more reliable and accurate results.

ADDRESS-SPACES

       Kernel and user pointers live in different address spaces which, depending on the CPU
       architecture, might overlap. Trying to read a pointer that is in the wrong address space
       results in a runtime error. This error is hidden by default but can be enabled with the
       -kk flag:

           stdin:1:9-12: WARNING: Failed to probe_read_user: Bad address (-14)
           BEGIN { @=*uptr(kaddr("do_poweroff")) }
                   ~~~

       bpftrace tries to automatically set the correct address space for a pointer based on the
       probe type, but might fail in cases where it is unclear. The address space can be changed
       with the kptr() and uptr() functions.

BUILTINS

       Builtins are special variables built into the language. Unlike the scratch and map
       variable they don’t need a $ or @ as prefix (except for the positional parameters).

       ┌──────────────┬─────────────┬────────────┬───────────────────────┬───────────────────┐
       │              │             │            │                       │                   │
       │Variable      │ Type        │ Kernel     │ BPF Helper            │ Description       │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │$1, $2, ...$n │ int64       │ n/a        │ n/a                   │ The nth           │
       │              │             │            │                       │ positional        │
       │              │             │            │                       │ parameter passed  │
       │              │             │            │                       │ to the bpftrace   │
       │              │             │            │                       │ program. If less  │
       │              │             │            │                       │ than n            │
       │              │             │            │                       │ parameters are    │
       │              │             │            │                       │ passed this       │
       │              │             │            │                       │ evaluates to 0.   │
       │              │             │            │                       │ For string        │
       │              │             │            │                       │ arguments use     │
       │              │             │            │                       │ the str() call    │
       │              │             │            │                       │ to retrieve the   │
       │              │             │            │                       │ value.            │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │$#            │ int64       │ n/a        │ n/a                   │ Total amount of   │
       │              │             │            │                       │ positional        │
       │              │             │            │                       │ parameters        │
       │              │             │            │                       │ passed.           │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │arg0, arg1,   │ int64       │ n/a        │ n/a                   │ nth argument      │
       │...argn       │             │            │                       │ passed to the     │
       │              │             │            │                       │ function being    │
       │              │             │            │                       │ traced. These     │
       │              │             │            │                       │ are extracted     │
       │              │             │            │                       │ from the CPU      │
       │              │             │            │                       │ registers. The    │
       │              │             │            │                       │ amount of args    │
       │              │             │            │                       │ passed in         │
       │              │             │            │                       │ registers         │
       │              │             │            │                       │ depends on the    │
       │              │             │            │                       │ CPU               │
       │              │             │            │                       │ architecture.     │
       │              │             │            │                       │ (kprobes,         │
       │              │             │            │                       │ uprobes, usdt).   │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │args          │ struct args │ n/a        │ n/a                   │ The struct of     │
       │              │             │            │                       │ all arguments of  │
       │              │             │            │                       │ the traced        │
       │              │             │            │                       │ function.         │
       │              │             │            │                       │ Available in      │
       │              │             │            │                       │ tracepoint,       │
       │              │             │            │                       │ kfunc, and        │
       │              │             │            │                       │ uprobe (with      │
       │              │             │            │                       │ DWARF) probes.    │
       │              │             │            │                       │ Use args.x to     │
       │              │             │            │                       │ access argument   │
       │              │             │            │                       │ x or args to get  │
       │              │             │            │                       │ a record with     │
       │              │             │            │                       │ all arguments.    │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │cgroup        │ uint64      │ 4.18       │ get_current_cgroup_id │ ID of the cgroup  │
       │              │             │            │                       │ the current task  │
       │              │             │            │                       │ is in. Only       │
       │              │             │            │                       │ works with        │
       │              │             │            │                       │ cgroupv2.         │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │comm          │ string[16]  │ 4.2        │ get_current_com       │ comm of the       │
       │              │             │            │                       │ current task.     │
       │              │             │            │                       │ Equal to the      │
       │              │             │            │                       │ value in          │
       │              │             │            │                       │ /proc/<pid>/comm  │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │cpid          │ uint32      │ n/a        │ n/a                   │ PID of the child  │
       │              │             │            │                       │ process           │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │numaid        │ uint32      │ 5.8        │ numa_node_id          │ ID of the NUMA    │
       │              │             │            │                       │ node executing    │
       │              │             │            │                       │ the BPF program   │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │cpu           │ uint32      │ 4.1        │ raw_smp_processor_id  │ ID of the         │
       │              │             │            │                       │ processor         │
       │              │             │            │                       │ executing the     │
       │              │             │            │                       │ BPF program       │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │curtask       │ uint64      │ 4.8        │ get_current_task      │ Pointer to        │
       │              │             │            │                       │ struct            │
       │              │             │            │                       │ task_struct of    │
       │              │             │            │                       │ the current task  │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │elapsed       │ uint64      │ (see nsec) │ ktime_get_ns /        │ Nanoseconds       │
       │              │             │            │ ktime_get_boot_ns     │ elapsed since     │
       │              │             │            │                       │ bpftrace          │
       │              │             │            │                       │ initialization,   │
       │              │             │            │                       │ based on nsecs    │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │func          │ string      │ n/a        │ n/a                   │ Name of the       │
       │              │             │            │                       │ current function  │
       │              │             │            │                       │ being traced      │
       │              │             │            │                       │ (kprobes,uprobes) │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │gid           │ uint64      │ 4.2        │ get_current_uid_gid   │ GID of current    │
       │              │             │            │                       │ task              │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │kstack        │ kstack      │            │ get_stackid           │ Kernel stack      │
       │              │             │            │                       │ trace             │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │nsecs         │ uint64      │ 4.1 / 5.7  │ ktime_get_ns /        │ nanoseconds since │
       │              │             │            │ ktime_get_boot_ns     │ kernel boot. On   │
       │              │             │            │                       │ kernels that      │
       │              │             │            │                       │ support           │
       │              │             │            │                       │ ktime_get_boot_ns │
       │              │             │            │                       │ this includes the │
       │              │             │            │                       │ time spent        │
       │              │             │            │                       │ suspended, on     │
       │              │             │            │                       │ older kernels it  │
       │              │             │            │                       │ does not.         │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │jiffies       │ uint64      │ 5.9        │ get_jiffies_64        │ Jiffies of the    │
       │              │             │            │                       │ kernel. In 32-bit │
       │              │             │            │                       │ system, using     │
       │              │             │            │                       │ this builtin      │
       │              │             │            │                       │ might be slower.  │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │pid           │ uint64      │ 4.2        │ get_current_pid_tgid  │ Process ID (or    │
       │              │             │            │                       │ thread group ID)  │
       │              │             │            │                       │ of the current    │
       │              │             │            │                       │ task.             │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │probe         │ string      │ n/na       │ n/a                   │ Name of the       │
       │              │             │            │                       │ current probe     │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │rand          │ uint32      │ 4.1        │ get_prandom_u32       │ Random number     │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │retval        │ int64       │ n/a        │ n/a                   │ Value returned by │
       │              │             │            │                       │ the function      │
       │              │             │            │                       │ being traced      │
       │              │             │            │                       │ (kretprobe,       │
       │              │             │            │                       │ uretprobe,        │
       │              │             │            │                       │ kretfunc)         │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │sarg0, sarg1, │ int64       │ n/a        │ n/a                   │ nth stack value   │
       │...sargn      │             │            │                       │ of the function   │
       │              │             │            │                       │ being traced.     │
       │              │             │            │                       │ (kprobes,         │
       │              │             │            │                       │ uprobes).         │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │tid           │ uint64      │ 4.2        │ get_current_pid_tgid  │ Thread ID of the  │
       │              │             │            │                       │ current task.     │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │uid           │ uint64      │ 4.2        │ get_current_uid_gid   │ UID of current    │
       │              │             │            │                       │ task              │
       ├──────────────┼─────────────┼────────────┼───────────────────────┼───────────────────┤
       │              │             │            │                       │                   │
       │ustack        │ ustack      │ 4.6        │ get_stackid           │ Userspace stack   │
       │              │             │            │                       │ trace             │
       └──────────────┴─────────────┴────────────┴───────────────────────┴───────────────────┘

MAP FUNCTIONS

       Map functions are built-in functions who’s return value can only be assigned to maps. The
       data type associated with these functions are only for internal use and are not compatible
       with the (integer) operators.

       Functions that are marked async are asynchronous which can lead to unexpected behavior,
       see the [Sync and Async] section for more information.

   avg
       variants

       •   avg(int64 n)

       Calculate the running average of n between consecutive calls.

           i:s:1 {
             @x++;
             @y = avg(@x);
             print(@x);
             print(@y);
           }

       Internally this keeps two values in the map: value count and running total. The average is
       computed in user-space when printing by dividing the total by the count.

   clear
       variants

       •   clear(map m)

       async

       Clear all keys/values from map m.

           i:ms:100 {
             @[rand % 10] = count();
           }

           i:s:10 {
             print(@);
             clear(@);
           }

   count
       variants

       •   count()

       Count how often this function is called.

       Using @=count() is conceptually similar to @++. The difference is that the count()
       function uses a map type optimized for this (PER_CPU), increasing performance. Due to this
       the map cannot be accessed as a regular integer.

           i:ms:100 {
             @ = count();
           }

           i:s:10 {
             print(@);
             clear(@);
           }

   delete
       variants

       •   delete(mapkey k)

       Delete a single key from a map. For a single value map this deletes the only element. For
       an associative-array the key to delete has to be specified.

           k:dummy {
             @scalar = 1;
             @associative[1,2] = 1;
             delete(@scalar);
             delete(@associative[1,2]);

             delete(@associative); // error
           }

   hist
       variants

       •   hist(int64 n[, int k])

       Create a log2 histogram of n using $2^k$ buckets per power of 2, 0 ⇐ k ⇐ 5, defaults to 0.

           kretprobe:vfs_read {
             @bytes = hist(retval);
           }

       Results in:

           @:
           [1M, 2M)               3 |                                                    |
           [2M, 4M)               2 |                                                    |
           [4M, 8M)               2 |                                                    |
           [8M, 16M)              6 |                                                    |
           [16M, 32M)            16 |                                                    |
           [32M, 64M)            27 |                                                    |
           [64M, 128M)           48 |@                                                   |
           [128M, 256M)          98 |@@@                                                 |
           [256M, 512M)         191 |@@@@@@                                              |
           [512M, 1G)           394 |@@@@@@@@@@@@@                                       |
           [1G, 2G)             820 |@@@@@@@@@@@@@@@@@@@@@@@@@@@                         |

   lhist
       variants

       •   lhist(int64 n, int64 min, int64 max, int64 step)

       Create a linear histogram of n. lhist creates M ((max - min) / step) buckets in the range
       [min,max) where each bucket is step in size. Values in the range (-inf, min) and (max,
       inf) get their get their own bucket too, bringing the total amount of buckets created to
       M+2.

           i:ms:1 {
             @ = lhist(rand %10, 0, 10, 1);
           }

           i:s:5 {
             exit();
           }

       Prints:

           @:
           [0, 1)               306 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@         |
           [1, 2)               284 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@            |
           [2, 3)               294 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@          |
           [3, 4)               318 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@       |
           [4, 5)               311 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@        |
           [5, 6)               362 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
           [6, 7)               336 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@    |
           [7, 8)               326 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@      |
           [8, 9)               328 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@     |
           [9, 10)              318 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@       |

   max
       variants

       •   max(int64 n)

       Update the map with n if n is bigger than the current value held.

   min
       variants

       •   min(int64 n)

       Update the map with n if n is smaller than the current value held.

   stats
       variants

       •   stats(int64 n)

       stats combines the count, avg and sum calls into one.

           kprobe:vfs_read {
             @bytes[comm] = stats(arg2);
           }

           @bytes[bash]: count 7, average 1, total 7
           @bytes[sleep]: count 5, average 832, total 4160
           @bytes[ls]: count 7, average 886, total 6208
           @

   sum
       variants

       •   sum(int64 n)

       Calculate the sum of all n passed.

   zero
       variants

       •   zero(map m)

       async

       Set all values for all keys to zero.

   len
       variants

       •   len(map m)

       Return the number of elements in the map.

FUNCTIONS

       Functions that are marked async are asynchronous which can lead to unexpected behaviour,
       see the [sync and async] section for more information.

       compile time functions are evaluated at compile time, a static value will be compiled into
       the program.

       unsafe functions can have dangerous side effects and should be used with care, the
       --unsafe flag is required for use.

   bswap
       variants

       •   uint8 bswap(uint8 n)

       •   uint16 bswap(uint16 n)

       •   uint32 bswap(uint32 n)

       •   uint64 bswap(uint64 n)

       bswap reverses the order of the bytes in integer n. In case of 8 bit integers, n is
       returned without being modified. The return type is an unsigned integer of the same width
       as n.

   buf
       variants

       •   buf_t buf(void * data, [int64 length])

       buf reads length amount of bytes from address data. The maximum value of length is limited
       to the BPFTRACE_MAX_STRLEN variable. For arrays the length is optional, it is
       automatically inferred from the signature.

       buf is address space aware and will call the correct helper based on the address space
       associated with data.

       The buf_t object returned by buf can safely be printed as a hex encoded string with the %r
       format specifier.

       Bytes with values >=32 and <=126 are printed using their ASCII character, other bytes are
       printed in hex form (e.g. \x00). The %rx format specifier can be used to print everything
       in hex form, including ASCII characters. The similar %rh format specifier prints
       everything in hex form without \x and with spaces between bytes (e.g. 0a fe).

           i:s:1 {
             printf("%r\n", buf(kaddr("avenrun"), 8));
           }

           \x00\x03\x00\x00\x00\x00\x00\x00
           \xc2\x02\x00\x00\x00\x00\x00\x00

   cat
       variants

       •   void cat(string namefmt, [...args])

       async

       Dump the contents of the named file to stdout. cat supports the same format string and
       arguments that printf does. If the file cannot be opened or read an error is printed to
       stderr.

           t:syscalls:sys_enter_execve {
             cat("/proc/%d/maps", pid);
           }

           55f683ebd000-55f683ec1000 r--p 00000000 08:01 1843399                    /usr/bin/ls
           55f683ec1000-55f683ed6000 r-xp 00004000 08:01 1843399                    /usr/bin/ls
           55f683ed6000-55f683edf000 r--p 00019000 08:01 1843399                    /usr/bin/ls
           55f683edf000-55f683ee2000 rw-p 00021000 08:01 1843399                    /usr/bin/ls
           55f683ee2000-55f683ee3000 rw-p 00000000 00:00 0

   cgroup_path
       variants

       •   cgroup_path cgroup_path(int cgroupid, string filter)

       Convert cgroup id to cgroup path. This is done asynchronously in userspace when the
       cgroup_path value is printed, therefore it can resolve to a different value if the cgroup
       id gets reassigned. This also means that the returned value can only be used for printing.

       A string literal may be passed as an optional second argument to filter cgroup hierarchies
       in which the cgroup id is looked up by a wildcard expression (cgroup2 is always
       represented by "unified", regardless of where it is mounted).

       The currently mounted hierarchy at /sys/fs/cgroup is used to do the lookup. If the cgroup
       with the given id isn’t present here (e.g. when running in a Docker container), the cgroup
       path won’t be found (unlike when looking up the cgroup path of a process via
       /proc/.../cgroup).

           BEGIN {
             $cgroup_path = cgroup_path(3436);
             print($cgroup_path);
             print($cgroup_path); /* This may print a different path */
             printf("%s %s", $cgroup_path, $cgroup_path); /* This may print two different paths */
           }

   cgroupid
       variants

       •   uint64 cgroupid(const string path)

       compile time

       cgroupid retrieves the cgroupv2 ID  of the cgroup available at path.

           BEGIN {
             print(cgroupid("/sys/fs/cgroup/system.slice"));
           }

   exit
       variants

       •   void exit()

       async

       Terminate bpftrace, as if a SIGTERM was received. The END probe will still trigger (if
       specified) and maps will be printed.

   join
       variants

       •   void join(char *arr[], [char * sep = ' '])

       async

       join joins all the string array arr with sep as separator into one string. This string
       will be printed to stdout directly, it cannot be used as string value.

       The concatenation of the array members is done in BPF and the printing happens in
       userspace.

           tracepoint:syscalls:sys_enter_execve {
             join(args.argv);
           }

   kaddr
       variants

       •   uint64 kaddr(const string name)

       compile time

       Get the address of the kernel symbol name.

       The following script:

   kptr
       variants

       •   T * kptr(T * ptr)

       Marks ptr as a kernel address space pointer. See the address-spaces section for more
       information on address-spaces. The pointer type is left unchanged.

   ksym
       variants

       •   ksym_t ksym(uint64 addr)

       async

       Retrieve the name of the function that contains address addr. The address to name mapping
       happens in user-space.

       The ksym_t type can be printed with the %s format specifier.

           kprobe:do_nanosleep
           {
             printf("%s\n", ksym(reg("ip")));
           }

       Prints:

           do_nanosleep

   macaddr
       variants

       •   macaddr_t macaddr(char [6] mac)

       Create a buffer that holds a macaddress as read from mac This buffer can be printed in the
       canonical string format using the %s format specifier.

           kprobe:arp_create {
             printf("SRC %s, DST %s\n", macaddr(sarg0), macaddr(sarg1));
           }

       Prints:

           SRC 18:C0:4D:08:2E:BB, DST 74:83:C2:7F:8C:FF

   ntop
       variants

       •   inet_t ntop([int64 af, ] int addr)

       •   inet_t ntop([int64 af, ] char addr[4])

       •   inet_t ntop([int64 af, ] char addr[16])

       ntop returns the string representation of an IPv4 or IPv6 address. ntop will infer the
       address type (IPv4 or IPv6) based on the addr type and size. If an integer or char[4] is
       given, ntop assumes IPv4, if a char[16] is given, ntop assumes IPv6. You can also pass the
       address type (e.g. AF_INET) explicitly as the first parameter.

   pton
       variants

       •   char addr[4] pton(const string *addr_v4)

       •   char addr[16] pton(const string *addr_v6)

       compile time

       pton converts a text representation of an IPv4 or IPv6 address to byte array. pton infers
       the address family based on . or : in the given argument. pton comes in handy when we need
       to select packets with certain IP addresses.

   override
       variants

       •   override(uint64 rc)

       unsafe

       Kernel 4.16

       Helper bpf_override

       Supported probes

       •   kprobe

       When using override the probed function will not be executed and instead rc will be
       returned.

           k:__x64_sys_getuid
           /comm == "id"/ {
             override(2<<21);
           }

           uid=4194304 gid=0(root) euid=0(root) groups=0(root)

       This feature only works on kernels compiled with CONFIG_BPF_KPROBE_OVERRIDE and only works
       on functions tagged ALLOW_ERROR_INJECTION.

       bpftrace does not test whether error injection is allowed for the probed function, instead
       if will fail to load the program into the kernel:

           ioctl(PERF_EVENT_IOC_SET_BPF): Invalid argument
           Error attaching probe: 'kprobe:vfs_read'

   reg
       variants

       •   reg(const string name)

       Supported probes

       •   kprobe

       •   uprobe

       Get the contents of the register identified by name. Valid names depend on the CPU
       architecture.

   signal
       variants

       •   signal(const string sig)

       •   signal(uint32 signum)

       unsafe

       Kernel 5.3

       Helper bpf_send_signal

       Probe types: k(ret)probe, u(ret)probe, USDT, profile

       Send a signal to the process being traced. The signal can either be identified by name,
       e.g. SIGSTOP or by ID, e.g. 19 as found in kill -l.

           kprobe:__x64_sys_execve
           /comm == "bash"/ {
             signal(5);
           }

           $ ls
           Trace/breakpoint trap (core dumped)

   sizeof
       variants

       •   sizeof(TYPE)

       •   sizeof(EXPRESSION)

       compile time

       Returns size of the argument in bytes. Similar to C/C++ sizeof operator. Note that the
       expression does not get evaluated.

   offsetof
       variants

       •   offsetof(STRUCT, FIELD)

       •   offsetof(EXPRESSION, FIELD)

       compile time

       Returns offset of the field offset bytes in struct. Similar to kernel offsetof operator.
       Note that subfields are not yet supported.

   str
       variants

       •   str(char * data [, uint32 length)

       Helper probe_read_str, probe_read_{kernel,user}_str

       str reads a NULL terminated (\0) string from data. The maximum string length is limited by
       the BPFTRACE_MAX_STRLEN env variable, unless length is specified and shorter than the
       maximum. In case the string is longer than the specified length only length - 1 bytes are
       copied and a NULL byte is appended at the end.

       When available (starting from kernel 5.5, see the --info flag) bpftrace will automatically
       use the kernel or user variant of probe_read_{kernel,user}_str based on the address space
       of data, see ADDRESS-SPACES for more information.

   strerror
       variants

       •   strerror strerror(int error)

       Convert errno code to string. This is done asynchronously in userspace when the strerror
       value is printed, hence the returned value can only be used for printing.

           #include <errno.h>
           BEGIN {
             print(strerror(EPERM));
           }

   strftime
       variants

       •   strtime_t strftime(const string fmt, int64 timestamp_ns)

       async

       Format the nanoseconds since boot timestamp timestamp_ns according to the format specified
       by fmt. The time conversion and formatting happens in user space, therefore  the timestr_t
       value returned can only be used for printing using the %s format specifier.

       bpftrace uses the strftime(3) function for formatting time and supports the same format
       specifiers.

           i:s:1 {
             printf("%s\n", strftime("%H:%M:%S", nsecs));
           }

       bpftrace also supports the following format string extensions:

       ┌──────────┬──────────────────────────────────┐
       │          │                                  │
       │Specifier │ Description                      │
       ├──────────┼──────────────────────────────────┤
       │          │                                  │
       │%f        │ Microsecond as a decimal number, │
       │          │ zero-padded on the left          │
       └──────────┴──────────────────────────────────┘

   strncmp
       variants

       •   int64 strncmp(char * s1, char * s2, int64 n)

       strncmp compares up to n characters string s1 and string s2. If they’re equal 0 is
       returned, else a non-zero value is returned.

       bpftrace doesn’t read past the length of the shortest string.

       The use of the == and != operators is recommended over calling strncmp directly.

   strcontains
       variants

       •   int64 strcontains(const char *haystack, const char *needle)

       strcontains compares whether the string haystack contains the string needle. If needle is
       contained 1 is returned, else zero is returned.

       bpftrace doesn’t read past the length of the shortest string.

   system
       variants

       •   void system(string namefmt [, ...args])

       unsafe async

       system lets bpftrace run the specified command (fork and exec) until it completes and
       print its stdout. The command is run with the same privileges as bpftrace and it blocks
       execution of the processing threads which can lead to missed events and delays processing
       of async events.

           i:s:1 {
             time("%H:%M:%S: ");
             printf("%d\n", @++);
           }
           i:s:10 {
             system("/bin/sleep 10");
           }
           i:s:30 {
             exit();
           }

       Note how the async time and printf first print every second until the i:s:10 probe hits,
       then they print every 10 seconds due to bpftrace blocking on sleep.

           Attaching 3 probes...
           08:50:37: 0
           08:50:38: 1
           08:50:39: 2
           08:50:40: 3
           08:50:41: 4
           08:50:42: 5
           08:50:43: 6
           08:50:44: 7
           08:50:45: 8
           08:50:46: 9
           08:50:56: 10
           08:50:56: 11
           08:50:56: 12
           08:50:56: 13
           08:50:56: 14
           08:50:56: 15
           08:50:56: 16
           08:50:56: 17
           08:50:56: 18
           08:50:56: 19

       system supports the same format string and arguments that printf does.

           t:syscalls:sys_enter_execve {
             system("/bin/grep %s /proc/%d/status", "vmswap", pid);
           }

   time
       variants

       •   void time(const string fmt)

       async

       Format the current wall time according to the format specifier fmt and print it to stdout.
       Unlike strftime() time() doesn’t send a timestamp from the probe, instead it is the time
       at which user-space processes the event.

       bpftrace uses the strftime(3) function for formatting time and supports the same format
       specifiers.

   uaddr
       variants

       •   T * uaddr(const string sym)

       Supported probes

       •   uprobes

       •   uretprobes

       •   USDT

       Does not work with ASLR, see issue #75 <https://github.com/iovisor/bpftrace/issues/75>

       The uaddr function returns the address of the specified symbol. This lookup happens during
       program compilation and cannot be used dynamically.

       The default return type is uint64*. If the ELF object size matches a known integer size
       (1, 2, 4 or 8 bytes) the return type is modified to match the width (uint8*, uint16*,
       uint32* or uint64* resp.). As ELF does not contain type info the type is always assumed to
       be unsigned.

           uprobe:/bin/bash:readline {
             printf("PS1: %s\n", str(*uaddr("ps1_prompt")));
           }

   uptr
       variants

       •   T * uptr(T * ptr)

       Marks ptr as a user address space pointer. See the address-spaces section for more
       information on address-spaces. The pointer type is left unchanged.

   usym
       variants

       •   usym_t usym(uint64 * addr)

       async

       Supported probes

       •   uprobes

       •   uretprobes

       Equal to ksym but resolves user space symbols.

       If ASLR is enabled, user space symbolication only works when the process is running at
       either the time of the symbol resolution or the time of the probe attachment. The latter
       requires BPFTRACE_CACHE_USER_SYMBOLS to be set to PER_PID, and might not work with older
       versions of BCC. A similar limitation also applies to dynamically loaded symbols.

           uprobe:/bin/bash:readline
           {
             printf("%s\n", usym(reg("ip")));
           }

       Prints:

           readline

   path
       variants

       •   char * path(struct path * path)

       Kernel 5.10

       Helper bpf_d_path

       Return full path referenced by struct path pointer in argument.

       This function can only be used by functions that are allowed to, these functions are
       contained in the btf_allowlist_d_path set in the kernel.

   unwatch
       variants

       •   void unwatch(void * addr)

       async

       Removes a watchpoint

   skboutput
       variants

       •   uint32 skboutput(const string path, struct sk_buff *skb, uint64 length, const uint64
           offset)

       Kernel 5.5

       Helper bpf_skb_output

       Write sk_buff skb 's data section to a PCAP file in the path, starting from offset to
       offset + length.

       The PCAP file is encapsulated in RAW IP, so no ethernet header is included. The data
       section in the struct skb may contain ethernet header in some kernel contexts, you may set
       offset to 14 bytes to exclude ethernet header.

       Each packet’s timestamp is determined by adding nsecs and boot time, the accuracy varies
       on different kernels, see nsecs.

       This function returns 0 on success, or a negative error in case of failure.

       Environment variable BPFTRACE_PERF_RB_PAGES should be increased in order to capture large
       packets, or else these packets will be dropped.

       Usage

           # cat dump.bt
           kfunc:napi_gro_receive {
             $ret = skboutput("receive.pcap", args.skb, args.skb->len, 0);
           }

           kfunc:dev_queue_xmit {
             // setting offset to 14, to exclude ethernet header
             $ret = skboutput("output.pcap", args.skb, args.skb->len, 14);
             printf("skboutput returns %d\n", $ret);
           }

           # export BPFTRACE_PERF_RB_PAGES=1024
           # bpftrace dump.bt
           ...

           # tcpdump -n -r ./receive.pcap  | head -3
           reading from file ./receive.pcap, link-type RAW (Raw IP)
           dropped privs to tcpdump
           10:23:44.674087 IP 22.128.74.231.63175 > 192.168.0.23.22: Flags [.], ack 3513221061, win 14009, options [nop,nop,TS val 721277750 ecr 3115333619], length 0
           10:23:45.823194 IP 100.101.2.146.53 > 192.168.0.23.46619: 17273 0/1/0 (130)
           10:23:45.823229 IP 100.101.2.146.53 > 192.168.0.23.46158: 45799 1/0/0 A 100.100.45.106 (60)

OUTPUT FORMATTING

   print
       variants

       •   void print(T val)

       async

       variants

       •   void print(T val)

       •   void print(@map)

       •   void print(@map, uint64 top)

       •   void print(@map, uint64 top, uint64 div)

       print prints a the value, which can be a map or a scalar value, with the default
       formatting for the type.

           i:ms:10 { @=hist(rand); }
           i:s:1 {
             print(@);
             print(123);
             print("abc");
             exit();
           }

       Prints:

           @:
           [16M, 32M)             3 |@@@                                                 |
           [32M, 64M)             2 |@@                                                  |
           [64M, 128M)            1 |@                                                   |
           [128M, 256M)           4 |@@@@                                                |
           [256M, 512M)           3 |@@@                                                 |
           [512M, 1G)            14 |@@@@@@@@@@@@@@                                      |
           [1G, 2G)              22 |@@@@@@@@@@@@@@@@@@@@@@                              |
           [2G, 4G)              51 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|

           123
           abc

       Note that maps are printed by reference while scalar values are copied. This means that
       updating and printing maps in a fast loop will likely result in bogus map values as the
       map will be updated before userspace gets the time to dump and print it.

       The printing of maps supports the optional top and div arguments. top limits the printing
       to the top N entries with the highest integer values

           BEGIN {
             $i = 11;
             while($i) {
               @[$i] = --$i;
             }
             print(@, 2);
             clear(@);
             exit()
           }

           @[9]: 9
           @[10]: 10

       The div argument scales the values prior to printing them. Scaling values before storing
       them can result in rounding errors. Consider the following program:

           k:f {
             @[func] += arg0/10;
           }

       With the following sequence as numbers for arg0: 134, 377, 111, 99. The total is 721 which
       rounds to 72 when scaled by 10 but the program would print 70 due to the rounding of
       individual values.

       Changing the print call to print(@, 5, 2) will take the top 5 values and scale them by 2:

           @[6]: 3
           @[7]: 3
           @[8]: 4
           @[9]: 4
           @[10]: 5

   printf
       variants

       •   void printf(const string fmt, args...)

       async

       printf() formats and prints data. It behaves similar to printf() found in C and many other
       languages.

       The format string has to be a constant, it cannot be modified at runtime. The formatting
       of the string happens in user space. Values are copied and passed by value.

       bpftrace supports all the typical format specifiers like %llx and %hhu. The non-standard
       ones can be found in the table below:

       ┌──────────┬────────┬─────────────────────────┐
       │          │        │                         │
       │Specifier │ Type   │ Description             │
       ├──────────┼────────┼─────────────────────────┤
       │          │        │                         │
       │r         │ buffer │ Hex-formatted string to │
       │          │        │ print arbitrary binary  │
       │          │        │ content returned by the │
       │          │        │ buf (buf) function.     │
       └──────────┴────────┴─────────────────────────┘

       Supported escape sequences

       Colors are supported too, using standard terminal escape sequences:

           print("\033[31mRed\t\033[33mYellow\033[0m\n")

PROBES

       bpftrace supports various probe types which allow the user to attach BPF programs to
       different types of events. Each probe starts with a provider (e.g. kprobe) followed by a
       colon (:) separated list of options. The amount of options and their meaning depend on the
       provider and are detailed below. The valid values for options can depend on the system or
       binary being traced, e.g. for uprobes it depends on the binary. Also see LISTING PROBES

       It is possible to associate multiple probes with a single action as long as the action is
       valid for all specified probes. Multiple probes can be specified as a comma (,) separated
       list:

           kprobe:tcp_reset,kprobe:tcp_v4_rcv {
             printf("Entered: %s\n", probe);
           }

       Wildcards are supported too:

           kprobe:tcp_* {
             printf("Entered: %s\n", probe);
           }

       Both can be combined:

           kprobe:tcp_reset,kprobe:*socket* {
             printf("Entered: %s\n", probe);
           }

       Most providers also support a short name which can be used instead of the full name, e.g.
       kprobe:f and k:f are identical.

   BEGIN and END
       These are special built-in events provided by the bpftrace runtime. BEGIN is triggered
       before all other probes are attached. END is triggered after all other probes are
       detached.

       Note that specifying an END probe doesn’t override the printing of 'non-empty' maps at
       exit. To prevent the printing all used maps need be cleared, which can be done in the END
       probe:

           END {
               clear(@map1);
               clear(@map2);
           }

   hardware
       variants

       •   hardware:event_name:

       •   hardware:event_name:count

       shortname

       •   h

       The hardware probe attaches to pre-defined hardware events provided by the kernel.

       They are implemented using performance monitoring counters (PMCs): hardware resources on
       the processor. There are about ten of these, and they are documented in the
       perf_event_open(2) man page. The event names are:

       •   cpu-cycles or cycles

       •   instructions

       •   cache-references

       •   cache-misses

       •   branch-instructions or branches

       •   branch-misses

       •   bus-cycles

       •   frontend-stalls

       •   backend-stalls

       •   ref-cycles

       The count option specifies how many events must happen before the probe fires. If count is
       left unspecified a default value is used.

           hardware:cache-misses:1e6 { @[pid] = count(); }

   interval
       variants

       •   interval:us:count

       •   interval:ms:count

       •   interval:s:count

       •   interval:hz:rate

       shortnames

       •   i

       The interval probe fires at a fixed interval as specified by its time spec. Interval fire
       on one CPU at the time, unlike [profile] probes.

   iterator
       variants

       •   iter:task

       •   iter:task:pin

       •   iter:task_file

       •   iter:task_file:pin

       •   iter:task_vma

       •   iter:task_vma:pin

       shortnames

       •   it

       These are eBPF iterator probes, that allow iteration over kernel objects.

       Iterator probe can’t be mixed with any other probe, not even other iterator.

       Each iterator probe provides set of fields that could be accessed with ctx pointer. User
       can display set of available fields for iterator via -lv options as described below.

       Examples:

           # bpftrace -e 'iter:task { printf("%s:%d\n", ctx->task->comm, ctx->task->pid); }'
           Attaching 1 probe...
           systemd:1
           kthreadd:2
           rcu_gp:3
           rcu_par_gp:4
           kworker/0:0H:6
           mm_percpu_wq:8
           ...

           # bpftrace -e 'iter:task_file { printf("%s:%d %d:%s\n", ctx->task->comm, ctx->task->pid, ctx->fd, path(ctx->file->f_path)); }'
           Attaching 1 probe...
           systemd:1 1:/dev/null
           systemd:1 2:/dev/null
           systemd:1 3:/dev/kmsg
           ...
           su:1622 1:/dev/pts/1
           su:1622 2:/dev/pts/1
           su:1622 3:/var/lib/sss/mc/passwd
           ...
           bpftrace:1892 1:pipe:[35124]
           bpftrace:1892 2:/dev/pts/1
           bpftrace:1892 3:anon_inode:bpf-map
           bpftrace:1892 4:anon_inode:bpf-map
           bpftrace:1892 5:anon_inode:bpf_link
           bpftrace:1892 6:anon_inode:bpf-prog
           bpftrace:1892 7:anon_inode:bpf_iter

           # bpftrace -e 'iter:task_vma {printf("%s %d %lx-%lx\n", comm, pid, ctx->vma->vm_start, ctx->vma->vm_end);}'
           Attaching 1 probe...
           bpftrace 119480 55b92c380000-55b92c386000
           bpftrace 119480 55b92c386000-55b92c391000
           bpftrace 119480 55b92c391000-55b92c397000
           bpftrace 119480 55b92c398000-55b92c399000
           bpftrace 119480 55b92c399000-55b92c39a000
           bpftrace 119480 55b92cce3000-55b92d010000
           ...
           bpftrace 119480 7ffd55dde000-7ffd55de2000
           bpftrace 119480 7ffd55de2000-7ffd55de4000

       It’s possible to pin iterator with specifying optional probe ':pin' part, that defines the
       pin file. It can be specified as absolute path or relative to /sys/fs/bpf.

       relative pin

           # bpftrace -e 'iter:task:list { printf("%s:%d\n", ctx->task->comm, ctx->task->pid); }'
           Program pinned to /sys/fs/bpf/list

           # cat /sys/fs/bpf/list
           systemd:1
           kthreadd:2
           rcu_gp:3
           rcu_par_gp:4
           kworker/0:0H:6
           mm_percpu_wq:8
           rcu_tasks_kthre:9
           ...

       Examples with absolute pin file:

       absolute pin

           # bpftrace -e '
           iter:task_file:/sys/fs/bpf/files {
             printf("%s:%d %s\n", ctx->task->comm, ctx->task->pid, path(ctx->file->f_path));
           }'

           Program pinned to /sys/fs/bpf/files

           # cat /sys/fs/bpf/files
           systemd:1 anon_inode:inotify
           systemd:1 anon_inode:[timerfd]
           ...
           systemd-journal:849 /dev/kmsg
           systemd-journal:849 anon_inode:[eventpoll]
           ...
           sssd:1146 /var/log/sssd/sssd.log
           sssd:1146 anon_inode:[eventpoll]
           ...
           NetworkManager:1155 anon_inode:[eventfd]
           NetworkManager:1155 /var/lib/sss/mc/passwd (deleted)

   kfunc and kretfunc
       variants

       •   kfunc[:mod]:fn

       •   fentry[:mod]:fn

       •   kretfunc[:mod]:fn

       •   fexit[:mod]:fn

       shortnames

       •   f (kfunc)

       •   fr (kretfunc)

       requires (--info)

       •   Kernel features:BTF

       •   Probe types:kfunc

       kfuncs attach to kernel function similar to kprobe and kretprobe. They make use of eBPF
       trampolines which allows kernel code to call into BPF programs with near zero overhead.
       kfunc and kretfunc are aliased as fentry and fexit to match how these are referenced in
       the kernel.

       kfunc s make use of BTF type information to derive the type of function arguments at
       compile time. This removes the need for manual type casting and makes the code more
       resilient against small signature changes in the kernel. The function arguments are
       available in the args struct which can be inspected by doing verbose listing (see LISTING
       PROBES). These arguments are also available in the return probe (kretfunc).

           # bpftrace -lv 'kfunc:tcp_reset'
           kfunc:tcp_reset
               struct sock * sk
               struct sk_buff * skb

           kfunc:x86_pmu_stop {
             printf("pmu %s stop\n", str(args.event->pmu->name));
           }

           kretfunc:fget {
             printf("fd %d name %s\n", args.fd, str(retval->f_path.dentry->d_name.name));
           }

           fd 3 name ld.so.cache
           fd 3 name libselinux.so.1
           fd 3 name libselinux.so.1
           ...

           kfunc:kvm:x86_emulate_insn { @ = count(); }

           @ = 347603

   kprobe and kretprobe
       variants

       •   kprobe:fn

       •   kprobe:fn+offset

       •   kretprobe:fn

       shortnames

       •   k

       •   kr

       kprobe s allow for dynamic instrumentation of kernel functions. Each time the specified
       kernel function is executed the attached BPF programs are ran.

           kprobe:tcp_reset {
             @tcp_resets = count()
           }

       Function arguments are available through the argX and sargX builtins, for register args
       and stack args respectively. Whether arguments passed on stack or in a register depends on
       the architecture and the number or arguments in used, e.g. on x86_64 the first
       non-floating point 6 arguments are passed in registers, all following arguments are passed
       on the stack. Note that floating point arguments are typically passed in special registers
       which don’t count as argX arguments which can cause confusion. Consider a function with
       the following signature:

           void func(int a, double d, int x)

       Due to d being a floating point x is accessed through arg1 where one might expect arg2.

       bpftrace does not detect the function signature so it is not aware of the argument count
       or their type. It is up to the user to perform Type conversion when needed, e.g.

           kprobe:tcp_connect
           {
             $sk = ((struct sock *) arg0);
             ...
           }

       kprobe s are not limited to function entry, they can be attached to any instruction in a
       function by specifying an offset from the start of the function.

       kretprobe s trigger on the return from a kernel function. Return probes do not have access
       to the function (input) arguments, only to the return value (through retval). A common
       pattern to work around this is by storing the arguments in a map on function entry and
       retrieving in the return probe:

           kprobe:d_lookup
           {
                   $name = (struct qstr *)arg1;
                   @fname[tid] = $name->name;
           }

           kretprobe:d_lookup
           /@fname[tid]/
           {
                   printf("%-8d %-6d %-16s M %s\n", elapsed / 1e6, pid, comm,
                       str(@fname[tid]));
           }

   profile
       variants

       •   profile:us:count

       •   profile:ms:count

       •   profile:s:count

       •   profile:hz:rate

       shortnames

       •   p

       Profile probes fire on each CPU on the specified interval.

   software
       variants

       •   software:event:

       •   software:event:count

       shortnames

       •   s

       The software probe attaches to pre-defined software events provided by the kernel. Event
       details can be found in the perf_event_open(2) man page.

       The event names are:

       •   cpu-clock or cpu

       •   task-clock

       •   page-faults or faults

       •   context-switches or cs

       •   cpu-migrations

       •   minor-faults

       •   major-faults

       •   alignment-faults

       •   emulation-faults

       •   dummy

       •   bpf-output

   tracepoint
       variants

       •   tracepoint:subsys:event

       shortnames

       •   t

       Tracepoints are hooks into events in the kernel. Tracepoints are defined in the kernel
       source and compiled into the kernel binary which makes them a form of static tracing.
       Which means that unlike kprobe s new tracepoints cannot be added without modifying the
       kernel.

       The advantage of tracepoints is that they generally provide a more stable interface than
       kprobe s do, they do not depend on the existence of a kernel function.

       Tracepoint arguments are available in the args struct which can be inspected with verbose
       listing, see the LISTING PROBES section for more details.

           tracepoint:syscalls:sys_enter_openat {
             printf("%s %s\n", comm, str(args.filename));
           }

           irqbalance /proc/interrupts
           irqbalance /proc/stat
           snmpd /proc/diskstats
           snmpd /proc/stat
           snmpd /proc/vmstat
           snmpd /proc/net/dev
           [...]

       Additional information

       •   https://www.kernel.org/doc/html/latest/trace/tracepoints.html

   rawtracepoint
       variants

       •   rawtracepoint:event

       shortnames

       •   rt

       The hook point triggered by tracepoint and rawtracepoint is the same. tracepoint and
       rawtracepoint are nearly identical in terms of functionality. The only difference is in
       the program context. rawtracepoint offers raw arguments to the tracepoint while tracepoint
       applies further processing to the raw arguments. The additional processing is defined
       inside the kernel.

       Tracepoint arguments are available via the argN builtins. The available arguments can be
       found in the relative path of the kernel source code include/trace/events/. Each arg is a
       64-bit integer.

           rawtracepoint:block_rq_insert {
             printf("%llx %llx\n", arg0, arg1);
           }

           ffff88810977d6f8 ffff8881097e8e80
           [...]

   uprobe, uretprobe
       variants

       •   uprobe:binary:func

       •   uprobe:binary:func+offset

       •   uprobe:binary:offset

       •   uretprobe:binary:func

       shortnames

       •   u

       •   ur

       uprobe s or user-space probes are the user-space equivalent of kprobe s. The same
       limitations that apply kprobe and kretprobe also apply to uprobe s and uretprobe s.

       When tracing libraries, it is sufficient to specify the library name instead of a full
       path. The path will be then automatically resolved using /etc/ld.so.cache:

           # bpftrace -e 'uprobe:libc:malloc { printf("Allocated %d bytes\n", arg0); }'
           Allocated 4 bytes
           ...

       If the traced binary has DWARF included, function arguments are available in the args
       struct which can be inspected with verbose listing, see the LISTING PROBES section for
       more details.

       When tracing C++ programs, it is possible to turn on automatic symbol demangling by using
       the :cpp prefix:

           # bpftrace -e 'u:src/bpftrace:cpp:"bpftrace::BPFtrace::add_probe" { print("adding probe\n"); }'
           Attaching 1 probe...
           adding probe

       It is important to note that for uretprobe s to work the kernel runs a special helper on
       user-space function entry which overrides the return address on the stack. This can cause
       issues with languages that have their own runtime like Golang:

       example.go

           func myprint(s string) {
             fmt.Printf("Input: %s\n", s)
           }

           func main() {
             ss := []string{"a", "b", "c"}
             for _, s := range ss {
               go myprint(s)
             }
             time.Sleep(1*time.Second)
           }

       bpftrace

           # bpftrace -e 'uretprobe:./test:main.myprint { @=count(); }' -c ./test
           runtime: unexpected return pc for main.myprint called from 0x7fffffffe000
           stack: frame={sp:0xc00008cf60, fp:0xc00008cfd0} stack=[0xc00008c000,0xc00008d000)
           fatal error: unknown caller pc

   usdt
       variants

       •   usdt:binary_path:probe_name

       •   usdt:binary_path:[probe_namespace]:probe_name

       •   usdt:library_path:probe_name

       •   usdt:library_path:[probe_namespace]:probe_name

       shortnames

       •   U

       You can target the entire host (or an entire process’s address space by using the -p arg)
       by using a single wildcard in place of the binary_path/library_path e.g. bpftrace -e
       'usdt:*:loop { printf("hi\n"); }. Please note that if you use wildcards for the probe_name
       or probe_namespace and end up targeting multiple USDTs for the same probe you might get
       errors if you also utilize the USDT argument builtins (e.g. arg0) as they could be of
       different types.

   watchpoint and asyncwatchpoint
       variants

       •   watchpoint:absolute_address:length:mode

       •   watchpoint:function+argN:length:mode

       shortnames

       •   w

       •   aw

       These are memory watchpoints provided by the kernel. Whenever a memory address is written
       to (w), read from (r), or executed (x), the kernel can generate an event.

       In the first form, an absolute address is monitored. If a pid (-p) or a command (-c) is
       provided, bpftrace takes the address as a userspace address and monitors the appropriate
       process. If not, bpftrace takes the address as a kernel space address.

       In the second form, the address present in argN when function is entered is monitored. A
       pid or command must be provided for this form. If synchronous (watchpoint), a SIGSTOP is
       sent to the tracee upon function entry. The tracee will be SIGCONTed after the watchpoint
       is attached. This is to ensure events are not missed. If you want to avoid the SIGSTOP +
       SIGCONT use asyncwatchpoint.

       Note that on most architectures you may not monitor for execution while monitoring read or
       write.

       Examples

       Print hit when a read from or write to 0x10000000 happens:

           # bpftrace -e 'watchpoint:0x10000000:8:rw { printf("hit!\n"); exit(); }' -c ./testprogs/watchpoint

       Print the call stack every time the jiffies variable is updated:

           # bpftrace -e "watchpoint:0x$(awk '$3 == "jiffies" {print $1}' /proc/kallsyms):8:w {
             @[kstack] = count();
           }

           i:s:1 { exit(); }"
           ......
           @[
               do_timer+12
               tick_do_update_jiffies64.part.22+89
               tick_sched_do_timer+103
               tick_sched_timer+39
               __hrtimer_run_queues+256
               hrtimer_interrupt+256
               smp_apic_timer_interrupt+106
               apic_timer_interrupt+15
               cpuidle_enter_state+188
               cpuidle_enter+41
               do_idle+536
               cpu_startup_entry+25
               start_secondary+355
               secondary_startup_64+164
           ]: 319

       "hit" and exit when the memory pointed to by arg1 of increment is written to.

           # cat wpfunc.c
           #include <stdio.h>
           #include <stdlib.h>
           #include <unistd.h>

           __attribute__((noinline))
           void increment(__attribute__((unused)) int _, int *i)
           {
             (*i)++;
           }

           int main()
           {
             int *i = malloc(sizeof(int));
             while (1)
             {
               increment(0, i);
               (*i)++;
               usleep(1000);
             }
           }

           # bpftrace -e 'watchpoint:increment+arg1:4:w { printf("hit!\n"); exit() }' -c ./wpfunc

LISTING PROBES

       Probe listing is the method to discover which probes are supported by the current system.
       Listing supports the same syntax as normal attachment does:

           # bpftrace -l 'kprobe:*'
           # bpftrace -l 't:syscalls:*openat*
           # bpftrace -l 'kprobe:tcp*,trace
           # bpftrace -l 'k:*socket*,tracepoint:syscalls:*tcp*'

       The verbose flag (-v) can be specified to inspect arguments (args) for providers that
       support it:

           # bpftrace -l 'fr:tcp_reset,t:syscalls:sys_enter_openat' -v
           kretfunc:tcp_reset
               struct sock * sk
               struct sk_buff * skb
           tracepoint:syscalls:sys_enter_openat
               int __syscall_nr
               int dfd
               const char * filename
               int flags
               umode_t mode
           # bpftrace -l 'uprobe:/bin/bash:rl_set_prompt' -v    # works only if /bin/bash has DWARF
           uprobe:/bin/bash:rl_set_prompt
               const char *prompt

                                            2024-04-10                                BPFTRACE(8)