Provided by: libdebuginfod-dev_0.189-4_amd64 
NAME
debuginfod_find_debuginfo - request debuginfo from debuginfod
SYNOPSIS
#include <elfutils/debuginfod.h>
Link with -ldebuginfod.
CONNECTION HANDLE
debuginfod_client *debuginfod_begin(void);
void debuginfod_end(debuginfod_client *client);
LOOKUP FUNCTIONS
int debuginfod_find_debuginfo(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
char ** path);
int debuginfod_find_executable(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
char ** path);
int debuginfod_find_source(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
const char *filename,
char ** path);
int debuginfod_find_section(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
const char * section,
char ** path);
OPTIONAL FUNCTIONS
typedef int (*debuginfod_progressfn_t)(debuginfod_client *client,
long a, long b);
void debuginfod_set_progressfn(debuginfod_client *client,
debuginfod_progressfn_t progressfn);
void debuginfod_set_verbose_fd(debuginfod_client *client,
int fd);
void debuginfod_set_user_data(debuginfod_client *client,
void *data);
void* debuginfod_get_user_data(debuginfod_client *client);
const char* debuginfod_get_url(debuginfod_client *client);
int debuginfod_add_http_header(debuginfod_client *client,
const char* header);
const char* debuginfod_get_headers(debuginfod_client *client);
DESCRIPTION
debuginfod_begin() creates a debuginfod_client connection handle that should be used with
all other calls. debuginfod_end() should be called on the client handle to release all
state and storage when done.
debuginfod_find_debuginfo(), debuginfod_find_executable(), and debuginfod_find_source()
query the debuginfod server URLs contained in $DEBUGINFOD_URLS (see below) for the
debuginfo, executable or source file with the given build_id. build_id should be a pointer
to either a null-terminated, lowercase hex string or a binary blob. If build_id is given
as a hex string, build_id_len should be 0. Otherwise build_id_len should be the number of
bytes in the binary blob.
debuginfod_find_source() also requires a filename in order to specify a particular source
file. filename should be an absolute path that includes the compilation directory of the
CU associated with the source file. Relative path names commonly appear in the DWARF
file's source directory, but these paths are relative to individual compilation unit
AT_comp_dir paths, and yet an executable is made up of multiple CUs. Therefore, to
disambiguate, debuginfod expects source queries to prefix relative path names with the CU
compilation-directory, followed by a mandatory "/".
Note: the caller may or may not elide ../ or /./ or extraneous /// sorts of path
components in the directory names. debuginfod accepts both forms. Specifically,
debuginfod canonicalizes path names according to RFC3986 section 5.2.4 (Remove Dot
Segments), plus reducing any // to / in the path.
debuginfod_find_section() queries the debuginfod server URLs contained in $DEBUGINFOD_URLS
for the binary contents of an ELF/DWARF section contained in a debuginfo or executable
file with the given build_id. section should be the name of the desired ELF/DWARF section.
If a server does not support section queries, debuginfod_find_section may query the server
for the debuginfo and/or executable with build_id in order to retrieve and extract the
section.
If path is not NULL and the query is successful, path is set to the path of the file in
the cache. The caller must free() this value.
The URLs in $DEBUGINFOD_URLS may be queried in parallel. As soon as a debuginfod server
begins transferring the target file all of the connections to the other servers are
closed.
A client handle should be used from only one thread at a time. A handle may be reused for
a series of lookups, which can improve performance due to retention of connections and
caches.
RETURN VALUE
debuginfod_begin returns the debuginfod_client handle to use with all other calls. On
error NULL will be returned and errno will be set.
If a find family function is successful, the resulting file is saved to the client cache
and a file descriptor to that file is returned. The caller needs to close() this
descriptor. Otherwise, a negative error code is returned.
OPTIONAL FUNCTIONS
A small number of optional functions are available to tune or query the operation of the
debuginfod client.
PROGRESS CALLBACK
As the debuginfod_find_*() functions may block for seconds or longer, a progress callback
function is called periodically, if configured with debuginfod_set_progressfn(). This
function sets a new progress callback function (or NULL) for the client handle.
The given callback function is called from the context of each thread that is invoking any
of the other lookup functions. It is given two numeric parameters that, if thought of as
a numerator a and denominator b, together represent a completion fraction a/b. The
denominator may be zero initially, until a quantity such as an exact download size becomes
known.
The progress callback function is also the supported way to interrupt the download
operation. (The library does not modify or trigger signals.) The progress callback must
return 0 to continue the work, or any other value to stop work as soon as possible.
Consequently, the debuginfod_find_*() function will likely return with an error, but might
still succeed.
VERBOSE OUTPUT
The debuginfod_find_*() functions may use several techniques to retrieve the requested
files, through the cache or through one or multiple servers or file URLs. To show how a
query is handled the debuginfod_set_verbose_fd() can be used to set a particular file
descriptor on which verbose output is given about the query steps and eventual errors
encountered.
USER DATA POINTER
A single void * pointer associated with the connection handle may be set any time via
debuginfod_set_user_data(), and retrieved via debuginfod_get_user_data(). The value is
undefined if unset.
URL
The URL of the current or most recent outgoing download, if known, may be retrieved via
debuginfod_get_url() from the progressfn callback, or afterwards. It may be NULL. The
resulting string is owned by the library, and must not be modified or freed. The caller
should copy it if it is needed beyond the release of the client object.
HTTP HEADER
Before each lookup function is initiated, a client application may add HTTP request
headers. These are reset after each lookup function. debuginfod_add_http_header() may be
called with strings of the form "Header: value". These strings are copied by the library.
A zero return value indicates success, but out-of-memory conditions may result in a non-
zero -ENOMEM. If the string is in the wrong form -EINVAL will be returned.
$DEBUGINFOD_HEADERS_FILE specifies a file to supply headers to outgoing requests. Each
non-whitespace line of this file is handled as if debuginfod_add_http_header() were called
on the contents.
Note that the current debuginfod-client library implementation uses libcurl, but you
shouldn't rely on that fact. Don't use this function for replacing any standard headers,
except for the User-Agent mentioned below. You can use this function to add authorization
information for access control, or to provide optional headers to the server for logging
purposes.
By default, the library adds a descriptive User-Agent: header to outgoing requests. If
the client application adds a header with the same name, this default is suppressed.
During or after a lookup, a client application may call debuginfod_get_headers() to gather
the subset of HTTP response headers received from the current or most recent debuginfod
server. Only those headers prefixed with X-DEBUGINFOD (case-insensitive) are kept. They
are returned as a single string, with each "header: value" terminated with a \n (not \r\n
as in HTTP). It may be NULL. The resulting string is owned by the library, and must not
be modified or freed. The caller should copy the returned string if it is needed beyond
the release of the client object.
MACROS
DEBUGINFOD_SONAME
Defined to the string that could be passed to dlopen(3) if the library is loaded at
runtime, for example
void *debuginfod_so = dlopen(DEBUGINFOD_SONAME, RTLD_LAZY);
SECURITY
debuginfod_find_*() functions do not include any particular security features. They trust
that the binaries returned by the debuginfod(s) are accurate. Therefore, the list of
servers should include only trustworthy ones. If accessed across HTTP rather than HTTPS,
the network should be trustworthy. Passing user authentication information through the
internal libcurl library is not currently enabled, except for the basic plaintext
http[s]://userid:password@hostname/ style. (The debuginfod server does not perform
authentication, but a front-end proxy server could.)
ERRORS
The following list is not comprehensive. Error codes may also originate from calls to
various C Library functions.
EACCESS
Denied access to resource located at the URL.
ECONNREFUSED
Unable to connect to remote host. Also returned when an HTTPS connection couldn't
be verified (bad certificate).
ECONNRESET
Unable to either send or receive network data.
EHOSTUNREACH
Unable to resolve remote host.
EINVAL One or more arguments are incorrectly formatted. build_id may be too long (greater
than 256 characters), filename may not be an absolute path or a debuginfod URL is
malformed.
EIO Unable to write data received from server to local file.
EMLINK Too many HTTP redirects.
ENETUNREACH
Unable to initialize network connection.
ENOENT Could not find the resource located at URL. Often this error code indicates that a
debuginfod server was successfully contacted but the server could not find the
target file.
ENOMEM System is unable to allocate resources.
ENOSYS $DEBUGINFOD_URLS is not defined.
ETIME Query failed due to timeout. $DEBUGINFOD_TIMEOUT and $DEBUGINFOD_MAXTIME control
this.
EF2BIG Query aborted due to the file requested being too big. The $DEBUGINFOD_MAXSIZE
controls this.
SEE ALSO
debuginfod(8)
DEBUGINFOD_FIND_*(3)