Ubuntu Manpage: warning::debuginfo - systemtap missing-debuginfo warnings

Provided by: systemtap-doc_3.1-3ubuntu0.1_all

NAME

       warning::debuginfo - systemtap missing-debuginfo warnings

DESCRIPTION

For many symbolic probing operations, systemtap needs DWARF debuginfo for the relevant
binaries. This often includes resolving function/statement probes, or $context variables
in related handlers. DWARF debuginfo is created by the compiler when using CFLAGS -g, and
may be found in the original binaries built during compilation, or may have been split
into separate files. The SYSTEMTAP_DEBUGINFO_PATH environment variable affects where
systemtap looks for these files.

If your operating system came from a distributor, check with them if debuginfo packages or
variants are available. If your distributor does not have debuginfo-equipped binaries at
all, you may need to rebuild it.

Systemtap uses the elfutils library to process ELF/DWARF files. The version of elfutils
used by systemtap is the number after the slash in the -V output:

% stap -V
Systemtap translator/driver (version 2.3/0.156, rpm 2.3-1.fc19)
Copyright (C) 2005-2014 Red Hat, Inc. and others
[...]

This indicates systemtap version 2.3 with elfutils version 0.156.

kernel debuginfo
For scripts that target the kernel, systemtap may search for the vmlinux file
created during its original build. This is distinct from the boot-loader's
compressed/stripped vmlinuz file, and much larger. If you have a hand-built
kernel, make sure it was built with the CONFIG_DEBUG_INFO=y option. Some Linux
distributions may include several kernel variants, including a confusingly named
kernel-debug (an alternative kernel, with its own kernel-debug-debuginfo package),
which is not the same thing as the kernel-debuginfo (DWARF data for the base
kernel). The stap-prep program can help install the right set.

process debuginfo
For scripts that target user-space, systemtap may search for debuginfo. If you
have hand-built binaries, use CFLAGS=-g -O2 to compile them.

minidebuginfo
On some systems, binaries may be compiled with a subset of debuginfo useful for
function tracing and backtraces. This 'Minidebuginfo' is a xz compressed section
labeled .gnu_debugdata. Support for minidebuginfo relies on elfutils version 0.156
or later.

compressed debuginfo
On some systems, debuginfo may be available, but compressed into .zdebug_*
sections. Support for compressed debuginfo relies on elfutils version 0.153 or
later.

unnecessary debuginfo
In some cases, a script may be altered to avoid requiring debuginfo. For example,
as script that uses probe syscall.* probes could try instead probe nd_syscall.*
(for non-DWARF syscall): these work similarly, and use more intricate (fragile)
tapset functions to extract system call arguments. Another option is use of
compiled-in instrumentation such as kernel tracepoints or user-space <sys/sdt.h>
markers in libraries or executables, which do not require debuginfo. If debuginfo
was required for resolving a complicated $var->foo->bar expression, it may be
possible to use @cast(var,"foo","foo.h")->foo->bar to synthesize debuginfo for that
type from a header file.

AUTOMATION

       On some platforms, systemtap may advise what commands to run, in order to download  needed
       debuginfo.  Another possibility is to invoke systemtap with the --download-debuginfo flag.
       The stap-prep script included with systemtap may  be  able  to  download  the  appropriate
       kernel  debuginfo.   Another  possibility  is  to  install  and  use a stap-server remote-
       compilation instance on a  machine  on  your  network,  where  debuginfo  and  compilation
       resources  can be centralized.  Try the stap --use-server option, in case such a server is
       already running.

NAME

DESCRIPTION

AUTOMATION

SEE ALSO