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

Provided by: systemtap-doc_2.9-2ubuntu2_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 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