WARNING::DEBUGINFO(7stap) WARNING::DEBUGINFO(7stap)
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 func-
tion/statement probes, or $context variables in related handlers. DWARF debuginfo may be found in the original binaries built during com-
pilation, 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) 2005-2013 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.
process debuginfo
For scripts that target user-space, systemtap may search for debuginfo. If you have hand-built binaries, use CFLAGS=-g -O2 to com-
pile them.
minidebuginfo
On some systems, binaries may be compiled with a subset of debuginfo useful for function tracing and backtraces. This 'Minidebugin-
fo' 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 el-
futils 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 compli-
cated $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 sys-
temtap with the --download-debuginfo flag. The stap-prep script included with systemtap may be able to download the appropriate kernel de-
buginfo. 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.
SEE ALSO
stap(1),
stappaths(7),
stap-server(8),
strip(1),
error::dwarf(7stap),
error::reporting(7stap),
error::contextvars(7stap),
http://fedorahosted.org/elfutils,
http://fedoraproject.org/wiki/Features/MiniDebugInfo
WARNING::DEBUGINFO(7stap)