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author | Török Edwin <edwintorok@gmail.com> | 2008-11-22 13:28:48 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-11-23 09:45:42 +0100 |
commit | b54d3de9f3b8956653b06f1a32e9f9321c6d9027 (patch) | |
tree | fef98e07a9327371304811191cafebdd65311502 /Documentation/ftrace.txt | |
parent | 74e2f334f4440cbcb63e9ebbcdcea430d41bdfa3 (diff) | |
download | linux-stable-b54d3de9f3b8956653b06f1a32e9f9321c6d9027.tar.gz linux-stable-b54d3de9f3b8956653b06f1a32e9f9321c6d9027.tar.bz2 linux-stable-b54d3de9f3b8956653b06f1a32e9f9321c6d9027.zip |
tracing: identify which executable object the userspace address belongs to
Impact: modify+improve the userstacktrace tracing visualization feature
Store thread group leader id, and use it to lookup the address in the
process's map. We could have looked up the address on thread's map,
but the thread might not exist by the time we are called. The process
might not exist either, but if you are reading trace_pipe, that is
unlikely.
Example usage:
mount -t debugfs nodev /sys/kernel/debug
cd /sys/kernel/debug/tracing
echo userstacktrace >iter_ctrl
echo sym-userobj >iter_ctrl
echo sched_switch >current_tracer
echo 1 >tracing_enabled
cat trace_pipe >/tmp/trace&
.... run application ...
echo 0 >tracing_enabled
cat /tmp/trace
You'll see stack entries like:
/lib/libpthread-2.7.so[+0xd370]
You can convert them to function/line using:
addr2line -fie /lib/libpthread-2.7.so 0xd370
Or:
addr2line -fie /usr/lib/debug/libpthread-2.7.so 0xd370
For non-PIC/PIE executables this won't work:
a.out[+0x73b]
You need to run the following: addr2line -fie a.out 0x40073b
(where 0x400000 is the default load address of a.out)
Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/ftrace.txt')
-rw-r--r-- | Documentation/ftrace.txt | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt index 79a80f79c062..35a78bc6651d 100644 --- a/Documentation/ftrace.txt +++ b/Documentation/ftrace.txt @@ -324,7 +324,7 @@ output. To see what is available, simply cat the file: cat /debug/tracing/trace_options print-parent nosym-offset nosym-addr noverbose noraw nohex nobin \ - noblock nostacktrace nosched-tree nouserstacktrace + noblock nostacktrace nosched-tree nouserstacktrace nosym-userobj To disable one of the options, echo in the option prepended with "no". @@ -381,6 +381,17 @@ Here are the available options: userstacktrace - This option changes the trace. It records a stacktrace of the current userspace thread. + sym-userobj - when user stacktrace are enabled, look up which object the + address belongs to, and print a relative address + This is especially useful when ASLR is on, otherwise you don't + get a chance to resolve the address to object/file/line after the app is no + longer running + + The lookup is performed when you read trace,trace_pipe,latency_trace. Example: + + a.out-1623 [000] 40874.465068: /root/a.out[+0x480] <-/root/a.out[+0 +x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6] + sched-tree - TBD (any users??) |