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git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - scripts/tracing/ftrace-bisect.sh
2 # SPDX-License-Identifier: GPL-2.0
4 # Here's how to use this:
6 # This script is used to help find functions that are being traced by function
7 # tracer or function graph tracing that causes the machine to reboot, hang, or
8 # crash. Here's the steps to take.
10 # First, determine if function tracing is working with a single function:
12 # (note, if this is a problem with function_graph tracing, then simply
13 # replace "function" with "function_graph" in the following steps).
15 # # cd /sys/kernel/debug/tracing
16 # # echo schedule > set_ftrace_filter
17 # # echo function > current_tracer
19 # If this works, then we know that something is being traced that shouldn't be.
21 # # echo nop > current_tracer
23 # # cat available_filter_functions > ~/full-file
24 # # ftrace-bisect ~/full-file ~/test-file ~/non-test-file
25 # # cat ~/test-file > set_ftrace_filter
27 # *** Note *** this will take several minutes. Setting multiple functions is
28 # an O(n^2) operation, and we are dealing with thousands of functions. So go
29 # have coffee, talk with your coworkers, read facebook. And eventually, this
32 # # echo function > current_tracer
34 # If it crashes, we know that ~/test-file has a bad function.
36 # Reboot back to test kernel.
38 # # cd /sys/kernel/debug/tracing
39 # # mv ~/test-file ~/full-file
43 # # echo nop > current_tracer
44 # # mv ~/non-test-file ~/full-file
46 # Get rid of the other test file from previous run (or save them off somewhere).
47 # # rm -f ~/test-file ~/non-test-file
51 # # ftrace-bisect ~/full-file ~/test-file ~/non-test-file
53 # The good thing is, because this cuts the number of functions in ~/test-file
54 # by half, the cat of it into set_ftrace_filter takes half as long each
55 # iteration, so don't talk so much at the water cooler the second time.
57 # Eventually, if you did this correctly, you will get down to the problem
58 # function, and all we need to do is to notrace it.
60 # The way to figure out if the problem function is bad, just do:
62 # # echo <problem-function> > set_ftrace_notrace
63 # # echo > set_ftrace_filter
64 # # echo function > current_tracer
66 # And if it doesn't crash, we are done.
68 # If it does crash, do this again (there's more than one problem function)
69 # but you need to echo the problem function(s) into set_ftrace_notrace before
70 # enabling function tracing in the above steps. Or if you can compile the
71 # kernel, annotate the problem functions with "notrace" and start again.
76 echo 'usage: ftrace-bisect full-file test-file non-test-file'
86 echo "There's only one function left, must be the bad one"
94 if [ ! -f $full ]; then
95 echo "$full does not exist"
100 echo -n "$test exists, delete it? [y/N]"
102 if [ "$a" != "y" -a "$a" != "Y" ]; then
107 if [ -f $nontest ]; then
108 echo -n "$nontest exists, delete it? [y/N]"
110 if [ "$a" != "y" -a "$a" != "Y" ]; then
115 sed -ne "1,${x}p" $full > $test
116 sed -ne "$y,\$p" $full > $nontest