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Diffstat (limited to '')
| -rwxr-xr-x | scripts/tracing/ftrace-bisect.sh | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/scripts/tracing/ftrace-bisect.sh b/scripts/tracing/ftrace-bisect.sh new file mode 100755 index 000000000..bb4f59262 --- /dev/null +++ b/scripts/tracing/ftrace-bisect.sh @@ -0,0 +1,134 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Here's how to use this: +# +# This script is used to help find functions that are being traced by function +# tracer or function graph tracing that causes the machine to reboot, hang, or +# crash. Here's the steps to take. +# +# First, determine if function tracing is working with a single function: +# +# (note, if this is a problem with function_graph tracing, then simply +# replace "function" with "function_graph" in the following steps). +# +# # cd /sys/kernel/tracing +# # echo schedule > set_ftrace_filter +# # echo function > current_tracer +# +# If this works, then we know that something is being traced that shouldn't be. +# +# # echo nop > current_tracer +# +# Starting with v5.1 this can be done with numbers, making it much faster: +# +# The old (slow) way, for kernels before v5.1. +# +# [old-way] # cat available_filter_functions > ~/full-file +# +# [old-way] *** Note *** this process will take several minutes to update the +# [old-way] filters. Setting multiple functions is an O(n^2) operation, and we +# [old-way] are dealing with thousands of functions. So go have coffee, talk +# [old-way] with your coworkers, read facebook. And eventually, this operation +# [old-way] will end. +# +# The new way (using numbers) is an O(n) operation, and usually takes less than a second. +# +# seq `wc -l available_filter_functions | cut -d' ' -f1` > ~/full-file +# +# This will create a sequence of numbers that match the functions in +# available_filter_functions, and when echoing in a number into the +# set_ftrace_filter file, it will enable the corresponding function in +# O(1) time. Making enabling all functions O(n) where n is the number of +# functions to enable. +# +# For either the new or old way, the rest of the operations remain the same. +# +# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file +# # cat ~/test-file > set_ftrace_filter +# +# # echo function > current_tracer +# +# If it crashes, we know that ~/test-file has a bad function. +# +# Reboot back to test kernel. +# +# # cd /sys/kernel/tracing +# # mv ~/test-file ~/full-file +# +# If it didn't crash. +# +# # echo nop > current_tracer +# # mv ~/non-test-file ~/full-file +# +# Get rid of the other test file from previous run (or save them off somewhere). +# # rm -f ~/test-file ~/non-test-file +# +# And start again: +# +# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file +# +# The good thing is, because this cuts the number of functions in ~/test-file +# by half, the cat of it into set_ftrace_filter takes half as long each +# iteration, so don't talk so much at the water cooler the second time. +# +# Eventually, if you did this correctly, you will get down to the problem +# function, and all we need to do is to notrace it. +# +# The way to figure out if the problem function is bad, just do: +# +# # echo <problem-function> > set_ftrace_notrace +# # echo > set_ftrace_filter +# # echo function > current_tracer +# +# And if it doesn't crash, we are done. +# +# If it does crash, do this again (there's more than one problem function) +# but you need to echo the problem function(s) into set_ftrace_notrace before +# enabling function tracing in the above steps. Or if you can compile the +# kernel, annotate the problem functions with "notrace" and start again. +# + + +if [ $# -ne 3 ]; then + echo 'usage: ftrace-bisect full-file test-file non-test-file' + exit +fi + +full=$1 +test=$2 +nontest=$3 + +x=`cat $full | wc -l` +if [ $x -eq 1 ]; then + echo "There's only one function left, must be the bad one" + cat $full + exit 0 +fi + +let x=$x/2 +let y=$x+1 + +if [ ! -f $full ]; then + echo "$full does not exist" + exit 1 +fi + +if [ -f $test ]; then + echo -n "$test exists, delete it? [y/N]" + read a + if [ "$a" != "y" -a "$a" != "Y" ]; then + exit 1 + fi +fi + +if [ -f $nontest ]; then + echo -n "$nontest exists, delete it? [y/N]" + read a + if [ "$a" != "y" -a "$a" != "Y" ]; then + exit 1 + fi +fi + +sed -ne "1,${x}p" $full > $test +sed -ne "$y,\$p" $full > $nontest |