1#!/bin/bash 2# 3# Here's how to use this: 4# 5# This script is used to help find functions that are being traced by function 6# tracer or function graph tracing that causes the machine to reboot, hang, or 7# crash. Here's the steps to take. 8# 9# First, determine if function tracing is working with a single function: 10# 11# (note, if this is a problem with function_graph tracing, then simply 12# replace "function" with "function_graph" in the following steps). 13# 14# # cd /sys/kernel/debug/tracing 15# # echo schedule > set_ftrace_filter 16# # echo function > current_tracer 17# 18# If this works, then we know that something is being traced that shouldn't be. 19# 20# # echo nop > current_tracer 21# 22# # cat available_filter_functions > ~/full-file 23# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file 24# # cat ~/test-file > set_ftrace_filter 25# 26# *** Note *** this will take several minutes. Setting multiple functions is 27# an O(n^2) operation, and we are dealing with thousands of functions. So go 28# have coffee, talk with your coworkers, read facebook. And eventually, this 29# operation will end. 30# 31# # echo function > current_tracer 32# 33# If it crashes, we know that ~/test-file has a bad function. 34# 35# Reboot back to test kernel. 36# 37# # cd /sys/kernel/debug/tracing 38# # mv ~/test-file ~/full-file 39# 40# If it didn't crash. 41# 42# # echo nop > current_tracer 43# # mv ~/non-test-file ~/full-file 44# 45# Get rid of the other test file from previous run (or save them off somewhere). 46# # rm -f ~/test-file ~/non-test-file 47# 48# And start again: 49# 50# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file 51# 52# The good thing is, because this cuts the number of functions in ~/test-file 53# by half, the cat of it into set_ftrace_filter takes half as long each 54# iteration, so don't talk so much at the water cooler the second time. 55# 56# Eventually, if you did this correctly, you will get down to the problem 57# function, and all we need to do is to notrace it. 58# 59# The way to figure out if the problem function is bad, just do: 60# 61# # echo <problem-function> > set_ftrace_notrace 62# # echo > set_ftrace_filter 63# # echo function > current_tracer 64# 65# And if it doesn't crash, we are done. 66# 67# If it does crash, do this again (there's more than one problem function) 68# but you need to echo the problem function(s) into set_ftrace_notrace before 69# enabling function tracing in the above steps. Or if you can compile the 70# kernel, annotate the problem functions with "notrace" and start again. 71# 72 73 74if [ $# -ne 3 ]; then 75 echo 'usage: ftrace-bisect full-file test-file non-test-file' 76 exit 77fi 78 79full=$1 80test=$2 81nontest=$3 82 83x=`cat $full | wc -l` 84if [ $x -eq 1 ]; then 85 echo "There's only one function left, must be the bad one" 86 cat $full 87 exit 0 88fi 89 90let x=$x/2 91let y=$x+1 92 93if [ ! -f $full ]; then 94 echo "$full does not exist" 95 exit 1 96fi 97 98if [ -f $test ]; then 99 echo -n "$test exists, delete it? [y/N]" 100 read a 101 if [ "$a" != "y" -a "$a" != "Y" ]; then 102 exit 1 103 fi 104fi 105 106if [ -f $nontest ]; then 107 echo -n "$nontest exists, delete it? [y/N]" 108 read a 109 if [ "$a" != "y" -a "$a" != "Y" ]; then 110 exit 1 111 fi 112fi 113 114sed -ne "1,${x}p" $full > $test 115sed -ne "$y,\$p" $full > $nontest 116