Steven Rostedt (Red Hat) | 951dbf5 | 2016-09-21 13:43:48 -0400 | [diff] [blame] | 1 | #!/bin/bash |
Greg Kroah-Hartman | b244131 | 2017-11-01 15:07:57 +0100 | [diff] [blame] | 2 | # SPDX-License-Identifier: GPL-2.0 |
Steven Rostedt (Red Hat) | 951dbf5 | 2016-09-21 13:43:48 -0400 | [diff] [blame] | 3 | # |
| 4 | # Here's how to use this: |
| 5 | # |
| 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. |
| 9 | # |
| 10 | # First, determine if function tracing is working with a single function: |
| 11 | # |
| 12 | # (note, if this is a problem with function_graph tracing, then simply |
| 13 | # replace "function" with "function_graph" in the following steps). |
| 14 | # |
| 15 | # # cd /sys/kernel/debug/tracing |
| 16 | # # echo schedule > set_ftrace_filter |
| 17 | # # echo function > current_tracer |
| 18 | # |
| 19 | # If this works, then we know that something is being traced that shouldn't be. |
| 20 | # |
| 21 | # # echo nop > current_tracer |
| 22 | # |
| 23 | # # cat available_filter_functions > ~/full-file |
| 24 | # # ftrace-bisect ~/full-file ~/test-file ~/non-test-file |
| 25 | # # cat ~/test-file > set_ftrace_filter |
| 26 | # |
| 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 |
| 30 | # operation will end. |
| 31 | # |
| 32 | # # echo function > current_tracer |
| 33 | # |
| 34 | # If it crashes, we know that ~/test-file has a bad function. |
| 35 | # |
| 36 | # Reboot back to test kernel. |
| 37 | # |
| 38 | # # cd /sys/kernel/debug/tracing |
| 39 | # # mv ~/test-file ~/full-file |
| 40 | # |
| 41 | # If it didn't crash. |
| 42 | # |
| 43 | # # echo nop > current_tracer |
| 44 | # # mv ~/non-test-file ~/full-file |
| 45 | # |
| 46 | # Get rid of the other test file from previous run (or save them off somewhere). |
| 47 | # # rm -f ~/test-file ~/non-test-file |
| 48 | # |
| 49 | # And start again: |
| 50 | # |
| 51 | # # ftrace-bisect ~/full-file ~/test-file ~/non-test-file |
| 52 | # |
| 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. |
| 56 | # |
| 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. |
| 59 | # |
| 60 | # The way to figure out if the problem function is bad, just do: |
| 61 | # |
| 62 | # # echo <problem-function> > set_ftrace_notrace |
| 63 | # # echo > set_ftrace_filter |
| 64 | # # echo function > current_tracer |
| 65 | # |
| 66 | # And if it doesn't crash, we are done. |
| 67 | # |
| 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. |
| 72 | # |
| 73 | |
| 74 | |
| 75 | if [ $# -ne 3 ]; then |
| 76 | echo 'usage: ftrace-bisect full-file test-file non-test-file' |
| 77 | exit |
| 78 | fi |
| 79 | |
| 80 | full=$1 |
| 81 | test=$2 |
| 82 | nontest=$3 |
| 83 | |
| 84 | x=`cat $full | wc -l` |
| 85 | if [ $x -eq 1 ]; then |
| 86 | echo "There's only one function left, must be the bad one" |
| 87 | cat $full |
| 88 | exit 0 |
| 89 | fi |
| 90 | |
| 91 | let x=$x/2 |
| 92 | let y=$x+1 |
| 93 | |
| 94 | if [ ! -f $full ]; then |
| 95 | echo "$full does not exist" |
| 96 | exit 1 |
| 97 | fi |
| 98 | |
| 99 | if [ -f $test ]; then |
| 100 | echo -n "$test exists, delete it? [y/N]" |
| 101 | read a |
| 102 | if [ "$a" != "y" -a "$a" != "Y" ]; then |
| 103 | exit 1 |
| 104 | fi |
| 105 | fi |
| 106 | |
| 107 | if [ -f $nontest ]; then |
| 108 | echo -n "$nontest exists, delete it? [y/N]" |
| 109 | read a |
| 110 | if [ "$a" != "y" -a "$a" != "Y" ]; then |
| 111 | exit 1 |
| 112 | fi |
| 113 | fi |
| 114 | |
| 115 | sed -ne "1,${x}p" $full > $test |
| 116 | sed -ne "$y,\$p" $full > $nontest |