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116 lines
3.1 KiB
116 lines
3.1 KiB
#!/bin/bash |
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# SPDX-License-Identifier: GPL-2.0 |
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# |
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# Here's how to use this: |
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# |
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# This script is used to help find functions that are being traced by function |
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# tracer or function graph tracing that causes the machine to reboot, hang, or |
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# crash. Here's the steps to take. |
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# |
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# First, determine if function tracing is working with a single function: |
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# |
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# (note, if this is a problem with function_graph tracing, then simply |
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# replace "function" with "function_graph" in the following steps). |
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# |
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# # cd /sys/kernel/debug/tracing |
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# # echo schedule > set_ftrace_filter |
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# # echo function > current_tracer |
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# |
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# If this works, then we know that something is being traced that shouldn't be. |
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# |
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# # echo nop > current_tracer |
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# |
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# # cat available_filter_functions > ~/full-file |
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# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file |
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# # cat ~/test-file > set_ftrace_filter |
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# |
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# *** Note *** this will take several minutes. Setting multiple functions is |
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# an O(n^2) operation, and we are dealing with thousands of functions. So go |
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# have coffee, talk with your coworkers, read facebook. And eventually, this |
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# operation will end. |
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# |
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# # echo function > current_tracer |
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# |
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# If it crashes, we know that ~/test-file has a bad function. |
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# |
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# Reboot back to test kernel. |
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# |
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# # cd /sys/kernel/debug/tracing |
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# # mv ~/test-file ~/full-file |
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# |
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# If it didn't crash. |
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# |
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# # echo nop > current_tracer |
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# # mv ~/non-test-file ~/full-file |
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# |
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# Get rid of the other test file from previous run (or save them off somewhere). |
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# # rm -f ~/test-file ~/non-test-file |
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# |
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# And start again: |
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# |
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# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file |
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# |
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# The good thing is, because this cuts the number of functions in ~/test-file |
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# by half, the cat of it into set_ftrace_filter takes half as long each |
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# iteration, so don't talk so much at the water cooler the second time. |
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# |
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# Eventually, if you did this correctly, you will get down to the problem |
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# function, and all we need to do is to notrace it. |
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# |
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# The way to figure out if the problem function is bad, just do: |
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# |
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# # echo <problem-function> > set_ftrace_notrace |
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# # echo > set_ftrace_filter |
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# # echo function > current_tracer |
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# |
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# And if it doesn't crash, we are done. |
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# |
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# If it does crash, do this again (there's more than one problem function) |
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# but you need to echo the problem function(s) into set_ftrace_notrace before |
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# enabling function tracing in the above steps. Or if you can compile the |
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# kernel, annotate the problem functions with "notrace" and start again. |
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# |
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if [ $# -ne 3 ]; then |
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echo 'usage: ftrace-bisect full-file test-file non-test-file' |
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exit |
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fi |
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full=$1 |
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test=$2 |
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nontest=$3 |
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x=`cat $full | wc -l` |
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if [ $x -eq 1 ]; then |
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echo "There's only one function left, must be the bad one" |
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cat $full |
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exit 0 |
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fi |
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let x=$x/2 |
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let y=$x+1 |
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if [ ! -f $full ]; then |
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echo "$full does not exist" |
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exit 1 |
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fi |
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if [ -f $test ]; then |
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echo -n "$test exists, delete it? [y/N]" |
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read a |
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if [ "$a" != "y" -a "$a" != "Y" ]; then |
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exit 1 |
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fi |
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fi |
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if [ -f $nontest ]; then |
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echo -n "$nontest exists, delete it? [y/N]" |
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read a |
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if [ "$a" != "y" -a "$a" != "Y" ]; then |
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exit 1 |
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fi |
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fi |
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sed -ne "1,${x}p" $full > $test |
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sed -ne "$y,\$p" $full > $nontest
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