From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- scripts/tracing/ftrace-bisect.sh | 134 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 134 insertions(+) create mode 100755 scripts/tracing/ftrace-bisect.sh (limited to 'scripts/tracing') 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 > 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 -- cgit v1.3.1