scripts/tracing/ftrace-bisect.sh

Source file repositories/reference/linux-study-clean/scripts/tracing/ftrace-bisect.sh

File Facts

System
Linux kernel
Corpus path
scripts/tracing/ftrace-bisect.sh
Extension
.sh
Size
3954 bytes
Lines
135
Domain
Support Tooling And Documentation
Bucket
scripts
Inferred role
Support Tooling And Documentation: scripts
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

#!/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
#

Annotation

Implementation Notes