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 --- Documentation/firmware-guide/acpi/debug.rst | 132 ++++++++++++++++++++++++++++ 1 file changed, 132 insertions(+) create mode 100644 Documentation/firmware-guide/acpi/debug.rst (limited to 'Documentation/firmware-guide/acpi/debug.rst') diff --git a/Documentation/firmware-guide/acpi/debug.rst b/Documentation/firmware-guide/acpi/debug.rst new file mode 100644 index 000000000..0639c9de0 --- /dev/null +++ b/Documentation/firmware-guide/acpi/debug.rst @@ -0,0 +1,132 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +ACPI CA Debug Output +==================== + +The ACPI CA can generate debug output. This document describes how to use this +facility. + +Compile-time configuration +========================== + +The ACPI CA debug output is globally enabled by CONFIG_ACPI_DEBUG. If this +config option is not set, the debug messages are not even built into the kernel. + +Boot- and run-time configuration +================================ + +When CONFIG_ACPI_DEBUG=y, you can select the component and level of messages +you're interested in. At boot-time, use the acpi.debug_layer and +acpi.debug_level kernel command line options. After boot, you can use the +debug_layer and debug_level files in /sys/module/acpi/parameters/ to control +the debug messages. + +debug_layer (component) +======================= + +The "debug_layer" is a mask that selects components of interest, e.g., a +specific part of the ACPI interpreter. To build the debug_layer bitmask, look +for the "#define _COMPONENT" in an ACPI source file. + +You can set the debug_layer mask at boot-time using the acpi.debug_layer +command line argument, and you can change it after boot by writing values +to /sys/module/acpi/parameters/debug_layer. + +The possible components are defined in include/acpi/acoutput.h. + +Reading /sys/module/acpi/parameters/debug_layer shows the supported mask values:: + + ACPI_UTILITIES 0x00000001 + ACPI_HARDWARE 0x00000002 + ACPI_EVENTS 0x00000004 + ACPI_TABLES 0x00000008 + ACPI_NAMESPACE 0x00000010 + ACPI_PARSER 0x00000020 + ACPI_DISPATCHER 0x00000040 + ACPI_EXECUTER 0x00000080 + ACPI_RESOURCES 0x00000100 + ACPI_CA_DEBUGGER 0x00000200 + ACPI_OS_SERVICES 0x00000400 + ACPI_CA_DISASSEMBLER 0x00000800 + ACPI_COMPILER 0x00001000 + ACPI_TOOLS 0x00002000 + +debug_level +=========== + +The "debug_level" is a mask that selects different types of messages, e.g., +those related to initialization, method execution, informational messages, etc. +To build debug_level, look at the level specified in an ACPI_DEBUG_PRINT() +statement. + +The ACPI interpreter uses several different levels, but the Linux +ACPI core and ACPI drivers generally only use ACPI_LV_INFO. + +You can set the debug_level mask at boot-time using the acpi.debug_level +command line argument, and you can change it after boot by writing values +to /sys/module/acpi/parameters/debug_level. + +The possible levels are defined in include/acpi/acoutput.h. Reading +/sys/module/acpi/parameters/debug_level shows the supported mask values, +currently these:: + + ACPI_LV_INIT 0x00000001 + ACPI_LV_DEBUG_OBJECT 0x00000002 + ACPI_LV_INFO 0x00000004 + ACPI_LV_INIT_NAMES 0x00000020 + ACPI_LV_PARSE 0x00000040 + ACPI_LV_LOAD 0x00000080 + ACPI_LV_DISPATCH 0x00000100 + ACPI_LV_EXEC 0x00000200 + ACPI_LV_NAMES 0x00000400 + ACPI_LV_OPREGION 0x00000800 + ACPI_LV_BFIELD 0x00001000 + ACPI_LV_TABLES 0x00002000 + ACPI_LV_VALUES 0x00004000 + ACPI_LV_OBJECTS 0x00008000 + ACPI_LV_RESOURCES 0x00010000 + ACPI_LV_USER_REQUESTS 0x00020000 + ACPI_LV_PACKAGE 0x00040000 + ACPI_LV_ALLOCATIONS 0x00100000 + ACPI_LV_FUNCTIONS 0x00200000 + ACPI_LV_OPTIMIZATIONS 0x00400000 + ACPI_LV_MUTEX 0x01000000 + ACPI_LV_THREADS 0x02000000 + ACPI_LV_IO 0x04000000 + ACPI_LV_INTERRUPTS 0x08000000 + ACPI_LV_AML_DISASSEMBLE 0x10000000 + ACPI_LV_VERBOSE_INFO 0x20000000 + ACPI_LV_FULL_TABLES 0x40000000 + ACPI_LV_EVENTS 0x80000000 + +Examples +======== + +For example, drivers/acpi/acpica/evxfevnt.c contains this:: + + #define _COMPONENT ACPI_EVENTS + ... + ACPI_DEBUG_PRINT((ACPI_DB_INIT, "ACPI mode disabled\n")); + +To turn on this message, set the ACPI_EVENTS bit in acpi.debug_layer +and the ACPI_LV_INIT bit in acpi.debug_level. (The ACPI_DEBUG_PRINT +statement uses ACPI_DB_INIT, which is a macro based on the ACPI_LV_INIT +definition.) + +Enable all AML "Debug" output (stores to the Debug object while interpreting +AML) during boot:: + + acpi.debug_layer=0xffffffff acpi.debug_level=0x2 + +Enable all ACPI hardware-related messages:: + + acpi.debug_layer=0x2 acpi.debug_level=0xffffffff + +Enable all ACPI_DB_INFO messages after boot:: + + # echo 0x4 > /sys/module/acpi/parameters/debug_level + +Show all valid component values:: + + # cat /sys/module/acpi/parameters/debug_layer -- cgit v1.3.1