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/ABI/README | 98 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 Documentation/ABI/README (limited to 'Documentation/ABI/README') diff --git a/Documentation/ABI/README b/Documentation/ABI/README new file mode 100644 index 000000000..27c962e6a --- /dev/null +++ b/Documentation/ABI/README @@ -0,0 +1,98 @@ +This part of the documentation inside Documentation/ABI directory +attempts to document the ABI between the Linux kernel and +userspace, and the relative stability of these interfaces. Due to the +everchanging nature of Linux, and the differing maturity levels, these +interfaces should be used by userspace programs in different ways. + +We have four different levels of ABI stability, as shown by the four +different subdirectories in this location. Interfaces may change levels +of stability according to the rules described below. + +The different levels of stability are: + + stable/ + This directory documents the interfaces that the developer has + defined to be stable. Userspace programs are free to use these + interfaces with no restrictions, and backward compatibility for + them will be guaranteed for at least 2 years. Most interfaces + (like syscalls) are expected to never change and always be + available. + + testing/ + This directory documents interfaces that are felt to be stable, + as the main development of this interface has been completed. + The interface can be changed to add new features, but the + current interface will not break by doing this, unless grave + errors or security problems are found in them. Userspace + programs can start to rely on these interfaces, but they must be + aware of changes that can occur before these interfaces move to + be marked stable. Programs that use these interfaces are + strongly encouraged to add their name to the description of + these interfaces, so that the kernel developers can easily + notify them if any changes occur (see the description of the + layout of the files below for details on how to do this.) + + obsolete/ + This directory documents interfaces that are still remaining in + the kernel, but are marked to be removed at some later point in + time. The description of the interface will document the reason + why it is obsolete and when it can be expected to be removed. + + removed/ + This directory contains a list of the old interfaces that have + been removed from the kernel. + +Every file in these directories will contain the following information: + +What: Short description of the interface +Date: Date created +KernelVersion: (Optional) Kernel version this feature first showed up in. + Note: git history often provides more accurate version + info, so this field may be omitted. +Contact: Primary contact for this interface (may be a mailing list) +Description: Long description of the interface and how to use it. +Users: All users of this interface who wish to be notified when + it changes. This is very important for interfaces in + the "testing" stage, so that kernel developers can work + with userspace developers to ensure that things do not + break in ways that are unacceptable. It is also + important to get feedback for these interfaces to make + sure they are working in a proper way and do not need to + be changed further. + + +Note: + The fields should use a simple notation, compatible with ReST markup. + Also, the file **should not** have a top-level index, like:: + + === + foo + === + +How things move between levels: + +Interfaces in stable may move to obsolete, as long as the proper +notification is given. + +Interfaces may be removed from obsolete and the kernel as long as the +documented amount of time has gone by. + +Interfaces in the testing state can move to the stable state when the +developers feel they are finished. They cannot be removed from the +kernel tree without going through the obsolete state first. + +It's up to the developer to place their interfaces in the category they +wish for it to start out in. + + +Notable bits of non-ABI, which should not under any circumstances be considered +stable: + +- Kconfig. Userspace should not rely on the presence or absence of any + particular Kconfig symbol, in /proc/config.gz, in the copy of .config + commonly installed to /boot, or in any invocation of the kernel build + process. + +- Kernel-internal symbols. Do not rely on the presence, absence, location, or + type of any kernel symbol, either in System.map files or the kernel binary + itself. See Documentation/process/stable-api-nonsense.rst. -- cgit v1.3.1