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 --- .../ABI/testing/sysfs-auxdisplay-linedisp | 90 ++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-auxdisplay-linedisp (limited to 'Documentation/ABI/testing/sysfs-auxdisplay-linedisp') diff --git a/Documentation/ABI/testing/sysfs-auxdisplay-linedisp b/Documentation/ABI/testing/sysfs-auxdisplay-linedisp new file mode 100644 index 000000000..55f1b559e --- /dev/null +++ b/Documentation/ABI/testing/sysfs-auxdisplay-linedisp @@ -0,0 +1,90 @@ +What: /sys/.../message +Date: October 2021 +KernelVersion: 5.16 +Description: + Controls the text message displayed on character line displays. + + Reading returns the current message with a trailing newline. + Writing updates the displayed message. Messages longer than the + display width will automatically scroll. Trailing newlines in + input are automatically trimmed. + + Writing an empty string clears the display. + + Example: + echo "Hello World" > message + cat message # Returns "Hello World\n" + +What: /sys/.../num_chars +Date: November 2025 +KernelVersion: 6.18 +Contact: Jean-François Lessard +Description: + Read-only attribute showing the character width capacity of + the line display device. Messages longer than this will scroll. + + Example: + cat num_chars # Returns "16\n" for 16-char display + +What: /sys/.../scroll_step_ms +Date: October 2021 +KernelVersion: 5.16 +Description: + Controls the scrolling speed for messages longer than the display + width, specified in milliseconds per scroll step. + + Setting to 0 disables scrolling. Default is 500ms. + + Example: + echo "250" > scroll_step_ms # 4Hz scrolling + cat scroll_step_ms # Returns "250\n" + +What: /sys/.../map_seg7 +Date: January 2024 +KernelVersion: 6.9 +Description: + Read/write binary blob representing the ASCII-to-7-segment + display conversion table used by the linedisp driver, as defined + by struct seg7_conversion_map in . + + Only visible on displays with 7-segment capability. + + This attribute is not human-readable. Writes must match the + struct size exactly, else -EINVAL is returned; reads return the + entire mapping as a binary blob. + + This interface and its implementation match existing conventions + used in segment-mapped display drivers since 2005. + + ABI note: This style of binary sysfs attribute *is an exception* + to current "one value per file, text only" sysfs rules, for + historical compatibility and driver uniformity. New drivers are + discouraged from introducing additional binary sysfs ABIs. + + Reference interface guidance: + - include/uapi/linux/map_to_7segment.h + +What: /sys/.../map_seg14 +Date: January 2024 +KernelVersion: 6.9 +Description: + Read/write binary blob representing the ASCII-to-14-segment + display conversion table used by the linedisp driver, as defined + by struct seg14_conversion_map in . + + Only visible on displays with 14-segment capability. + + This attribute is not human-readable. Writes must match the + struct size exactly, else -EINVAL is returned; reads return the + entire mapping as a binary blob. + + This interface and its implementation match existing conventions + used by segment-mapped display drivers since 2005. + + ABI note: This style of binary sysfs attribute *is an exception* + to current "one value per file, text only" sysfs rules, for + historical compatibility and driver uniformity. New drivers are + discouraged from introducing additional binary sysfs ABIs. + + Reference interface guidance: + - include/uapi/linux/map_to_14segment.h -- cgit v1.3.1