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 --- drivers/video/console/dummycon.c | 159 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 drivers/video/console/dummycon.c (limited to 'drivers/video/console/dummycon.c') diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c new file mode 100644 index 000000000..7d02470f1 --- /dev/null +++ b/drivers/video/console/dummycon.c @@ -0,0 +1,159 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/drivers/video/dummycon.c -- A dummy console driver + * + * To be used if there's no other console driver (e.g. for plain VGA text) + * available, usually until fbcon takes console over. + */ + +#include +#include +#include +#include +#include +#include +#include + +/* + * Dummy console driver + */ + +#if defined(CONFIG_ARCH_FOOTBRIDGE) && defined(CONFIG_VGA_CONSOLE) +#include +#define DUMMY_COLUMNS vgacon_screen_info.orig_video_cols +#define DUMMY_ROWS vgacon_screen_info.orig_video_lines +#else +/* set by Kconfig. Use 80x25 for 640x480 and 160x64 for 1280x1024 */ +#define DUMMY_COLUMNS CONFIG_DUMMY_CONSOLE_COLUMNS +#define DUMMY_ROWS CONFIG_DUMMY_CONSOLE_ROWS +#endif + +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER +/* These are both protected by the console_lock */ +static RAW_NOTIFIER_HEAD(dummycon_output_nh); +static bool dummycon_putc_called; + +void dummycon_register_output_notifier(struct notifier_block *nb) +{ + WARN_CONSOLE_UNLOCKED(); + + raw_notifier_chain_register(&dummycon_output_nh, nb); + + if (dummycon_putc_called) + nb->notifier_call(nb, 0, NULL); +} + +void dummycon_unregister_output_notifier(struct notifier_block *nb) +{ + WARN_CONSOLE_UNLOCKED(); + + raw_notifier_chain_unregister(&dummycon_output_nh, nb); +} + +static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y, + unsigned int x) +{ + WARN_CONSOLE_UNLOCKED(); + + dummycon_putc_called = true; + raw_notifier_call_chain(&dummycon_output_nh, 0, NULL); +} + +static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, + unsigned int ypos, unsigned int xpos) +{ + unsigned int i; + + if (!dummycon_putc_called) { + /* Ignore erases */ + for (i = 0 ; i < count; i++) { + if (s[i] != vc->vc_video_erase_char) + break; + } + if (i == count) + return; + + dummycon_putc_called = true; + } + + raw_notifier_call_chain(&dummycon_output_nh, 0, NULL); +} + +static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank, + bool mode_switch) +{ + /* Redraw, so that we get putc(s) for output done while blanked */ + return true; +} + +static bool dummycon_switch(struct vc_data *vc) +{ + /* + * Redraw, so that we get putc(s) for output done while switched + * away. Informs deferred consoles to take over the display. + */ + return true; +} +#else +static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y, + unsigned int x) { } +static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, + unsigned int ypos, unsigned int xpos) { } +static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank, + bool mode_switch) +{ + return false; +} +static bool dummycon_switch(struct vc_data *vc) +{ + return false; +} +#endif + +static const char *dummycon_startup(void) +{ + return "dummy device"; +} + +static void dummycon_init(struct vc_data *vc, bool init) +{ + vc->vc_can_do_color = 1; + if (init) { + vc->vc_cols = DUMMY_COLUMNS; + vc->vc_rows = DUMMY_ROWS; + } else + vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS); +} + +static void dummycon_deinit(struct vc_data *vc) { } +static void dummycon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx, + unsigned int width) { } +static void dummycon_cursor(struct vc_data *vc, bool enable) { } + +static bool dummycon_scroll(struct vc_data *vc, unsigned int top, + unsigned int bottom, enum con_scroll dir, + unsigned int lines) +{ + return false; +} + +/* + * The console `switch' structure for the dummy console + * + * Most of the operations are dummies. + */ + +const struct consw dummy_con = { + .owner = THIS_MODULE, + .con_startup = dummycon_startup, + .con_init = dummycon_init, + .con_deinit = dummycon_deinit, + .con_clear = dummycon_clear, + .con_putc = dummycon_putc, + .con_putcs = dummycon_putcs, + .con_cursor = dummycon_cursor, + .con_scroll = dummycon_scroll, + .con_switch = dummycon_switch, + .con_blank = dummycon_blank, +}; +EXPORT_SYMBOL_GPL(dummy_con); -- cgit v1.3.1