user/sven/linux.git/include/linux/perf_event.h, branch v6.1.152

perf: Avoid the read if the count is already updated

2025-06-04T12:40:16Z

[ Upstream commit 8ce939a0fa194939cc1f92dbd8bc1a7806e7d40a ] The event may have been updated in the PMU-specific implementation, e.g., Intel PEBS counters snapshotting. The common code should not read and overwrite the value. The PERF_SAMPLE_READ in the data->sample_type can be used to detect whether the PMU-specific value is available. If yes, avoid the pmu->read() in the common code. Add a new flag, skip_read, to track the case. Factor out a perf_pmu_read() to clean up the code. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250121152303.3128733-3-kan.liang@linux.intel.com Signed-off-by: Sasha Levin

perf: Fix event leak upon exec and file release

2024-08-03T06:49:41Z

commit 3a5465418f5fd970e86a86c7f4075be262682840 upstream. The perf pending task work is never waited upon the matching event release. In the case of a child event, released via free_event() directly, this can potentially result in a leaked event, such as in the following scenario that doesn't even require a weak IRQ work implementation to trigger: schedule() prepare_task_switch() =======> perf_event_overflow() event->pending_sigtrap = ... irq_work_queue(&event->pending_irq) <======= perf_event_task_sched_out() event_sched_out() event->pending_sigtrap = 0; atomic_long_inc_not_zero(&event->refcount) task_work_add(&event->pending_task) finish_lock_switch() =======> perf_pending_irq() //do nothing, rely on pending task work <======= begin_new_exec() perf_event_exit_task() perf_event_exit_event() // If is child event free_event() WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1) // event is leaked Similar scenarios can also happen with perf_event_remove_on_exec() or simply against concurrent perf_event_release(). Fix this with synchonizing against the possibly remaining pending task work while freeing the event, just like is done with remaining pending IRQ work. This means that the pending task callback neither need nor should hold a reference to the event, preventing it from ever beeing freed. Fixes: 517e6a301f34 ("perf: Fix perf_pending_task() UaF") Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240621091601.18227-5-frederic@kernel.org Signed-off-by: Greg Kroah-Hartman

perf: Disallow mis-matched inherited group reads

2023-10-25T10:03:15Z

commit 32671e3799ca2e4590773fd0e63aaa4229e50c06 upstream. Because group consistency is non-atomic between parent (filedesc) and children (inherited) events, it is possible for PERF_FORMAT_GROUP read() to try and sum non-matching counter groups -- with non-sensical results. Add group_generation to distinguish the case where a parent group removes and adds an event and thus has the same number, but a different configuration of events as inherited groups. This became a problem when commit fa8c269353d5 ("perf/core: Invert perf_read_group() loops") flipped the order of child_list and sibling_list. Previously it would iterate the group (sibling_list) first, and for each sibling traverse the child_list. In this order, only the group composition of the parent is relevant. By flipping the order the group composition of the child (inherited) events becomes an issue and the mis-match in group composition becomes evident. That said; even prior to this commit, while reading of a group that is not equally inherited was not broken, it still made no sense. (Ab)use ECHILD as error return to indicate issues with child process group composition. Fixes: fa8c269353d5 ("perf/core: Invert perf_read_group() loops") Reported-by: Budimir Markovic Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20231018115654.GK33217@noisy.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman

hw_breakpoint: fix single-stepping when using bpf_overflow_handler

2023-09-23T09:11:00Z

[ Upstream commit d11a69873d9a7435fe6a48531e165ab80a8b1221 ] Arm platforms use is_default_overflow_handler() to determine if the hw_breakpoint code should single-step over the breakpoint trigger or let the custom handler deal with it. Since bpf_overflow_handler() currently isn't recognized as a default handler, attaching a BPF program to a PERF_TYPE_BREAKPOINT event causes it to keep firing (the instruction triggering the data abort exception is never skipped). For example: # bpftrace -e 'watchpoint:0x10000:4:w { print("hit") }' -c ./test Attaching 1 probe... hit hit [...] ^C (./test performs a single 4-byte store to 0x10000) This patch replaces the check with uses_default_overflow_handler(), which accounts for the bpf_overflow_handler() case by also testing if one of the perf_event_output functions gets invoked indirectly, via orig_default_handler. Signed-off-by: Tomislav Novak Tested-by: Samuel Gosselin # arm64 Reviewed-by: Catalin Marinas Acked-by: Alexei Starovoitov Link: https://lore.kernel.org/linux-arm-kernel/20220923203644.2731604-1-tnovak@fb.com/ Link: https://lore.kernel.org/r/20230605191923.1219974-1-tnovak@meta.com Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

perf: Fix missing SIGTRAPs

2022-10-17T14:32:05Z

Marco reported: Due to the implementation of how SIGTRAP are delivered if perf_event_attr::sigtrap is set, we've noticed 3 issues: 1. Missing SIGTRAP due to a race with event_sched_out() (more details below). 2. Hardware PMU events being disabled due to returning 1 from perf_event_overflow(). The only way to re-enable the event is for user space to first "properly" disable the event and then re-enable it. 3. The inability to automatically disable an event after a specified number of overflows via PERF_EVENT_IOC_REFRESH. The worst of the 3 issues is problem (1), which occurs when a pending_disable is "consumed" by a racing event_sched_out(), observed as follows: CPU0 | CPU1 --------------------------------+--------------------------- __perf_event_overflow() | perf_event_disable_inatomic() | pending_disable = CPU0 | ... | _perf_event_enable() | event_function_call() | task_function_call() | /* sends IPI to CPU0 */ | ... __perf_event_enable() +--------------------------- ctx_resched() task_ctx_sched_out() ctx_sched_out() group_sched_out() event_sched_out() pending_disable = -1 perf_pending_event() perf_pending_event_disable() /* Fails to send SIGTRAP because no pending_disable! */ In the above case, not only is that particular SIGTRAP missed, but also all future SIGTRAPs because 'event_limit' is not reset back to 1. To fix, rework pending delivery of SIGTRAP via IRQ-work by introduction of a separate 'pending_sigtrap', no longer using 'event_limit' and 'pending_disable' for its delivery. Additionally; and different to Marco's proposed patch: - recognise that pending_disable effectively duplicates oncpu for the case where it is set. As such, change the irq_work handler to use ->oncpu to target the event and use pending_* as boolean toggles. - observe that SIGTRAP targets the ctx->task, so the context switch optimization that carries contexts between tasks is invalid. If the irq_work were delayed enough to hit after a context switch the SIGTRAP would be delivered to the wrong task. - observe that if the event gets scheduled out (rotation/migration/context-switch/...) the irq-work would be insufficient to deliver the SIGTRAP when the event gets scheduled back in (the irq-work might still be pending on the old CPU). Therefore have event_sched_out() convert the pending sigtrap into a task_work which will deliver the signal at return_to_user. Fixes: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") Reported-by: Dmitry Vyukov Debugged-by: Dmitry Vyukov Reported-by: Marco Elver Debugged-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Marco Elver Tested-by: Marco Elver

perf: Fix lockdep_assert_event_ctx()

2022-10-04T11:32:08Z

I'm a flamin' moron; because even after Mark told me it should be '&&' I still got it wrong in the final commit. Fixes: f3c0eba28704 ("perf: Add a few assertions") Reported-by: Borislav Petkov Reported-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Tested-by: Borislav Petkov Link: https://lkml.kernel.org/r/YvvIWmDBWdIUCMZj@FVFF77S0Q05N

perf: Use sample_flags for raw_data

2022-09-27T20:50:24Z

Use the new sample_flags to indicate whether the raw data field is filled by the PMU driver. Although it could check with the NULL, follow the same rule with other fields. Remove the raw field from the perf_sample_data_init() to minimize the number of cache lines touched. Signed-off-by: Namhyung Kim Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220921220032.2858517-2-namhyung@kernel.org

perf: Use sample_flags for addr

2022-09-27T20:50:24Z

Use the new sample_flags to indicate whether the addr field is filled by the PMU driver. As most PMU drivers pass 0, it can set the flag only if it has a non-zero value. And use 0 in perf_sample_output() if it's not filled already. Signed-off-by: Namhyung Kim Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220921220032.2858517-1-namhyung@kernel.org

perf: Add a few assertions

2022-09-07T19:54:01Z

While auditing 6b959ba22d34 ("perf/core: Fix reentry problem in perf_output_read_group()") a few spots were found that wanted assertions. Notable for_each_sibling_event() relies on exclusion from modification. This would normally be holding either ctx->lock or ctx->mutex, however due to how things are constructed disabling IRQs is a valid and sufficient substitute for ctx->lock. Another possible site to add assertions would be the various pmu::{add,del,read,..}() methods, but that's not trivially expressable in C -- the best option is wrappers, but those are easy enough to forget. Signed-off-by: Peter Zijlstra (Intel)

perf/core: Assert PERF_EVENT_FLAG_ARCH does not overlap with generic flags

2022-09-07T19:54:00Z

This just ensures that PERF_EVENT_FLAG_ARCH does not overlap with generic hardware event flags. Signed-off-by: Anshuman Khandual Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: James Clark Link: https://lkml.kernel.org/r/20220907091924.439193-3-anshuman.khandual@arm.com