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- Two more fixes to the perf sigtrap handling:

Browse Source 
- output the address in the sample only when it has been requested
  - handle the case where user-only events can hit in kernel and thus
    upset the sigtrap sanity checking
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Merge tag 'perf_urgent_for_v6.1_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf fixes from Borislav Petkov:
 "Two more fixes to the perf sigtrap handling:

   - output the address in the sample only when it has been requested

   - handle the case where user-only events can hit in kernel and thus
     upset the sigtrap sanity checking"

* tag 'perf_urgent_for_v6.1_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf: Consider OS filter fail
  perf: Fixup SIGTRAP and sample_flags interaction
This commit is contained in:
Linus Torvalds 2022-11-27 11:53:41 -08:00
commit 5afcab2217
1 changed files with 25 additions and 2 deletions
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27
kernel/events/core.c
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@ -9273,6 +9273,19 @@ int perf_event_account_interrupt(struct perf_event *event)
return __perf_event_account_interrupt(event, 1);
}
static inline bool sample_is_allowed(struct perf_event *event, struct pt_regs *regs)
{
/*
* Due to interrupt latency (AKA "skid"), we may enter the
* kernel before taking an overflow, even if the PMU is only
* counting user events.
*/
if (event->attr.exclude_kernel && !user_mode(regs))
return false;
return true;
}
/*
* Generic event overflow handling, sampling.
*/
@ -9306,6 +9319,13 @@ static int __perf_event_overflow(struct perf_event *event,
}
if (event->attr.sigtrap) {
/*
* The desired behaviour of sigtrap vs invalid samples is a bit
* tricky; on the one hand, one should not loose the SIGTRAP if
* it is the first event, on the other hand, we should also not
* trigger the WARN or override the data address.
*/
bool valid_sample = sample_is_allowed(event, regs);
unsigned int pending_id = 1;
if (regs)
@ -9313,7 +9333,7 @@ static int __perf_event_overflow(struct perf_event *event,
if (!event->pending_sigtrap) {
event->pending_sigtrap = pending_id;
local_inc(&event->ctx->nr_pending);
} else if (event->attr.exclude_kernel) {
} else if (event->attr.exclude_kernel && valid_sample) {
/*
* Should not be able to return to user space without
* consuming pending_sigtrap; with exceptions:
@ -9328,7 +9348,10 @@ static int __perf_event_overflow(struct perf_event *event,
*/
WARN_ON_ONCE(event->pending_sigtrap != pending_id);
}
event->pending_addr = data->addr;
event->pending_addr = 0;
if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR))
event->pending_addr = data->addr;
irq_work_queue(&event->pending_irq);
}