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perf/x86: Fix RDPMC vs. mm_struct tracking 

Vince reported the following rdpmc() testcase failure:

 > Failing test case:
 >
 >	fd=perf_event_open();
 >	addr=mmap(fd);
 >	exec()  // without closing or unmapping the event
 >	fd=perf_event_open();
 >	addr=mmap(fd);
 >	rdpmc()	// GPFs due to rdpmc being disabled

The problem is of course that exec() plays tricks with what is
current->mm, only destroying the old mappings after having
installed the new mm.

Fix this confusion by passing along vma->vm_mm instead of relying on
current->mm.

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Tested-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 1e0fb9ec67 ("perf: Add pmu callbacks to track event mapping and unmapping")
Link: http://lkml.kernel.org/r/20170802173930.cstykcqefmqt7jau@hirez.programming.kicks-ass.net
[ Minor cleanups. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-08-02 19:39:30 +02:00 committed by Ingo Molnar
parent 8d31f80eb3
commit bfe334924c
3 changed files with 12 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/events/core.c
View File

@ -2114,7 +2114,7 @@ static void refresh_pce(void *ignored)
load_mm_cr4(this_cpu_read(cpu_tlbstate.loaded_mm));
}
static void x86_pmu_event_mapped(struct perf_event *event)
static void x86_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
{
if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
return;
@ -2129,22 +2129,20 @@ static void x86_pmu_event_mapped(struct perf_event *event)
* For now, this can't happen because all callers hold mmap_sem
* for write. If this changes, we'll need a different solution.
*/
lockdep_assert_held_exclusive(&current->mm->mmap_sem);
lockdep_assert_held_exclusive(&mm->mmap_sem);
if (atomic_inc_return(&current->mm->context.perf_rdpmc_allowed) == 1)
on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
if (atomic_inc_return(&mm->context.perf_rdpmc_allowed) == 1)
on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);
}
static void x86_pmu_event_unmapped(struct perf_event *event)
static void x86_pmu_event_unmapped(struct perf_event *event, struct mm_struct *mm)
{
if (!current->mm)
return;
if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
return;
if (atomic_dec_and_test(&current->mm->context.perf_rdpmc_allowed))
on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
if (atomic_dec_and_test(&mm->context.perf_rdpmc_allowed))
on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);
}
static int x86_pmu_event_idx(struct perf_event *event)

4
include/linux/perf_event.h
View File

@ -310,8 +310,8 @@ struct pmu {
* Notification that the event was mapped or unmapped. Called
* in the context of the mapping task.
*/
void (*event_mapped) (struct perf_event *event); /*optional*/
void (*event_unmapped) (struct perf_event *event); /*optional*/
void (*event_mapped) (struct perf_event *event, struct mm_struct *mm); /* optional */
void (*event_unmapped) (struct perf_event *event, struct mm_struct *mm); /* optional */
/*
* Flags for ->add()/->del()/ ->start()/->stop(). There are

6
kernel/events/core.c
View File

@ -5090,7 +5090,7 @@ static void perf_mmap_open(struct vm_area_struct *vma)
atomic_inc(&event->rb->aux_mmap_count);
if (event->pmu->event_mapped)
event->pmu->event_mapped(event);
event->pmu->event_mapped(event, vma->vm_mm);
}
static void perf_pmu_output_stop(struct perf_event *event);
@ -5113,7 +5113,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
unsigned long size = perf_data_size(rb);
if (event->pmu->event_unmapped)
event->pmu->event_unmapped(event);
event->pmu->event_unmapped(event, vma->vm_mm);
/*
* rb->aux_mmap_count will always drop before rb->mmap_count and
@ -5411,7 +5411,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
vma->vm_ops = &perf_mmap_vmops;
if (event->pmu->event_mapped)
event->pmu->event_mapped(event);
event->pmu->event_mapped(event, vma->vm_mm);
return ret;
}