lkml.org 
[lkml]   [2017]   [Aug]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.12 28/41] perf/x86: Fix RDPMC vs. mm_struct tracking
    Date
    4.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Peter Zijlstra <peterz@infradead.org>

    commit bfe334924ccd9f4a53f30240c03cf2f43f5b2df1 upstream.

    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>
    Fixes: 1e0fb9ec679c ("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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/events/core.c | 16 +++++++---------
    include/linux/perf_event.h | 4 ++--
    kernel/events/core.c | 6 +++---
    3 files changed, 12 insertions(+), 14 deletions(-)

    --- a/arch/x86/events/core.c
    +++ b/arch/x86/events/core.c
    @@ -2105,7 +2105,7 @@ static void refresh_pce(void *ignored)
    load_mm_cr4(current->active_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;
    @@ -2120,22 +2120,20 @@ static void x86_pmu_event_mapped(struct
    * 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)
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -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
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -5084,7 +5084,7 @@ static void perf_mmap_open(struct vm_are
    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);
    @@ -5107,7 +5107,7 @@ static void perf_mmap_close(struct vm_ar
    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
    @@ -5405,7 +5405,7 @@ aux_unlock:
    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;
    }

    \
     
     \ /
      Last update: 2017-08-22 21:21    [W:2.957 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site