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    Subject[PATCH 4.19 228/639] perf: Copy parents address filter offsets on clone
    Date
    From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

    [ Upstream commit 18736eef12137c59f60cc9f56dc5bea05c92e0eb ]

    When a child event is allocated in the inherit_event() path, the VMA
    based filter offsets are not copied from the parent, even though the
    address space mapping of the new task remains the same, which leads to
    no trace for the new task until exec.

    Reported-by: Mansour Alharthi <malharthi9@gatech.edu>
    Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Acked-by: Peter Zijlstra <peterz@infradead.org>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Fixes: 375637bc5249 ("perf/core: Introduce address range filtering")
    Link: http://lkml.kernel.org/r/20190215115655.63469-2-alexander.shishkin@linux.intel.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/events/core.c | 15 +++++++++++++++
    1 file changed, 15 insertions(+)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 460d5fd3ec4e4..9a5559f5938a5 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -1254,6 +1254,7 @@ static void put_ctx(struct perf_event_context *ctx)
    * perf_event_context::lock
    * perf_event::mmap_mutex
    * mmap_sem
    + * perf_addr_filters_head::lock
    *
    * cpu_hotplug_lock
    * pmus_lock
    @@ -10136,6 +10137,20 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
    goto err_per_task;
    }

    + /*
    + * Clone the parent's vma offsets: they are valid until exec()
    + * even if the mm is not shared with the parent.
    + */
    + if (event->parent) {
    + struct perf_addr_filters_head *ifh = perf_event_addr_filters(event);
    +
    + raw_spin_lock_irq(&ifh->lock);
    + memcpy(event->addr_filters_offs,
    + event->parent->addr_filters_offs,
    + pmu->nr_addr_filters * sizeof(unsigned long));
    + raw_spin_unlock_irq(&ifh->lock);
    + }
    +
    /* force hw sync on the address filters */
    event->addr_filters_gen = 1;
    }
    --
    2.20.1


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