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Groups > linux.kernel > #1726730

[RFC PATCH 01/17] perf: Allow mmapping only user page

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The 'user page' contains offsets and sizes of data and aux areas of the
ring buffer. If a user wants to mmap a pre-existing buffer, they need to
know these in order to issue mmap()s with correct offsets and sizes.

This enables mmapping of the user page if the ring buffer already exists.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index cb7eaf0f91..9389e27cb0 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5366,7 +5366,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 again:
 	mutex_lock(&event->mmap_mutex);
 	if (event->rb) {
-		if (event->rb->nr_pages != nr_pages) {
+		if (nr_pages && event->rb->nr_pages != nr_pages) {
 			ret = -EINVAL;
 			goto unlock;
 		}
-- 
2.14.1

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[RFC PATCH 00/17] perf: Detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:40 +0200
  [RFC PATCH 04/17] tracefs: Add ->unlink callback to tracefs_dir_ops Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:40 +0200
  [RFC PATCH 05/17] perf: Introduce detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:40 +0200
  [RFC PATCH 01/17] perf: Allow mmapping only user page Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:40 +0200
    Re: [RFC PATCH 01/17] perf: Allow mmapping only user page Borislav Petkov <bp@alien8.de> - 2017-09-06 18:30 +0200
  [RFC PATCH 03/17] tracefs: De-globalize instances' callbacks Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:40 +0200
  [RFC PATCH 02/17] perf: Factor out mlock accounting Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:40 +0200
  [RFC PATCH 08/17] perf: Allow inheritance for detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:50 +0200
  [RFC PATCH 10/17] perf: Implement pinning and scheduling for SHMEM events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:50 +0200
  [RFC PATCH 07/17] perf: Add pmu_info to user page Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:50 +0200
  [RFC PATCH 06/17] perf: Add buffers to the detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:50 +0200
  [RFC PATCH 09/17] perf: Use shmemfs pages for userspace-only per-thread detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:50 +0200
  [RFC PATCH 11/17] perf: Implement mlock accounting for shmem ring buffers Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 15:50 +0200
  [RFC PATCH 12/17] perf: Track pinned events per user Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 16:00 +0200
  [RFC PATCH 13/17] perf: Re-inject shmem buffers after exec Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 16:00 +0200
  [RFC PATCH 14/17] perf: Add ioctl(REATTACH) for detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 16:00 +0200
  [RFC PATCH 16/17] perf/x86/intel/pt: Add PMU info Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 16:10 +0200
  [RFC PATCH 17/17] perf/x86/intel/bts: Add PMU info Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 16:10 +0200
  [RFC PATCH 15/17] perf: Allow controlled non-root access to detached events Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-09-05 16:10 +0200
  Re: [RFC PATCH 00/17] perf: Detached events Borislav Petkov <bp@alien8.de> - 2017-09-06 18:30 +0200

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