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Subject[RFC PATCH 1/3] perf: Add persistent events
Date
Add the needed pieces for persistent events which makes them
process-agnostic. Also, make their buffers read-only when mmaping them
from userspace.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
include/uapi/linux/perf_event.h | 3 ++-
kernel/events/core.c | 8 +++++++-
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 9fa9c622a7f4..4a4ae56195e1 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -270,8 +270,9 @@ struct perf_event_attr {

exclude_callchain_kernel : 1, /* exclude kernel callchains */
exclude_callchain_user : 1, /* exclude user callchains */
+ persistent : 1, /* always-on event */

- __reserved_1 : 41;
+ __reserved_1 : 40;

union {
__u32 wakeup_events; /* wakeup every n events */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b0cd86501c30..7c712b0c3b9a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3560,6 +3560,9 @@ static void perf_mmap_close(struct vm_area_struct *vma)
{
struct perf_event *event = vma->vm_file->private_data;

+ if (event->attr.persistent)
+ return atomic_dec(&event->mmap_count);
+
if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
unsigned long size = perf_data_size(event->rb);
struct user_struct *user = event->mmap_user;
@@ -3603,7 +3606,10 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
if (event->cpu == -1 && event->attr.inherit)
return -EINVAL;

- if (!(vma->vm_flags & VM_SHARED))
+ if (!(vma->vm_flags & VM_SHARED) && !event->attr.persistent)
+ return -EINVAL;
+
+ if (event->attr.persistent && (vma->vm_flags & VM_WRITE))
return -EINVAL;

vma_size = vma->vm_end - vma->vm_start;
--
1.8.1.3.535.ga923c31


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