From: Borislav Petkov <b...@alien8.de>
Add the needed pieces for persistent events which makes them
process-agnostic. Also, make their buffers read-only when mmaping them
from userspace.
While at it, do not return a void function, as caught by Fengguang's
build robot.
Changes made by Robert Richter <robert.rich...@linaro.org>:
* mmap should return EACCES error if fd can not be opened writable.
This error code also helps userland to map buffers readonly on
failure.
Signed-off-by: Borislav Petkov <b...@suse.de>
[ Return -EACCES if mapped buffers must be readonly ]
Signed-off-by: Robert Richter <robert.rich...@linaro.org>
Signed-off-by: Robert Richter <r...@kernel.org>
---
include/uapi/linux/perf_event.h | 3 ++-
kernel/events/core.c | 10 +++++++++-
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index fb104e5..6032361 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -272,8 +272,9 @@ 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 b790ab6..a13e457 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3713,6 +3713,11 @@ static void perf_mmap_close(struct vm_area_struct *vma)
{
struct perf_event *event = vma->vm_file->private_data;
+ if (event->attr.persistent) {
+ atomic_dec(&event->mmap_count);
+ return;
+ }
+
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;
@@ -3756,9 +3761,12 @@ 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 -EACCES;
+
vma_size = vma->vm_end - vma->vm_start;
nr_pages = (vma_size / PAGE_SIZE) - 1;
--
1.8.1.1
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