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Commit 5919b309 authored by Jiri Olsa's avatar Jiri Olsa Committed by Ingo Molnar
Browse files

perf: Fix vmalloc ring buffer pages handling 



If we allocate perf ring buffer with the size of single (user)
page, we will get memory corruption when releasing itin
rb_free_work function (for CONFIG_PERF_USE_VMALLOC option).

For single page sized ring buffer the page_order is -1 (because
nr_pages is 0). This needs to be recognized in the rb_free_work
function to release proper amount of pages.

Adding data_page_nr function that returns number of allocated
data pages. Customizing the rest of the code to use it.

Reported-by: default avatarJan Stancek <jstancek@redhat.com>
Original-patch-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarJiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20130319143509.GA1128@krava.brq.redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1b0dac2a

kernel/events/ring_buffer.c

+10 −4
Original line number Diff line number Diff line
@@ -326,11 +326,16 @@ void rb_free(struct ring_buffer *rb) 
}



#else

static int data_page_nr(struct ring_buffer *rb)

{

	return rb->nr_pages << page_order(rb);

}



struct page *

perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)

{

	if (pgoff > (1UL << page_order(rb)))

	/* The '>' counts in the user page. */

	if (pgoff > data_page_nr(rb))

		return NULL;



	return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
@@ -350,10 +355,11 @@ static void rb_free_work(struct work_struct *work) 
	int i, nr;



	rb = container_of(work, struct ring_buffer, work);

	nr = 1 << page_order(rb);

	nr = data_page_nr(rb);



	base = rb->user_page;

	for (i = 0; i < nr + 1; i++)

	/* The '<=' counts in the user page. */

	for (i = 0; i <= nr; i++)

		perf_mmap_unmark_page(base + (i * PAGE_SIZE));



	vfree(base);
@@ -387,7 +393,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) 
	rb->user_page = all_buf;

	rb->data_pages[0] = all_buf + PAGE_SIZE;

	rb->page_order = ilog2(nr_pages);

	rb->nr_pages = 1;

	rb->nr_pages = !!nr_pages;



	ring_buffer_init(rb, watermark, flags);