A helper function to sequentially walk through the AUX buffer with a given callback. This is useful to copy the AUX data out of its buffer.
Signed-off-by: Alexander Shishkin <[email protected]> --- kernel/events/internal.h | 5 +++++ kernel/events/ring_buffer.c | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+) diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 6dc725a7e7bc..eb6cd6b370f9 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -56,6 +56,9 @@ struct ring_buffer { void *data_pages[0]; }; +typedef unsigned long (*aux_copyfn)(void *data, const void *src, + unsigned long len); + extern void rb_free(struct ring_buffer *rb); static inline void rb_free_rcu(struct rcu_head *rcu_head) @@ -80,6 +83,8 @@ extern void perf_event_wakeup(struct perf_event *event); extern int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, pgoff_t pgoff, int nr_pages, long watermark, int flags); extern void rb_free_aux(struct ring_buffer *rb); +extern long rb_output_aux(struct ring_buffer *rb, unsigned long from, + unsigned long to, aux_copyfn copyfn, void *data); extern struct ring_buffer *ring_buffer_get(struct perf_event *event); extern void ring_buffer_put(struct ring_buffer *rb); diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 141aa2ca8728..d6157143f054 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -519,6 +519,40 @@ void *perf_get_aux(struct perf_output_handle *handle) } EXPORT_SYMBOL_GPL(perf_get_aux); +/* + * Copy out AUX data from a ring_buffer using a supplied callback. + */ +long rb_output_aux(struct ring_buffer *rb, unsigned long from, + unsigned long to, aux_copyfn copyfn, void *data) +{ + unsigned long tocopy, remainder, len = 0; + void *addr; + + from &= (rb->aux_nr_pages << PAGE_SHIFT) - 1; + to &= (rb->aux_nr_pages << PAGE_SHIFT) - 1; + + do { + tocopy = PAGE_SIZE - offset_in_page(from); + if (to > from) + tocopy = min(tocopy, to - from); + if (!tocopy) + break; + + addr = rb->aux_pages[from >> PAGE_SHIFT]; + addr += offset_in_page(from); + + remainder = copyfn(data, addr, tocopy); + if (remainder) + return -EFAULT; + + len += tocopy; + from += tocopy; + from &= (rb->aux_nr_pages << PAGE_SHIFT) - 1; + } while (to != from); + + return len; +} + #define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY) static struct page *rb_alloc_aux_page(int node, int order) -- 2.17.1
