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/*
* Copyright (C) 2011-2017, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
*
* Parts came from evlist.c builtin-{top,stat,record}.c, see those files for further
* copyright notes.
*
* Released under the GPL v2. (and only v2, not any later version)
*/
#include <sys/mman.h>
#include <inttypes.h>
#include <asm/bug.h>
#include "debug.h"
#include "event.h"
#include "mmap.h"
#include "util.h" /* page_size */
size_t perf_mmap__mmap_len(struct perf_mmap *map)
{
return map->mask + 1 + page_size;
}
/* When check_messup is true, 'end' must points to a good entry */
static union perf_event *perf_mmap__read(struct perf_mmap *map,
u64 start, u64 end, u64 *prev)
{
unsigned char *data = map->base + page_size;
union perf_event *event = NULL;
int diff = end - start;
if (diff >= (int)sizeof(event->header)) {
size_t size;
event = (union perf_event *)&data[start & map->mask];
size = event->header.size;
if (size < sizeof(event->header) || diff < (int)size) {
event = NULL;
goto broken_event;
}
/*
* Event straddles the mmap boundary -- header should always
* be inside due to u64 alignment of output.
*/
if ((start & map->mask) + size != ((start + size) & map->mask)) {
unsigned int offset = start;
unsigned int len = min(sizeof(*event), size), cpy;
void *dst = map->event_copy;
do {
cpy = min(map->mask + 1 - (offset & map->mask), len);
memcpy(dst, &data[offset & map->mask], cpy);
offset += cpy;
dst += cpy;
len -= cpy;
} while (len);
event = (union perf_event *)map->event_copy;
}
start += size;
}
broken_event:
if (prev)
*prev = start;
return event;
}
union perf_event *perf_mmap__read_forward(struct perf_mmap *map)
{
u64 head;
u64 old = map->prev;
/*
* Check if event was unmapped due to a POLLHUP/POLLERR.
*/
if (!refcount_read(&map->refcnt))
return NULL;
head = perf_mmap__read_head(map);
return perf_mmap__read(map, old, head, &map->prev);
}
union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
{
u64 head, end;
u64 start = map->prev;
/*
* Check if event was unmapped due to a POLLHUP/POLLERR.
*/
if (!refcount_read(&map->refcnt))
return NULL;
head = perf_mmap__read_head(map);
if (!head)
return NULL;
/*
* 'head' pointer starts from 0. Kernel minus sizeof(record) form
* it each time when kernel writes to it, so in fact 'head' is
* negative. 'end' pointer is made manually by adding the size of
* the ring buffer to 'head' pointer, means the validate data can
* read is the whole ring buffer. If 'end' is positive, the ring
* buffer has not fully filled, so we must adjust 'end' to 0.
*
* However, since both 'head' and 'end' is unsigned, we can't
* simply compare 'end' against 0. Here we compare '-head' and
* the size of the ring buffer, where -head is the number of bytes
* kernel write to the ring buffer.
*/
if (-head < (u64)(map->mask + 1))
end = 0;
else
end = head + map->mask + 1;
return perf_mmap__read(map, start, end, &map->prev);
}
void perf_mmap__read_catchup(struct perf_mmap *map)
{
u64 head;
if (!refcount_read(&map->refcnt))
return;
head = perf_mmap__read_head(map);
map->prev = head;
}
static bool perf_mmap__empty(struct perf_mmap *map)
{
return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base;
}
void perf_mmap__get(struct perf_mmap *map)
{
refcount_inc(&map->refcnt);
}
void perf_mmap__put(struct perf_mmap *map)
{
BUG_ON(map->base && refcount_read(&map->refcnt) == 0);
if (refcount_dec_and_test(&map->refcnt))
perf_mmap__munmap(map);
}
void perf_mmap__consume(struct perf_mmap *map, bool overwrite)
{
if (!overwrite) {
u64 old = map->prev;
perf_mmap__write_tail(map, old);
}
if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map))
perf_mmap__put(map);
}
int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused,
struct auxtrace_mmap_params *mp __maybe_unused,
void *userpg __maybe_unused,
int fd __maybe_unused)
{
return 0;
}
void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused)
{
}
void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_unused,
off_t auxtrace_offset __maybe_unused,
unsigned int auxtrace_pages __maybe_unused,
bool auxtrace_overwrite __maybe_unused)
{
}
void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused,
struct perf_evlist *evlist __maybe_unused,
int idx __maybe_unused,
bool per_cpu __maybe_unused)
{
}
void perf_mmap__munmap(struct perf_mmap *map)
{
if (map->base != NULL) {
munmap(map->base, perf_mmap__mmap_len(map));
map->base = NULL;
map->fd = -1;
refcount_set(&map->refcnt, 0);
}
auxtrace_mmap__munmap(&map->auxtrace_mmap);
}
int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
{
/*
* The last one will be done at perf_evlist__mmap_consume(), so that we
* make sure we don't prevent tools from consuming every last event in
* the ring buffer.
*
* I.e. we can get the POLLHUP meaning that the fd doesn't exist
* anymore, but the last events for it are still in the ring buffer,
* waiting to be consumed.
*
* Tools can chose to ignore this at their own discretion, but the
* evlist layer can't just drop it when filtering events in
* perf_evlist__filter_pollfd().
*/
refcount_set(&map->refcnt, 2);
map->prev = 0;
map->mask = mp->mask;
map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,
MAP_SHARED, fd, 0);
if (map->base == MAP_FAILED) {
pr_debug2("failed to mmap perf event ring buffer, error %d\n",
errno);
map->base = NULL;
return -1;
}
map->fd = fd;
if (auxtrace_mmap__mmap(&map->auxtrace_mmap,
&mp->auxtrace_mp, map->base, fd))
return -1;
return 0;
}
static int backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)
{
struct perf_event_header *pheader;
u64 evt_head = head;
int size = mask + 1;
pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);
pheader = (struct perf_event_header *)(buf + (head & mask));
*start = head;
while (true) {
if (evt_head - head >= (unsigned int)size) {
pr_debug("Finished reading backward ring buffer: rewind\n");
if (evt_head - head > (unsigned int)size)
evt_head -= pheader->size;
*end = evt_head;
return 0;
}
pheader = (struct perf_event_header *)(buf + (evt_head & mask));
if (pheader->size == 0) {
pr_debug("Finished reading backward ring buffer: get start\n");
*end = evt_head;
return 0;
}
evt_head += pheader->size;
pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
}
WARN_ONCE(1, "Shouldn't get here\n");
return -1;
}
static int rb_find_range(void *data, int mask, u64 head, u64 old,
u64 *start, u64 *end, bool backward)
{
if (!backward) {
*start = old;
*end = head;
return 0;
}
return backward_rb_find_range(data, mask, head, start, end);
}
int perf_mmap__push(struct perf_mmap *md, bool backward,
void *to, int push(void *to, void *buf, size_t size))
{
u64 head = perf_mmap__read_head(md);
u64 old = md->prev;
u64 end = head, start = old;
unsigned char *data = md->base + page_size;
unsigned long size;
void *buf;
int rc = 0;
if (rb_find_range(data, md->mask, head, old, &start, &end, backward))
return -1;
if (start == end)
return 0;
size = end - start;
if (size > (unsigned long)(md->mask) + 1) {
WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
md->prev = head;
perf_mmap__consume(md, backward);
return 0;
}
if ((start & md->mask) + size != (end & md->mask)) {
buf = &data[start & md->mask];
size = md->mask + 1 - (start & md->mask);
start += size;
if (push(to, buf, size) < 0) {
rc = -1;
goto out;
}
}
buf = &data[start & md->mask];
size = end - start;
start += size;
if (push(to, buf, size) < 0) {
rc = -1;
goto out;
}
md->prev = head;
perf_mmap__consume(md, backward);
out:
return rc;
}
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