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Date: Sun, 21 Oct 2018 02:09:28 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: alexei.starovoitov@...il.com
Cc: netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf-next 6/6] bpf, libbpf: simplify and cleanup perf ring buffer walk
Simplify bpf_perf_event_read_simple() a bit and fix up some minor
things along the way: the return code in the header is not of type
int but enum bpf_perf_event_ret instead. Once callback indicated
to break the loop walking event data, it also needs to be consumed
in data_tail since it has been processed already.
Moreover, bpf_perf_event_print_t callback should avoid void * as
we actually get a pointer to struct perf_event_header and thus
applications can make use of container_of() to have type checks.
The walk also doesn't have to use modulo op since the ring size is
required to be power of two.
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
tools/bpf/bpftool/map_perf_ring.c | 10 +++--
tools/lib/bpf/libbpf.c | 67 +++++++++++++----------------
tools/lib/bpf/libbpf.h | 15 ++++---
tools/testing/selftests/bpf/trace_helpers.c | 7 +--
4 files changed, 47 insertions(+), 52 deletions(-)
diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c
index 6d41323..bdaf406 100644
--- a/tools/bpf/bpftool/map_perf_ring.c
+++ b/tools/bpf/bpftool/map_perf_ring.c
@@ -50,15 +50,17 @@ static void int_exit(int signo)
stop = true;
}
-static enum bpf_perf_event_ret print_bpf_output(void *event, void *priv)
+static enum bpf_perf_event_ret
+print_bpf_output(struct perf_event_header *event, void *private_data)
{
- struct event_ring_info *ring = priv;
- struct perf_event_sample *e = event;
+ struct perf_event_sample *e = container_of(event, struct perf_event_sample,
+ header);
+ struct event_ring_info *ring = private_data;
struct {
struct perf_event_header header;
__u64 id;
__u64 lost;
- } *lost = event;
+ } *lost = (typeof(lost))event;
if (json_output) {
jsonw_start_object(json_wtr);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0c21355..b607be7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2415,56 +2415,47 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
}
enum bpf_perf_event_ret
-bpf_perf_event_read_simple(void *mem, unsigned long size,
- unsigned long page_size, void **buf, size_t *buf_len,
- bpf_perf_event_print_t fn, void *priv)
+bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
+ void **copy_mem, size_t *copy_size,
+ bpf_perf_event_print_t fn, void *private_data)
{
- struct perf_event_mmap_page *header = mem;
+ struct perf_event_mmap_page *header = mmap_mem;
__u64 data_head = ring_buffer_read_head(header);
__u64 data_tail = header->data_tail;
- int ret = LIBBPF_PERF_EVENT_ERROR;
- void *base, *begin, *end;
-
- if (data_head == data_tail)
- return LIBBPF_PERF_EVENT_CONT;
-
- base = ((char *)header) + page_size;
-
- begin = base + data_tail % size;
- end = base + data_head % size;
-
- while (begin != end) {
- struct perf_event_header *ehdr;
-
- ehdr = begin;
- if (begin + ehdr->size > base + size) {
- long len = base + size - begin;
-
- if (*buf_len < ehdr->size) {
- free(*buf);
- *buf = malloc(ehdr->size);
- if (!*buf) {
+ void *base = ((__u8 *)header) + page_size;
+ int ret = LIBBPF_PERF_EVENT_CONT;
+ struct perf_event_header *ehdr;
+ size_t ehdr_size;
+
+ while (data_head != data_tail) {
+ ehdr = base + (data_tail & (mmap_size - 1));
+ ehdr_size = ehdr->size;
+
+ if (((void *)ehdr) + ehdr_size > base + mmap_size) {
+ void *copy_start = ehdr;
+ size_t len_first = base + mmap_size - copy_start;
+ size_t len_secnd = ehdr_size - len_first;
+
+ if (*copy_size < ehdr_size) {
+ free(*copy_mem);
+ *copy_mem = malloc(ehdr_size);
+ if (!*copy_mem) {
+ *copy_size = 0;
ret = LIBBPF_PERF_EVENT_ERROR;
break;
}
- *buf_len = ehdr->size;
+ *copy_size = ehdr_size;
}
- memcpy(*buf, begin, len);
- memcpy(*buf + len, base, ehdr->size - len);
- ehdr = (void *)*buf;
- begin = base + ehdr->size - len;
- } else if (begin + ehdr->size == base + size) {
- begin = base;
- } else {
- begin += ehdr->size;
+ memcpy(*copy_mem, copy_start, len_first);
+ memcpy(*copy_mem + len_first, base, len_secnd);
+ ehdr = *copy_mem;
}
- ret = fn(ehdr, priv);
+ ret = fn(ehdr, private_data);
+ data_tail += ehdr_size;
if (ret != LIBBPF_PERF_EVENT_CONT)
break;
-
- data_tail += ehdr->size;
}
ring_buffer_write_tail(header, data_tail);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 1354cc9..1f3468d 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -297,13 +297,14 @@ enum bpf_perf_event_ret {
LIBBPF_PERF_EVENT_CONT = -2,
};
-typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(void *event,
- void *priv);
-LIBBPF_API int bpf_perf_event_read_simple(void *mem, unsigned long size,
- unsigned long page_size,
- void **buf, size_t *buf_len,
- bpf_perf_event_print_t fn,
- void *priv);
+struct perf_event_header;
+typedef enum bpf_perf_event_ret
+ (*bpf_perf_event_print_t)(struct perf_event_header *hdr,
+ void *private_data);
+LIBBPF_API enum bpf_perf_event_ret
+bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
+ void **copy_mem, size_t *copy_size,
+ bpf_perf_event_print_t fn, void *private_data);
struct nlattr;
typedef int (*libbpf_dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index a3d1dac..4cdb63b 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -125,10 +125,11 @@ struct perf_event_sample {
char data[];
};
-static enum bpf_perf_event_ret bpf_perf_event_print(void *event, void *priv)
+static enum bpf_perf_event_ret
+bpf_perf_event_print(struct perf_event_header *hdr, void *private_data)
{
- struct perf_event_sample *e = event;
- perf_event_print_fn fn = priv;
+ struct perf_event_sample *e = (struct perf_event_sample *)hdr;
+ perf_event_print_fn fn = private_data;
int ret;
if (e->header.type == PERF_RECORD_SAMPLE) {
--
2.9.5
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