* [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link
@ 2019-08-06 23:42 Daniel Xu
2019-08-06 23:42 ` [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE Daniel Xu
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Daniel Xu @ 2019-08-06 23:42 UTC (permalink / raw)
To: songliubraving, yhs, andriin; +Cc: Daniel Xu, bpf, kernel-team
It is sometimes necessary to perform ioctl's on the underlying perf fd.
There is not currently a way to extract the fd given a bpf_link, so add a
helper for it.
---
tools/lib/bpf/libbpf.c | 13 +++++++++++++
tools/lib/bpf/libbpf.h | 1 +
tools/lib/bpf/libbpf.map | 5 +++++
3 files changed, 19 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ead915aec349..8469d69448ae 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link)
return err;
}
+int bpf_link__get_perf_fd(struct bpf_link *link)
+{
+ struct bpf_link_fd *l = (void *)link;
+
+ if (!link)
+ return -1;
+
+ if (link->destroy != &bpf_link__destroy_perf_event)
+ return -1;
+
+ return l->fd;
+}
+
struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
int pfd)
{
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 8a9d462a6f6d..5391ac95e4fa 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
struct bpf_link;
LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
+LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link);
LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index f9d316e873d8..0f844ce29b04 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -184,3 +184,8 @@ LIBBPF_0.0.4 {
perf_buffer__new_raw;
perf_buffer__poll;
} LIBBPF_0.0.3;
+
+LIBBPF_0.0.5 {
+ global:
+ bpf_link__get_perf_fd;
+} LIBBPF_0.0.4;
--
2.20.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE
2019-08-06 23:42 [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Daniel Xu
@ 2019-08-06 23:42 ` Daniel Xu
2019-08-07 6:01 ` Yonghong Song
2019-08-07 21:49 ` Andrii Nakryiko
2019-08-07 18:19 ` [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Song Liu
2019-08-07 18:57 ` Andrii Nakryiko
2 siblings, 2 replies; 7+ messages in thread
From: Daniel Xu @ 2019-08-06 23:42 UTC (permalink / raw)
To: songliubraving, yhs, andriin; +Cc: Daniel Xu, bpf, kernel-team
---
tools/include/uapi/linux/perf_event.h | 23 ++++++++++
.../selftests/bpf/prog_tests/attach_probe.c | 43 +++++++++++++++++++
2 files changed, 66 insertions(+)
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 7198ddd0c6b1..4a5e18606baf 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -447,6 +447,28 @@ struct perf_event_query_bpf {
__u32 ids[0];
};
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_KPROE command
+ * to query information about the kprobe attached to the perf
+ * event.
+ */
+struct perf_event_query_kprobe {
+ /*
+ * Size of structure for forward/backward compatibility
+ */
+ __u32 size;
+ /*
+ * Set by the kernel to indicate number of times this kprobe
+ * was temporarily disabled
+ */
+ __u64 nmissed;
+ /*
+ * Set by the kernel to indicate number of times this kprobe
+ * was hit
+ */
+ __u64 nhit;
+};
+
/*
* Ioctls that can be done on a perf event fd:
*/
@@ -462,6 +484,7 @@ struct perf_event_query_bpf {
#define PERF_EVENT_IOC_PAUSE_OUTPUT _IOW('$', 9, __u32)
#define PERF_EVENT_IOC_QUERY_BPF _IOWR('$', 10, struct perf_event_query_bpf *)
#define PERF_EVENT_IOC_MODIFY_ATTRIBUTES _IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_QUERY_KPROBE _IOWR('$', 12, struct perf_event_query_kprobe *)
enum perf_event_ioc_flags {
PERF_IOC_FLAG_GROUP = 1U << 0,
diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 5ecc267d98b0..5f118e9a1469 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -38,9 +38,12 @@ void test_attach_probe(void)
struct bpf_link *kretprobe_link = NULL;
struct bpf_link *uprobe_link = NULL;
struct bpf_link *uretprobe_link = NULL;
+ int kprobe_fd, kretprobe_fd;
int results_map_fd;
size_t uprobe_offset;
ssize_t base_addr;
+ struct perf_event_query_kprobe kprobe_query;
+ struct perf_event_query_kprobe kretprobe_query;
base_addr = get_base_addr();
if (CHECK(base_addr < 0, "get_base_addr",
@@ -116,6 +119,46 @@ void test_attach_probe(void)
/* trigger & validate kprobe && kretprobe */
usleep(1);
+ kprobe_fd = bpf_link__get_perf_fd(kprobe_link);
+ if (CHECK(kprobe_fd < 0, "kprobe_get_perf_fd",
+ "failed to get perf fd from kprobe link\n"))
+ goto cleanup;
+
+ kretprobe_fd = bpf_link__get_perf_fd(kretprobe_link);
+ if (CHECK(kprobe_fd < 0, "kprobe_get_perf_fd",
+ "failed to get perf fd from kprobe link\n"))
+ goto cleanup;
+
+ memset(&kprobe_query, 0, sizeof(kprobe_query));
+ kprobe_query.size = sizeof(kprobe_query);
+ err = ioctl(kprobe_fd, PERF_EVENT_IOC_QUERY_KPROBE, &kprobe_query);
+ if (CHECK(err, "get_kprobe_ioctl",
+ "failed to issue kprobe query ioctl\n"))
+ goto cleanup;
+ if (CHECK(kprobe_query.nmissed > 0, "get_kprobe_ioctl",
+ "read incorect nmissed from kprobe_ioctl: %llu\n",
+ kprobe_query.nmissed))
+ goto cleanup;
+ if (CHECK(kprobe_query.nhit <= 0, "get_kprobe_ioctl",
+ "read incorect nhit from kprobe_ioctl: %llu\n",
+ kprobe_query.nhit))
+ goto cleanup;
+
+ memset(&kretprobe_query, 0, sizeof(kretprobe_query));
+ kretprobe_query.size = sizeof(kretprobe_query);
+ err = ioctl(kretprobe_fd, PERF_EVENT_IOC_QUERY_KPROBE, &kretprobe_query);
+ if (CHECK(err, "get_kretprobe_ioctl",
+ "failed to issue kprobe query ioctl\n"))
+ goto cleanup;
+ if (CHECK(kretprobe_query.nmissed > 0, "get_kretprobe_ioctl",
+ "read incorect nmissed from kretprobe_ioctl: %llu\n",
+ kretprobe_query.nmissed))
+ goto cleanup;
+ if (CHECK(kretprobe_query.nhit <= 0, "get_kretprobe_ioctl",
+ "read incorect nhit from kretprobe_ioctl: %llu\n",
+ kretprobe_query.nhit))
+ goto cleanup;
+
err = bpf_map_lookup_elem(results_map_fd, &kprobe_idx, &res);
if (CHECK(err, "get_kprobe_res",
"failed to get kprobe res: %d\n", err))
--
2.20.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE
2019-08-06 23:42 ` [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE Daniel Xu
@ 2019-08-07 6:01 ` Yonghong Song
2019-08-07 21:49 ` Andrii Nakryiko
1 sibling, 0 replies; 7+ messages in thread
From: Yonghong Song @ 2019-08-07 6:01 UTC (permalink / raw)
To: Daniel Xu, Song Liu, Andrii Nakryiko; +Cc: bpf, Kernel Team
On 8/6/19 4:42 PM, Daniel Xu wrote:
> ---
> tools/include/uapi/linux/perf_event.h | 23 ++++++++++
> .../selftests/bpf/prog_tests/attach_probe.c | 43 +++++++++++++++++++
Could you separate this into two patches?
one patch for uapi update tools/include/uapi/linux/perf_event.h
and the other for .../selftests/bpf/prog_tests/attach_probe.c
The reason is to help libbpf mirror sync'ing.
> 2 files changed, 66 insertions(+)
>
> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> index 7198ddd0c6b1..4a5e18606baf 100644
> --- a/tools/include/uapi/linux/perf_event.h
> +++ b/tools/include/uapi/linux/perf_event.h
> @@ -447,6 +447,28 @@ struct perf_event_query_bpf {
> __u32 ids[0];
> };
>
> +/*
> + * Structure used by below PERF_EVENT_IOC_QUERY_KPROE command
> + * to query information about the kprobe attached to the perf
> + * event.
> + */
> +struct perf_event_query_kprobe {
> + /*
> + * Size of structure for forward/backward compatibility
> + */
> + __u32 size;
> + /*
> + * Set by the kernel to indicate number of times this kprobe
> + * was temporarily disabled
> + */
> + __u64 nmissed;
> + /*
> + * Set by the kernel to indicate number of times this kprobe
> + * was hit
> + */
> + __u64 nhit;
> +};
> +
> /*
> * Ioctls that can be done on a perf event fd:
> */
> @@ -462,6 +484,7 @@ struct perf_event_query_bpf {
> #define PERF_EVENT_IOC_PAUSE_OUTPUT _IOW('$', 9, __u32)
> #define PERF_EVENT_IOC_QUERY_BPF _IOWR('$', 10, struct perf_event_query_bpf *)
> #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES _IOW('$', 11, struct perf_event_attr *)
> +#define PERF_EVENT_IOC_QUERY_KPROBE _IOWR('$', 12, struct perf_event_query_kprobe *)
>
> enum perf_event_ioc_flags {
> PERF_IOC_FLAG_GROUP = 1U << 0,
> diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> index 5ecc267d98b0..5f118e9a1469 100644
> --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> @@ -38,9 +38,12 @@ void test_attach_probe(void)
> struct bpf_link *kretprobe_link = NULL;
> struct bpf_link *uprobe_link = NULL;
> struct bpf_link *uretprobe_link = NULL;
> + int kprobe_fd, kretprobe_fd;
> int results_map_fd;
> size_t uprobe_offset;
> ssize_t base_addr;
> + struct perf_event_query_kprobe kprobe_query;
> + struct perf_event_query_kprobe kretprobe_query;
Since you are adding new fields, could you try to maintain reverse
Christmas coding style?
>
> base_addr = get_base_addr();
> if (CHECK(base_addr < 0, "get_base_addr",
> @@ -116,6 +119,46 @@ void test_attach_probe(void)
> /* trigger & validate kprobe && kretprobe */
> usleep(1);
>
> + kprobe_fd = bpf_link__get_perf_fd(kprobe_link);
> + if (CHECK(kprobe_fd < 0, "kprobe_get_perf_fd",
> + "failed to get perf fd from kprobe link\n"))
> + goto cleanup;
> +
> + kretprobe_fd = bpf_link__get_perf_fd(kretprobe_link);
> + if (CHECK(kprobe_fd < 0, "kprobe_get_perf_fd",
typo: kprobe_fd => kretprobe_fd, kretprobe_get_perf_fd?
> + "failed to get perf fd from kprobe link\n"))
kretprobe link?
> + goto cleanup;
> +
> + memset(&kprobe_query, 0, sizeof(kprobe_query));
> + kprobe_query.size = sizeof(kprobe_query);
> + err = ioctl(kprobe_fd, PERF_EVENT_IOC_QUERY_KPROBE, &kprobe_query);
> + if (CHECK(err, "get_kprobe_ioctl",
> + "failed to issue kprobe query ioctl\n"))
> + goto cleanup;
> + if (CHECK(kprobe_query.nmissed > 0, "get_kprobe_ioctl",
> + "read incorect nmissed from kprobe_ioctl: %llu\n",
> + kprobe_query.nmissed))
> + goto cleanup;
> + if (CHECK(kprobe_query.nhit <= 0, "get_kprobe_ioctl",
nhit is __u64, it cannot be less than 0.
> + "read incorect nhit from kprobe_ioctl: %llu\n",
> + kprobe_query.nhit))
> + goto cleanup;
> +
> + memset(&kretprobe_query, 0, sizeof(kretprobe_query));
> + kretprobe_query.size = sizeof(kretprobe_query);
> + err = ioctl(kretprobe_fd, PERF_EVENT_IOC_QUERY_KPROBE, &kretprobe_query);
> + if (CHECK(err, "get_kretprobe_ioctl",
> + "failed to issue kprobe query ioctl\n"))
> + goto cleanup;
> + if (CHECK(kretprobe_query.nmissed > 0, "get_kretprobe_ioctl",
> + "read incorect nmissed from kretprobe_ioctl: %llu\n",
> + kretprobe_query.nmissed))
> + goto cleanup;
> + if (CHECK(kretprobe_query.nhit <= 0, "get_kretprobe_ioctl",
<= 0 => == 0?
> + "read incorect nhit from kretprobe_ioctl: %llu\n",
> + kretprobe_query.nhit))
> + goto cleanup;
> +
> err = bpf_map_lookup_elem(results_map_fd, &kprobe_idx, &res);
> if (CHECK(err, "get_kprobe_res",
> "failed to get kprobe res: %d\n", err))
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link
2019-08-06 23:42 [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Daniel Xu
2019-08-06 23:42 ` [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE Daniel Xu
@ 2019-08-07 18:19 ` Song Liu
2019-08-07 18:57 ` Andrii Nakryiko
2 siblings, 0 replies; 7+ messages in thread
From: Song Liu @ 2019-08-07 18:19 UTC (permalink / raw)
To: Daniel Xu; +Cc: Song Liu, Yonghong Song, Andrii Nakryiko, bpf, Kernel Team
On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> It is sometimes necessary to perform ioctl's on the underlying perf fd.
> There is not currently a way to extract the fd given a bpf_link, so add a
> helper for it.
Missing "Signed-off-by" tag. Please run scripts/checkpatch.pl on the patches.
Otherwise, looks good to me.
Acked-by: Song Liu <songliubraving@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 13 +++++++++++++
> tools/lib/bpf/libbpf.h | 1 +
> tools/lib/bpf/libbpf.map | 5 +++++
> 3 files changed, 19 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ead915aec349..8469d69448ae 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link)
> return err;
> }
>
> +int bpf_link__get_perf_fd(struct bpf_link *link)
> +{
> + struct bpf_link_fd *l = (void *)link;
> +
> + if (!link)
> + return -1;
> +
> + if (link->destroy != &bpf_link__destroy_perf_event)
> + return -1;
> +
> + return l->fd;
> +}
> +
> struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
> int pfd)
> {
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8a9d462a6f6d..5391ac95e4fa 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
> struct bpf_link;
>
> LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
> +LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link);
>
> LIBBPF_API struct bpf_link *
> bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index f9d316e873d8..0f844ce29b04 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -184,3 +184,8 @@ LIBBPF_0.0.4 {
> perf_buffer__new_raw;
> perf_buffer__poll;
> } LIBBPF_0.0.3;
> +
> +LIBBPF_0.0.5 {
> + global:
> + bpf_link__get_perf_fd;
> +} LIBBPF_0.0.4;
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link
2019-08-06 23:42 [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Daniel Xu
2019-08-06 23:42 ` [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE Daniel Xu
2019-08-07 18:19 ` [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Song Liu
@ 2019-08-07 18:57 ` Andrii Nakryiko
2019-08-09 1:31 ` Daniel Xu
2 siblings, 1 reply; 7+ messages in thread
From: Andrii Nakryiko @ 2019-08-07 18:57 UTC (permalink / raw)
To: Daniel Xu; +Cc: Song Liu, Yonghong Song, Andrii Nakryiko, bpf, Kernel Team
On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> It is sometimes necessary to perform ioctl's on the underlying perf fd.
> There is not currently a way to extract the fd given a bpf_link, so add a
> helper for it.
> ---
So I've been going back and forth with this approach and the
alternative one, and I think I'm leaning towards the alternative one
still.
I think it's better to have a broad "categories" of bpf_links, e.g.:
- FD-based bpf_link (which is the only one we have right now):
bpf_link_fd. It's not just for perf FD-based ones, raw tracepoint is
not, but it's still FD-based;
- for cgroup-related links (once they are added), it will be
bpf_link_cg (or something along the lines);
- there probably should be separate XDP-related bpf_link with device
ID/name inside;
- etc, whatever we'll need.
Then we can have a set of casting APIs and getter APIs that extract
useful information from specific type of bpf_link. We can also add
direct bpf_link creation API (e.g., from known FD), for cases where it
makes sense.
So something like (in libbpf.h):
struct bpf_link_fd;
struct bpf_link_cg;
/* casting APIs */
const struct bpf_link_fd *bpf_link__as_fd(const struct bpf_link *link);
const struct bpf_link_cg *bpf_link__as_cg(const struct bpf_link *link);
/* getters APIs */
int bpf_link_fd__fd(const struct bpf_link_fd *link);
int bpf_link_cg__cgroup_fd(const struct bpf_link_cg *link);
/* link factories (in addition to attach APIs) */
const struct bpf_link_fd *bpf_link__from_fd(int fd);
const struct bpf_link_cg *bpf_link__from_cg(int cg_fd, /* whatever
else necessary */);
I think this way it becomes obvious what you can expect to get of each
possible type of bpf_link and you'll have to explicitly cast to the
right type. Yet we still hide implementation details, allow no-brainer
bpf_link__destroy regardless of specific type of link (which probably
will be a common case).
Thoughts?
> tools/lib/bpf/libbpf.c | 13 +++++++++++++
> tools/lib/bpf/libbpf.h | 1 +
> tools/lib/bpf/libbpf.map | 5 +++++
> 3 files changed, 19 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ead915aec349..8469d69448ae 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link)
> return err;
> }
>
> +int bpf_link__get_perf_fd(struct bpf_link *link)
this seems like a bit too specific name (and we should avoid "get"
words, as we do in a bunch of other libbpf APIs for getters). Maybe
just `bpf_link__fd`? This especially makes sense with a "file-based
bpf_link" abstraction I proposed above.
> +{
> + struct bpf_link_fd *l = (void *)link;
> +
> + if (!link)
> + return -1;
> +
> + if (link->destroy != &bpf_link__destroy_perf_event)
> + return -1;
> +
> + return l->fd;
> +}
> +
> struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
> int pfd)
> {
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8a9d462a6f6d..5391ac95e4fa 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
> struct bpf_link;
>
> LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
> +LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link);
>
> LIBBPF_API struct bpf_link *
> bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index f9d316e873d8..0f844ce29b04 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -184,3 +184,8 @@ LIBBPF_0.0.4 {
> perf_buffer__new_raw;
> perf_buffer__poll;
> } LIBBPF_0.0.3;
> +
> +LIBBPF_0.0.5 {
> + global:
> + bpf_link__get_perf_fd;
> +} LIBBPF_0.0.4;
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE
2019-08-06 23:42 ` [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE Daniel Xu
2019-08-07 6:01 ` Yonghong Song
@ 2019-08-07 21:49 ` Andrii Nakryiko
1 sibling, 0 replies; 7+ messages in thread
From: Andrii Nakryiko @ 2019-08-07 21:49 UTC (permalink / raw)
To: Daniel Xu; +Cc: Song Liu, Yonghong Song, Andrii Nakryiko, bpf, Kernel Team
On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> ---
> tools/include/uapi/linux/perf_event.h | 23 ++++++++++
> .../selftests/bpf/prog_tests/attach_probe.c | 43 +++++++++++++++++++
> 2 files changed, 66 insertions(+)
>
> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> index 7198ddd0c6b1..4a5e18606baf 100644
> --- a/tools/include/uapi/linux/perf_event.h
> +++ b/tools/include/uapi/linux/perf_event.h
Please split header sync into separate patch, this will cause problems
syncing libbpf to Github.
> @@ -447,6 +447,28 @@ struct perf_event_query_bpf {
> __u32 ids[0];
> };
>
[...]
> ssize_t base_addr;
> + struct perf_event_query_kprobe kprobe_query;
> + struct perf_event_query_kprobe kretprobe_query;
Add = {} and avoid using memsets below.
>
> base_addr = get_base_addr();
> if (CHECK(base_addr < 0, "get_base_addr",
> @@ -116,6 +119,46 @@ void test_attach_probe(void)
> /* trigger & validate kprobe && kretprobe */
> usleep(1);
>
[...]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link
2019-08-07 18:57 ` Andrii Nakryiko
@ 2019-08-09 1:31 ` Daniel Xu
0 siblings, 0 replies; 7+ messages in thread
From: Daniel Xu @ 2019-08-09 1:31 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Song Liu, Yonghong Song, Andrii Nakryiko, bpf, Kernel Team
On Wed, Aug 7, 2019, at 11:57 AM, Andrii Nakryiko wrote:
> On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
> >
> > It is sometimes necessary to perform ioctl's on the underlying perf fd.
> > There is not currently a way to extract the fd given a bpf_link, so add a
> > helper for it.
> > ---
>
> So I've been going back and forth with this approach and the
> alternative one, and I think I'm leaning towards the alternative one
> still.
>
> I think it's better to have a broad "categories" of bpf_links, e.g.:
>
> - FD-based bpf_link (which is the only one we have right now):
> bpf_link_fd. It's not just for perf FD-based ones, raw tracepoint is
> not, but it's still FD-based;
> - for cgroup-related links (once they are added), it will be
> bpf_link_cg (or something along the lines);
> - there probably should be separate XDP-related bpf_link with device
> ID/name inside;
> - etc, whatever we'll need.
>
> Then we can have a set of casting APIs and getter APIs that extract
> useful information from specific type of bpf_link. We can also add
> direct bpf_link creation API (e.g., from known FD), for cases where it
> makes sense.
>
> So something like (in libbpf.h):
>
> struct bpf_link_fd;
> struct bpf_link_cg;
>
> /* casting APIs */
> const struct bpf_link_fd *bpf_link__as_fd(const struct bpf_link *link);
> const struct bpf_link_cg *bpf_link__as_cg(const struct bpf_link *link);
>
> /* getters APIs */
> int bpf_link_fd__fd(const struct bpf_link_fd *link);
> int bpf_link_cg__cgroup_fd(const struct bpf_link_cg *link);
>
> /* link factories (in addition to attach APIs) */
> const struct bpf_link_fd *bpf_link__from_fd(int fd);
> const struct bpf_link_cg *bpf_link__from_cg(int cg_fd, /* whatever
> else necessary */);
>
> I think this way it becomes obvious what you can expect to get of each
> possible type of bpf_link and you'll have to explicitly cast to the
> right type. Yet we still hide implementation details, allow no-brainer
> bpf_link__destroy regardless of specific type of link (which probably
> will be a common case).
>
> Thoughts?
Makes sense to me. This would probably result in a more predictable API when
new types are added. I'll make it this way in V2.
>
> > tools/lib/bpf/libbpf.c | 13 +++++++++++++
> > tools/lib/bpf/libbpf.h | 1 +
> > tools/lib/bpf/libbpf.map | 5 +++++
> > 3 files changed, 19 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index ead915aec349..8469d69448ae 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link)
> > return err;
> > }
> >
> > +int bpf_link__get_perf_fd(struct bpf_link *link)
>
> this seems like a bit too specific name (and we should avoid "get"
> words, as we do in a bunch of other libbpf APIs for getters). Maybe
> just `bpf_link__fd`? This especially makes sense with a "file-based
> bpf_link" abstraction I proposed above.
Ok.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2019-08-09 1:31 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-06 23:42 [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Daniel Xu
2019-08-06 23:42 ` [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE Daniel Xu
2019-08-07 6:01 ` Yonghong Song
2019-08-07 21:49 ` Andrii Nakryiko
2019-08-07 18:19 ` [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link Song Liu
2019-08-07 18:57 ` Andrii Nakryiko
2019-08-09 1:31 ` Daniel Xu
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