Re: [PATCH 3/3] tracing/kprobe: Add self test for PERF_EVENT_IOC_QUERY_KPROBE

[Yonghong Song <yhs@fb.com>]

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))
>