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From: Yonghong Song <yhs@fb.com>
To: Jiri Olsa <jolsa@kernel.org>, Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Song Liu <songliubraving@fb.com>,
	lkml <linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Michael Petlan <mpetlan@redhat.com>,
	Ian Rogers <irogers@google.com>,
	Stephane Eranian <eranian@google.com>,
	Alexei Budankov <abudankov@huawei.com>,
	Andi Kleen <ak@linux.intel.com>,
	Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCH bpf-next 2/3] bpf: Add size arg to build_id_parse function
Date: Thu, 14 Jan 2021 10:56:33 -0800	[thread overview]
Message-ID: <19f16729-96d6-cc8e-5bd5-c3f5940365d4@fb.com> (raw)
In-Reply-To: <20210114134044.1418404-3-jolsa@kernel.org>



On 1/14/21 5:40 AM, Jiri Olsa wrote:
> It's possible to have other build id types (other than default SHA1).
> Currently there's also ld support for MD5 build id.

Currently, bpf build_id based stackmap does not returns the size of
the build_id. Did you see an issue here? I guess user space can check
the length of non-zero bits of the build id to decide what kind of
type it is, right?

> 
> Adding size argument to build_id_parse function, that returns (if defined)
> size of the parsed build id, so we can recognize the build id type.
> 
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Song Liu <songliubraving@fb.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>   include/linux/buildid.h |  3 ++-
>   kernel/bpf/stackmap.c   |  2 +-
>   lib/buildid.c           | 29 +++++++++++++++++++++--------
>   3 files changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/buildid.h b/include/linux/buildid.h
> index 08028a212589..40232f90db6e 100644
> --- a/include/linux/buildid.h
> +++ b/include/linux/buildid.h
> @@ -6,6 +6,7 @@
>   
>   #define BUILD_ID_SIZE_MAX 20
>   
> -int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id);
> +int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
> +		   __u32 *size);
>   
>   #endif
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index 55d254a59f07..cabaf7db8efc 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -189,7 +189,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
>   
>   	for (i = 0; i < trace_nr; i++) {
>   		vma = find_vma(current->mm, ips[i]);
> -		if (!vma || build_id_parse(vma, id_offs[i].build_id)) {
> +		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
>   			/* per entry fall back to ips */
>   			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
>   			id_offs[i].ip = ips[i];
> diff --git a/lib/buildid.c b/lib/buildid.c
> index 4a4f520c0e29..6156997c3895 100644
> --- a/lib/buildid.c
> +++ b/lib/buildid.c
> @@ -12,6 +12,7 @@
>    */
>   static inline int parse_build_id(void *page_addr,
>   				 unsigned char *build_id,
> +				 __u32 *size,
>   				 void *note_start,
>   				 Elf32_Word note_size)
>   {
> @@ -38,6 +39,8 @@ static inline int parse_build_id(void *page_addr,
>   			       nhdr->n_descsz);
>   			memset(build_id + nhdr->n_descsz, 0,
>   			       BUILD_ID_SIZE_MAX - nhdr->n_descsz);
> +			if (size)
> +				*size = nhdr->n_descsz;
>   			return 0;
>   		}
>   		new_offs = note_offs + sizeof(Elf32_Nhdr) +
> @@ -50,7 +53,8 @@ static inline int parse_build_id(void *page_addr,
>   }
>   
[...]

  reply	other threads:[~2021-01-14 18:58 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-14 13:40 [PATCHv7 bpf-next 0/3] perf: Add mmap2 build id support Jiri Olsa
2021-01-14 13:40 ` [PATCH bpf-next 1/3] bpf: Move stack_map_get_build_id into lib Jiri Olsa
2021-01-14 13:40 ` [PATCH bpf-next 2/3] bpf: Add size arg to build_id_parse function Jiri Olsa
2021-01-14 18:56   ` Yonghong Song [this message]
2021-01-14 20:01     ` Jiri Olsa
2021-01-14 21:05       ` Yonghong Song
2021-01-14 22:02         ` Jiri Olsa
2021-01-14 23:43           ` Yonghong Song
2021-01-15  3:47             ` Alexei Starovoitov
2021-01-26 20:52               ` Jiri Olsa
2021-01-26 21:00                 ` Yonghong Song
2021-01-14 13:40 ` [PATCH bpf-next 3/3] perf: Add build id data in mmap2 event Jiri Olsa
2021-01-15  3:50 ` [PATCHv7 bpf-next 0/3] perf: Add mmap2 build id support patchwork-bot+netdevbpf

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