From: Eduard Zingerman <eddyz87@gmail.com>
To: Andrii Nakryiko <andrii@kernel.org>, bpf@vger.kernel.org
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
adobriyan@gmail.com, shakeel.butt@linux.dev, hannes@cmpxchg.org,
ak@linux.intel.com, osandov@osandov.com, song@kernel.org,
jannh@google.com, linux-fsdevel@vger.kernel.org,
willy@infradead.org
Subject: Re: [PATCH v6 bpf-next 08/10] bpf: decouple stack_map_get_build_id_offset() from perf_callchain_entry
Date: Thu, 22 Aug 2024 13:32:17 -0700 [thread overview]
Message-ID: <ba3c59b71cc3f9260ed3373975972d560a511258.camel@gmail.com> (raw)
In-Reply-To: <20240814185417.1171430-9-andrii@kernel.org>
On Wed, 2024-08-14 at 11:54 -0700, Andrii Nakryiko wrote:
> Change stack_map_get_build_id_offset() which is used to convert stack
> trace IP addresses into build ID+offset pairs. Right now this function
> accepts an array of u64s as an input, and uses array of
> struct bpf_stack_build_id as an output.
>
> This is problematic because u64 array is coming from
> perf_callchain_entry, which is (non-sleepable) RCU protected, so once we
> allows sleepable build ID fetching, this all breaks down.
>
> But its actually pretty easy to make stack_map_get_build_id_offset()
> works with array of struct bpf_stack_build_id as both input and output.
> Which is what this patch is doing, eliminating the dependency on
> perf_callchain_entry. We require caller to fill out
> bpf_stack_build_id.ip fields (all other can be left uninitialized), and
> update in place as we do build ID resolution.
>
> We make sure to READ_ONCE() and cache locally current IP value as we
> used it in a few places to find matching VMA and so on. Given this data
> is directly accessible and modifiable by user's BPF code, we should make
> sure to have a consistent view of it.
>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> ---
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
[...]
next prev parent reply other threads:[~2024-08-22 20:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-14 18:54 [PATCH v6 bpf-next 00/10] Harden and extend ELF build ID parsing logic Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 01/10] lib/buildid: harden " Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 02/10] lib/buildid: add single folio-based file reader abstraction Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 03/10] lib/buildid: take into account e_phoff when fetching program headers Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 04/10] lib/buildid: remove single-page limit for PHDR search Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 05/10] lib/buildid: rename build_id_parse() into build_id_parse_nofault() Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 06/10] lib/buildid: implement sleepable build_id_parse() API Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 07/10] lib/buildid: don't limit .note.gnu.build-id to the first page in ELF Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 08/10] bpf: decouple stack_map_get_build_id_offset() from perf_callchain_entry Andrii Nakryiko
2024-08-22 20:32 ` Eduard Zingerman [this message]
2024-08-14 18:54 ` [PATCH v6 bpf-next 09/10] bpf: wire up sleepable bpf_get_stack() and bpf_get_task_stack() helpers Andrii Nakryiko
2024-08-23 22:22 ` Eduard Zingerman
2024-08-26 16:19 ` Andrii Nakryiko
2024-08-14 18:54 ` [PATCH v6 bpf-next 10/10] selftests/bpf: add build ID tests Andrii Nakryiko
2024-08-22 22:30 ` Eduard Zingerman
2024-08-22 22:55 ` Andrii Nakryiko
2024-08-22 23:07 ` Eduard Zingerman
2024-08-23 23:22 ` [PATCH v6 bpf-next 00/10] Harden and extend ELF build ID parsing logic Eduard Zingerman
2024-08-25 19:35 ` Alexei Starovoitov
2024-08-26 21:30 ` Andrii Nakryiko
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