From: Yonghong Song <yonghong.song@linux.dev>
To: Puranjay Mohan <puranjay@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Xu Kuohai <xukuohai@huaweicloud.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next 1/3] bpf: arm64: simplify exception table handling
Date: Wed, 6 Aug 2025 15:58:47 -0700 [thread overview]
Message-ID: <75940147-d026-485c-b7fa-fa769bc6e82f@linux.dev> (raw)
In-Reply-To: <20250806085847.18633-2-puranjay@kernel.org>
On 8/6/25 1:58 AM, Puranjay Mohan wrote:
> BPF loads with BPF_PROBE_MEM(SX) can load from unsafe pointers and the
> JIT adds an exception table entry for the JITed instruction which allows
> the exeption handler to set the destination register of the load to zero
> and continue execution from the next instruction.
>
> As all arm64 instructions are AARCH64_INSN_SIZE size, the exception
> handler can just increment the pc by AARCH64_INSN_SIZE without needing
> the exact address of the instruction following the the faulting
> instruction.
>
> Simplify the exception table usage in arm64 JIT by only saving the
> destination register in ex->fixup and drop everything related to
> the fixup_offset. The fault handler is modified to add AARCH64_INSN_SIZE
> to the pc.
>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
next prev parent reply other threads:[~2025-08-06 22:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-06 8:58 [PATCH bpf-next 0/3] bpf: Report arena faults to BPF streams Puranjay Mohan
2025-08-06 8:58 ` [PATCH bpf-next 1/3] bpf: arm64: simplify exception table handling Puranjay Mohan
2025-08-06 22:58 ` Yonghong Song [this message]
2025-08-06 8:58 ` [PATCH bpf-next 2/3] bpf: Report arena faults to BPF stderr Puranjay Mohan
2025-08-06 23:57 ` Yonghong Song
2025-08-07 13:22 ` puranjay
2025-08-06 8:58 ` [PATCH bpf-next 3/3] selftests/bpf: Add tests for arena fault reporting Puranjay Mohan
2025-08-07 0:04 ` Yonghong Song
2025-08-07 13:25 ` puranjay
2025-08-07 15:25 ` Kumar Kartikeya Dwivedi
2025-08-11 10:35 ` Puranjay Mohan
2025-08-11 20:31 ` Kumar Kartikeya Dwivedi
2025-08-11 17:14 ` Eduard Zingerman
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