linux-kernel - Re: [PATCH bpf-next 08/10] riscv, bpf: Add ex_insn_off and ex_jmp

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Message-ID: <874ium2spa.fsf@all.your.base.are.belong.to.us>
Date: Tue, 05 Aug 2025 08:22:41 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Pu Lehui <pulehui@...weicloud.com>, bpf@...r.kernel.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: Puranjay Mohan <puranjay@...nel.org>, Palmer Dabbelt
 <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko
 <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard
 Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, Yonghong Song
 <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, KP
 Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo
 <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Pu Lehui
 <pulehui@...wei.com>
Subject: Re: [PATCH bpf-next 08/10] riscv, bpf: Add ex_insn_off and
 ex_jmp_off for exception table handling

Pu Lehui <pulehui@...weicloud.com> writes:

> From: Pu Lehui <pulehui@...wei.com>
>
> Add ex_insn_off and ex_jmp_off fields to struct rv_jit_context so that
> add_exception_handler() does not need to be immediately followed by the
> instruction to add the exception table. ex_insn_off indicates the offset
> of the instruction to add the exception table, and ex_jmp_off indicates
> the offset to jump over the faulting instruction. This is to prepare for
> adding the exception table to atomic instructions later, because some
> atomic instructions need to perform zext or other operations.
>
> Signed-off-by: Pu Lehui <pulehui@...wei.com>

[...]

> @@ -748,7 +745,7 @@ static int add_exception_handler(const struct bpf_insn *insn,
>  	 * that may fault. The execution will jump to this after handling the
>  	 * fault.
>  	 */

Nit: After the upcoming change, the comment ^^^ is not entierly true.
Don't respin for this, but a follow up would be nice!

Reviewed-by: Björn Töpel <bjorn@...osinc.com>