From: Yonghong Song <yonghong.song@linux.dev>
To: bot+bpf-ci@kernel.org, puranjay@kernel.org, bpf@vger.kernel.org
Cc: puranjay12@gmail.com, ast@kernel.org, andrii@kernel.org,
daniel@iogearbox.net, martin.lau@kernel.org, eddyz87@gmail.com,
memxor@gmail.com, mykyta.yatsenko5@gmail.com, qmo@kernel.org,
kernel-team@meta.com, clm@meta.com, ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next v2] bpftool: Enable aarch64 ISA extensions for JIT disassembly
Date: Tue, 10 Mar 2026 20:51:19 -0700 [thread overview]
Message-ID: <41c6f48d-1e45-40b2-b2b0-7035cadfa1de@linux.dev> (raw)
In-Reply-To: <3d287b2ab8fe7ee19b3e6c98a58aba501ac191339b7f34960b5bc804ae6a23ab@mail.kernel.org>
On 3/10/26 4:05 PM, bot+bpf-ci@kernel.org wrote:
>> diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c
>> --- a/tools/bpf/bpftool/jit_disasm.c
>> +++ b/tools/bpf/bpftool/jit_disasm.c
>> @@ -93,7 +93,16 @@ init_context(disasm_ctx_t *ctx, const char *arch,
>> p_err("Failed to retrieve triple");
>> return -1;
>> }
>> - *ctx = LLVMCreateDisasm(triple, NULL, 0, NULL, symbol_lookup_callback);
>> +
>> + /*
>> + * Enable all aarch64 ISA extensions so the disassembler can handle any
>> + * instruction the kernel JIT might emit (e.g. ARM64 LSE atomics).
>> + */
>> + if (strncmp(triple, "aarch64", 7))
>> + *ctx = LLVMCreateDisasmCPUFeatures(triple, "", "+all", NULL, 0, NULL,
>> + symbol_lookup_callback);
>> + else
>> + *ctx = LLVMCreateDisasm(triple, NULL, 0, NULL, symbol_lookup_callback);
> Isn't this condition inverted? strncmp() returns 0 when the
> strings match, so when triple starts with "aarch64" the condition
> is false and the else branch runs, which calls the old
> LLVMCreateDisasm() without any features enabled.
>
> Conversely, for non-aarch64 targets (e.g. x86_64), strncmp()
> returns non-zero, making the condition true, and
> LLVMCreateDisasmCPUFeatures() with "+all" gets called on the
> wrong architecture.
>
> It looks like this should be:
>
> if (!strncmp(triple, "aarch64", 7))
>
> The v1 of this patch used strstr(triple, "aarch64") which has the
> correct polarity (returns non-NULL on match). The switch to
> strncmp() for v2 appears to have lost the negation.
AI is correct. The condition should be
if (strncmp(triple, "aarch64", 7) == 0)
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/22927610334
next prev parent reply other threads:[~2026-03-11 3:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-10 22:34 [PATCH bpf-next v2] bpftool: Enable aarch64 ISA extensions for JIT disassembly Puranjay Mohan
2026-03-10 23:05 ` bot+bpf-ci
2026-03-11 3:51 ` Yonghong Song [this message]
2026-03-11 6:20 ` Leon Hwang
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