Re: [PATCH] bpf, riscv: fix missing extable entry for arena load_acquire

[Feng Jiang]

On 2026/7/16 15:01, Pu Lehui wrote:
> 
> On 2026/7/16 14:15, Feng Jiang wrote:
>> emit_atomic_ld_st() returns 1 to have build_body() skip the zext after
>> a sub-word load_acquire. The caller does "ret = ret ?:
>> add_exception_handler(...)", which skips add_exception_handler() on any
>> non-zero ret, so the extable entry is missing and a faulting
>> PROBE_ATOMIC load_acquire oopses.
>>
>> Check ret >= 0 before calling add_exception_handler(), and return ret
>> unchanged so build_body() still skips the zext.
>>
>> Fixes: fb7cefabae81 ("riscv, bpf: Add support arena atomics for RV64")
>> Signed-off-by: Feng Jiang <jiangfeng@xxxxxxxxxx>
>> ---
>>   arch/riscv/net/bpf_jit_comp64.c | 12 ++++++++----
>>   1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
>> index f9d5347ba966..4fd4392dd080 100644
>> --- a/arch/riscv/net/bpf_jit_comp64.c
>> +++ b/arch/riscv/net/bpf_jit_comp64.c
>> @@ -1986,10 +1986,14 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>>           else
>>               ret = emit_atomic_rmw(rd, rs, insn, ctx);
>>   -        ret = ret ?: add_exception_handler(insn, REG_DONT_CLEAR_MARKER, ctx);
>> -        if (ret)
>> -            return ret;
>> -        break;
>> +        /* ret can be 1 (skip-zext); extable entry still needs to be added */
>> +        if (ret >= 0) {
>> +            int err = add_exception_handler(insn, REG_DONT_CLEAR_MARKER, ctx);
> 
> Thanks Feng Jiang. Maybe we could remove this additional variable.
> 
> ```
> /* ret can be 1 (skip-zext); extable entry still needs to be added */
> if (ret >= 0)
>   ret = add_exception_handler(insn, REG_DONT_CLEAR_MARKER, ctx) ?: ret;
> 
> if (ret)
>   return ret;
> 
> break;
> ```
> 

Thanks for the review! Your suggestion is indeed cleaner and more concise. I'll send v2 shortly.

> 
>> +
>> +            if (err)
>> +                return err;
>> +        }
>> +        return ret;
>>         default:
>>           pr_err("bpf-jit: unknown opcode %02x\n", code);
>>
>> ---
>> base-commit: a13c140cc289c0b7b3770bce5b3ad42ab35074aa
>> change-id: 20260716-bpf-riscv-fix-extable-399947ca778d
>>
>> Best regards,

-- 
With Best Regards,
Feng Jiang