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

[Pu Lehui]

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 at kylinos.cn>
> ---
>   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;
```


> +
> +			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,