Re: [PATCH] Make sure fetch_instruction exist before calling it

[Richard Henderson <richard.henderson@linaro.org>]

On 11/14/25 09:29, phind.uet@gmail.com wrote:
> From: Nguyen Dinh Phi <phind.uet@gmail.com>
> 
> Currently, this function is only available in MSHV. If a different accelerator
> is used, and the code jumps to this section, a segfault will occur.
> (I ran into this with HVF)
> 
> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
> ---
>   target/i386/emulate/x86_decode.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/emulate/x86_decode.c b/target/i386/emulate/x86_decode.c
> index 97bd6f1a3b..d037ed1142 100644
> --- a/target/i386/emulate/x86_decode.c
> +++ b/target/i386/emulate/x86_decode.c
> @@ -77,7 +77,11 @@ static inline uint64_t decode_bytes(CPUX86State *env, struct x86_decode *decode,
>           memcpy(&val, decode->stream->bytes + decode->len, size);
>       } else {
>           target_ulong va = linear_rip(env_cpu(env), env->eip) + decode->len;
> -        emul_ops->fetch_instruction(env_cpu(env), &val, va, size);
> +        if (emul_ops->fetch_instruction) {
> +            emul_ops->fetch_instruction(env_cpu(env), &val, va, size);
> +        } else {
> +            emul_ops->read_mem(env_cpu(env), &val, va, size);
> +        }
>       }
>       decode->len += size;
>   

We should instead have fetch_instruction == read_mem for the cases that do not require a 
specialized version.


r~