Re: [PATCH v2 3/5] linux-user/i386: Emulate x86_64 vsyscalls

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

On 1/21/20 12:13 AM, Alex Bennée wrote:
> 
> Richard Henderson <richard.henderson@linaro.org> writes:
> 
>> On 1/20/20 1:48 AM, Alex Bennée wrote:
>>>> +    default:
>>>> +    sigsegv:
>>>
>>> this label looks a little extraneous.
>>>
>>> Otherwise:
>>>
>>> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>>>
>>
>> Look a little further down:
>>
>>> +    default:
>>> +    sigsegv:
>>> +        /* Like force_sig(SIGSEGV).  */
>>> +        gen_signal(env, TARGET_SIGSEGV, TARGET_SI_KERNEL, 0);
>>> +        return;
>>> +    }
>>> +
>>> +    /*
>>> +     * Validate the return address.
>>> +     * Note that the kernel treats this the same as an invalid entry point.
>>> +     */
>>> +    if (get_user_u64(caller, env->regs[R_ESP])) {
>>> +        goto sigsegv;
>>> +    }
> 
> Wouldn't this read better:
> 
>     /*
>      * Validate the entry point.  We have already validated the page
>      * during translation, now verify the offset.
>      */
>     switch (env->eip & ~TARGET_PAGE_MASK) {
>     case 0x000:
>         syscall = TARGET_NR_gettimeofday;
>         break;
>     case 0x400:
>         syscall = TARGET_NR_time;
>         break;
>     case 0x800:
>         syscall = TARGET_NR_getcpu;
>         break;
>     default:
>         syscall = -1;
>         break;
>     }
> 
>     /*
>      * If we have an invalid entry point or an invalid return address we
>      * generate a SIGSEG.
>      */
>     if (syscall < 0 || get_user_u64(caller, env->regs[R_ESP])) {
>         gen_signal(env, TARGET_SIGSEGV, TARGET_SI_KERNEL, 0);
>         return;
>     }
> 

Only if you have a violent goto allergy.


r~