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

[Richard Henderson]

On 1/16/20 6:26 AM, Alex Bennée wrote:
>> +    /*
>> +     * Perform the syscall.  None of the vsyscalls should need restarting,
>> +     * and all faults should have been caught above.
>> +     */
>> +    ret = do_syscall(env, syscall, env->regs[R_EDI], env->regs[R_ESI],
>> +                     env->regs[R_EDX], env->regs[10], env->regs[8],
>> +                     env->regs[9], 0, 0);
> 
> How come the register ABI to the syscall is different to the others. I
> can see why syscall doesn't come from EAX but the others are a different
> set to normal syscalls which might be why:

Cut and paste error, I assume.

That said, the three syscalls have a maximum of 2 arguments,
so I could really just pass EDI and ESI and 0 for the rest...

> I'm seeing a EFAULT on the gettimeofday failure:

What getttimeofday failure?  Is this related to the mention of /sbin/ldconfig
in your previous message?

>    #0  do_syscall (cpu_env=cpu_env@entry=0x5555577d2b10, num=num@entry=96, 
> arg1=0, arg2=0, arg3=4211016, arg4=8, arg5=274888677184, arg6=274886295415, 
> arg7=0, arg8=0) at /home/alex/lsrc/qemu.git/linux-user/syscall.c:12076        
>                                        
>    #1  0x0000555555609b6e in emulate_vsyscall (env=0x5555577d2b10) at 
> /home/alex/lsrc/qemu.git/linux-user/x86_64/../i386/cpu_loop.c:180
>    #2  cpu_loop (env=0x5555577d2b10) at 
> /home/alex/lsrc/qemu.git/linux-user/x86_64/../i386/cpu_loop.c:246             
>                  
>    #3  0x000055555559640e in main (argc=<optimized out>, argv=<optimized
>    #out>, envp=<optimized out>) at
>    #/home/alex/lsrc/qemu.git/linux-user/main.c:865
> 
> arg1/arg2 don't seem right here.

Why?  NULL value for arg1 is legal, though semi-useless.

Ah, I see that our implementation of gettimeofday doesn't honor NULL.


r~