[PATCH] Linux: Add execveat system call wrapper

[Florian Weimer]

* Adhemerval Zanella via Libc-alpha:

>> +{
>> +  /* Avoid implicit array coercion in syscall macros.  */
>> +  INLINE_SYSCALL_CALL (execveat, dirfd, path, &argv[0], &envp[0], flags);
>> +#ifndef __ASSUME_EXECVEAT
>> +  if (errno != ENOSYS)
>> +    return -1;
>
> You need get the INLINE_SYSCALL_CALL and check if it was sucessful as well,
> instead of just check for the errno value. Also, this implementation always 
> return '-1' (as below):
>
>     int r = INLINE_SYSCALL_CALL (execveat, dirfd, path, &argv[0], &envp[0],
>                                  flags);
>   #if __ASSUME_EXECVEAT
>     return r;
>   #else
>     if (r == 0 || errno != ENOSYS)
>       return r;
>     [...]

>> +  return -1;
>> +}
>
> This will make the function always return -1.  Hasn't it shown in
> testing?

This is the expected behavior for execve and execveat.  It does not
return successfully, which is why it is not necessary to check the value
of the INLINE_SYSCALL_CALL macro, either.

Thanks,
Florian
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