Re: [PATCH] [BZ #19371] Properly handle x32 syscall

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Wed, Dec 16, 2015 at 8:54 AM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
> On 16-12-2015 14:52, H.J. Lu wrote:
>> On Wed, Dec 16, 2015 at 8:48 AM, Dmitry V. Levin <ldv@altlinux.org> wrote:
>>> On Wed, Dec 16, 2015 at 07:01:39AM -0800, H.J. Lu wrote:
>>>> X32 syscall() may return 64-bit integer as lseek, time and times.  Its
>>>> return type should be __syscall_slong_t instead of long int.  We need
>>>> to properly return 64-bit error value.
>>> [...]
>>>> +#include <sysdep.h>
>>>> +
>>>> +/* Return -1LL in a full 64 bits.  */
>>>> +#undef SYSCALL_ERROR_HANDLER
>>>> +#define SYSCALL_ERROR_HANDLER        \
>>>> +0:                           \
>>>> +     SYSCALL_SET_ERRNO;      \
>>>> +     orq $-1, %rax;          \
>>>> +     ret;
>>>> +
>>>> +/* Always use our own error handler.  */
>>>> +#undef SYSCALL_ERROR_LABEL
>>>> +#define SYSCALL_ERROR_LABEL 0f
>>>> +
>>>> +#include <sysdeps/unix/sysv/linux/x86_64/syscall.S>
>>>
>>> While this looks technically OK, I don't understand why RAX_LP is used
>>> at all in default SYSCALL_ERROR_HANDLER in place for rax.  Everything
>>> would be simpler if glibc finally admitted that return code of any
>>> x32 linux syscall is stored in %rax and not in %eax.
>>
>> Only 3 system calls return 64-bit value.  %eax is one-byte shorter.
>>
>
> I still fail the see the performance gains over the re-engineering and
> code duplication required to avoid make the syscall return 64-bit values.

What code duplication?

-- 
H.J.