This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] [BZ #19371] Properly handle x32 syscall
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Wed, 16 Dec 2015 08:52:34 -0800
- Subject: Re: [PATCH] [BZ #19371] Properly handle x32 syscall
- Authentication-results: sourceware.org; auth=none
- References: <20151216150139 dot GA24629 at gmail dot com> <20151216164812 dot GA23391 at altlinux dot org>
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.
--
H.J.