On Wednesday 15 July 2015 11:18:31 Bamvor Zhang Jian wrote:
Hi, Arnd
On 07/09/2015 06:26 PM, Arnd Bergmann wrote:
On Thursday 09 July 2015 17:02:47 Bamvor Zhang Jian wrote:
On 07/09/2015 04:09 AM, John Stultz wrote:
On Mon, Jun 29, 2015 at 7:23 AM, Bamvor Zhang Jian bamvor.zhangjian@linaro.org wrote:
+int get_timeval64(struct timeval64 *tv,
const struct __kernel_timeval __user *utv)+{
struct __kernel_timeval ktv;int ret;ret = copy_from_user(&ktv, utv, sizeof(ktv));if (ret)return -EFAULT;tv->tv_sec = ktv.tv_sec;if (!IS_ENABLED(CONFIG_64BIT)+#ifdef CONFIG_COMPAT
|| is_compat_task()+#endif
These sorts of ifdefs are to be avoided inside of functions.
Instead, it seems is_compat_task() should be defined to 0 in the !CONFIG_COMPAT case, so you can avoid the ifdefs and the compiler can still optimize it out.
I add this ifdef because I got compile failure on arm platform. This file do not include the <linux/compat.h> directly. And in arm64, compat.h is included implicitily. So, I am not sure what I should do here. Include <linux/compat.h> in this file directly or add a this check at the beginning of this file?
#ifndef is_compat_task #define is_compat_task() (0) #endif
Actually I think we can completely skip this test here: Unlike timespec, timeval is defined in a way that always lets user space use a 64-bit type for the microsecond portion (suseconds_t tv_usec).
I do not familar with this type. I grep the suseconds_t in glibc, it seems that suseconds_t(__SUSECONDS_T_TYPE) is defined as __SYSCALL_SLONG_TYPE which is __SLONGWORD_TYPE(32bit on 32bit architecture).
Correct, but POSIX allows it to be redefined along with time_t, so timeval can be a pair of 64-bit values. In contrast, timespec is required by POSIX (and C11) to be a time_t and a 'long', which is why we need a hack to check the size of the second word of the timespec structure.
Arnd