This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH v3 2/2] sysdeps/clock_gettime: Use clock_gettime64 if avaliable
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Wed, 4 Dec 2019 14:24:29 -0300
- Subject: Re: [PATCH v3 2/2] sysdeps/clock_gettime: Use clock_gettime64 if avaliable
- References: <20191123222708.17021-1-alistair.francis@wdc.com> <20191123222708.17021-2-alistair.francis@wdc.com> <621b67c9-028e-e913-8b9a-7978d2d05e04@linaro.org>
On 03/12/2019 16:29, Adhemerval Zanella wrote:
>
>
> On 23/11/2019 19:27, Alistair Francis wrote:
>> With the clock_gettime64 call we prefer to use vDSO. There is no call
>> to clock_gettime64 on glibc with older headers and kernel 5.1+ if it
>> doesn't support vDSO.
>
> Ok with the fix below regarding HAVE_CLOCK_GETTIME64_VSYSCALL.
As [1] I think we can handle both the cases:
8. Define both __NR_clock_gettime64, provide a 64-bit vDSO, define
__NR_clock_gettime, and provide a 32-bit vDSO.
- i.e: some 32-bits ports built against kernel header equal or newer
then v5.1 (i386, arm, and mips).
9. Define both __NR_clock_gettime64, provide a 64-bit vDSO, and
define __NR_clock_gettime (unlikely, but possible)..
With my vDSO refactor to use relro data structures.
This patch is ok.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
[1] https://sourceware.org/ml/libc-alpha/2019-12/msg00142.html
>
>> ---
>> This was patch was runtime tested with RV32 and RV64
>> It was build tested using the ./scripts/build-many-glibcs.py script.
>>
>> I also ran:
>> $ make ; make install ; make check
>> tests on native ARM (32-bit) with the following three confiugrations:
>> - 4.19 Kernel and 4.19 Headers
>> - 5.2 Kernel and 4.19 Headers
>> - 5.2 Kernel and 5.2 Headers
>> and didn't see any regressions
>>
>> v3:
>> - Assume HAVE_CLOCK_GETTIME64_VSYSCALL means we have __NR_clock_gettime64
>> - Change code style to be more glibc-ish
>> v2:
>> - Add commit message
>> - Change ret_64 to int
>>
>> include/time.h | 3 ++
>> sysdeps/unix/sysv/linux/clock_gettime.c | 44 ++++++++++++++++++++++++-
>> 2 files changed, 46 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/time.h b/include/time.h
>> index d7800eb30f..c19c73ae09 100644
>> --- a/include/time.h
>> +++ b/include/time.h
>> @@ -211,11 +211,14 @@ extern double __difftime (time_t time1, time_t time0);
>>
>> #if __TIMESIZE == 64
>> # define __clock_nanosleep_time64 __clock_nanosleep
>> +# define __clock_gettime64 __clock_gettime
>> #else
>> extern int __clock_nanosleep_time64 (clockid_t clock_id,
>> int flags, const struct __timespec64 *req,
>> struct __timespec64 *rem);
>> libc_hidden_proto (__clock_nanosleep_time64)
>> +extern int __clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp);
>> +libc_hidden_proto (__clock_gettime64)
>> #endif
>>
>> /* Use in the clock_* functions. Size of the field representing the
>> diff --git a/sysdeps/unix/sysv/linux/clock_gettime.c b/sysdeps/unix/sysv/linux/clock_gettime.c
>> index ca40983f6c..875c4fe905 100644
>> --- a/sysdeps/unix/sysv/linux/clock_gettime.c
>> +++ b/sysdeps/unix/sysv/linux/clock_gettime.c
>> @@ -17,6 +17,7 @@
>> <https://www.gnu.org/licenses/>. */
>>
>> #include <sysdep.h>
>> +#include <kernel-features.h>
>> #include <errno.h>
>> #include <time.h>
>> #include "kernel-posix-cpu-timers.h"
>> @@ -30,10 +31,51 @@
>>
>> /* Get current value of CLOCK and store it in TP. */
>> int
>> +__clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp)
>> +{
>> +#ifdef __ASSUME_TIME64_SYSCALLS
>> +# ifndef __NR_clock_gettime64
>> +# define __NR_clock_gettime64 __NR_clock_gettime
>> +# define __vdso_clock_gettime64 __vdso_clock_gettime
>> +# endif
>> + return INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp);
>
> Ok, in this case either __vdso_clock_gettime/__NR_clock_gettime or
> __vdso_clock_gettime64/__NR_clock_gettime64 will be called.
>
>> +#else
>> +# if defined HAVE_CLOCK_GETTIME64_VSYSCALL
>> + int ret64 = INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp);
>> + if (ret64 == 0 || errno != ENOSYS)
>> + return ret64;
>> +# endif
> This should be:
>
> #if defined __NR_clock_gettime64
> int ret64 = INLINE_VSYSCALL (clock_gettime64, ...)
> [...]
>
> And before sysdep-vdso.h it should be.
>
> #if defined HAVE_CLOCK_GETTIME_VSYSCALL || defined HAVE_CLOCK_GETTIME64_VSYSCALL
> # define HAVE_SYSCALL
> #endif
>
> If !HAVE_SYSCALL the INLINE_VSYSCALL is defined as INLINE_SYCALL.
> It means that if an architecture does provide __NR_clock_gettime64
> but not provide HAVE_CLOCK_GETTIME64_VSYSCALL, it will still use
> the syscall. This code only uses the syscall if the vDSO is still
> present.
>
> I hope I can get my vDSO refactor, which would simplify a bit this
> code.
>
>> + struct timespec tp32;
>> + int ret = INLINE_VSYSCALL (clock_gettime, 2, clock_id, &tp32);
>> + if (ret == 0)
>> + *tp = valid_timespec_to_timespec64 (tp32);
>> + return ret;
>> +#endif
>> +}
>
> Ok, old fallback to time32 vdso/syscall.
>
>> +
>> +#if __TIMESIZE != 64
>> +int
>> __clock_gettime (clockid_t clock_id, struct timespec *tp)
>> {
>> - return INLINE_VSYSCALL (clock_gettime, 2, clock_id, tp);
>> + int ret;
>> + struct __timespec64 tp64;
>> +
>> + ret = __clock_gettime64 (clock_id, &tp64);
>> +
>> + if (ret == 0)
>> + {
>> + if (! in_time_t_range (tp64.tv_sec))
>> + {
>> + __set_errno (EOVERFLOW);
>> + return -1;
>> + }
>> +
>> + *tp = valid_timespec64_to_timespec (tp64);
>> + }
>> +
>> + return ret;
>> }
>> +#endif
>> libc_hidden_def (__clock_gettime)
>>
>> versioned_symbol (libc, __clock_gettime, clock_gettime, GLIBC_2_17);
>>
>
> Ok.
>