[PATCH 01/12] linux: Fix vDSO macros build with time64 interfaces

[Adhemerval Zanella]

On 13/12/2019 08:51, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> diff --git a/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c b/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c
>> index 7e772e05ce..07d38466e2 100644
>> --- a/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c
>> +++ b/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c
>> @@ -22,10 +22,6 @@
>>  
>>  #include <time.h>
>>  #include <sysdep.h>
>> -
>> -#ifdef HAVE_GETTIMEOFDAY_VSYSCALL
>> -# define HAVE_VSYSCALL
>> -#endif
>>  #include <sysdep-vdso.h>
>>  
>>  /* Used as a fallback in the ifunc resolver if VDSO is not available
>> @@ -36,7 +32,9 @@ __gettimeofday_vsyscall (struct timeval *restrict tv, void *restrict tz)
>>    if (__glibc_unlikely (tz != 0))
>>      memset (tz, 0, sizeof *tz);
>>  
>> -  return INLINE_VSYSCALL (gettimeofday, 2, tv, tz);
>> +  if (INLINE_VSYSCALL (gettimeofday, 2, tv, tz) == 0)
>> +    return 0;
>> +  return INLINE_SYSCALL_CALL (gettimeofday, tv, tz);
>>  }
> 
> Given that this is the fallback function why do we try INLINE_VSYSCALL
> first?
> 
> (The static case would need adjusting, of course.)

Because it will be used on static build and the fallback case will be
unlikely. But I can add static only case that uses vDSO plus syscall and
change the shared fallback case that just issues the syscall.

My idea is to eventually consolidate the aarch64/powerpc64/x86_64
gettimeofday implementation, since they are essentially the same.

> 
>> diff --git a/sysdeps/unix/sysv/linux/clock_gettime.c b/sysdeps/unix/sysv/linux/clock_gettime.c
>> index 875c4fe905..4ea56c9a4b 100644
>> --- a/sysdeps/unix/sysv/linux/clock_gettime.c
>> +++ b/sysdeps/unix/sysv/linux/clock_gettime.c
>> @@ -21,10 +21,6 @@
>>  #include <errno.h>
>>  #include <time.h>
>>  #include "kernel-posix-cpu-timers.h"
>> -
>> -#ifdef HAVE_CLOCK_GETTIME_VSYSCALL
>> -# define HAVE_VSYSCALL
>> -#endif
>>  #include <sysdep-vdso.h>
>>  
>>  #include <shlib-compat.h>
>> @@ -33,24 +29,39 @@
>>  int
>>  __clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp)
>>  {
>> +  int r = -1;
>> +
>>  #ifdef __ASSUME_TIME64_SYSCALLS
>> +  /* 64 bit ABIs or Newer 32-bit ABIs that only support 64-bit time_t.  */
>> +# ifdef __NR_clock_gettime64
>> +  r = INLINE_SYSCALL_CALL (clock_gettime64, clock_id, tp);
>> +# else
>> +#  ifdef HAVE_CLOCK_GETTIME_VSYSCALL
>> +  r = INLINE_VSYSCALL (clock_gettime, 2, clock_id, tp);
>> +#  endif
>> +  if (r == -1)
>> +    r = INLINE_SYSCALL_CALL (clock_gettime, clock_id, tp);
> 
> Why do you check __NR_clock_gettime64 first?  Won't this make the vDSO
> unused?

The vDSO support for clock_gettime64 was added later in this set. I 
explicit removed because even if an architecture sets 
HAVE_CLOCK_GETTIME64_VSYSCALL, it won't build.