[PATCH 0/5] Fix vDSO clock_getres()

[Vincenzo Frascino]

clock_getres in the vDSO library has to preserve the same behaviour
of posix_get_hrtimer_res().

In particular, posix_get_hrtimer_res() does:
    sec = 0;
    ns = hrtimer_resolution;
and hrtimer_resolution depends on the enablement of the high
resolution timers that can happen either at compile or at run time.

A possible fix is to change the vdso implementation of clock_getres,
keeping a copy of hrtimer_resolution in vdso data and using that
directly [1].

This patchset implements the proposed fix for arm64, powerpc, s390,
nds32 and adds a test to verify that the syscall and the vdso library
implementation of clock_getres return the same values.

[1] https://marc.info/?l=linux-arm-kernel&m=155110381930196&w=2 

Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Martin Schwidefsky <schwidefsky at de.ibm.com>
Cc: Heiko Carstens <heiko.carstens at de.ibm.com>
Cc: Greentime Hu <green.hu at gmail.com>
Cc: Vincent Chen <deanbo422 at gmail.com>
Cc: Shuah Khan <shuah at kernel.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Arnd Bergmann <arnd at arndb.de>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>

Vincenzo Frascino (5):
  arm64: Fix vDSO clock_getres()
  powerpc: Fix vDSO clock_getres()
  s390: Fix vDSO clock_getres()
  nds32: Fix vDSO clock_getres()
  kselftest: Extend vDSO selftest to clock_getres

 arch/arm64/include/asm/vdso_datapage.h        |   1 +
 arch/arm64/kernel/asm-offsets.c               |   2 +-
 arch/arm64/kernel/vdso.c                      |   2 +
 arch/arm64/kernel/vdso/gettimeofday.S         |  25 ++--
 arch/nds32/include/asm/vdso_datapage.h        |   1 +
 arch/nds32/kernel/vdso.c                      |   1 +
 arch/nds32/kernel/vdso/gettimeofday.c         |   4 +-
 arch/powerpc/include/asm/vdso_datapage.h      |   2 +
 arch/powerpc/kernel/asm-offsets.c             |   2 +-
 arch/powerpc/kernel/time.c                    |   1 +
 arch/powerpc/kernel/vdso32/gettimeofday.S     |  22 ++--
 arch/powerpc/kernel/vdso64/gettimeofday.S     |  22 ++--
 arch/s390/include/asm/vdso.h                  |   1 +
 arch/s390/kernel/asm-offsets.c                |   2 +-
 arch/s390/kernel/time.c                       |   1 +
 arch/s390/kernel/vdso32/clock_getres.S        |  17 ++-
 arch/s390/kernel/vdso64/clock_getres.S        |  15 ++-
 tools/testing/selftests/vDSO/Makefile         |   2 +
 .../selftests/vDSO/vdso_clock_getres.c        | 107 ++++++++++++++++++
 19 files changed, 191 insertions(+), 39 deletions(-)
 create mode 100644 tools/testing/selftests/vDSO/vdso_clock_getres.c

-- 
2.21.0