Hi Heiko, On 6/9/20 3:46 PM, Heiko Carstens wrote: > Hello Vincenzo, > > sorry it took such a long time to answer! > >> 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. >> >> Fix the s390 vdso implementation of clock_getres keeping a copy of >> hrtimer_resolution in vdso data and using that directly. >> >> Cc: Heiko Carstens <[email protected]> >> Cc: Vasily Gorbik <[email protected]> >> Cc: Christian Borntraeger <[email protected]> >> Signed-off-by: Vincenzo Frascino <[email protected]> >> Acked-by: Martin Schwidefsky <[email protected]> >> --- >> arch/s390/include/asm/vdso.h | 1 + >> arch/s390/kernel/asm-offsets.c | 2 +- >> arch/s390/kernel/time.c | 1 + >> arch/s390/kernel/vdso64/clock_getres.S | 10 +++++----- >> 4 files changed, 8 insertions(+), 6 deletions(-) > ... > >> diff --git a/arch/s390/kernel/vdso64/clock_getres.S >> b/arch/s390/kernel/vdso64/clock_getres.S >> index 081435398e0a..022b58c980db 100644 >> --- a/arch/s390/kernel/vdso64/clock_getres.S >> +++ b/arch/s390/kernel/vdso64/clock_getres.S >> @@ -17,12 +17,14 @@ >> .type __kernel_clock_getres,@function >> __kernel_clock_getres: >> CFI_STARTPROC >> - larl %r1,4f >> + larl %r1,3f >> + lg %r0,0(%r1) >> cghi %r2,__CLOCK_REALTIME_COARSE >> je 0f >> cghi %r2,__CLOCK_MONOTONIC_COARSE >> je 0f >> - larl %r1,3f >> + larl %r1,_vdso_data >> + l %r0,__VDSO_CLOCK_REALTIME_RES(%r1) > > This should be llgf for proper zero extension. The code works anyway, > since the upper lg would clear the high order bits, however this looks > like it works more or less by accident ;) > > I changed it and applied your patch. Thanks a lot!
Thank you for this and for the explanation. I must admit that this was the first attempt to write s390 assembly. I had to go through most of the "Principles of Operation" before I could get something meaningful going ;) > -- Regards, Vincenzo P.S. Now I can finally say that once in my life I wrote s390 assembler ;)
