On Wed, Jul 01, 2020 at 05:18:22PM +0100, Marc Zyngier wrote: > We have a class of errata (grouped under the ARM64_WORKAROUND_1418040 > banner) that force the trapping of counter access from 32bit EL0. > > We would normally disable the whole vdso for such defect, except that > it would disable it for 64bit userspace as well, which is a shame. > > Instead, add a new vdso_clock_mode, which signals that the vdso > isn't usable for compat tasks. This gets checked in the new > vdso_clocksource_ok() helper, now provided for the 32bit vdso. > > Signed-off-by: Marc Zyngier <[email protected]>
As-is this looks sound to me. It's not entirely clear to me how this will compose with VDSO_CLOCKMODE_TIMENS, but given this series is fixing an existing brokenness I think this has higher priority. Minor comment below, but regardless: Acked-by: Mark Rutland <[email protected]> > --- > arch/arm64/include/asm/vdso/clocksource.h | 7 +++++-- > arch/arm64/include/asm/vdso/compat_gettimeofday.h | 8 +++++++- > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/vdso/clocksource.h > b/arch/arm64/include/asm/vdso/clocksource.h > index df6ea65c1dec..b054d9febfb5 100644 > --- a/arch/arm64/include/asm/vdso/clocksource.h > +++ b/arch/arm64/include/asm/vdso/clocksource.h > @@ -2,7 +2,10 @@ > #ifndef __ASM_VDSOCLOCKSOURCE_H > #define __ASM_VDSOCLOCKSOURCE_H > > -#define VDSO_ARCH_CLOCKMODES \ > - VDSO_CLOCKMODE_ARCHTIMER > +#define VDSO_ARCH_CLOCKMODES \ > + /* vdso clocksource for both 32 and 64bit tasks */ \ > + VDSO_CLOCKMODE_ARCHTIMER, \ > + /* vdso clocksource for 64bit tasks only */ \ > + VDSO_CLOCKMODE_ARCHTIMER_NOCOMPAT > > #endif > diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h > b/arch/arm64/include/asm/vdso/compat_gettimeofday.h > index b6907ae78e53..9a625e8947ff 100644 > --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h > +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h > @@ -111,7 +111,7 @@ static __always_inline u64 __arch_get_hw_counter(s32 > clock_mode) > * update. Return something. Core will do another round and then > * see the mode change and fallback to the syscall. > */ > - if (clock_mode == VDSO_CLOCKMODE_NONE) > + if (clock_mode != VDSO_CLOCKMODE_ARCHTIMER) > return 0; > > /* > @@ -152,6 +152,12 @@ static __always_inline const struct vdso_data > *__arch_get_vdso_data(void) > return ret; > } > > +static inline bool vdso_clocksource_ok(const struct vdso_data *vd) > +{ > + return vd->clock_mode == VDSO_CLOCKMODE_ARCHTIMER; > +} > +#define vdso_clocksource_ok vdso_clocksource_ok Existing issue, but it's a shame this doesn't take the clock mode directly, then we wouldn't have to duplicate the conditions (as above, inverted). Mark.
