| Message ID | 20171215155101.23505-2-james.morse@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 15/12/17 15:50, James Morse wrote: > this_cpu_has_cap() tests caps->desc not caps->matches, so it stops > walking the list when it finds a 'silent' feature, instead of > walking to the end of the list. > > Prior to v4.6's 644c2ae198412 ("arm64: cpufeature: Test 'matches' pointer > to find the end of the list") we always tested desc to find the end of > a capability list. This was changed for dubious things like PAN_NOT_UAO. > v4.7's e3661b128e53e ("arm64: Allow a capability to be checked on > single CPU") added this_cpu_has_cap() using the old desc style test. > > CC: Suzuki K Poulose <suzuki.poulose@arm.com> > CC: Marc Zyngier <marc.zyngier@arm.com> > Signed-off-by: James Morse <james.morse@arm.com> > --- > So far only ARM64_HAS_SYSREG_GIC_CPUIF and errata use this_cpu_has_cap(), > all the errata have descriptions, and the GIC_CPUIF feature is first in > the list, so its not possible to hit this with mainline. I don't think > this should go to stable - this is not intended as a fix. > > arch/arm64/kernel/cpufeature.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index c5ba0097887f..68a49f7fb75c 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1236,8 +1236,8 @@ static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array, > if (WARN_ON(preemptible())) > return false; > > - for (caps = cap_array; caps->desc; caps++) > - if (caps->capability == cap && caps->matches) > + for (caps = cap_array; caps->matches; caps++) > + if (caps->capability == cap) > return caps->matches(caps, SCOPE_LOCAL_CPU); Thanks for catching this ! Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index c5ba0097887f..68a49f7fb75c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1236,8 +1236,8 @@ static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array, if (WARN_ON(preemptible())) return false; - for (caps = cap_array; caps->desc; caps++) - if (caps->capability == cap && caps->matches) + for (caps = cap_array; caps->matches; caps++) + if (caps->capability == cap) return caps->matches(caps, SCOPE_LOCAL_CPU); return false;
this_cpu_has_cap() tests caps->desc not caps->matches, so it stops walking the list when it finds a 'silent' feature, instead of walking to the end of the list. Prior to v4.6's 644c2ae198412 ("arm64: cpufeature: Test 'matches' pointer to find the end of the list") we always tested desc to find the end of a capability list. This was changed for dubious things like PAN_NOT_UAO. v4.7's e3661b128e53e ("arm64: Allow a capability to be checked on single CPU") added this_cpu_has_cap() using the old desc style test. CC: Suzuki K Poulose <suzuki.poulose@arm.com> CC: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: James Morse <james.morse@arm.com> --- So far only ARM64_HAS_SYSREG_GIC_CPUIF and errata use this_cpu_has_cap(), all the errata have descriptions, and the GIC_CPUIF feature is first in the list, so its not possible to hit this with mainline. I don't think this should go to stable - this is not intended as a fix. arch/arm64/kernel/cpufeature.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)