[PATCH v5 01/13] arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early

James Morse
2017-12-15T15:49:46Z

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);

return false;
--
2.15.0