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KVM: arm64: Add build-time sanity checks for flags

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Flags are great, but flags can also be dangerous: it is easy
to encode a flag that is bigger than its container (unless the
container is a u64), and it is easy to construct a flag value
that doesn't fit in the mask that is associated with it.

Add a couple of build-time sanity checks that ensure we catch
these two cases.

Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2022-05-28 12:38:26 +01:00
parent e19f2c6cd1
commit 5a3984f4ec
1 changed files with 16 additions and 0 deletions
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16
arch/arm64/include/asm/kvm_host.h
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@ -433,8 +433,20 @@ struct kvm_vcpu_arch {
#define __unpack_flag(_set, _f, _m) _f
#define unpack_vcpu_flag(...) __unpack_flag(__VA_ARGS__)
#define __build_check_flag(v, flagset, f, m) \
do { \
typeof(v->arch.flagset) *_fset; \
\
/* Check that the flags fit in the mask */ \
BUILD_BUG_ON(HWEIGHT(m) != HWEIGHT((f) | (m))); \
/* Check that the flags fit in the type */ \
BUILD_BUG_ON((sizeof(*_fset) * 8) <= __fls(m)); \
} while (0)
#define __vcpu_get_flag(v, flagset, f, m) \
({ \
__build_check_flag(v, flagset, f, m); \
\
v->arch.flagset & (m); \
})
@ -442,6 +454,8 @@ struct kvm_vcpu_arch {
do { \
typeof(v->arch.flagset) *fset; \
\
__build_check_flag(v, flagset, f, m); \
\
fset = &v->arch.flagset; \
if (HWEIGHT(m) > 1) \
*fset &= ~(m); \
@ -452,6 +466,8 @@ struct kvm_vcpu_arch {
do { \
typeof(v->arch.flagset) *fset; \
\
__build_check_flag(v, flagset, f, m); \
\
fset = &v->arch.flagset; \
*fset &= ~(m); \
} while (0)