KVM: selftests: Assert that vcpu_{g,s}et_reg() won't truncate

Assert that the register being read/written by vcpu_{g,s}et_reg() is no
larger than a uint64_t, i.e. that a selftest isn't unintentionally
truncating the value being read/written.

Ideally, the assert would be done at compile-time, but that would limit
the checks to hardcoded accesses and/or require fancier compile-time
assertion infrastructure to filter out dynamic usage.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20241128005547.4077116-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 287a3ec06df47b440311b15c0d31bfccbd235557..4c4e5a847f67c58d5e68a3a6fa8def4161216de3 100644 (file)
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -707,6 +707,8 @@ static inline uint64_t vcpu_get_reg(struct kvm_vcpu *vcpu, uint64_t id)
        uint64_t val;
        struct kvm_one_reg reg = { .id = id, .addr = (uint64_t)&val };
 
+       TEST_ASSERT(KVM_REG_SIZE(id) <= sizeof(val), "Reg %lx too big", id);
+
        vcpu_ioctl(vcpu, KVM_GET_ONE_REG, &reg);
        return val;
 }
@@ -714,6 +716,8 @@ static inline void vcpu_set_reg(struct kvm_vcpu *vcpu, uint64_t id, uint64_t val
 {
        struct kvm_one_reg reg = { .id = id, .addr = (uint64_t)&val };
 
+       TEST_ASSERT(KVM_REG_SIZE(id) <= sizeof(val), "Reg %lx too big", id);
+
        vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
 }