From f9ac33e45d57bc4aa365363ffb650c830e5bb325 Mon Sep 17 00:00:00 2001 From: Fuad Tabba Date: Tue, 9 Sep 2025 08:24:28 +0100 Subject: [PATCH] KVM: arm64: Add build-time check for duplicate DECLARE_REG use The DECLARE_REG() macro provides a convenient way to create a local variable initialized from a cpu context in the hyp trap handlers. However, a common error is to use the macro multiple times in the same scope with the same register index, but for different logical purposes. This results in valid C code that compiles without error, but introduces subtle bugs where a developer expects two different variables to hold values from two different registers, when in fact they are both sourced from the same one. To prevent this entire class of bugs, modify the DECLARE_REG() macro to declare a dummy variable whose name is derived from the register index. If the macro is used again with the same index in the same scope, the compiler will fail with a "redeclaration of variable" error, turning a subtle runtime bug into an obvious build-time failure. Signed-off-by: Fuad Tabba Tested-by: Mark Brown Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/include/nvhe/trap_handler.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/include/nvhe/trap_handler.h b/arch/arm64/kvm/hyp/include/nvhe/trap_handler.h index 1e6d995968a1f..ba5382c127870 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/trap_handler.h +++ b/arch/arm64/kvm/hyp/include/nvhe/trap_handler.h @@ -12,7 +12,8 @@ #include #define cpu_reg(ctxt, r) (ctxt)->regs.regs[r] -#define DECLARE_REG(type, name, ctxt, reg) \ +#define DECLARE_REG(type, name, ctxt, reg) \ + __always_unused int ___check_reg_ ## reg; \ type name = (type)cpu_reg(ctxt, (reg)) #endif /* __ARM64_KVM_NVHE_TRAP_HANDLER_H__ */ -- 2.47.3