From: Fuad Tabba Date: Tue, 9 Sep 2025 07:24:28 +0000 (+0100) Subject: KVM: arm64: Add build-time check for duplicate DECLARE_REG use X-Git-Tag: v6.18-rc1~95^2~5^2~9^2~8 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f9ac33e45d57bc4aa365363ffb650c830e5bb325;p=thirdparty%2Flinux.git 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 --- 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__ */