From 9a3784a897d37af33c922984985f9dd4c82bc292 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 21 May 2026 02:04:33 +0200 Subject: [PATCH] riscv: Implement _THIS_IP_ using inline asm Both GCC [1] and Clang [2] consider the generic version of _THIS_IP_ to be broken: #define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; }) In particular, the address of a label is only expected to be used with a computed goto. While the generic version more or less works today, it is known to be brittle and may break with current and future optimizations. For example, Clang -O2 always returns 1 when this function is inlined: static inline unsigned long get_ip(void) { return ({ __label__ __here; __here: (unsigned long)&&__here; }); } Fix it by overriding _THIS_IP_ in (which is included by ) using an architecture-specific inline asm version. Additionally, avoiding taking the address of a label prevents compilers from emitting spurious indirect branch targets (e.g. ENDBR or BTI) under control-flow integrity schemes. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120071 [1] Link: https://github.com/llvm/llvm-project/issues/138272 [2] Signed-off-by: Marco Elver Signed-off-by: Linux RISC-V bot --- arch/riscv/include/asm/linkage.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/riscv/include/asm/linkage.h b/arch/riscv/include/asm/linkage.h index 9e88ba23cd2bc9..7e0210ef4eb4d6 100644 --- a/arch/riscv/include/asm/linkage.h +++ b/arch/riscv/include/asm/linkage.h @@ -9,4 +9,6 @@ #define __ALIGN .balign 4 #define __ALIGN_STR ".balign 4" +#define _THIS_IP_ ({ unsigned long __ip; asm volatile("auipc %0, 0" : "=r" (__ip)); __ip; }) + #endif /* _ASM_RISCV_LINKAGE_H */