[PATCH] x86: uapi: ptrace: guard register offset macros with __ASSEMBLER__ or __FRAME_OFFSETS

The register offset macros in <asm/ptrace-abi.h> are guarded by
`defined(__ASSEMBLER__) || defined(__FRAME_OFFSETS)` for 64-bit, but
were left unguarded for 32-bit. This causes havoc for userspace that
happens to use identifiers colliding with these short macro names
(e.g., EBX, ECX, EAX, DS, ES, FS, GS, CS, SS). Without this guard,
userspace is forced to be super extra careful with include ordering to
minimize the chance of collision.

Wrap both the 32-bit and 64-bit register definitions under
`#if defined(__ASSEMBLER__) || defined(__FRAME_OFFSETS)`, and ensure
User-Mode Linux (UML) defines `__FRAME_OFFSETS` for 32-bit as well.

Assisted-by: Gemini
Link: https://github.com/llvm/llvm-project/issues/217413
Signed-off-by: Nick Desaulniers <[email protected]>
---
 arch/x86/include/uapi/asm/ptrace-abi.h | 4 ++--
 arch/x86/um/asm/ptrace.h               | 4 +---
 arch/x86/um/ptrace_32.c                | 1 +
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/uapi/asm/ptrace-abi.h b/arch/x86/include/uapi/asm/ptrace-abi.h
index 5823584dea13..3656955c6faa 100644
--- a/arch/x86/include/uapi/asm/ptrace-abi.h
+++ b/arch/x86/include/uapi/asm/ptrace-abi.h
@@ -2,6 +2,7 @@
 #ifndef _ASM_X86_PTRACE_ABI_H
 #define _ASM_X86_PTRACE_ABI_H
 
+#if defined(__ASSEMBLER__) || defined(__FRAME_OFFSETS)
 #ifdef __i386__
 
 #define EBX 0
@@ -25,7 +26,6 @@
 
 #else /* __i386__ */
 
-#if defined(__ASSEMBLER__) || defined(__FRAME_OFFSETS)
 /*
  * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
  * unless syscall needs a complete, fully filled "struct pt_regs".
@@ -57,12 +57,12 @@
 #define EFLAGS 144
 #define RSP 152
 #define SS 160
-#endif /* __ASSEMBLER__ */
 
 /* top of stack page */
 #define FRAME_SIZE 168
 
 #endif /* !__i386__ */
+#endif /* defined(__ASSEMBLER__) || defined(__FRAME_OFFSETS) */
 
 /* Arbitrarily choose the same ptrace numbers as used by the Sparc code. */
 #define PTRACE_GETREGS            12
diff --git a/arch/x86/um/asm/ptrace.h b/arch/x86/um/asm/ptrace.h
index 2641d28d115c..439c4151f6b7 100644
--- a/arch/x86/um/asm/ptrace.h
+++ b/arch/x86/um/asm/ptrace.h
@@ -13,9 +13,7 @@ enum {
 };
 
 #include <linux/compiler.h>
-#ifndef CONFIG_X86_32
-#define __FRAME_OFFSETS /* Needed to get the R* macros */
-#endif
+#define __FRAME_OFFSETS /* Needed to get the register macros */
 #include <asm/ptrace-generic.h>
 
 #define user_mode(r) UPT_IS_USER(&(r)->regs)
diff --git a/arch/x86/um/ptrace_32.c b/arch/x86/um/ptrace_32.c
index 3af3cb821524..9e9155b0e918 100644
--- a/arch/x86/um/ptrace_32.c
+++ b/arch/x86/um/ptrace_32.c
@@ -7,6 +7,7 @@
 #include <linux/sched.h>
 #include <linux/uaccess.h>
 #include <linux/regset.h>
+#define __FRAME_OFFSETS
 #include <asm/ptrace-abi.h>
 #include <registers.h>
 #include <skas.h>

---
base-commit: 26260251022fbc2f248a3d747a9b2b961b18d2d8
change-id: 20260821-ptrace_uapi-462350036cbd

Best regards,
-- 
Nick Desaulniers <[email protected]>