[PATCH v8 2/3] x86/asm: add ASM_UNREACHABLE

From: Kees Cook
Date: Mon Jul 24 2017 - 14:36:12 EST


This creates an unreachable annotation in asm for CONFIG_STACK_VALIDATION.
While here, adjust earlier uses of \t\n into \n\t.

Suggested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
include/linux/compiler-gcc.h | 13 +++++++++----
include/linux/compiler.h | 3 +++
2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index cd4bbe8242bd..179375b2d862 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -203,11 +203,16 @@

#ifdef CONFIG_STACK_VALIDATION
#define annotate_unreachable() ({ \
- asm("%c0:\t\n" \
- ".pushsection .discard.unreachable\t\n" \
- ".long %c0b - .\t\n" \
- ".popsection\t\n" : : "i" (__LINE__)); \
+ asm("%c0:\n\t" \
+ ".pushsection .discard.unreachable\n\t" \
+ ".long %c0b - .\n\t" \
+ ".popsection\n\t" : : "i" (__LINE__)); \
})
+#define ASM_UNREACHABLE \
+ "999:\n\t" \
+ ".pushsection .discard.unreachable\n\t" \
+ ".long 999b - .\n\t" \
+ ".popsection\n\t"
#else
#define annotate_unreachable()
#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 219f82f3ec1a..641f5912d75f 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -185,6 +185,9 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
#endif

/* Unreachable code */
+#ifndef ASM_UNREACHABLE
+# define ASM_UNREACHABLE
+#endif
#ifndef unreachable
# define unreachable() do { } while (1)
#endif
--
2.7.4