x86/asm: Add ASM_UNREACHABLE

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

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Hans Liljestrand <ishkamiel@gmail.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Jann Horn <jannh@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arozansk@redhat.com
Cc: axboe@kernel.dk
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch <linux-arch@vger.kernel.org>
Link: http://lkml.kernel.org/r/1500921349-10803-3-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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