objtool, compiler.h: Fix __unreachable section relocation size

Linus reported the following commit broke module loading on his laptop:

  d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")

It showed errors like the following:

  module: overflow in relocation type 10 val ffffffffc02afc81
  module: 'nvme' likely not compiled with -mcmodel=kernel

The problem is that the __unreachable section addresses are stored using
the '.long' asm directive, which isn't big enough for .text section
kernel addresses.  Use relative addresses instead:

  ".long %c0b - .\t\n"

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/20170301060504.oltm3iws6fmubnom@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 76e28c22980586a6aa1cc3114b79de7cb5001fcd..b6bb9019d87f5e011e424a15a468d437815b3eae 100644 (file)
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -201,7 +201,7 @@
 #define annotate_unreachable() ({                                      \
        asm("%c0:\t\n"                                                  \
            ".pushsection __unreachable, \"a\"\t\n"                     \
-           ".long %c0b\t\n"                                            \
+           ".long %c0b - .\t\n"                                        \
            ".popsection\t\n" : : "i" (__LINE__));                      \
 })
 #else