From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

Fix the alignment of the struct marker declaration in the trace_mark()
macro.  Otherwise, we run into problems on 64 bits architectures where the
struct marker structure is bigger than 32 bytes : gcc becomes
alignment-happy and align these structures on 32 bytes while the iteration
on the markers is itself only aligned on 8 bytes, as specified by the type
attribute.  Specifying the alignmentof the type only is not enough to
restrain gcc happiness; we must specify a variable alignment attribute too.

This bug causes NULL pointer dereference at module load time on x86_64 when
we load marker-example.ko.

Thanks to Mike Mason for reporting this.

It applies to 2.6.23-rc8-mm2, after the linux kernel markers coding style
fixes. This is an important bugfix that should be merged with the
markers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mike Mason <mmlnx@us.ibm.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


diff -puN include/linux/marker.h~linux-kernel-markers-alignment-fix include/linux/marker.h
--- a/include/linux/marker.h~linux-kernel-markers-alignment-fix
+++ a/include/linux/marker.h
@@ -58,7 +58,7 @@ struct marker {
 		__attribute__((section("__markers_strings")))		\
 		= format;						\
 		static struct marker __mark_##name			\
-		__attribute__((section("__markers"))) =			\
+		__attribute__((section("__markers"), aligned(8))) =	\
 		{ __mstrtab_name_##name, __mstrtab_format_##name,	\
 		0, __mark_empty_function, NULL };			\
 		asm volatile("" : : "i" (&__mark_##name));		\
_