Linux Kernel Markers - Alignment Fix
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 <[email protected]>
CC: Christoph Hellwig <[email protected]>
CC: Mike Mason <[email protected]>
CC: "Frank Ch. Eigler" <[email protected]>
---
include/linux/marker.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux-2.6-lttng/include/linux/marker.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/marker.h 2007-10-02 07:33:21.000000000 -0400
+++ linux-2.6-lttng/include/linux/marker.h 2007-10-02 07:33:58.000000000 -0400
@@ -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)); \
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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