Messages in this thread Patch in this message | | | Date | Tue, 2 Oct 2007 08:10:08 -0400 | From | Mathieu Desnoyers <> | Subject | [PATCH] Linux Kernel Markers - Alignment Fix |
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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 <mathieu.desnoyers@polymtl.ca> CC: Christoph Hellwig <hch@infradead.org> CC: Mike Mason <mmlnx@us.ibm.com> CC: "Frank Ch. Eigler" <fche@redhat.com> --- 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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