kernel oops due to aligment error in cmdlinepart.c

George G. Davis
2003-08-01T00:02:50Z

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Greetings,

I've been using the latest MTD CVS (+/- a few days) on an ARM Integrator/CM920T
running linux-2.4.20'ish and have found that cmdlinepart.c has a struct alignment
problem which causes a kernel oops. The attached patch fixes the alignment problem
for me (YMMV : ). I've successfully tested this on an ARM Integrator/CM920T, ADS
Graphics Client Plus and TI Innovator/OMAP1510, FWIW. : )

--
Regards,
George

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Index: drivers/mtd/cmdlinepart.c
===================================================================
RCS file: /home/cvs/mtd/drivers/mtd/cmdlinepart.c,v
retrieving revision 1.10
diff -u -r1.10 cmdlinepart.c
--- drivers/mtd/cmdlinepart.c 29 May 2003 09:25:22 -0000 1.10
+++ drivers/mtd/cmdlinepart.c 31 Jul 2003 23:48:20 -0000
@@ -241,6 +241,7 @@
&num_parts, /* out: number of parts */
0, /* first partition */
(unsigned char**)&this_mtd, /* out: extra mem */
+ __alignof__(*this_mtd) - 1 +
mtd_id_len + 1 + sizeof(*this_mtd));
if(!parts)
{
@@ -252,7 +253,21 @@
* unlikely to succeed in parsing any more
*/
return 0;
- }
+ }
+
+ if ((unsigned long)(this_mtd) & (__alignof__(*this_mtd) - 1))
+ {
+ /* Some archs do not allow non-aligned accesses
+ * within the kernel. So make sure we're properly
+ * aligned here.
+ */
+ unsigned long fixup = (unsigned long) this_mtd;
+ dbg(("this_mtd: 0x%0x\n", this_mtd));
+ fixup += __alignof__(*this_mtd) - 1;
+ fixup &= ~(__alignof__(*this_mtd) - 1);
+ this_mtd = (struct cmdline_mtd_partition *) fixup;
+ dbg(("this_mtd: 0x%0x (aligned)\n", this_mtd));
+ }

/* enter results */
this_mtd->parts = parts;