Omnibook Configuration Tools & Patches / Bugs / #14 Doesn't work in kernel 2.6.33.3 and higher

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Anonymous - 2011-01-12

I've tracked this to an alignment issue in the initialization code. This module uses a section(.features) directive to register all of its features into a portion of the .data section, and then defines a start and end pointer via sections.lds which it pulls back into init.c. It then iterates over &_start_features_driver[i] to test all of the defined features, one at a time.

The failed paging request appears to be happening because of unexpected linker behavior, possibly only on x86_64, and possibly due to a change in GNU ld or gcc since 2007. I used objdump -t on omnibook.ko, and found that while the sizeof(omnibook_feature) was 104, the alignment was sometimes 104 and sometimes 108. This caused the array math in the feature loop to misaddress the struct omnibook_feature found in the .feature section, eventually leading to invalid calls and the above crash.

Now, I'm not a kernel hacker, and I haven't done any C programming since college. I fixed this on my Toshiba Satellite L355D-S7901 running kernel 2.6.35 on arch x86_64 by padding struct omnibook_feature to 128 bytes, via a char pad[24] at the end of the struct. Perhaps someone who is a more skilled C programmer or kernel hacker can think of a better way to make this work, and to guarantee that it works on both 32 and 64 bit architectures.

I've tracked this to an alignment issue in the initialization code. This module uses a section\(.features\) directive to register all of its features into a portion of the .data section, and then defines a start and end pointer via sections.lds which it pulls back into init.c. It then iterates over &\_start\_features\_driver\[i\] to test all of the defined features, one at a time. The failed paging request appears to be happening because of unexpected linker behavior, possibly only on x86\_64, and possibly due to a change in GNU ld or gcc since 2007. I used objdump -t on omnibook.ko, and found that while the sizeof\(omnibook\_feature\) was 104, the alignment was sometimes 104 and sometimes 108. This caused the array math in the feature loop to misaddress the struct omnibook\_feature found in the .feature section, eventually leading to invalid calls and the above crash. Now, I'm not a kernel hacker, and I haven't done any C programming since college. I fixed this on my Toshiba Satellite L355D-S7901 running kernel 2.6.35 on arch x86\_64 by padding struct omnibook\_feature to 128 bytes, via a char pad\[24\] at the end of the struct. Perhaps someone who is a more skilled C programmer or kernel hacker can think of a better way to make this work, and to guarantee that it works on both 32 and 64 bit architectures.

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Anonymous - 2011-01-12

diff -upr omnibook-2.20090714/omnibook.h omnibook-devel/omnibook.h
--- omnibook-2.20090714/omnibook.h 2009-03-09 13:17:06.000000000 -0400
+++ omnibook-devel/omnibook.h 2011-01-12 18:37:23.105608868 -0500
@@ -66,6 +66,7 @@ struct omnibook_feature {
struct omnibook_tbl *tbl;
struct omnibook_operation *io_op;
struct list_head list;
+ char pad[24];
};

/*

diff -upr omnibook-2.20090714/omnibook.h omnibook-devel/omnibook.h \--- omnibook-2.20090714/omnibook.h 2009-03-09 13:17:06.000000000 -0400 +++ omnibook-devel/omnibook.h 2011-01-12 18:37:23.105608868 -0500 @@ -66,6 +66,7 @@ struct omnibook\_feature \{ struct omnibook\_tbl \*tbl; struct omnibook\_operation \*io\_op; struct list\_head list; \+ char pad\[24\]; \}; /\*

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Anonymous - 2011-01-13

see more info at https://bugzilla.redhat.com/show_bug.cgi?id=669239

see more info at https://bugzilla.redhat.com/show\_bug.cgi?id=669239

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Ryan Martin - 2011-01-13

Sorry, I posted those comments from google accounts using an OpenID that wasn't associated to my account. Please follow up with me!

I'm not sure how to get my patches into the upstream project, hoping someone can help with that!

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Anonymous - 2011-08-13

seems to work on 2.6.38-7 with one change to your patch with a Toshiba A100 ...
using long pad[3] which i only found after doing more digging around online after reading your post

seems to work on 2.6.38-7 with one change to your patch with a Toshiba A100 ... using long pad\[3\] which i only found after doing more digging around online after reading your post

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Doesn't work in kernel 2.6.33.3 and higher

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#14 Doesn't work in kernel 2.6.33.3 and higher

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