![]() Build a set of section headers for features right after the datas. Each implemented feature will have one of such section header that provides the offset and the size of the data manipulated by the feature. The trace informations have moved after the data and are recorded on exit time. The new layout is as follows: ----------------------- ___ [ magic ] | [ header size ] | [ attr size ] | [ attr content offset ] | [ attr content size ] | [ data offset ] File Headers [ data size ] | [ event_types offset ] | [ event_types size ] | [ feature bitmap ] v [ attr section ] [ events section ] ___ [ X ] | [ X ] | [ X ] Datas [ X ] | [ X ] v ___ [ Feature 1 offset ] | [ Feature 1 size ] Features headers [ Feature 2 offset ] | [ Feature 2 size ] v [ Feature 1 content ] [ Feature 2 content ] ----------------------- We have as many feature's section headers as we have features in use for the current file. Say Feat 1 and Feat 3 are used by the file, but not Feat 2. Then the feature headers will be like follows: [ Feature 1 offset ] | [ Feature 1 size ] Features headers [ Feature 3 offset ] | [ Feature 3 size ] v There is no hole to cover Feature 2 that is not in use here. We only need to cover the needed headers in order, from the lowest feature bit to the highest. Currently we have two features: HEADER_TRACE_INFO and HEADER_BUILD_ID. Both have their contents that follow the feature headers. Putting the contents right after the feature headers is not mandatory though. While we keep the feature headers right after the data and in order, their offsets can point everywhere. We have just put the two above feature contents in the end of the file for convenience. The purpose of this layout change is to have a file format that scales while keeping it simple: having such linear feature headers is less error prone wrt forward/backward compatibility as the content of a feature can be put anywhere, its location can even change by the time, it's fine because its headers will tell where it is. And we know how to find these headers, following the above rules. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> LKML-Reference: <1257911467-28276-6-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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bitmap.h | ||
bitops.h | ||
compiler.h | ||
ctype.h | ||
kernel.h | ||
list.h | ||
module.h | ||
poison.h | ||
prefetch.h | ||
rbtree.h | ||
string.h | ||
types.h |