Mike McGrath c7a89c
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		Kernel package tips & tricks.
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		~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The kernel is one of the more complicated packages in the distro, and
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for the newcomer, some of the voodoo in the spec file can be somewhat scary.
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This file attempts to document some of the magic.
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Speeding up make prep
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The kernel is nearly 500MB of source code, and as such, 'make prep'
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takes a while. The spec file employs some trickery so that repeated
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invocations of make prep don't take as long.  Ordinarily the %prep
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phase of a package will delete the tree it is about to untar/patch.
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The kernel %prep keeps around an unpatched version of the tree,
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and makes a symlink tree clone of that clean tree and than applies
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the patches listed in the spec to the symlink tree.
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This makes a huge difference if you're doing multiple make preps a day.
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As an added bonus, doing a diff between the clean tree and the symlink
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tree is slightly faster than it would be doing two proper copies of the tree.
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build logs.
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-----------
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There's a convenience helper script in scripts/grab-logs.sh
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that will grab the build logs from koji for the kernel version reported
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by make verrel
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config heirarchy.
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-----------------
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Instead of having to maintain a config file for every arch variant we build on,
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the kernel spec uses a nested system of configs. Each option CONFIG_FOO is
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represented by a single file named CONFIG_FOO which contains the state (=y, =m,
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=n). These options are collected in the folder base-generic. Architecture
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specific options are set in nested folders. An option set in a nested folder
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will override the same option set in one of the higher levels.
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The individual CONFIG_FOO files only exist in the pkg-git repository. The RPM
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contains kernel-foo.config files which are the result of combining all the
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CONFIG_FOO files. The files are combined by running build_configs.sh. This
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script _must_ be run each time one of the options is changed.
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Example flow:
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# Enable the option CONFIG_ABC123 as a module for all arches
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echo "CONFIG_ABC123=m" > configs/base-generic/CONFIG_ABC1234
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# enable the option CONFIG_XYZ321 for only x86
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echo "# CONFIG_XYZ321 is not set" > configs/base-generic/CONFIG_XYZ321
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echo "CONFIG_XYZ321=m" > configs/base-generic/x86/CONFIG_XYZ321
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# regenerate the combined config files
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./build_configs.sh
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The file config_generation gives a listing of what folders go into each
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config file generated.
Dave Jones ac34e0
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debug options.
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--------------
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This is a little complicated, as the purpose & meaning of this changes
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depending on where we are in the release cycle.
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If we are building for a current stable release, 'make release' has
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typically been run already, which sets up the following..
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- Two builds occur, a 'kernel' and a 'kernel-debug' flavor.
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- kernel-debug will get various heavyweight debugging options like
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  lockdep etc turned on.
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If we are building for rawhide, 'make debug' has been run, which changes
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the status quo to:
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- We only build one kernel 'kernel'
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- The debug options are always turned on.
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This is done to increase coverage testing, as not many people actually
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run kernel-debug.
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The debug options are managed in a separate heierarchy under base-debug. This
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works in a similar manner to base-generic. More deeply nested folders, again,
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override options. The file config_generation gives a listing of what folders
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go into each config file generated.