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.  At the top level, is
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config-generic. Add options here that should be present in every possible
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config on all architectures.
Dave Jones ac34e0
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Beneath this are per-arch overrides. For example config-x86-generic add
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additional x86 specific options, and also _override_ any options that were
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set in config-generic.
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The heirarchy looks like this..
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                           config-generic
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                                 |
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                         config-x86-generic
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                         |                |
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             config-x86-32-generic   config-x86-64-generic
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An option set in a lower level will override the same option set in one
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of the higher levels.
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There exist two additional overrides, config-debug, and config-nodebug,
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which override -generic, and the per-arch overrides. It is documented
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further below.
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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 from 'config-debug' 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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To add new debug options, add an option to _both_ config-debug and config-nodebug,
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and also new stanzas to the Makefile 'debug' and 'release' targets.
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Sometimes debug options get added to config-generic, or per-arch overrides
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instead of config-[no]debug. In this instance, the options should have no
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discernable performance impact, otherwise they belong in the debug files.
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