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d98dba8852
Currently, Kbuild produces inconsistent results in some cases.
You can do an interesting experiment using the --shuffle option, which
is supported by GNU Make 4.4 or later.
Set CONFIG_KVM_INTEL=y and CONFIG_KVM_AMD=m (or vice versa), and repeat
incremental builds w/wo --shuffle=reverse.
$ make
[ snip ]
CC arch/x86/kvm/kvm-asm-offsets.s
$ make --shuffle=reverse
[ snip ]
CC [M] arch/x86/kvm/kvm-asm-offsets.s
$ make
[ snip ]
CC arch/x86/kvm/kvm-asm-offsets.s
arch/x86/kvm/kvm-asm-offsets.s is rebuilt every time w/wo the [M] marker.
arch/x86/kvm/kvm-asm-offsets.s is built as built-in when it is built as
a prerequisite of arch/x86/kvm/kvm-intel.o, which is built-in.
arch/x86/kvm/kvm-asm-offsets.s is built as modular when it is built as
a prerequisite of arch/x86/kvm/kvm-amd.o, which is a module.
Another odd example is single target builds.
When CONFIG_LKDTM=m, drivers/misc/lkdtm/rodata.o can be built as
built-in or modular, depending on how it is built.
$ make drivers/misc/lkdtm/lkdtm.o
[ snip ]
CC [M] drivers/misc/lkdtm/rodata.o
$ make drivers/misc/lkdtm/rodata.o
[ snip ]
CC drivers/misc/lkdtm/rodata.o
drivers/misc/lkdtm/rodata.o is built as modular when it is built as a
prerequisite of another, but built as built-in when it is a final
target.
The same thing happens to drivers/memory/emif-asm-offsets.s when
CONFIG_TI_EMIF_SRAM=m.
$ make drivers/memory/ti-emif-sram.o
[ snip ]
CC [M] drivers/memory/emif-asm-offsets.s
$ make drivers/memory/emif-asm-offsets.s
[ snip ]
CC drivers/memory/emif-asm-offsets.s
This is because the part-of-module=y flag defined for the modules is
inherited by its prerequisites.
Target-specific variables are likely intended only for local use.
This commit adds 'private' to them.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.