kbuild: change module.order to list *.o instead of *.ko

scripts/Makefile.build replaces the suffix .o with .ko, then
scripts/Makefile.modpost calls the sed command to change .ko back
to the original .o suffix.

Instead of converting the suffixes back-and-forth, store the .o paths
in modules.order, and replace it with .ko in 'make modules_install'.

This avoids the unneeded sed command.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

kbuild: check module name conflict for external modules as well

If there are multiple modules with the same name in the same external
module tree, there is ambiguity about which one will be loaded, and
very likely something odd is happening.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

kbuild: make module name conflict fatal error

I think all the warnings have been fixed by now. Make it a fatal error.

Check it before modpost because we need to stop building *.ko files.
Also, pass modules.order via a script parameter.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

kbuild: get rid of kernel/ prefix from in-tree modules.{order,builtin}

Removing the 'kernel/' prefix will make our life easier because we can
simply do 'cat modules.order' to get all built modules with full paths.

Currently, we parse the first line of '*.mod' files in $(MODVERDIR).
Since we have duplicated functionality here, I plan to remove MODVERDIR
entirely.

In fact, modules.order is generated also for external modules in a
broken format. It adds the 'kernel/' prefix to the absolute path of
the module, like this:

kernel//path/to/your/external/module/foo.ko

This is fine for now since modules.order is not used for external
modules. However, I want to sanitize the format everywhere towards
the goal of removing MODVERDIR.

We cannot change the format of installed module.{order,builtin}.
So, 'make modules_install' will add the 'kernel/' prefix while copying
them to $(MODLIB)/.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

kbuild: do not check name uniqueness of builtin modules

I just thought it was a good idea to scan builtin.modules in the name
uniqueness checking, but a couple of false positives were found.

Stephen reported a false positive for ppc64_defconfig:

warning: same basename if the following are built as modules:
arch/powerpc/platforms/powermac/nvram.ko
drivers/char/nvram.ko

The former is never built as a module as you see in
arch/powerpc/platforms/powermac/Makefile:

# CONFIG_NVRAM is an arch. independent tristate symbol, for pmac32 we really
# need this to be a bool. Cheat here and pretend CONFIG_NVRAM=m is really
# CONFIG_NVRAM=y
obj-$(CONFIG_NVRAM:m=y) += nvram.o

Another example of false positive is arm64 defconfig:

warning: same basename if the following are built as modules:
arch/arm64/lib/crc32.ko
lib/crc32.ko

It is true CONFIG_CRC32 is a tristate option but it is always 'y' since
it is select'ed by ARM64. Hence, neither of them is built as a module
for the arm64 build.

From the above, modules.builtin essentially contains false positives.
I do not think it is a big deal as far as kmod is concerned, but false
positive warnings in the kernel build make people upset. It is better
to not check it.

Even without builtin.modules checked, we have enough (and more solid)
test coverage with allmodconfig.

While I touched this part, I replaced the sed code with neater one
provided by Stephen.

Link: https://lkml.org/lkml/2019/5/19/120
Link: https://lkml.org/lkml/2019/5/19/123
Fixes: 3a48a91901c5 ("kbuild: check uniqueness of module names")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kbuild: check uniqueness of module names

In the recent build test of linux-next, Stephen saw a build error
caused by a broken .tmp_versions/*.mod file:

https://lkml.org/lkml/2019/5/13/991

drivers/net/phy/asix.ko and drivers/net/usb/asix.ko have the same
basename, and there is a race in generating .tmp_versions/asix.mod

Kbuild has not checked this before, and it suddenly shows up with
obscure error messages when this kind of race occurs.

Non-unique module names cause various sort of problems, but it is
not trivial to catch them by eyes.

Hence, this script.

It checks not only real modules, but also built-in modules (i.e.
controlled by tristate CONFIG option, but currently compiled with =y).
Non-unique names for built-in modules also cause problems because
/sys/modules/ would fall over.

For the latest kernel, I tested "make allmodconfig all" (or more
quickly "make allyesconfig modules"), and it detected the following:

warning: same basename if the following are built as modules:
drivers/regulator/88pm800.ko
drivers/mfd/88pm800.ko
warning: same basename if the following are built as modules:
drivers/gpu/drm/bridge/adv7511/adv7511.ko
drivers/media/i2c/adv7511.ko
warning: same basename if the following are built as modules:
drivers/net/phy/asix.ko
drivers/net/usb/asix.ko
warning: same basename if the following are built as modules:
fs/coda/coda.ko
drivers/media/platform/coda/coda.ko
warning: same basename if the following are built as modules:
drivers/net/phy/realtek.ko
drivers/net/dsa/realtek.ko

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>