kbuild: replace $(dot-target).tmp in filechk with $(tmp-target)

$(tmp-target) is a better fit for local use like this.

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

kbuild: replace $(dot-target).tmp in filechk with $(tmp-target)

$(tmp-target) is a better fit for local use like this.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: add more comments for KBUILD_NOCMDDEP=1

The cmd-check for KBUILD_NOCMDDEP=1 may not be clear until you see
commit c4d5ee13984f ("kbuild: make KBUILD_NOCMDDEP=1 handle empty
built-in.o").

Wh

kbuild: add more comments for KBUILD_NOCMDDEP=1

The cmd-check for KBUILD_NOCMDDEP=1 may not be clear until you see
commit c4d5ee13984f ("kbuild: make KBUILD_NOCMDDEP=1 handle empty
built-in.o").

When a phony target (i.e. FORCE) is the only prerequisite, Kbuild
uses a tricky way to detect that the target does not exist.

Add more comments.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: rename cmd_$@ to savedcmd_$@ in *.cmd files

The cmd-check macro compares $(cmd_$@) and $(cmd_$1), but a pitfall is
that you cannot use cmd_<target> as the variable name for the command.

For

kbuild: rename cmd_$@ to savedcmd_$@ in *.cmd files

The cmd-check macro compares $(cmd_$@) and $(cmd_$1), but a pitfall is
that you cannot use cmd_<target> as the variable name for the command.

For example, the following code will not work in the top Makefile
or ./Kbuild.

quiet_cmd_foo = GEN $@
cmd_foo = touch $@

targets += foo
foo: FORCE
$(call if_changed,foo)

In this case, both $@ and $1 are expanded to 'foo', so $(cmd_check)
is always empty.

We do not need to use the same prefix for cmd_$@ and cmd_$1.
Rename the former to savedcmd_$@.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: allow to combine multiple V= levels

Commit a6de553da01c ("kbuild: Allow to combine multiple W= levels")
supported W=123 to enable all the extra warning groups.

I think a similar idea is app

kbuild: allow to combine multiple V= levels

Commit a6de553da01c ("kbuild: Allow to combine multiple W= levels")
supported W=123 to enable all the extra warning groups.

I think a similar idea is applicable to the V= option.

V=1 echos the whole command
V=2 prints the reason for rebuilding

These are orthogonal, and can be enabled at the same time.

This commit supports V=12 to enable both of them.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: print short log in addition to the whole command with V=1

"make V=1" prints the whole command instead of the short log, but I
think it is nicer to print both so that you can easily spot the

kbuild: print short log in addition to the whole command with V=1

"make V=1" prints the whole command instead of the short log, but I
think it is nicer to print both so that you can easily spot the build
rule of your interest.

This commit changes V=1 to print the short log (the line starts with
'#'), followed by the full log.

In parallel builds, the short/full logs from the same build rule may
be interspersed. If you want to avoid it, please add -Otarget option.
Kbuild will never set it by default because Make would buffer the logs
and lose the escape sequences. (Modern compilers print warnings and
errors in color, but only when they write to a terminal.)

This is also a preparation for supporting V=12 because V=2 appends the
reason for rebuilding to the short log.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: use .NOTINTERMEDIATE for future GNU Make versions

In Kbuild, some files are generated by chains of pattern/implicit rules.
For example, *.dtb.o files in drivers/of/unittest-data/Makefile are

kbuild: use .NOTINTERMEDIATE for future GNU Make versions

In Kbuild, some files are generated by chains of pattern/implicit rules.
For example, *.dtb.o files in drivers/of/unittest-data/Makefile are
generated by the chain of 3 pattern rules, like this:

%.dts -> %.dtb -> %.dtb.S -> %.dtb.o

Here, %.dts is the real source, %.dtb.o is the final target.
%.dtb and %.dtb.S are called "intermediate files".

As GNU Make manual [1] says, intermediate files are treated differently
in two ways:

(a) The first difference is what happens if the intermediate file does
not exist. If an ordinary file 'b' does not exist, and make considers
a target that depends on 'b', it invariably creates 'b' and then
updates the target from 'b'. But if 'b' is an intermediate file, then
make can leave well enough alone: it won't create 'b' unless one of
its prerequisites is out of date. This means the target depending
on 'b' won't be rebuilt either, unless there is some other reason
to update that target: for example the target doesn't exist or a
different prerequisite is newer than the target.

(b) The second difference is that if make does create 'b' in order to
update something else, it deletes 'b' later on after it is no longer
needed. Therefore, an intermediate file which did not exist before
make also does not exist after make. make reports the deletion to
you by printing a 'rm' command showing which file it is deleting.

The combination of these is problematic for Kbuild because most of the
build rules depend on FORCE and the if_changed* macros really determine
if the target should be updated. So, all missing files, whether they
are intermediate or not, are always rebuilt.

To see the problem, delete ".SECONDARY:" from scripts/Kbuild.include,
and repeat this command:

$ make allmodconfig drivers/of/unittest-data/

The intermediate files will be deleted, which results in rebuilding
intermediate and final objects in the next run of make.

In the old days, people suppressed (b) in inconsistent ways.
As commit 54a702f70589 ("kbuild: mark $(targets) as .SECONDARY and
remove .PRECIOUS markers") noted, you should not use .PRECIOUS because
.PRECIOUS has the following behavior (c), which is not likely what you
want.

(c) If make is killed or interrupted during the execution of their
recipes, the target is not deleted. Also, the target is not deleted
on error even if .DELETE_ON_ERROR is specified.

.SECONDARY is a much better way to disable (b), but a small problem
is that .SECONDARY enables (a), which gives a side-effect to $?;
prerequisites marked as .SECONDARY do not appear in $?. This is a
drawback for Kbuild.

I thought it was a bug and opened a bug report. As Paul, the GNU Make
maintainer, concluded in [2], this is not a bug.

A good news is that, GNU Make 4.4 added the perfect solution,
.NOTINTERMEDIATE, which cancels both (a) and (b).

For clarificaton, my understanding of .INTERMEDIATE, .SECONDARY,
.PRECIOUS and .NOTINTERMEDIATE are as follows:

(a) (b) (c)
.INTERMEDIATE enable enable disable
.SECONDARY enable disable disable
.PRECIOUS disable disable enable
.NOTINTERMEDIATE disable disable disable

However, GNU Make 4.4 has a bug for the global .NOTINTERMEDIATE. [3]
It was fixed by commit 6164608900ad ("[SV 63417] Ensure global
.NOTINTERMEDIATE disables all intermediates"), and will be available
in the next release of GNU Make.

The following is the gain for .NOTINTERMEDIATE:

[Current Make]

$ make allnoconfig vmlinux
[ full build ]
$ rm include/linux/device.h
$ make vmlinux
CALL scripts/checksyscalls.sh

Make does not notice the removal of <linux/device.h>.

[Future Make]

$ make-latest allnoconfig vmlinux
[ full build ]
$ rm include/linux/device.h
$ make-latest vmlinux
CC arch/x86/kernel/asm-offsets.s
In file included from ./include/linux/writeback.h:13,
from ./include/linux/memcontrol.h:22,
from ./include/linux/swap.h:9,
from ./include/linux/suspend.h:5,
from arch/x86/kernel/asm-offsets.c:13:
./include/linux/blk_types.h:11:10: fatal error: linux/device.h: No such file or directory
11 | #include <linux/device.h>
| ^~~~~~~~~~~~~~~~
compilation terminated.
make-latest[1]: *** [scripts/Makefile.build:114: arch/x86/kernel/asm-offsets.s] Error 1
make-latest: *** [Makefile:1282: prepare0] Error 2

Make notices the removal of <linux/device.h>, and rebuilds objects
that depended on <linux/device.h>. There exists a source file that
includes <linux/device.h>, and it raises an error.

To see detailed background information, refer to commit 2d3b1b8f0da7
("kbuild: drop $(wildcard $^) check in if_changed* for faster rebuild").

[1]: https://www.gnu.org/software/make/manual/make.html#Chained-Rules
[2]: https://savannah.gnu.org/bugs/?55532
[3]: https://savannah.gnu.org/bugs/?63417

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

show more ...

kbuild: add read-file macro

Since GNU Make 4.2, $(file ...) supports the read operater '<', which
is useful to read a file without forking a new process. No warning is
shown even if the input file i

kbuild: add read-file macro

Since GNU Make 4.2, $(file ...) supports the read operater '<', which
is useful to read a file without forking a new process. No warning is
shown even if the input file is missing.

For older Make versions, it falls back to the cat command.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Tested-by: Alexander Lobakin <alexandr.lobakin@intel.com>

show more ...

kbuild: add test-{ge,gt,le,lt} macros

GNU Make 4.4 introduced $(intcmp ...), which is useful to compare two
integers without forking a new process.

Add test-{ge,gt,le,lt} macros, which work more ef

kbuild: add test-{ge,gt,le,lt} macros

GNU Make 4.4 introduced $(intcmp ...), which is useful to compare two
integers without forking a new process.

Add test-{ge,gt,le,lt} macros, which work more efficiently with GNU
Make >= 4.4. For older Make versions, they fall back to the 'test'
shell command.

The first two parameters to $(intcmp ...) must not be empty. To avoid
the syntax error, I appended '0' to them. Fortunately, '00' is treated
as '0'. This is needed because CONFIG options may expand to an empty
string when the kernel configuration is not included.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: add kbuild-file macro

While building, installing, cleaning, Kbuild visits sub-directories
and includes 'Kbuild' or 'Makefile' that exists there.

Add 'kbuild-file' macro, and reuse it from s

kbuild: add kbuild-file macro

While building, installing, cleaning, Kbuild visits sub-directories
and includes 'Kbuild' or 'Makefile' that exists there.

Add 'kbuild-file' macro, and reuse it from scripts/Makefie.*

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Tested-by: Alexander Lobakin <alobakin@pm.me>

show more ...

kbuild: remove the target in signal traps when interrupted

When receiving some signal, GNU Make automatically deletes the target if
it has already been changed by the interrupted recipe.

If the tar

kbuild: remove the target in signal traps when interrupted

When receiving some signal, GNU Make automatically deletes the target if
it has already been changed by the interrupted recipe.

If the target is possibly incomplete due to interruption, it must be
deleted so that it will be remade from scratch on the next run of make.
Otherwise, the target would remain corrupted permanently because its
timestamp had already been updated.

Thanks to this behavior of Make, you can stop the build any time by
pressing Ctrl-C, and just run 'make' to resume it.

Kbuild also relies on this feature, but it is equivalently important
for any build systems that make decisions based on timestamps (if you
want to support Ctrl-C reliably).

However, this does not always work as claimed; Make immediately dies
with Ctrl-C if its stderr goes into a pipe.

[Test Makefile]

foo:
echo hello > $@
sleep 3
echo world >> $@

[Test Result]

$ make # hit Ctrl-C
echo hello > foo
sleep 3
^Cmake: *** Deleting file 'foo'
make: *** [Makefile:3: foo] Interrupt

$ make 2>&1 | cat # hit Ctrl-C
echo hello > foo
sleep 3
^C$ # 'foo' is often left-over

The reason is because SIGINT is sent to the entire process group.
In this example, SIGINT kills 'cat', and 'make' writes the message to
the closed pipe, then dies with SIGPIPE before cleaning the target.

A typical bad scenario (as reported by [1], [2]) is to save build log
by using the 'tee' command:

$ make 2>&1 | tee log

This can be problematic for any build systems based on Make, so I hope
it will be fixed in GNU Make. The maintainer of GNU Make stated this is
a long-standing issue and difficult to fix [3]. It has not been fixed
yet as of writing.

So, we cannot rely on Make cleaning the target. We can do it by
ourselves, in signal traps.

As far as I understand, Make takes care of SIGHUP, SIGINT, SIGQUIT, and
SITERM for the target removal. I added the traps for them, and also for
SIGPIPE just in case cmd_* rule prints something to stdout or stderr
(but I did not observe an actual case where SIGPIPE was triggered).

[Note 1]

The trap handler might be worth explaining.

rm -f $@; trap - $(sig); kill -s $(sig) $$

This lets the shell kill itself by the signal it caught, so the parent
process can tell the child has exited on the signal. Generally, this is
a proper manner for handling signals, in case the calling program (like
Bash) may monitor WIFSIGNALED() and WTERMSIG() for WCE although this may
not be a big deal here because GNU Make handles SIGHUP, SIGINT, SIGQUIT
in WUE and SIGTERM in IUE.

IUE - Immediate Unconditional Exit
WUE - Wait and Unconditional Exit
WCE - Wait and Cooperative Exit

For details, see "Proper handling of SIGINT/SIGQUIT" [4].

[Note 2]

Reverting 392885ee82d3 ("kbuild: let fixdep directly write to .*.cmd
files") would directly address [1], but it only saves if_changed_dep.
As reported in [2], all commands that use redirection can potentially
leave an empty (i.e. broken) target.

[Note 3]

Another (even safer) approach might be to always write to a temporary
file, and rename it to $@ at the end of the recipe.

<command> > $(tmp-target)
mv $(tmp-target) $@

It would require a lot of Makefile changes, and result in ugly code,
so I did not take it.

[Note 4]

A little more thoughts about a pattern rule with multiple targets (or
a grouped target).

%.x %.y: %.z
<recipe>

When interrupted, GNU Make deletes both %.x and %.y, while this solution
only deletes $@. Probably, this is not a big deal. The next run of make
will execute the rule again to create $@ along with the other files.

[1]: https://lore.kernel.org/all/YLeot94yAaM4xbMY@gmail.com/
[2]: https://lore.kernel.org/all/20220510221333.2770571-1-robh@kernel.org/
[3]: https://lists.gnu.org/archive/html/help-make/2021-06/msg00001.html
[4]: https://www.cons.org/cracauer/sigint.html

Fixes: 392885ee82d3 ("kbuild: let fixdep directly write to .*.cmd files")
Reported-by: Ingo Molnar <mingo@kernel.org>
Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

show more ...

kbuild: add cmd_and_savecmd macro

Separate out the command execution part of if_changed, as we did
for if_changed_dep.

This allows us to reuse it in if_changed_rule.

define rule_foo
$(

kbuild: add cmd_and_savecmd macro

Separate out the command execution part of if_changed, as we did
for if_changed_dep.

This allows us to reuse it in if_changed_rule.

define rule_foo
$(call cmd_and_savecmd,foo)
$(call cmd,bar)
endef

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

show more ...

kbuild: do not create *.prelink.o for Clang LTO or IBT

When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted

kbuild: do not create *.prelink.o for Clang LTO or IBT

When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted
to ELF.

CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until
objects are merged together.

This commit stops generating *.prelink.o, so the build flow will look
similar with/without LTO.

The following figures show how the LTO build currently works, and
how this commit is changing it.

Current build flow
==================

[1] single-object module

$(LD)
$(CC) +objtool $(LD)
foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko
(LLVM IR) (ELF) | (ELF)
|
foo.mod.o --/
(LLVM IR)

[2] multi-object module
$(LD)
$(CC) $(AR) +objtool $(LD)
foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko
| (archive) (ELF) | (ELF)
foo2.c -----> foo2.o --/ |
(LLVM IR) foo.mod.o --/
(LLVM IR)

One confusion is that foo.o in multi-object module is an archive
despite of its suffix.

New build flow
==============

[1] single-object module

Since there is only one object, there is no need to keep the LLVM IR.
Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO
is disabled, $(LD) is unneeded because $(CC) produces an ELF object.

$(CC)+$(LD)+objtool $(LD)
foo.c ----------------------------> foo.o ---------> foo.ko
(ELF) | (ELF)
|
foo.mod.o --/
(LLVM IR)

[2] multi-object module

Previously, $(AR) was used to combine LLVM IR files into an archive,
but there was no technical reason to do so. Use $(LD) to merge them
into a single ELF object.

$(LD)
$(CC) +objtool $(LD)
foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko
| (ELF) | (ELF)
foo2.c ---------> foo2.o ----/ |
(LLVM IR) foo.mod.o --/
(LLVM IR)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>

show more ...

certs: simplify $(srctree)/ handling and remove config_filename macro

The complex macro, config_filename, was introduced to do:

[1] drop double-quotes from the string value
[2] add $(srctree)/ pr

certs: simplify $(srctree)/ handling and remove config_filename macro

The complex macro, config_filename, was introduced to do:

[1] drop double-quotes from the string value
[2] add $(srctree)/ prefix in case the file is not found in $(objtree)
[3] escape spaces and more

[1] will be more generally handled by Kconfig later.

As for [2], Kbuild uses VPATH to search for files in $(objtree),
$(srctree) in this order. GNU Make can natively handle it.

As for [3], converting $(space) to $(space_escape) back and forth looks
questionable to me. It is well-known that GNU Make cannot handle file
paths with spaces in the first place.

Instead of using the complex macro, use $< so it will be expanded to
the file path of the key.

Remove config_filename, finally.

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

show more ...

kbuild: remove the target in signal traps when interrupted

[ Upstream commit a7f3257da8a86b96fb9bf1bba40ae0bbd7f1885a ]

When receiving some signal, GNU Make automatically deletes the target if
it h

kbuild: remove the target in signal traps when interrupted

[ Upstream commit a7f3257da8a86b96fb9bf1bba40ae0bbd7f1885a ]

When receiving some signal, GNU Make automatically deletes the target if
it has already been changed by the interrupted recipe.

If the target is possibly incomplete due to interruption, it must be
deleted so that it will be remade from scratch on the next run of make.
Otherwise, the target would remain corrupted permanently because its
timestamp had already been updated.

Thanks to this behavior of Make, you can stop the build any time by
pressing Ctrl-C, and just run 'make' to resume it.

Kbuild also relies on this feature, but it is equivalently important
for any build systems that make decisions based on timestamps (if you
want to support Ctrl-C reliably).

However, this does not always work as claimed; Make immediately dies
with Ctrl-C if its stderr goes into a pipe.

[Test Makefile]

foo:
echo hello > $@
sleep 3
echo world >> $@

[Test Result]

$ make # hit Ctrl-C
echo hello > foo
sleep 3
^Cmake: *** Deleting file 'foo'
make: *** [Makefile:3: foo] Interrupt

$ make 2>&1 | cat # hit Ctrl-C
echo hello > foo
sleep 3
^C$ # 'foo' is often left-over

The reason is because SIGINT is sent to the entire process group.
In this example, SIGINT kills 'cat', and 'make' writes the message to
the closed pipe, then dies with SIGPIPE before cleaning the target.

A typical bad scenario (as reported by [1], [2]) is to save build log
by using the 'tee' command:

$ make 2>&1 | tee log

This can be problematic for any build systems based on Make, so I hope
it will be fixed in GNU Make. The maintainer of GNU Make stated this is
a long-standing issue and difficult to fix [3]. It has not been fixed
yet as of writing.

So, we cannot rely on Make cleaning the target. We can do it by
ourselves, in signal traps.

As far as I understand, Make takes care of SIGHUP, SIGINT, SIGQUIT, and
SITERM for the target removal. I added the traps for them, and also for
SIGPIPE just in case cmd_* rule prints something to stdout or stderr
(but I did not observe an actual case where SIGPIPE was triggered).

[Note 1]

The trap handler might be worth explaining.

rm -f $@; trap - $(sig); kill -s $(sig) $$

This lets the shell kill itself by the signal it caught, so the parent
process can tell the child has exited on the signal. Generally, this is
a proper manner for handling signals, in case the calling program (like
Bash) may monitor WIFSIGNALED() and WTERMSIG() for WCE although this may
not be a big deal here because GNU Make handles SIGHUP, SIGINT, SIGQUIT
in WUE and SIGTERM in IUE.

IUE - Immediate Unconditional Exit
WUE - Wait and Unconditional Exit
WCE - Wait and Cooperative Exit

For details, see "Proper handling of SIGINT/SIGQUIT" [4].

[Note 2]

Reverting 392885ee82d3 ("kbuild: let fixdep directly write to .*.cmd
files") would directly address [1], but it only saves if_changed_dep.
As reported in [2], all commands that use redirection can potentially
leave an empty (i.e. broken) target.

[Note 3]

Another (even safer) approach might be to always write to a temporary
file, and rename it to $@ at the end of the recipe.

<command> > $(tmp-target)
mv $(tmp-target) $@

It would require a lot of Makefile changes, and result in ugly code,
so I did not take it.

[Note 4]

A little more thoughts about a pattern rule with multiple targets (or
a grouped target).

%.x %.y: %.z
<recipe>

When interrupted, GNU Make deletes both %.x and %.y, while this solution
only deletes $@. Probably, this is not a big deal. The next run of make
will execute the rule again to create $@ along with the other files.

[1]: https://lore.kernel.org/all/YLeot94yAaM4xbMY@gmail.com/
[2]: https://lore.kernel.org/all/20220510221333.2770571-1-robh@kernel.org/
[3]: https://lists.gnu.org/archive/html/help-make/2021-06/msg00001.html
[4]: https://www.cons.org/cracauer/sigint.html

Fixes: 392885ee82d3 ("kbuild: let fixdep directly write to .*.cmd files")
Reported-by: Ingo Molnar <mingo@kernel.org>
Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

kbuild: warn if FORCE is missing for if_changed(_dep,_rule) and filechk

if_changed, if_changed_dep, and if_changed_rule must have FORCE as a
prerequisite so the command line change is detected.

Doc

kbuild: warn if FORCE is missing for if_changed(_dep,_rule) and filechk

if_changed, if_changed_dep, and if_changed_rule must have FORCE as a
prerequisite so the command line change is detected.

Documentation/kbuild/makefiles.rst clearly explains it:

Note: It is a typical mistake to forget the FORCE prerequisite.

However, not all people follow the document.

This mistake occurred again and again, so a compelling force is needed.

Show a warning if FORCE is missing in the prerequisite of if_changed
and friends. Same for filechk.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <n.schier@avm.de>

show more ...

kbuild: macrofy the condition of if_changed and friends

Add a new macro that expands into $(newer-prereqs)$(cmd-check).

It makes it easier to add common code for if_changed, if_changed_dep,
and if_

kbuild: macrofy the condition of if_changed and friends

Add a new macro that expands into $(newer-prereqs)$(cmd-check).

It makes it easier to add common code for if_changed, if_changed_dep,
and if_changed_rule.

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

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kbuild: sink stdout from cmd for silent build

When building with 'make -s', no output to stdout should be printed.

As Arnd Bergmann reported [1], mkimage shows the detailed information
of the gener

kbuild: sink stdout from cmd for silent build

When building with 'make -s', no output to stdout should be printed.

As Arnd Bergmann reported [1], mkimage shows the detailed information
of the generated images.

I think this should be suppressed by the 'cmd' macro instead of by
individual scripts.

Insert 'exec >/dev/null;' in order to redirect stdout to /dev/null for
silent builds.

[Note about this implementation]

'exec >/dev/null;' may look somewhat tricky, but this has a reason.

Appending '>/dev/null' at the end of command line is a common way for
redirection, so I first tried this:

cmd = @set -e; $(echo-cmd) $(cmd_$(1)) >/dev/null

... but it would not work if $(cmd_$(1)) itself contains a redirection.

For example, cmd_wrap in scripts/Makefile.asm-generic redirects the
output from the 'echo' command into the target file.

It would be expanded into:

echo "#include <asm-generic/$*.h>" > $@ >/dev/null

Then, the target file gets empty because the string will go to /dev/null
instead of $@.

Next, I tried this:

cmd = @set -e; $(echo-cmd) { $(cmd_$(1)); } >/dev/null

The form above would be expanded into:

{ echo "#include <asm-generic/$*.h>" > $@; } >/dev/null

This works as expected. However, it would be a syntax error if
$(cmd_$(1)) is empty.

When CONFIG_TRIM_UNUSED_KSYMS is disabled, $(call cmd,gen_ksymdeps) in
scripts/Makefile.build would be expanded into:

set -e; { ; } >/dev/null

..., which causes an syntax error.

I also tried this:

cmd = @set -e; $(echo-cmd) ( $(cmd_$(1)) ) >/dev/null

... but this causes a syntax error for the same reason.

So, finally I adopted:

cmd = @set -e; $(echo-cmd) exec >/dev/null; $(cmd_$(1))

[1]: https://lore.kernel.org/lkml/20210514135752.2910387-1-arnd@kernel.org/

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

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kbuild: split cc-option and friends to scripts/Makefile.compiler

scripts/Kbuild.include is included everywhere, but macros such as
cc-option are needed by build targets only.

For example, when 'mak

kbuild: split cc-option and friends to scripts/Makefile.compiler

scripts/Kbuild.include is included everywhere, but macros such as
cc-option are needed by build targets only.

For example, when 'make clean' traverses the tree, it does not need
to evaluate $(call cc-option,).

Split cc-option, ld-option, etc. to scripts/Makefile.compiler, which
is only included from the top Makefile and scripts/Makefile.build.

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

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kbuild: remove ld-version macro

There is no direct user of ld-version; you can use CONFIG_LD_VERSION
if needed.

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

kbuild: remove ld-version macro

There is no direct user of ld-version; you can use CONFIG_LD_VERSION
if needed.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>

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kbuild: sink stdout from cmd for silent build

[ Upstream commit 174a1dcc96429efce4ef7eb2f5c4506480da2182 ]

When building with 'make -s', no output to stdout should be printed.

As Arnd Bergmann rep

kbuild: sink stdout from cmd for silent build

[ Upstream commit 174a1dcc96429efce4ef7eb2f5c4506480da2182 ]

When building with 'make -s', no output to stdout should be printed.

As Arnd Bergmann reported [1], mkimage shows the detailed information
of the generated images.

I think this should be suppressed by the 'cmd' macro instead of by
individual scripts.

Insert 'exec >/dev/null;' in order to redirect stdout to /dev/null for
silent builds.

[Note about this implementation]

'exec >/dev/null;' may look somewhat tricky, but this has a reason.

Appending '>/dev/null' at the end of command line is a common way for
redirection, so I first tried this:

cmd = @set -e; $(echo-cmd) $(cmd_$(1)) >/dev/null

... but it would not work if $(cmd_$(1)) itself contains a redirection.

For example, cmd_wrap in scripts/Makefile.asm-generic redirects the
output from the 'echo' command into the target file.

It would be expanded into:

echo "#include <asm-generic/$*.h>" > $@ >/dev/null

Then, the target file gets empty because the string will go to /dev/null
instead of $@.

Next, I tried this:

cmd = @set -e; $(echo-cmd) { $(cmd_$(1)); } >/dev/null

The form above would be expanded into:

{ echo "#include <asm-generic/$*.h>" > $@; } >/dev/null

This works as expected. However, it would be a syntax error if
$(cmd_$(1)) is empty.

When CONFIG_TRIM_UNUSED_KSYMS is disabled, $(call cmd,gen_ksymdeps) in
scripts/Makefile.build would be expanded into:

set -e; { ; } >/dev/null

..., which causes an syntax error.

I also tried this:

cmd = @set -e; $(echo-cmd) ( $(cmd_$(1)) ) >/dev/null

... but this causes a syntax error for the same reason.

So, finally I adopted:

cmd = @set -e; $(echo-cmd) exec >/dev/null; $(cmd_$(1))

[1]: https://lore.kernel.org/lkml/20210514135752.2910387-1-arnd@kernel.org/

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

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kbuild: remove leftover comment for filechk utility

After commit 43fee2b23895 ("kbuild: do not redirect the first
prerequisite for filechk"), the rule is no longer automatically passed
$< as stdin,

kbuild: remove leftover comment for filechk utility

After commit 43fee2b23895 ("kbuild: do not redirect the first
prerequisite for filechk"), the rule is no longer automatically passed
$< as stdin, so remove the stale comment.

Fixes: 43fee2b23895 ("kbuild: do not redirect the first prerequisite for filechk")
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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kbuild: stop filtering out $(GCC_PLUGINS_CFLAGS) from cc-option base

Commit d26e94149276 ("kbuild: no gcc-plugins during cc-option tests")
was neeeded because scripts/Makefile.gcc-plugins was too ea

kbuild: stop filtering out $(GCC_PLUGINS_CFLAGS) from cc-option base

Commit d26e94149276 ("kbuild: no gcc-plugins during cc-option tests")
was neeeded because scripts/Makefile.gcc-plugins was too early.

This is unneeded by including scripts/Makefile.gcc-plugins last,
and being careful to not add cc-option tests after it.

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

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kbuild: improve cc-option to clean up all temporary files

When cc-option and friends evaluate compiler flags, the temporary file
$$TMP is created as an output object, and automatically cleaned up.
T

kbuild: improve cc-option to clean up all temporary files

When cc-option and friends evaluate compiler flags, the temporary file
$$TMP is created as an output object, and automatically cleaned up.
The actual file path of $$TMP is .<pid>.tmp, here <pid> is the process
ID of $(shell ...) invoked from cc-option. (Please note $$$$ is the
escape sequence of $$).

Such garbage files are cleaned up in most cases, but some compiler flags
create additional output files.

For example, -gsplit-dwarf creates a .dwo file.

When CONFIG_DEBUG_INFO_SPLIT=y, you will see a bunch of .<pid>.dwo files
left in the top of build directories. You may not notice them unless you
do 'ls -a', but the garbage files will increase every time you run 'make'.

This commit changes the temporary object path to .tmp_<pid>/tmp, and
removes .tmp_<pid> directory when exiting. Separate build artifacts such
as *.dwo will be cleaned up all together because their file paths are
usually determined based on the base name of the object.

Another example is -ftest-coverage, which outputs the coverage data into
<base-name-of-object>.gcno

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

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kbuild: use -MMD instead of -MD to exclude system headers from dependency

This omits system headers from the generated header dependency.

System headers are not updated unless you upgrade the compi

kbuild: use -MMD instead of -MD to exclude system headers from dependency

This omits system headers from the generated header dependency.

System headers are not updated unless you upgrade the compiler. Nor do
they contain CONFIG options, so fixdep does not need to parse them.

Having said that, the effect of this optimization will be quite small
because the kernel code generally does not include system headers
except <stdarg.h>. Host programs include a lot of system headers,
but there are not so many in the kernel tree.

At first, keeping system headers in .*.cmd files might be useful to
detect the compiler update, but there is no guarantee that <stdarg.h>
is included from every file. So, I implemented a more reliable way in
the previous commit.

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

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kbuild: remove *.tmp file when filechk fails

Bartosz Golaszewski reports that when "make {menu,n,g,x}config" fails
due to missing packages, a temporary file is left over, which is not
ignored by git

kbuild: remove *.tmp file when filechk fails

Bartosz Golaszewski reports that when "make {menu,n,g,x}config" fails
due to missing packages, a temporary file is left over, which is not
ignored by git.

For example, if GTK+ is not installed:

$ make gconfig
*
* Unable to find the GTK+ installation. Please make sure that
* the GTK+ 2.0 development package is correctly installed.
* You need gtk+-2.0 gmodule-2.0 libglade-2.0
*
scripts/kconfig/Makefile:208: recipe for target 'scripts/kconfig/gconf-cfg' failed
make[1]: *** [scripts/kconfig/gconf-cfg] Error 1
Makefile:567: recipe for target 'gconfig' failed
make: *** [gconfig] Error 2
$ git status
HEAD detached at v5.4
Untracked files:
(use "git add <file>..." to include in what will be committed)

scripts/kconfig/gconf-cfg.tmp

nothing added to commit but untracked files present (use "git add" to track)

This is because the check scripts are run with filechk, which misses
to clean up the temporary file on failure.

When the line

{ $(filechk_$(1)); } > $@.tmp;

... fails, it exits immediately due to the 'set -e'. Use trap to make
sure to delete the temporary file on exit.

For extra safety, I replaced $@.tmp with $(dot-target).tmp to make it
a hidden file.

Reported-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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