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  1. Jul 10, 2019
    • Masahiro Yamada's avatar
      kbuild: add a flag to force absolute path for srctree · 95fd3f87
      Masahiro Yamada authored 
      
In old days, Kbuild always used an absolute path for $(srctree).

Since commit 890676c6 ("kbuild: Use relative path when building in
the source tree"), $(srctree) is '.' when O= was not passed from the
command line.

Yet, using absolute paths is useful in some cases even without O=, for
instance, to create a cscope file with absolute path tags.

'O=.' was known to work as a workaround to force Kbuild to use absolute
paths even when you are building in the source tree.

Since commit 25b146c5 ("kbuild: allow Kbuild to start from any
directory"), Kbuild is too clever to be tricked. Even if you pass 'O=.'
Kbuild notices you are building in the source tree, then use '.' for
$(srctree).

So, 'make O=. cscope' is no help to create absolute path tags.

We cannot force one or the other according to commit e93bc1a0
("Revert "kbuild: specify absolute paths for cscope""). Both of
relative path and absolute path have pros and cons.

This commit adds a new flag KBUILD_ABS_SRCTREE to allow users to
choose the absolute path for $(srctree).

'make KBUILD_ABS_SRCTREE=1 cscope' will work as a replacement of
'make O=. cscope'.

Reported-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      95fd3f87
    • Masahiro Yamada's avatar
      kbuild: replace KBUILD_SRCTREE with boolean building_out_of_srctree · 051f278e
      Masahiro Yamada authored 
      
Commit 25b146c5 ("kbuild: allow Kbuild to start from any directory")
deprecated KBUILD_SRCTREE.

It is only used in tools/testing/selftest/ to distinguish out-of-tree
build. Replace it with a new boolean flag, building_out_of_srctree.

I also replaced the conditional ($(srctree),.) because the next commit
will allow an absolute path to be used for $(srctree) even when building
in the source tree.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      051f278e
  3. Jul 09, 2019
    • Masahiro Yamada's avatar
      scripts/tags.sh: remove unused environment variables from comments · b3b3eb9d
      Masahiro Yamada authored 
      
This script has no reference to ${ARCH}, ${src}, ${obj}.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      b3b3eb9d
    • Masahiro Yamada's avatar
      scripts/tags.sh: drop SUBARCH support for ARM · d1db881d
      Masahiro Yamada authored 
      
Our goal is to have more and more sub-architectures to join the
ARM multi-platform, and support them in a single configuration.

Remove the ARM SUBARCH support because it is ugly.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      d1db881d
    • Masahiro Yamada's avatar
      kbuild: support header-test-pattern-y · 1e21cbfa
      Masahiro Yamada authored 
      
In my view, most of headers can be self-contained. So, it would be
tedious to add every header to header-test-y explicitly. We usually
end up with "all headers with some exceptions".

There are two types in exceptions:

[1] headers that are never compiled as standalone units

  For examples, include/linux/compiler-gcc.h is not intended for
  direct inclusion. We should always exclude such ones.

[2] headers that are conditionally compiled as standalone units

  Some headers can be compiled only for particular architectures.
  For example, include/linux/arm-cci.h can be compiled only for
  arm/arm64 because it requires <asm/arm-cci.h> to exist.
  Clang can compile include/soc/nps/mtm.h only for arc because
  it contains an arch-specific register in inline assembler.

So, you can write Makefile like this:

  header-test-                += linux/compiler-gcc.h
  header-test-$(CONFIG_ARM)   += linux/arm-cci.h
  header-test-$(CONFIG_ARM64) += linux/arm-cci.h
  header-test-$(CONFIG_ARC)   += soc/nps/mtm.h

The new syntax header-test-pattern-y will be useful to specify
"the rest".

The typical usage is like this:

  header-test-pattern-y += */*.h

This will add all the headers in sub-directories to the test coverage,
excluding $(header-test-). In this regards, header-test-pattern-y
behaves like a weaker variant of header-test-y.

Caveat:
The patterns in header-test-pattern-y are prefixed with $(srctree)/$(src)/
but not $(objtree)/$(obj)/. Stale generated headers are often left over
when you traverse the git history without cleaning. Wildcard patterns for
$(objtree) may match to stale headers, which could fail to compile.
One pitfall is $(srctree)/$(src)/ and $(objtree)/$(obj)/ point to the
same directory for in-tree building. So, header-test-pattern-y should
be used with care since it can potentially match to stale headers.

Caveat2:
You could use wildcard for header-test-. For example,

  header-test- += asm-generic/%

... will exclude headers in asm-generic directory. Unfortunately, the
wildcard character is '%' instead of '*' here because this is evaluated
by $(filter-out ...) whereas header-test-pattern-y is evaluated by
$(wildcard ...). This is a kludge, but seems useful in some places...

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: default avatarJani Nikula <jani.nikula@intel.com>
      1e21cbfa
    • Masahiro Yamada's avatar
      kbuild: do not create wrappers for header-test-y · c93a0368
      Masahiro Yamada authored 
      
header-test-y does not work with headers in sub-directories.

For example, you may want to write a Makefile, like this:

include/linux/Kbuild:

  header-test-y += mtd/nand.h

This entry will create a wrapper include/linux/mtd/nand.hdrtest.c
with the following content:

  #include "mtd/nand.h"

To make this work, we need to add $(srctree)/include/linux to the
header search path. It would be tedious to add ccflags-y.

Instead, we could change the *.hdrtest.c rule to wrap:

  #include "nand.h"

This works for in-tree build since #include "..." searches in the
relative path from the header with this directive. For O=... build,
we need to add $(srctree)/include/linux/mtd to the header search path,
which will be even more tedious.

After all, I thought it would be handier to compile headers directly
without creating wrappers.

I added a new build rule to compile %.h into %.h.s

The target is %.h.s instead of %.h.o because it is slightly faster.
Also, as for GCC, an empty assembly is smaller than an empty object.

I wrote the build rule:

  $(CC) $(c_flags) -S -o $@ -x c /dev/null -include $<

instead of:

  $(CC) $(c_flags) -S -o $@ -x c $<

Both work fine with GCC, but the latter is bad for Clang.

This comes down to the difference in the -Wunused-function policy.
GCC does not warn about unused 'static inline' functions at all.
Clang does not warn about the ones in included headers, but does
about the ones in the source. So, we should handle headers as
headers, not as source files.

In fact, this has been hidden since commit abb2ea7d ("compiler,
clang: suppress warning for unused static inline functions"), but we
should not rely on that.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: default avatarJani Nikula <jani.nikula@intel.com>
Tested-by: default avatarJani Nikula <jani.nikula@intel.com>
      c93a0368
  5. Jul 07, 2019
  7. Jul 01, 2019
    • Masahiro Yamada's avatar
      fixdep: check return value of printf() and putchar() · 6f9ac9f4
      Masahiro Yamada authored 
      
When there is not enough space on your storage device, the build will
fail with 'No space left on device' error message.

The reason is obvious from the message, so you will free up some disk
space, then you will resume the build.

However, sometimes you may still see a mysterious error message:

  unterminated call to function 'wildcard': missing ')'.

If you run out of the disk space, fixdep may end up with generating
incomplete .*.cmd files.

For example, if the disk-full error occurs while fixdep is running
print_dep(), the .*.cmd might be truncated like this:

   $(wildcard include/config/

When you run 'make' next time, this broken .*.cmd will be included,
then Make will terminate parsing since it is a wrong syntax.

Once this happens, you need to run 'make clean' or delete the broken
.*.cmd file manually.

Even if you do not see any error message, the .*.cmd files after any
error could be potentially incomplete, and unreliable. You may miss
the re-compilation due to missing header dependency.

If printf() cannot output the string for disk shortage or whatever
reason, it returns a negative value, but currently fixdep does not
check it at all. Consequently, fixdep *successfully* generates a
broken .*.cmd file. Make never notices that since fixdep exits with 0,
which means success.

Given the intended usage of fixdep, it must respect the return value
of not only malloc(), but also printf() and putchar().

This seems a long-standing issue since the introduction of fixdep.

In old days, Kbuild tried to provide an extra safety by letting fixdep
output to a temporary file and renaming it after everything is done:

  scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\
  rm -f $(depfile);                                                    \
  mv -f $(dot-target).tmp $(dot-target).cmd)

It was no help to avoid the current issue; fixdep successfully created
a truncated tmp file, which would be renamed to a .*.cmd file.

This problem should be fixed by propagating the error status to the
build system because:

[1] Since commit 9c2af1c7 ("kbuild: add .DELETE_ON_ERROR special
    target"), Make will delete the target automatically on any failure
    in the recipe.

[2] Since commit 392885ee ("kbuild: let fixdep directly write to
    .*.cmd files"), .*.cmd file is included only when the corresponding
    target already exists.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      6f9ac9f4
    • Masahiro Yamada's avatar
      kbuild: save $(strip ...) for calling if_changed and friends · c2341e2a
      Masahiro Yamada authored 
      
The string returned by $(filter-out ...) does not contain any leading
or trailing spaces.

With the previous commit, 'any-prereq' no longer contains any
excessive spaces.

Nor does 'cmd-check' since it expands to a $(filter-out ...) call.

So, only the space that matters is the one between 'any-prereq'
and 'cmd-check'.

By removing it from the code, we can save $(strip ...) evaluation.
This refactoring is possible because $(any-prereq)$(cmd-check) is only
passed to the first argument of $(if ...), so we are only interested
in whether or not it is empty.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      c2341e2a
    • Masahiro Yamada's avatar
      kbuild: save $(strip ...) for calling any-prepreq · 93f31bbd
      Masahiro Yamada authored 
      
The string returned by $(filter-out ...) does not contain any leading
or trailing spaces.

So, only the space that matters is the one between

  $(filter-out $(PHONY),$?)

and

  $(filter-out $(PHONY) $(wildcard $^),$^)

By removing it from the code, we can save $(strip ...) evaluation.
This refactoring is possible because $(any-prereq) is only passed to
the first argument of $(if ...), so we are only interested in whether
or not it is empty.

This is also the prerequisite for the next commit.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      93f31bbd
    • Masahiro Yamada's avatar
      kbuild: rename arg-check to cmd-check · 50bcca6a
      Masahiro Yamada authored 
      
I prefer 'cmd-check' for consistency.

We have 'echo-cmd', 'cmd', 'cmd_and_fixdep', etc. in this file.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      50bcca6a
  9. Jun 23, 2019
  11. Jun 15, 2019
    • Jani Nikula's avatar
      kbuild: add support for ensuring headers are self-contained · e846f0dc
      Jani Nikula authored 
      
Sometimes it's useful to be able to explicitly ensure certain headers
remain self-contained, i.e. that they are compilable as standalone
units, by including and/or forward declaring everything they depend on.

Add special target header-test-y where individual Makefiles can add
headers to be tested if CONFIG_HEADER_TEST is enabled. This will
generate a dummy C file per header that gets built as part of extra-y.

Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Reviewed-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      e846f0dc
    • Masahiro Yamada's avatar
      kbuild: deb-pkg: do not run headers_check · 0315bb7a
      Masahiro Yamada authored 
      
It is absolutely fine to add extra sanity checks in package scripts,
but it is not necessary to do so.

This is already covered by the daily compile-testing (0day bot etc.)
because headers_check is run as a part of the normal build process
when CONFIG_HEADERS_CHECK=y.

Replace it with the newly-added "make headers".

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      0315bb7a
    • Masahiro Yamada's avatar
      kbuild: simplify scripts/headers_install.sh · 555187a8
      Masahiro Yamada authored 
      
Now that headers_install.sh is invoked per file, remove the for-loop
in the shell script.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      555187a8
    • Masahiro Yamada's avatar
      kbuild: move hdr-inst shorthand to top Makefile · a5bae54c
      Masahiro Yamada authored 
      
Now that hdr-inst is used only in the top Makefile, move it there
from scripts/Kbuild.include.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      a5bae54c
    • Masahiro Yamada's avatar
      kbuild: re-implement Makefile.headersinst without recursion · d5470d14
      Masahiro Yamada authored 
      
Since commit fcc8487d ("uapi: export all headers under uapi
directories"), the headers in uapi directories are all exported by
default although exceptional cases are still allowed by the syntax
'no-export-headers'.

The traditional directory descending has been kept (in a somewhat
hacky way), but it is actually unneeded.

Get rid of it to simplify the code.

Also, handle files one by one instead of the previous per-directory
processing. This will emit much more log, but I like it.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      d5470d14
    • Masahiro Yamada's avatar
      kbuild: add 'headers' target to build up uapi headers in usr/include · 59b2bd05
      Masahiro Yamada authored 
      
In Linux build system, build targets and installation targets are
separated.

Examples are:

 - 'make vmlinux' -> 'make install'
 - 'make modules' -> 'make modules_install'
 - 'make dtbs'    -> 'make dtbs_install'
 - 'make vdso'    -> 'make vdso_install'

The intention is to run the build targets under the normal privilege,
then the installation targets under the root privilege since we need
the write permission to the system directories.

We have 'make headers_install' but the corresponding 'make headers'
stage does not exist. The purpose of headers_install is to provide
the kernel interface to C library. So, nobody would try to install
headers to /usr/include directly.

If 'sudo make INSTALL_HDR_PATH=/usr/include headers_install' were run,
some build artifacts in the kernel tree would be owned by root because
some of uapi headers are generated by 'uapi-asm-generic', 'archheaders'
targets.

Anyway, I believe it makes sense to split the header installation into
two stages.

 [1] 'make headers'
    Process headers in uapi directories by scripts/headers_install.sh
    and copy them to usr/include

 [2] 'make headers_install'
    Copy '*.h' verbatim from usr/include to $(INSTALL_HDR_PATH)/include

For the backward compatibility, 'headers_install' depends on 'headers'.

Some samples expect uapi headers in usr/include. So, the 'headers'
target is useful to build up them in the fixed location usr/include
irrespective of INSTALL_HDR_PATH.

Another benefit is to stop polluting the final destination with the
time-stamp files '.install' and '.check'. Maybe you can see them in
your toolchains.

Lastly, my main motivation is to prepare for compile-testing uapi
headers. To build something, we have to save an object and .*.cmd
somewhere. The usr/include/ will be the work directory for that.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      59b2bd05
    • Masahiro Yamada's avatar
      kbuild: remove build_unifdef target in scripts/Makefile · 2b8481be
      Masahiro Yamada authored 
      
Since commit 2aedcd09 ("kbuild: suppress annoying "... is up to date."
message"), if_changed and friends nicely suppress "is up to date" messages.

We do not need per-Makefile tricks.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      2b8481be
    • Masahiro Yamada's avatar
      kbuild: remove headers_{install,check}_all · f3c8d4c7
      Masahiro Yamada authored 
      
headers_install_all does not make much sense any more because different
architectures export different set of uapi/linux/ headers. As you see
in include/uapi/linux/Kbuild, the installation of a.out.h, kvm.h, and
kvm_para.h is arch-dependent. So, headers_install_all repeats the
installation/removal of them.

If somebody really thinks it is useful to do headers_install for all
architectures, it would be possible by small shell-scripting, but
the top Makefile does not have to provide entry targets just for that
purpose.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
      f3c8d4c7
  13. Jun 09, 2019
    • Mathieu Malaterre's avatar
      kbuild: Remove -Waggregate-return from scripts/Makefile.extrawarn · 869ee58b
      Mathieu Malaterre authored 
      
It makes little sense to pass -Waggregate-return these days since large
part of the linux kernel rely on returning struct(s). For instance:

  ../include/linux/timekeeping.h: In function 'show_uptime':
  ../include/linux/ktime.h:91:34: error: function call has aggregate value [-Werror=aggregate-return]
   #define ktime_to_timespec64(kt)  ns_to_timespec64((kt))
                                    ^~~~~~~~~~~~~~~~~~~~~~
  ../include/linux/timekeeping.h:166:8: note: in expansion of macro 'ktime_to_timespec64'
    *ts = ktime_to_timespec64(ktime_get_coarse_boottime());

Remove this warning from W=2 completely.

Signed-off-by: default avatarMathieu Malaterre <malat@debian.org>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      869ee58b
  15. Jun 07, 2019
    • Masahiro Yamada's avatar
      kbuild: use more portable 'command -v' for cc-cross-prefix · 913ab978
      Masahiro Yamada authored 
      To print the pathname that will be used by shell in the current
environment, 'command -v' is a standardized way. [1]

'which' is also often used in scripts, but it is less portable.

When I worked on commit bd55f96f ("kbuild: refactor cc-cross-prefix
implementation"), I was eager to use 'command -v' but it did not work.
(The reason is explained below.)

I kept 'which' as before but got rid of '> /dev/null 2>&1' as I
thought it was no longer needed. Sorry, I was wrong.

It works well on my Ubuntu machine, but Alexey Brodkin reports noisy
warnings on CentOS7 when 'which' fails to find the given command in
the PATH environment.

  $ which foo
  which: no foo in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin)

Given that behavior of 'which' depends on system (and it may not be
installed by default), I want to try 'command -v' once again.

The specification [1] clearly describes the behavior of 'command -v'
when the given command is not found:

  Otherwise, no output shall be written and the exit status shall reflect
  that the name was not found.

However, we need a little magic to use 'command -v' from Make.

$(shell ...) passes the argument to a subshell for execution, and
returns the standard output of the command.

Here is a trick. GNU Make may optimize this by executing the command
directly instead of forking a subshell, if no shell special characters
are found in the command and omitting the subshell will not change the
behavior.

In this case, no shell special character is used. So, Make will try
to run it directly. However, 'command' is a shell-builtin command,
then Make would fail to find it in the PATH environment:

  $ make ARCH=m68k defconfig
  make: command: Command not found
  make: command: Command not found
  make: command: Command not found

In fact, Make has a table of shell-builtin commands because it must
ask the shell to execute them.

Until recently, 'command' was missing in the table.

This issue was fixed by the following commit:

| commit 1af314465e5dfe3e8baa839a32a72e83c04f26ef
| Author: Paul Smith <psmith@gnu.org>
| Date:   Sun Nov 12 18:10:28 2017 -0500
|
|     * job.c: Add "command" as a known shell built-in.
|
|     This is not a POSIX shell built-in but it's common in UNIX shells.
|     Reported by Nick Bowler <nbowler@draconx.ca>.

Because the latest release is GNU Make 4.2.1 in 2016, this commit is
not included in any released versions. (But some distributions may
have back-ported it.)

We need to trick Make to spawn a subshell. There are various ways to
do so:

 1) Use a shell special character '~' as dummy

    $(shell : ~; command -v $(c)gcc)

 2) Use a variable reference that always expands to the empty string
    (suggested by David Laight)

    $(shell command$${x:+} -v $(c)gcc)

 3) Use redirect

    $(shell command -v $(c)gcc 2>/dev/null)

I chose 3) to not confuse people. The stderr would not be polluted
anyway, but it will provide extra safety, and is easy to understand.

Tested on Make 3.81, 3.82, 4.0, 4.1, 4.2, 4.2.1

[1] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html



Fixes: bd55f96f ("kbuild: refactor cc-cross-prefix implementation")
Cc: linux-stable <stable@vger.kernel.org> # 5.1
Reported-by: default avatarAlexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: default avatarAlexey Brodkin <abrodkin@synopsys.com>
      913ab978
  17. Jun 05, 2019
  19. Jun 04, 2019
  21. Jun 01, 2019