linux.git/scripts/Kbuild.include, branch v5.0-rc2

kbuild: use assignment instead of define ... endef for filechk_* rules

2019-01-06T01:22:35+00:00

You do not have to use define ... endef for filechk_* rules.

For simple cases, the use of assignment looks cleaner, IMHO.

I updated the usage for scripts/Kbuild.include in case somebody
misunderstands the 'define ... endif' is the requirement.

Signed-off-by: Masahiro Yamada 
Acked-by: Heiko Carstens

kbuild: change filechk to surround the given command with { }

2019-01-06T00:46:51+00:00

filechk_* rules often consist of multiple 'echo' lines. They must be
surrounded with { } or ( ) to work correctly. Otherwise, only the
string from the last 'echo' would be written into the target.

Let's take care of that in the 'filechk' in scripts/Kbuild.include
to clean up filechk_* rules.

Signed-off-by: Masahiro Yamada

Merge tag 'kbuild-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2018-12-29T20:03:17+00:00

Pull Kbuild updates from Masahiro Yamada:
 "Kbuild core:
   - remove unneeded $(call cc-option,...) switches
   - consolidate Clang compiler flags into CLANG_FLAGS
   - announce the deprecation of SUBDIRS
   - fix single target build for external module
   - simplify the dependencies of 'prepare' stage targets
   - allow fixdep to directly write to .*.cmd files
   - simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS
   - change if_changed_rule to accept multi-line recipe
   - move .SECONDARY special target to scripts/Kbuild.include
   - remove redundant 'set -e'
   - improve parallel execution for CONFIG_HEADERS_CHECK
   - misc cleanups

  Treewide fixes and cleanups
   - set Clang flags correctly for PowerPC boot images
   - fix UML build error with CONFIG_GCC_PLUGINS
   - remove unneeded patterns from .gitignore files
   - refactor firmware/Makefile
   - remove unneeded rules for *offsets.s
   - avoid unneeded regeneration of intermediate .s files
   - clean up ./Kbuild

  Modpost:
   - remove unused -M, -K options
   - fix false positive warnings about section mismatch
   - use simple devtable lookup instead of linker magic
   - misc cleanups

  Coccinelle:
   - relax boolinit.cocci checks for overall consistency
   - fix warning messages of boolinit.cocci

  Other tools:
   - improve -dirty check of scripts/setlocalversion
   - add a tool to generate compile_commands.json from .*.cmd files"

* tag 'kbuild-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (51 commits)
  kbuild: remove unused cmd_gentimeconst
  kbuild: remove $(obj)/ prefixes in ./Kbuild
  treewide: add intermediate .s files to targets
  treewide: remove explicit rules for *offsets.s
  firmware: refactor firmware/Makefile
  firmware: remove unnecessary patterns from .gitignore
  scripts: remove unnecessary ihex2fw and check-lc_ctypes from .gitignore
  um: remove unused filechk_gen_header in Makefile
  scripts: add a tool to produce a compile_commands.json file
  kbuild: add -Werror=implicit-int flag unconditionally
  kbuild: add -Werror=strict-prototypes flag unconditionally
  kbuild: add -fno-PIE flag unconditionally
  scripts: coccinelle: Correct warning message
  scripts: coccinelle: only suggest true/false in files that already use them
  kbuild: handle part-of-module correctly for *.ll and *.symtypes
  kbuild: refactor part-of-module
  kbuild: refactor quiet_modtag
  kbuild: remove redundant quiet_modtag for $(obj-m)
  kbuild: refactor Makefile.asm-generic
  user/Makefile: Fix typo and capitalization in comment section
  ...

Revert "kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs"

2018-12-19T11:00:28+00:00

This reverts commit 77b0bf55bc675233d22cd5df97605d516d64525e.

See this commit for details about the revert:

  e769742d3584 ("Revert "x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs"")

 Conflicts:
	arch/x86/Makefile

Reported-by: Masahiro Yamada 
Reviewed-by: Borislav Petkov 
Reviewed-by: Thomas Gleixner 
Cc: Juergen Gross 
Cc: Richard Biener 
Cc: Kees Cook 
Cc: Segher Boessenkool 
Cc: Ard Biesheuvel 
Cc: Peter Zijlstra 
Cc: Josh Poimboeuf 
Cc: Nadav Amit 
Cc: Linus Torvalds 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

kbuild: move .SECONDARY special target to Kbuild.include

2018-12-02T05:11:49+00:00

In commit 54a702f70589 ("kbuild: mark $(targets) as .SECONDARY and
remove .PRECIOUS markers"), I missed one important feature of the
.SECONDARY target:

    .SECONDARY with no prerequisites causes all targets to be
    treated as secondary.

... which agrees with the policy of Kbuild.

Let's move it to scripts/Kbuild.include, with no prerequisites.

Note:
If an intermediate file is generated by $(call if_changed,...), you
still need to add it to "targets" so its .*.cmd file is included.

The arm/arm64 crypto files are generated by $(call cmd,shipped),
so they do not need to be added to "targets", but need to be added
to "clean-files" so "make clean" can properly clean them away.

Signed-off-by: Masahiro Yamada

kbuild: refactor if_changed

2018-12-01T14:13:14+00:00

'@set -e; $(echo-cmd) $(cmd_$(1)' can be replaced with '$(cmd)'.

Signed-off-by: Masahiro Yamada

kbuild: remove trailing semicolon from cmd_* passed to if_changed_rule

2018-12-01T14:13:14+00:00

With the change of rule_cc_o_c / rule_as_o_S in the last commit, each
command is executed in a separate subshell. Rip off unneeded semicolons.

Signed-off-by: Masahiro Yamada

kbuild: change if_changed_rule for multi-line recipe

2018-12-01T14:13:14+00:00

The 'define' ... 'endef' directive is useful to confine a series of
shell commands into a single macro:

  define foo
          [action1]
          [action2]
          [action3]
  endif

Each action is executed in a separate subshell.

However, rule_cc_o_c and rule_as_o_S in scripts/Makefile.build are
written as follows (with a trailing semicolon in each cmd_*):

  define rule_cc_o_c
          [action1] ; \
          [action2] ; \
          [action3] ;
  endef

All shell commands are concatenated with '; \' so that it looks like
a single command from the Makefile point of view. This does not
exploit the benefits of 'define' ... 'endef' form because a single
shell command can be more simply written, like this:

  rule_cc_o_c = \
          [action1] ; \
          [action2] ; \
          [action3] ;

I guess the intention for the command concatenation was to let the
'@set -e' in if_changed_rule cover all the commands.

We can improve the readability by moving '@set -e' to the 'cmd' macro.
The combo of $(call echo-cmd,*) $(cmd_*) in rule_cc_o_c and rule_as_o_S
have been replaced with $(call cmd,*). The trailing back-slashes have
been removed.

Here is a note about the performance: the commands in rule_cc_o_c and
rule_as_o_S were previously executed all together in a single subshell,
but now each line in a separate subshell. This means Make will spawn
extra subshells [1]. I measured the build performance for
  x86_64_defconfig + CONFIG_MODVERSIONS + CONFIG_TRIM_UNUSED_KSYMS
and I saw slight performance regression, but I believe code readability
and maintainability wins.

[1] Precisely, 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 line and omitting the subshell
    will not change the behavior.

Signed-off-by: Masahiro Yamada

kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS

2018-12-01T14:13:14+00:00

My main motivation of this commit is to clean up scripts/Kbuild.include
and scripts/Makefile.build.

Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
possibly exported symbols are detected by letting $(CPP) replace
EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
post-processed by sed, and passed to fixdep. The extra preprocessing
is costly, and hacking cmd_and_fixdep is ugly.

I came up with a new way to find exported symbols; insert a dummy
symbol __ksym_marker_* to each potentially exported symbol. Those
dummy symbols are picked up by $(NM), post-processed by sed, then
appended to .*.cmd files. I collected the post-process part to a
new shell script scripts/gen_ksymdeps.sh for readability. The dummy
symbols are put into the .discard.* section so that the linker
script rips them off the final vmlinux or modules.

A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
be much faster.

Signed-off-by: Masahiro Yamada 
Reviewed-by: Nicolas Pitre

kbuild: let fixdep directly write to .*.cmd files

2018-12-01T14:13:14+00:00

Currently, fixdep writes dependencies to .*.tmp, which is renamed to
.*.cmd after everything succeeds. This is a very safe way to avoid
corrupted .*.cmd files. The if_changed_dep has carried this safety
mechanism since it was added in 2002.

If fixdep fails for some reasons or a user terminates the build while
fixdep is running, the incomplete output from the fixdep could be
troublesome.

This is my insight about some bad scenarios:

[1] If the compiler succeeds to generate *.o file, but fixdep fails
    to write necessary dependencies to .*.cmd file, Make will miss
    to rebuild the object when headers or CONFIG options are changed.
    In this case, fixdep should not generate .*.cmd file at all so
    that 'arg-check' will surely trigger the rebuild of the object.

[2] A partially constructed .*.cmd file may not be a syntactically
    correct makefile. The next time Make runs, it would include it,
    then fail to parse it. Once this happens, 'make clean' is be the
    only way to fix it.

In fact, [1] is no longer a problem since commit 9c2af1c7377a ("kbuild:
add .DELETE_ON_ERROR special target"). Make deletes a target file on
any failure in its recipe. Because fixdep is a part of the recipe of
*.o target, if it fails, the *.o is deleted anyway. However, I am a
bit worried about the slight possibility of [2].

So, here is a solution. Let fixdep directly write to a .*.cmd file,
but allow makefiles to include it only when its corresponding target
exists.

This effectively reverts commit 2982c953570b ("kbuild: remove redundant
$(wildcard ...) for cmd_files calculation"), and commit 00d78ab2ba75
("kbuild: remove dead code in cmd_files calculation in top Makefile")
because now we must check the presence of targets.

Signed-off-by: Masahiro Yamada