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

This reverts commit 77b0bf55bc675233d22cd5df97605d516d64525e.

See this comm

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

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 <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Richard Biener <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Segher Boessenkool <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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kbuild: move .SECONDARY special target to Kbuild.include

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

kbuild: move .SECONDARY special target to Kbuild.include

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 <[email protected]>

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kbuild: refactor if_changed

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

Signed-off-by: Masahiro Yamada <[email protected]>

kbuild: remove trailing semicolon from cmd_* passed to if_changed_rule

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 unnee

kbuild: remove trailing semicolon from cmd_* passed to if_changed_rule

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 <[email protected]>

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kbuild: change if_changed_rule for multi-line recipe

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

define foo
[action1]

kbuild: change if_changed_rule for multi-line recipe

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 <[email protected]>

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kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS

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

Currently, CONFIG_TRIM_UNUSED

kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS

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 <[email protected]>
Reviewed-by: Nicolas Pitre <[email protected]>

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

Currently, fixdep writes dependencies to .*.tmp, which is renamed to
.*.cmd after everything succeeds. This is a very safe way to avoid
corrupted .*

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

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 <[email protected]>

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kbuild: remove cc-name variable

There is one more user of $(cc-name) in the top Makefile. It is supposed
to detect Clang before invoking Kconfig, so it should still be there
in the $(shell ...) form

kbuild: remove cc-name variable

There is one more user of $(cc-name) in the top Makefile. It is supposed
to detect Clang before invoking Kconfig, so it should still be there
in the $(shell ...) form. All the other users of $(cc-name) have been
replaced with $(CONFIG_CC_IS_CLANG). Hence, scripts/Kbuild.include does
not need to define cc-name any more.

Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: remove unused cc-fullversion variable

The last user of cc-fullversion was removed by commit f2910f0e6835
("powerpc: remove old GCC version checks").

Signed-off-by: Masahiro Yamada <yamada.m

kbuild: remove unused cc-fullversion variable

The last user of cc-fullversion was removed by commit f2910f0e6835
("powerpc: remove old GCC version checks").

Signed-off-by: Masahiro Yamada <[email protected]>

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

Using macros in inline assembly allows us to work around bugs
in GCC's inlining decis

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

Using macros in inline assembly allows us to work around bugs
in GCC's inlining decisions.

Compile macros.S and use it to assemble all C files.
Currently only x86 will use it.

Background:

The inlining pass of GCC doesn't include an assembler, so it's not aware
of basic properties of the generated code, such as its size in bytes,
or that there are such things as discontiuous blocks of code and data
due to the newfangled linker feature called 'sections' ...

Instead GCC uses a lazy and fragile heuristic: it does a linear count of
certain syntactic and whitespace elements in inlined assembly block source
code, such as a count of new-lines and semicolons (!), as a poor substitute
for "code size and complexity".

Unsurprisingly this heuristic falls over and breaks its neck whith certain
common types of kernel code that use inline assembly, such as the frequent
practice of putting useful information into alternative sections.

As a result of this fresh, 20+ years old GCC bug, GCC's inlining decisions
are effectively disabled for inlined functions that make use of such asm()
blocks, because GCC thinks those sections of code are "large" - when in
reality they are often result in just a very low number of machine
instructions.

This absolute lack of inlining provess when GCC comes across such asm()
blocks both increases generated kernel code size and causes performance
overhead, which is particularly noticeable on paravirt kernels, which make
frequent use of these inlining facilities in attempt to stay out of the
way when running on baremetal hardware.

Instead of fixing the compiler we use a workaround: we set an assembly macro
and call it from the inlined assembly block. As a result GCC considers the
inline assembly block as a single instruction. (Which it often isn't but I digress.)

This uglifies and bloats the source code - for example just the refcount
related changes have this impact:

Makefile | 9 +++++++--
arch/x86/Makefile | 7 +++++++
arch/x86/kernel/macros.S | 7 +++++++
scripts/Kbuild.include | 4 +++-
scripts/mod/Makefile | 2 ++
5 files changed, 26 insertions(+), 3 deletions(-)

Yay readability and maintainability, it's not like assembly code is hard to read
and maintain ...

We also hope that GCC will eventually get fixed, but we are not holding
our breath for that. Yet we are optimistic, it might still happen, any decade now.

[ mingo: Wrote new changelog describing the background. ]

Tested-by: Kees Cook <[email protected]>
Signed-off-by: Nadav Amit <[email protected]>
Acked-by: Masahiro Yamada <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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kbuild: prefix Makefile.dtbinst path with $(srctree) unconditionally

$(srctree) always points to the top of the source tree whether
KBUILD_SRC is set or not.

Signed-off-by: Masahiro Yamada <yamada.

kbuild: prefix Makefile.dtbinst path with $(srctree) unconditionally

$(srctree) always points to the top of the source tree whether
KBUILD_SRC is set or not.

Signed-off-by: Masahiro Yamada <[email protected]>

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x86/build: Remove jump label quirk for GCC older than 4.5.2

Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
bumped the minimum GCC version to 4.6 for all architectures.

Remove

x86/build: Remove jump label quirk for GCC older than 4.5.2

Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
bumped the minimum GCC version to 4.6 for all architectures.

Remove the workaround code.

It was the only user of cc-if-fullversion. Remove the macro as well.

Signed-off-by: Masahiro Yamada <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

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kbuild: rename LDFLAGS to KBUILD_LDFLAGS

Commit a0f97e06a43c ("kbuild: enable 'make CFLAGS=...' to add
additional options to CC") renamed CFLAGS to KBUILD_CFLAGS.

Commit 222d394d30e7 ("kbuild: enab

kbuild: rename LDFLAGS to KBUILD_LDFLAGS

Commit a0f97e06a43c ("kbuild: enable 'make CFLAGS=...' to add
additional options to CC") renamed CFLAGS to KBUILD_CFLAGS.

Commit 222d394d30e7 ("kbuild: enable 'make AFLAGS=...' to add
additional options to AS") renamed AFLAGS to KBUILD_AFLAGS.

Commit 06c5040cdb13 ("kbuild: enable 'make CPPFLAGS=...' to add
additional options to CPP") renamed CPPFLAGS to KBUILD_CPPFLAGS.

For some reason, LDFLAGS was not renamed.

Using a well-known variable like LDFLAGS may result in accidental
override of the variable.

Kbuild generally uses KBUILD_ prefixed variables for the internally
appended options, so here is one more conversion to sanitize the
naming convention.

I did not touch Makefiles under tools/ since the tools build system
is a different world.

Signed-off-by: Masahiro Yamada <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Palmer Dabbelt <[email protected]>

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kbuild: do not redirect the first prerequisite for filechk

Currently, filechk unconditionally opens the first prerequisite and
redirects it as the stdin of a filechk_* rule. Hence, every target
usi

kbuild: do not redirect the first prerequisite for filechk

Currently, filechk unconditionally opens the first prerequisite and
redirects it as the stdin of a filechk_* rule. Hence, every target
using $(call filechk,...) must list something as the first prerequisite
even if it is unneeded.

'< $<' is actually unneeded in most cases. Each rule can explicitly
adds it if necessary.

Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: add .DELETE_ON_ERROR special target

If Make gets a fatal signal while a shell is executing, it may delete
the target file that the recipe was supposed to update. This is needed
to make sure

kbuild: add .DELETE_ON_ERROR special target

If Make gets a fatal signal while a shell is executing, it may delete
the target file that the recipe was supposed to update. This is needed
to make sure that it is remade from scratch when Make is next run; if
Make is interrupted after the recipe has begun to write the target file,
it results in an incomplete file whose time stamp is newer than that
of the prerequisites files. Make automatically deletes the incomplete
file on interrupt unless the target is marked .PRECIOUS.

The situation is just the same as when the shell fails for some reasons.
Usually when a recipe line fails, if it has changed the target file at
all, the file is corrupted, or at least it is not completely updated.
Yet the file’s time stamp says that it is now up to date, so the next
time Make runs, it will not try to update that file.

However, Make does not cater to delete the incomplete target file in
this case. We need to add .DELETE_ON_ERROR somewhere in the Makefile
to request it.

scripts/Kbuild.include seems a suitable place to add it because it is
included from almost all sub-makes.

Please note .DELETE_ON_ERROR is not effective for phony targets.

The external module building should never ever touch the kernel tree.
The following recipe fails if include/generated/autoconf.h is missing.
However, include/config/auto.conf is not deleted since it is a phony
target.

PHONY += include/config/auto.conf

include/config/auto.conf:
$(Q)test -e include/generated/autoconf.h -a -e $@ || ( \
echo >&2; \
echo >&2 " ERROR: Kernel configuration is invalid."; \
echo >&2 " include/generated/autoconf.h or $@ are missing.";\
echo >&2 " Run 'make oldconfig && make prepare' on kernel src to fix it."; \
echo >&2 ; \
/bin/false)

Signed-off-by: Masahiro Yamada <[email protected]>

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arm64: build with baremetal linker target instead of Linux when available

Not all toolchains have the baremetal elf targets, RedHat/Fedora ones
in particular. So, probe for whether it's available an

arm64: build with baremetal linker target instead of Linux when available

Not all toolchains have the baremetal elf targets, RedHat/Fedora ones
in particular. So, probe for whether it's available and use the previous
(linux) targets if it isn't.

Reported-by: Laura Abbott <[email protected]>
Tested-by: Laura Abbott <[email protected]>
Acked-by: Masahiro Yamada <[email protected]>
Cc: Paul Kocialkowski <[email protected]>
Signed-off-by: Olof Johansson <[email protected]>
Signed-off-by: Will Deacon <[email protected]>

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kbuild: Rename HOSTCFLAGS to KBUILD_HOSTCFLAGS

In preparation for enabling command line CFLAGS, re-name HOSTCFLAGS to
KBUILD_HOSTCFLAGS as the internal use only flags. This should not have
any visib

kbuild: Rename HOSTCFLAGS to KBUILD_HOSTCFLAGS

In preparation for enabling command line CFLAGS, re-name HOSTCFLAGS to
KBUILD_HOSTCFLAGS as the internal use only flags. This should not have
any visible effects.

Signed-off-by: Laura Abbott <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: do not drop -I without parameter

The comment line for addtree says "skip if -I has no parameter".

What it actually does is "drop if -I has no parameter". For example,
if you have the compi

kbuild: do not drop -I without parameter

The comment line for addtree says "skip if -I has no parameter".

What it actually does is "drop if -I has no parameter". For example,
if you have the compiler flag '-I foo' (a space between), it will be
converted to 'foo'. This completely changes the meaning.

What we want is, "do nothing" for -I without parameter so that
'-I foo' is kept as-is.

Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: remove kbuild cache

The kbuild cache was introduced to remember the result of shell
commands, some of which are expensive to compute, such as
$(call cc-option,...).

However, this turned out

kbuild: remove kbuild cache

The kbuild cache was introduced to remember the result of shell
commands, some of which are expensive to compute, such as
$(call cc-option,...).

However, this turned out not so clever as I had first expected.
Actually, it is problematic. For example, "$(CC) -print-file-name"
is cached. If the compiler is updated, the stale search path causes
build error, which is difficult to figure out. Another problem
scenario is cache files could be touched while install targets are
running under the root permission. We can patch them if desired,
but the build infrastructure is getting uglier and uglier.

Now, we are going to move compiler flag tests to the configuration
phase. If this is completed, the result of compiler tests will be
naturally cached in the .config file. We will not have performance
issues of incremental building since this testing only happens at
Kconfig time.

To start this work with a cleaner code base, remove the kbuild
cache first.

Revert the following commits:
Commit 9a234a2e3843 ("kbuild: create directory for make cache only when necessary")
Commit e17c400ae194 ("kbuild: shrink .cache.mk when it exceeds 1000 lines")
Commit 4e56207130ed ("kbuild: Cache a few more calls to the compiler")
Commit 3298b690b21c ("kbuild: Add a cache for generated variables")

Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Kees Cook <[email protected]>

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kbuild: do not display CHK for filechk

filechk displays two short logs; CHK for creating a temporary file,
and UPD for really updating the target.

IMHO, the build system can be quiet when the targe

kbuild: do not display CHK for filechk

filechk displays two short logs; CHK for creating a temporary file,
and UPD for really updating the target.

IMHO, the build system can be quiet when the target file has not
been updated.

Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Sam Ravnborg <[email protected]>

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Kbuild: fix # escaping in .cmd files for future Make

I tried building using a freshly built Make (4.2.1-69-g8a731d1), but
already the objtool build broke with

orc_dump.c: In function ‘orc_dump’:
or

Kbuild: fix # escaping in .cmd files for future Make

I tried building using a freshly built Make (4.2.1-69-g8a731d1), but
already the objtool build broke with

orc_dump.c: In function ‘orc_dump’:
orc_dump.c:106:2: error: ‘elf_getshnum’ is deprecated [-Werror=deprecated-declarations]
if (elf_getshdrnum(elf, &nr_sections)) {

Turns out that with that new Make, the backslash was not removed, so cpp
didn't see a #include directive, grep found nothing, and
-DLIBELF_USE_DEPRECATED was wrongly put in CFLAGS.

Now, that new Make behaviour is documented in their NEWS file:

* WARNING: Backward-incompatibility!
Number signs (#) appearing inside a macro reference or function invocation
no longer introduce comments and should not be escaped with backslashes:
thus a call such as:
foo := $(shell echo '#')
is legal. Previously the number sign needed to be escaped, for example:
foo := $(shell echo '\#')
Now this latter will resolve to "\#". If you want to write makefiles
portable to both versions, assign the number sign to a variable:
C := \#
foo := $(shell echo '$C')
This was claimed to be fixed in 3.81, but wasn't, for some reason.
To detect this change search for 'nocomment' in the .FEATURES variable.

This also fixes up the two make-cmd instances to replace # with $(pound)
rather than with \#. There might very well be other places that need
similar fixup in preparation for whatever future Make release contains
the above change, but at least this builds an x86_64 defconfig with the
new make.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=197847
Cc: Randy Dunlap <[email protected]>
Signed-off-by: Rasmus Villemoes <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: move include/config/ksym/* to include/ksym/*

The idea of using fixdep was inspired by Kconfig, but autoksyms
belongs to a different group. So, I want to move those touched
files under inclu

kbuild: move include/config/ksym/* to include/ksym/*

The idea of using fixdep was inspired by Kconfig, but autoksyms
belongs to a different group. So, I want to move those touched
files under include/config/ksym/ to include/ksym/.

The directory include/ksym/ can be removed by 'make clean' because
it is meaningless for the external module building.

Signed-off-by: Masahiro Yamada <[email protected]>
Acked-by: Nicolas Pitre <[email protected]>

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kbuild: simplify ld-option implementation

Currently, linker options are tested by the coordination of $(CC) and
$(LD) because $(LD) needs some object to link.

As commit 86a9df597cdd ("kbuild: fix l

kbuild: simplify ld-option implementation

Currently, linker options are tested by the coordination of $(CC) and
$(LD) because $(LD) needs some object to link.

As commit 86a9df597cdd ("kbuild: fix linker feature test macros when
cross compiling with Clang") addressed, we need to make sure $(CC)
and $(LD) agree the underlying architecture of the passed object.

This could be a bit complex when we combine tools from different groups.
For example, we can use clang for $(CC), but we still need to rely on
GCC toolchain for $(LD).

So, I was searching for a way of standalone testing of linker options.
A trick I found is to use '-v'; this not only prints the version string,
but also tests if the given option is recognized.

If a given option is supported,

$ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419
GNU ld (Linaro_Binutils-2017.11) 2.28.2.20170706
$ echo $?
0

If unsupported,

$ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419
GNU ld (crosstool-NG linaro-1.13.1-4.7-2013.04-20130415 - Linaro GCC 2013.04) 2.23.1
aarch64-linux-gnu-ld: unrecognized option '--fix-cortex-a53-843419'
aarch64-linux-gnu-ld: use the --help option for usage information
$ echo $?
1

Gold works likewise.

$ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-843419
GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14
masahiro@pug:~/ref/linux$ echo $?
0
$ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-999999
GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14
aarch64-linux-gnu-ld.gold: --fix-cortex-a53-999999: unknown option
aarch64-linux-gnu-ld.gold: use the --help option for usage information
$ echo $?
1

LLD too.

$ ld.lld -v --gc-sections
LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
$ echo $?
0
$ ld.lld -v --fix-cortex-a53-843419
LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
$ echo $?
0
$ ld.lld -v --fix-cortex-a53-999999
ld.lld: error: unknown argument: --fix-cortex-a53-999999
LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
$ echo $?
1

Signed-off-by: Masahiro Yamada <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>

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kbuild: Improve portability of some sed invocations

* Use BREs where EREs aren't necessary.
* Pass -E instead of -r to use EREs. This will be standardized in the
next POSIX revision[0]. GNU sed su

kbuild: Improve portability of some sed invocations

* Use BREs where EREs aren't necessary.
* Pass -E instead of -r to use EREs. This will be standardized in the
next POSIX revision[0]. GNU sed supports this since 4.2 (May 2009),
and busybox since 1.22.0 (Jan 2014).
* Use the [:space:] character class instead of ` \t` in bracket
expressions. In bracket expressions, POSIX says that <backslash> loses
its special meaning, so a conforming implementation cannot expand \t
to <tab>[1].
* In BREs, use interval expressions (\{n,m\}) instead of non-standard
features like \+ and \?.
* Use a loop instead of -s flag.

There are still plenty of other cases of non-standard sed invocations
(use of ERE features in BREs, in-place editing), but this fixes some
core ones.

[0] http://austingroupbugs.net/view.php?id=528
[1] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05

Signed-off-by: Michael Forney <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: create directory for make cache only when necessary

Currently, the existence of $(dir $(make-cache)) is always checked,
and created if it is missing.

We can avoid unnecessary system calls b

kbuild: create directory for make cache only when necessary

Currently, the existence of $(dir $(make-cache)) is always checked,
and created if it is missing.

We can avoid unnecessary system calls by some tricks.

[1] If KBUILD_SRC is unset, we are building in the source tree.
The output directory checks can be entirely skipped.
[2] If at least one cache data is found, it means the cache file
was included. Obviously its directory exists. Skip "mkdir -p".
[3] If Makefile does not contain any call of __run-and-store, it will
not create a cache file. No need to create its directory.
[4] The "mkdir -p" should be only invoked by the first call of
__run-and-store

Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Douglas Anderson <[email protected]>

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