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  1. 25 4月, 2021 8 次提交
    • M
      kbuild: dwarf: use AS_VERSION instead of test_dwarf5_support.sh · 2e988157
      由 Masahiro Yamada 提交于 
      The test code in scripts/test_dwarf5_support.sh is somewhat difficult
to understand, but after all, we want to check binutils >= 2.35.2

From the former discussion, the requirement for generating DWARF v5 from
C code is as follows:

 - gcc + gnu as          -> requires gcc 5.0+ (but 7.0+ for full support)
 - clang + gnu as        -> requires binutils 2.35.2+
 - clang + integrated as -> OK
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
      2e988157
    • M
      kbuild: check the minimum assembler version in Kconfig · ba64beb1
      由 Masahiro Yamada 提交于 
      Documentation/process/changes.rst defines the minimum assembler version
(binutils version), but we have never checked it in the build time.

Kbuild never invokes 'as' directly because all assembly files in the
kernel tree are *.S, hence must be preprocessed. I do not expect
raw assembly source files (*.s) would be added to the kernel tree.

Therefore, we always use $(CC) as the assembler driver, and commit
aa824e0c ("kbuild: remove AS variable") removed 'AS'. However,
we are still interested in the version of the assembler acting behind.

As usual, the --version option prints the version string.

  $ as --version | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

But, we do not have $(AS). So, we can add the -Wa prefix so that
$(CC) passes --version down to the backing assembler.

  $ gcc -Wa,--version | head -n 1
  gcc: fatal error: no input files
  compilation terminated.

OK, we need to input something to satisfy gcc.

  $ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

The combination of Clang and GNU assembler works in the same way:

  $ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

Clang with the integrated assembler fails like this:

  $ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  clang: error: unsupported argument '--version' to option 'Wa,'

For the last case, checking the error message is fragile. If the
proposal for -Wa,--version support [1] is accepted, this may not be
even an error in the future.

One easy way is to check if -integrated-as is present in the passed
arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
we can make it explicit.

Nathan pointed out -integrated-as is the default for all of the
architectures/targets that the kernel cares about, but it goes
along with "explicit is better than implicit" policy. [2]

With all this in my mind, I implemented scripts/as-version.sh to
check the assembler version in Kconfig time.

  $ scripts/as-version.sh gcc
  GNU 23501
  $ scripts/as-version.sh clang -no-integrated-as
  GNU 23501
  $ scripts/as-version.sh clang -integrated-as
  LLVM 0

[1]: https://github.com/ClangBuiltLinux/linux/issues/1320
[2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
      ba64beb1
    • M
      kbuild: collect minimum tool versions into scripts/min-tool-version.sh · e24b3ffc
      由 Masahiro Yamada 提交于 
      The kernel build uses various tools, many of which are provided by the
same software suite, for example, LLVM and Binutils.

When you raise the minimum version of Clang/LLVM, you need to update
clang_min_version in scripts/cc-version.sh and also lld_min_version in
scripts/ld-version.sh.

Kbuild can handle CC=clang and LD=ld.lld independently, but it does not
make much sense to maintain their versions separately.

Let's create a central place of minimum tool versions so you do not need
to touch multiple files. scripts/min-tool-version.sh prints the minimum
version of the given tool.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
Acked-by: NMiguel Ojeda <ojeda@kernel.org>
Tested-by: NSedat Dilek <sedat.dilek@gmail.com>
      e24b3ffc
    • M
      kbuild: move $(strip ) to suffix-search definition · a34e6d1e
      由 Masahiro Yamada 提交于 
      Move $(strip ...) to the callee from the callers of suffix-search. It
shortens the code slightly. Adding a space after a comma will not be
a matter. I also dropped parentheses from single character variables.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      a34e6d1e
    • M
      kbuild: rename multi-used-* to multi-obj-* · a6601e01
      由 Masahiro Yamada 提交于 
      I think multi-obj-* is clearer, and more consistent with real-obj-*.

Rename as follows:

  multi-used-y  ->  multi-obj-y
  multi-used-m  ->  multi-obj-m
  multi-used    ->  multi-obj-ym
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      a6601e01
    • R
      kbuild: apply fixdep logic to link-vmlinux.sh · 0b956e20
      由 Rasmus Villemoes 提交于 
      The patch adding CONFIG_VMLINUX_MAP revealed a small defect in the
build system: link-vmlinux.sh takes decisions based on CONFIG_*
options, but changing one of those does not always lead to vmlinux
being linked again.

For most of the CONFIG_* knobs referenced previously, this has
probably been hidden by those knobs also affecting some object file,
hence indirectly also vmlinux.

But CONFIG_VMLINUX_MAP is only handled inside link-vmlinux.sh, and
changing CONFIG_VMLINUX_MAP=n to CONFIG_VMLINUX_MAP=y does not cause
the build system to re-link (and hence have vmlinux.map
emitted). Since that map file is mostly a debugging aid, this is
merely a nuisance which is easily worked around by just deleting
vmlinux and building again.

But one could imagine other (possibly future) CONFIG options that
actually do affect the vmlinux binary but which are not captured
through some object file dependency.

To fix this, make link-vmlinux.sh emit a .vmlinux.d file in the same
format as the dependency files generated by gcc, and apply the fixdep
logic to that. I've tested that this correctly works with both in-tree
and out-of-tree builds.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      0b956e20
    • R
      kbuild: add CONFIG_VMLINUX_MAP expert option · 5cc12472
      由 Rasmus Villemoes 提交于 
      It can be quite useful to have ld emit a link map file, in order to
debug or verify that special sections end up where they are supposed
to, and to see what LD_DEAD_CODE_DATA_ELIMINATION manages to get rid
of.

The only reason I'm not just adding this unconditionally is that the
.map file can be rather large (several MB), and that's a waste of
space when one isn't interested in these things. Also make it depend
on CONFIG_EXPERT.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      5cc12472
    • M
      kbuild: split cc-option and friends to scripts/Makefile.compiler · 57fd251c
      由 Masahiro Yamada 提交于 
      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: NMasahiro Yamada <masahiroy@kernel.org>
      57fd251c
  3. 15 3月, 2021 1 次提交
    • M
      kbuild: prefix $(srctree)/ to some included Makefiles · 3204a7fb
      由 Masahiro Yamada 提交于 
      VPATH is used in Kbuild to make pattern rules search for prerequisites
in both $(objtree) and $(srctree). Some of *.c, *.S files are not real
sources, but generated by tools such as flex, bison, perl.

In contrast, I doubt the benefit of --include-dir=$(abs_srctree) because
it is always clear which Makefiles are real sources, and which are not.

So, my hope is to add $(srctree)/ prefix to all check-in Makefiles,
then remove --include-dir=$(abs_srctree) flag in the future.

I am touching only some Kbuild core parts for now. Treewide fixes will
be needed to achieve this goal.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      3204a7fb
  5. 13 3月, 2021 1 次提交
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  21. 24 2月, 2021 2 次提交