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kbuild: get rid of misleading $(AS) from documents 

The assembler files in the kernel are *.S instead of *.s, so they must
be preprocessed. Since 'as' of GNU binutils is not able to preprocess,
we always use $(CC) as an assembler driver.

$(AS) is almost unused in Kbuild. As of v5.2, there is just one place
that directly invokes $(AS).

  $ git grep -e '$(AS)' -e '${AS}' -e '$AS' -e '$(AS:' -e '${AS:' -- :^Documentation
  drivers/net/wan/Makefile:  AS68K = $(AS)

The documentation about *_AFLAGS* sounds like the flags were passed
to $(AS). This is somewhat misleading.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
This commit is contained in:
Masahiro Yamada 2019-07-13 11:45:58 +09:00
parent 8e2442a5f8
commit 5ef872636c
2 changed files with 8 additions and 9 deletions
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5
Documentation/kbuild/kbuild.rst
View File

@ -38,12 +38,11 @@ Additional options to the assembler (for built-in and modules).
AFLAGS_MODULE
-------------
Additional module specific options to use for $(AS).
Additional assembler options for modules.
AFLAGS_KERNEL
-------------
Additional options for $(AS) when used for assembler
code for code that is compiled as built-in.
Additional assembler options for built-in.
KCFLAGS
-------

12
Documentation/kbuild/makefiles.rst
View File

@ -328,7 +328,7 @@ more details, with real examples.
variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
entire tree.
asflags-y specifies options for assembling with $(AS).
asflags-y specifies assembler options.
Example::
@ -489,7 +489,7 @@ more details, with real examples.
as-instr checks if the assembler reports a specific instruction
and then outputs either option1 or option2
C escapes are supported in the test instruction
Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
Note: as-instr-option uses KBUILD_AFLAGS for assembler options
cc-option
cc-option is used to check if $(CC) supports a given option, and if
@ -905,7 +905,7 @@ When kbuild executes, the following steps are followed (roughly):
vmlinux. The usage of $(call if_changed,xxx) will be described later.
KBUILD_AFLAGS
$(AS) assembler flags
Assembler flags
Default value - see top level Makefile
Append or modify as required per architecture.
@ -948,16 +948,16 @@ When kbuild executes, the following steps are followed (roughly):
to 'y' when selected.
KBUILD_AFLAGS_KERNEL
$(AS) options specific for built-in
Assembler options specific for built-in
$(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile
resident kernel code.
KBUILD_AFLAGS_MODULE
Options for $(AS) when building modules
Assembler options specific for modules
$(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that
are used for $(AS).
are used for assembler.
From commandline AFLAGS_MODULE shall be used (see kbuild.txt).