Message-ID: <20170411180354.GD28657@google.com>
Date:   Tue, 11 Apr 2017 11:03:54 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Michal Marek <mmarek@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Grant Grundler <grundler@...omium.org>,
        Michael Davidson <md@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Behan Webster <behanw@...verseincode.com>,
        Peter Foley <pefoley2@...oley.com>
Subject: Re: [RFC PATCH] kbuild: Fix asm-offset generation to work with clang

Hi Masahiro,

El Tue, Apr 11, 2017 at 09:01:41PM +0900 Masahiro Yamada ha dit:

> 2017-04-04 6:25 GMT+09:00 Matthias Kaehlcke <mka@...omium.org>:
> > When using clang with -no-integerated-as clang will use the gnu
> > assembler instead of the integrated assembler. However clang will
> > still perform asm error checking before sending the inline assembly
> > language to gas.
> >
> > The generation of asm-offsets from within C code is dependent on gcc's
> > blind passing of whatever is in asm() through to gas. Arbirary text is
> > passed through which is then modified by a sed script into the
> > appropriate .h and .S code. Since the arbitrary text is not valid
> > assembly language, clang fails.
> >
> > This can be fixed by making the arbitrary text into an ASM comment and
> > then updating the sed scripts accordingly to work as expected.
> >
> > This solution works for both gcc and clang.
> >
> > Based-on-patch-from: Behan Webster <behanw@...verseincode.com>
> > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> 
> 
> 
> Could you check Jeroen Hofstee's work for U-Boot?
> 
> http://patchwork.ozlabs.org/patch/375026/

No I didn't come across it, thanks for the pointer!

> His idea is to use .ascii string
> in order to handle this in arch-agnostic way.

Looks good, way cleaner than my proposed solution :)

> If you are happy about this idea,
> I can forward his patch (with a little bit adjustment).

With forward you mean you plan to port it? Otherwise I'm also happy to
give it a go, just let me know.

> We may want to refactor the patch because
> the double mark ".ascii" and "->" seem redundant,
> but it is just a detail.

Agree, since we are already touching this part we might as well remove
the "->".

Cheers

Matthias

> > Dependencies
> >   all architectures
> >     kbuild: Consolidate header generation from ASM offset information
> >       https://patchwork.kernel.org/patch/9660459/
> >
> >   um
> >     um: Include kbuild.h instead of duplicating its macros
> >       https://patchwork.kernel.org/patch/9660503/
> >
> >   frv
> >     frv: Use OFFSET macro in DEF_*REG()
> >       https://patchwork.kernel.org/patch/9660473/
> >
> > The change has been build tested on a wide range of architectures.
> >
> > The if cascade in kbuild.h and the comment symbol list in
> > Makefile.asm-offsets won't win a beauty price. Alternatively the comment
> > symbol could be specified in arch/Kconfig. Personally I don't have a
> > strong preference on this point.
> >
> >  include/linux/kbuild.h       | 34 ++++++++++++++++++++++++++++---
> >  scripts/Makefile.asm-offsets | 48 ++++++++++++++++++++++++++++++++++++++++----
> >  2 files changed, 75 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/linux/kbuild.h b/include/linux/kbuild.h
> > index 22a72198c14b..632e33d3b70c 100644
> > --- a/include/linux/kbuild.h
> > +++ b/include/linux/kbuild.h
> > @@ -1,15 +1,43 @@
> >  #ifndef __LINUX_KBUILD_H
> >  #define __LINUX_KBUILD_H
> >
> > +#if defined(CONFIG_ALPHA) || defined(CONFIG_AVR32) ||        \
> > +       defined(CONFIG_MICROBLAZE) || defined(CONFIG_MIPS) || \
> > +       defined(CONFIG_MN10300) || defined(CONFIG_PPC) || \
> > +       defined(CONFIG_S390) || defined(CONFIG_SCORE) ||      \
> > +       defined(CONFIG_UML_X86) || defined(CONFIG_X86) ||     \
> > +       defined(CONFIG_XTENSA)
> > +#define ASM_COMMENT_SYM "#"
> > +#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
> > +#define ASM_COMMENT_SYM "@"
> > +#elif defined(CONFIG_ARC) || defined(CONFIG_C6X) ||            \
> > +       defined(CONFIG_CRIS) || defined(CONFIG_FRV) ||          \
> > +       defined(CONFIG_H8300) || defined(CONFIG_M32R) ||        \
> > +       defined(CONFIG_PARISC)
> > +#define ASM_COMMENT_SYM ";"
> > +#elif defined(CONFIG_BLACKFIN) || defined(CONFIG_HEXAGON) || \
> > +       defined(CONFIG_IA64) || defined(CONFIG_NIOS2) ||     \
> > +       defined(CONFIG_OPENRISC)
> > +#define ASM_COMMENT_SYM "//"
> > +#elif defined(CONFIG_METAG) || defined(CONFIG_SUPERH) ||       \
> > +       defined(CONFIG_SPARC) || defined(CONFIG_TILE) ||        \
> > +       defined(CONFIG_UNICORE32)
> > +#define ASM_COMMENT_SYM "!"
> > +#elif defined(CONFIG_M68K)
> > +#define ASM_COMMENT_SYM "|"
> > +#else
> > +#error Symbol for ASM inline comments is not defined for ARCH
> > +#endif
> > +
> >  #define DEFINE(sym, val) \
> > -        asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> > +       asm volatile("\n" ASM_COMMENT_SYM "->" #sym " %0 " #val : : "i" (val))
> >
> > -#define BLANK() asm volatile("\n->" : : )
> > +#define BLANK() asm volatile("\n" ASM_COMMENT_SYM "->" : : )
> >
> >  #define OFFSET(sym, str, mem) \
> >         DEFINE(sym, offsetof(struct str, mem))
> >
> >  #define COMMENT(x) \
> > -       asm volatile("\n->#" x)
> > +       asm volatile("\n" ASM_COMMENT_SYM "->#" x)
> >
> >  #endif
> > diff --git a/scripts/Makefile.asm-offsets b/scripts/Makefile.asm-offsets
> > index 4ba80ba29b82..7f8d3cbc5901 100644
> > --- a/scripts/Makefile.asm-offsets
> > +++ b/scripts/Makefile.asm-offsets
> > @@ -1,9 +1,49 @@
> > +# Symbols for ASM inline comments for all architectures
> > +asm_comment_sym_arch_alpha = \#
> > +asm_comment_sym_arch_arc = \;
> > +asm_comment_sym_arch_arm = @
> > +asm_comment_sym_arch_arm64 = @
> > +asm_comment_sym_arch_avr32 = \#
> > +asm_comment_sym_arch_blackfin = //
> > +asm_comment_sym_arch_c6x = \;
> > +asm_comment_sym_arch_cris = \;
> > +asm_comment_sym_arch_frv = \;
> > +asm_comment_sym_arch_h8300 = \;
> > +asm_comment_sym_arch_hexagon = //
> > +asm_comment_sym_arch_ia64 = //
> > +asm_comment_sym_arch_m32r = \;
> > +asm_comment_sym_arch_m68k = |
> > +asm_comment_sym_arch_metag = !
> > +asm_comment_sym_arch_microblaze = \#
> > +asm_comment_sym_arch_mips = \#
> > +asm_comment_sym_arch_mn10300 = \#
> > +asm_comment_sym_arch_nios2 = //
> > +asm_comment_sym_arch_openrisc = //
> > +asm_comment_sym_arch_parisc = \;
> > +asm_comment_sym_arch_powerpc = \#
> > +asm_comment_sym_arch_s390 = \#
> > +asm_comment_sym_arch_score = \#
> > +asm_comment_sym_arch_sh = !
> > +asm_comment_sym_arch_sparc = !
> > +asm_comment_sym_arch_tile = !
> > +# Note: assumes uml_x86
> > +asm_comment_sym_arch_um = \#
> > +asm_comment_sym_arch_unicore32 = !
> > +asm_comment_sym_arch_x86 = \#
> > +asm_comment_sym_arch_xtensa = \#
> > +
> > +ASM_COMMENT_SYM = $(asm_comment_sym_arch_$(SRCARCH))
> > +
> > +ifeq ($(ASM_COMMENT_SYM),)
> > +$(error Symbol for ASM inline comments is not defined for ARCH=$(SRCARCH))
> > +endif
> > +
> >  # Default sed regexp - multiline due to syntax constraints
> >  define sed-asm-offsets-to-c
> > -       "/^->/{s:->#\(.*\):/* \1 */:; \
> > -       s:^->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 \2 /* \3 */:; \
> > -       s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
> > -       s:->::; p;}"
> > +       "\:^$(ASM_COMMENT_SYM)->:{s:$(ASM_COMMENT_SYM)->#\(.*\):/* \1 */:; \
> > +       s:^$(ASM_COMMENT_SYM)->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 \2 /* \3 */:; \
> > +       s:^$(ASM_COMMENT_SYM)->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
> > +       s:$(ASM_COMMENT_SYM)->::; p;}"
> >  endef
> >
> >  define gen_header_from_asm_offsets
> > --

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