linux-kernel - [RFC PATCH] kbuild: Fix asm-offset generation to work with clang

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Message-Id: <20170403212537.124217-1-mka@chromium.org>
Date:   Mon,  3 Apr 2017 14:25:37 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Michal Marek <mmarek@...e.com>
Cc:     linux-kernel@...r.kernel.org, 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>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [RFC PATCH] kbuild: Fix asm-offset generation to work with clang

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>
---
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
-- 
2.12.2.715.g7642488e1d-goog