linux-kernel - [PATCH v2 2/2] kbuild: fix asm-offset generation to work with clang

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Message-Id: <1492755671-19005-3-git-send-email-yamada.masahiro@socionext.com>
Date:   Fri, 21 Apr 2017 15:21:11 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        David Howells <dhowells@...hat.com>,
        Michael Davidson <md@...gle.com>,
        Michal Marek <mmarek@...e.com>,
        Jan Beulich <JBeulich@...ell.com>,
        Alexander van Heukelum <heukelum@...tmail.fm>,
        Jeroen Hofstee <jeroen@...pectrum.nl>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] kbuild: fix asm-offset generation to work with clang

From: Jeroen Hofstee <jeroen@...pectrum.nl>

KBuild abuses the asm statement to write to a file and
clang chokes about these invalid asm statements. Hack it
even more by fooling this is actual valid asm code.

[masahiro:
 Import Jeroen's work for U-Boot:
 http://patchwork.ozlabs.org/patch/375026/
 Tweak sed script a little to avoid garbage '#' for GCC case, like
 #define NR_PAGEFLAGS 23 /* __NR_PAGEFLAGS       # */ ]

Signed-off-by: Jeroen Hofstee <jeroen@...pectrum.nl>
Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
Tested-by: Matthias Kaehlcke <mka@...omium.org>
---

Changes in v2:
  - V1 did not work with LLVM's integrated assembler because
    it uses <tab> instead of <space> around the .ascii string.
    Restore [:space:].

 include/linux/kbuild.h | 6 +++---
 scripts/Makefile.lib   | 8 ++++++--
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/linux/kbuild.h b/include/linux/kbuild.h
index 22a7219..4e80f3a 100644
--- a/include/linux/kbuild.h
+++ b/include/linux/kbuild.h
@@ -2,14 +2,14 @@
 #define __LINUX_KBUILD_H
 
 #define DEFINE(sym, val) \
-        asm volatile("\n->" #sym " %0 " #val : : "i" (val))
+	asm volatile("\n.ascii \"->" #sym " %0 " #val "\"" : : "i" (val))
 
-#define BLANK() asm volatile("\n->" : : )
+#define BLANK() asm volatile("\n.ascii \"->\"" : : )
 
 #define OFFSET(sym, str, mem) \
 	DEFINE(sym, offsetof(struct str, mem))
 
 #define COMMENT(x) \
-	asm volatile("\n->#" x)
+	asm volatile("\n.ascii \"->#" x "\"")
 
 #endif
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 9c20690..9e70196 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -413,10 +413,14 @@ cmd_xzmisc = (cat $(filter-out FORCE,$^) | \
 # ---------------------------------------------------------------------------
 
 # Default sed regexp - multiline due to syntax constraints
+#
+# Use [:space:] because LLVM's integrated assembler inserts <tab> around
+# the .ascii directive whereas GCC keeps the <space> as-is.
 define sed-offsets
-	"/^->/{s:->#\(.*\):/* \1 */:; \
+	's:^[[:space:]]*\.ascii[[:space:]]*"\(.*\)".*:\1:; \
+	/^->/{s:->#\(.*\):/* \1 */:; \
 	s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
-	s:->::; p;}"
+	s:->::; p;}'
 endef
 
 # Use filechk to avoid rebuilds when a header changes, but the resulting file
-- 
2.7.4