linux-kernel - [PATCH 1/3] Makefile.compiler: s/KBUILD_CFLAGS/KBUILD

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Date:   Fri, 26 Aug 2022 11:10:33 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, x86@...nel.org,
        Dmitrii Bundin <dmitrii.bundin.a@...il.com>,
        Fangrui Song <maskray@...gle.com>,
        Alexey Alexandrov <aalexand@...gle.com>,
        Bill Wendling <morbo@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 1/3] Makefile.compiler: s/KBUILD_CFLAGS/KBUILD_AFLAGS/ for as-option

as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS.  This can
cause as-option to fail unexpectedly because clang will emit
-Werror,-Wunused-command-line-argument for various -m and -f flags for
assembler sources.

Callers of as-option (and as-instr) likely want to be adding flags to
KBUILD_AFLAGS/aflags-y, not KBUILD_CFLAGS/cflags-y.

Link: https://github.com/ClangBuiltLinux/linux/issues/1699
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 arch/x86/boot/compressed/Makefile | 5 +++--
 scripts/Makefile.compiler         | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 35ce1a64068b..fb3db714a028 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -48,8 +48,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign
 KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
 KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS += -D__DISABLE_EXPORTS
-# Disable relocation relaxation in case the link is not PIE.
-KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
 KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
 
 # sev.c indirectly inludes inat-table.h which is generated during
@@ -58,6 +56,9 @@ KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
 CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
+# Disable relocation relaxation in case the link is not PIE.
+KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
+
 GCOV_PROFILE := n
 UBSAN_SANITIZE :=n
 
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index 94d0d40cddb3..d1739f0d3ce3 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -29,13 +29,13 @@ try-run = $(shell set -e;		\
 	fi)
 
 # as-option
-# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
+# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
 
 as-option = $(call try-run,\
-	$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) $(KBUILD_AFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
 
 # as-instr
-# Usage: cflags-y += $(call as-instr,instr,option1,option2)
+# Usage: aflags-y += $(call as-instr,instr,option1,option2)
 
 as-instr = $(call try-run,\
 	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
-- 
2.37.2.672.g94769d06f0-goog