[PATCH] kbuild: Fix gcc -x syntax

[PATCH] kbuild: Fix gcc -x syntax

[Jean Delvare]

The correct syntax for gcc -x is "gcc -x assembler", not
"gcc -xassembler". Even though the latter happens to work, the former
is what is documented in the manual page and thus what gcc wrappers
such as icecream do expect.

This isn't a cosmetic change. The missing space prevents icecream from
recognizing compilation tasks it can't handle, leading to silent kernel
miscompilations.

Besides me, credits go to Richard Guenther and Dirk Mueller for
investigating the miscompilation issue and tracking it down to this
incorrect -x parameter syntax.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: stable@vger.kernel.org
Cc: Bernhard Walle <bernhard@bwalle.de>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Ralf Baechle <ralf@linux-mips.org>
---
 arch/mips/Makefile            |    2 +-
 arch/mips/kernel/Makefile     |    2 +-
 arch/x86/Makefile             |    2 +-
 scripts/Kbuild.include        |   12 ++++++------
 tools/power/cpupower/Makefile |    2 +-
 5 files changed, 10 insertions(+), 10 deletions(-)

--- linux-3.6-rc7.orig/arch/mips/Makefile	2012-07-21 22:58:29.000000000 +0200
+++ linux-3.6-rc7/arch/mips/Makefile	2012-09-28 20:26:57.426173426 +0200
@@ -225,7 +225,7 @@ KBUILD_CPPFLAGS += -DDATAOFFSET=$(if $(d
 LDFLAGS			+= -m $(ld-emul)
 
 ifdef CONFIG_MIPS
-CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -xc /dev/null | \
+CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null | \
 	egrep -vw '__GNUC_(|MINOR_|PATCHLEVEL_)_' | \
 	sed -e "s/^\#define /-D'/" -e "s/ /'='/" -e "s/$$/'/")
 ifdef CONFIG_64BIT
--- linux-3.6-rc7.orig/arch/mips/kernel/Makefile	2012-07-21 22:58:29.000000000 +0200
+++ linux-3.6-rc7/arch/mips/kernel/Makefile	2012-09-28 20:27:02.099174587 +0200
@@ -104,7 +104,7 @@ obj-$(CONFIG_MIPS_MACHINE)	+= mips_machi
 
 obj-$(CONFIG_OF)		+= prom.o
 
-CFLAGS_cpu-bugs64.o	= $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
+CFLAGS_cpu-bugs64.o	= $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -x c /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
 
 obj-$(CONFIG_HAVE_STD_PC_SERIAL_PORT)	+= 8250-platform.o
 
--- linux-3.6-rc7.orig/arch/x86/Makefile	2012-09-24 09:31:59.000000000 +0200
+++ linux-3.6-rc7/arch/x86/Makefile	2012-09-28 20:26:52.039172190 +0200
@@ -92,7 +92,7 @@ endif
 ifdef CONFIG_X86_X32
 	x32_ld_ok := $(call try-run,\
 			/bin/echo -e '1: .quad 1b' | \
-			$(CC) $(KBUILD_AFLAGS) -c -xassembler -o "$$TMP" - && \
+			$(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
 			$(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMPO" && \
 			$(LD) -m elf32_x86_64 "$$TMPO" -o "$$TMP",y,n)
         ifeq ($(x32_ld_ok),y)
--- linux-3.6-rc7.orig/scripts/Kbuild.include	2012-07-21 22:58:29.000000000 +0200
+++ linux-3.6-rc7/scripts/Kbuild.include	2012-09-28 20:27:25.556178734 +0200
@@ -98,24 +98,24 @@ try-run = $(shell set -e;		\
 # Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
 
 as-option = $(call try-run,\
-	$(CC) $(KBUILD_CFLAGS) $(1) -c -xassembler /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
 
 # as-instr
 # Usage: cflags-y += $(call as-instr,instr,option1,option2)
 
 as-instr = $(call try-run,\
-	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -xassembler -o "$$TMP" -,$(2),$(3))
+	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
 
 # cc-option
 # Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)
 
 cc-option = $(call try-run,\
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -xc /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
 
 # cc-option-yn
 # Usage: flag := $(call cc-option-yn,-march=winchip-c6)
 cc-option-yn = $(call try-run,\
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -xc /dev/null -o "$$TMP",y,n)
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n)
 
 # cc-option-align
 # Prefix align with either -falign or -malign
@@ -125,7 +125,7 @@ cc-option-align = $(subst -functions=0,,
 # cc-disable-warning
 # Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
 cc-disable-warning = $(call try-run,\
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -xc /dev/null -o "$$TMP",-Wno-$(strip $(1)))
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
 
 # cc-version
 # Usage gcc-ver := $(call cc-version)
@@ -143,7 +143,7 @@ cc-ifversion = $(shell [ $(call cc-versi
 # cc-ldoption
 # Usage: ldflags += $(call cc-ldoption, -Wl$(comma)--hash-style=both)
 cc-ldoption = $(call try-run,\
-	$(CC) $(1) -nostdlib -xc /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) $(1) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2))
 
 # ld-option
 # Usage: LDFLAGS += $(call ld-option, -X)
--- linux-3.6-rc7.orig/tools/power/cpupower/Makefile	2012-07-21 22:58:29.000000000 +0200
+++ linux-3.6-rc7/tools/power/cpupower/Makefile	2012-09-28 20:26:45.218170854 +0200
@@ -111,7 +111,7 @@ GMO_FILES = ${shell for HLANG in ${LANGU
 export CROSS CC AR STRIP RANLIB CFLAGS LDFLAGS LIB_OBJS
 
 # check if compiler option is supported
-cc-supports = ${shell if $(CC) ${1} -S -o /dev/null -xc /dev/null > /dev/null 2>&1; then echo "$(1)"; fi;}
+cc-supports = ${shell if $(CC) ${1} -S -o /dev/null -x c /dev/null > /dev/null 2>&1; then echo "$(1)"; fi;}
 
 # use '-Os' optimization if available, else use -O2
 OPTIMIZATION := $(call cc-supports,-Os,-O2)

-- 
Jean Delvare
Suse L3

Re: [PATCH] kbuild: Fix gcc -x syntax

[Ingo Molnar]

* Jean Delvare <jdelvare@suse.de> wrote:

> The correct syntax for gcc -x is "gcc -x assembler", not "gcc 
> -xassembler". Even though the latter happens to work, the 
> former is what is documented in the manual page and thus what 
> gcc wrappers such as icecream do expect.
> 
> This isn't a cosmetic change. The missing space prevents 
> icecream from recognizing compilation tasks it can't handle, 
> leading to silent kernel miscompilations.

Although we can apply this patch, it won't solve the problem of 
building older kernels (and bisecting, etc.).

Wouldn't it be prudent to increase the compatibility of 
icecream, so that it accepts what GCC accepts in practice,
such as -xassembler?

Thanks,

	Ingo

Re: [PATCH] kbuild: Fix gcc -x syntax

[Bernhard Walle]

Hi,

* Ingo Molnar <mingo@kernel.org> [2012-09-29 08:37]:
> * Jean Delvare <jdelvare@suse.de> wrote:
> 
> > The correct syntax for gcc -x is "gcc -x assembler", not "gcc 
> > -xassembler". Even though the latter happens to work, the 
> > former is what is documented in the manual page and thus what 
> > gcc wrappers such as icecream do expect.
> > 
> > This isn't a cosmetic change. The missing space prevents 
> > icecream from recognizing compilation tasks it can't handle, 
> > leading to silent kernel miscompilations.
> 
> Although we can apply this patch, it won't solve the problem of 
> building older kernels (and bisecting, etc.).
> 
> Wouldn't it be prudent to increase the compatibility of 
> icecream, so that it accepts what GCC accepts in practice,
> such as -xassembler?

Wouldn't it make sense to do both? Using the documented syntax in the
build system *and* increase compatibility in 3rd party tools?


Regards,
Bernhard

Re: [PATCH] kbuild: Fix gcc -x syntax

[Ingo Molnar]

* Bernhard Walle <bernhard@bwalle.de> wrote:

> Hi,
> 
> * Ingo Molnar <mingo@kernel.org> [2012-09-29 08:37]:
> > * Jean Delvare <jdelvare@suse.de> wrote:
> > 
> > > The correct syntax for gcc -x is "gcc -x assembler", not "gcc 
> > > -xassembler". Even though the latter happens to work, the 
> > > former is what is documented in the manual page and thus what 
> > > gcc wrappers such as icecream do expect.
> > > 
> > > This isn't a cosmetic change. The missing space prevents 
> > > icecream from recognizing compilation tasks it can't handle, 
> > > leading to silent kernel miscompilations.
> > 
> > Although we can apply this patch, it won't solve the problem of 
> > building older kernels (and bisecting, etc.).
> > 
> > Wouldn't it be prudent to increase the compatibility of 
> > icecream, so that it accepts what GCC accepts in practice,
> > such as -xassembler?
> 
> Wouldn't it make sense to do both? Using the documented syntax 
> in the build system *and* increase compatibility in 3rd party 
> tools?

Yes.

Thanks,

	Ingo

Re: [PATCH] kbuild: Fix gcc -x syntax

[Jean Delvare]

Hi Ingo, hi Bernhard,

Le samedi 29 septembre 2012 à 09:24 +0100, Bernhard Walle a écrit :
> * Ingo Molnar <mingo@kernel.org> [2012-09-29 08:37]:
> > * Jean Delvare <jdelvare@suse.de> wrote:
> > 
> > > The correct syntax for gcc -x is "gcc -x assembler", not "gcc 
> > > -xassembler". Even though the latter happens to work, the 
> > > former is what is documented in the manual page and thus what 
> > > gcc wrappers such as icecream do expect.
> > > 
> > > This isn't a cosmetic change. The missing space prevents 
> > > icecream from recognizing compilation tasks it can't handle, 
> > > leading to silent kernel miscompilations.
> > 
> > Although we can apply this patch, it won't solve the problem of 
> > building older kernels (and bisecting, etc.).

WRT older kernels, I recommend that we apply the fix to all stable and
longterm kernel branches.

> > Wouldn't it be prudent to increase the compatibility of 
> > icecream, so that it accepts what GCC accepts in practice,
> > such as -xassembler?
> 
> Wouldn't it make sense to do both? Using the documented syntax in the
> build system *and* increase compatibility in 3rd party tools?

Yes of course, this is exactly the plan. Silent micompilations are very
painful so we want to fix the problem on every side we can.

Thanks,
-- 
Jean Delvare
Suse L3