Re: [PATCH] fix miscompiling with GCC 4.5 -finline-functions

[Denis Kaganovich]

On Thu, 6 Jan 2011 13:07:01 -0500, Arnaud Lacombe wrote:
> On Thu, Jan 6, 2011 at 12:42 PM, Dzianis Kahanovich
> <mahatma@xxxxxxxxxxxxxx> wrote:
> > Andrew Morton wrote:
> >
> > > > Fixing broken automatic inlining for GCC 4.5+ Â(breaks build with
> > > > -finline-functions or -O3 on x86_*).
> > >
> > > Please always quote the compiler output when addressing build 
> > > errors
> > > and warnings.
> >
> > Sorry. linux-next, yesterday, gcc version 4.5.1 (Gentoo 4.5.1-r1 
> > p1.4, pie-0.4.5):
> >
> > make -j5 -s HOSTCC=x86_64-pc-linux-gnu-gcc ARCH=i386
> > CROSS_COMPILE=i586-pc-linux-gnu- all -i
> > arch/x86/kvm/vmx.c: Assembler messages:
> > arch/x86/kvm/vmx.c:4036: Error: symbol `.Llaunched' is already 
> > defined
> > arch/x86/kvm/vmx.c:4048: Error: symbol `.Lkvm_vmx_return' is already 
> > defined
> > i586-pc-linux-gnu-ld: cannot find arch/x86/kvm/vmx.o: No such file 
> > or directory
> > ...
> > ERROR: "__bad_udelay" [drivers/media/radio/radio-aimslab.ko] 
> > undefined!
> did you report this to gcc folks ?
>
> Btw, you said it showed with "-O3" or "-finline-functions", but I do
> not see any specific option passed to make. Could you remove the 
> "-j5"
> switch and add "V=1" to see the full compiler command line ?

Yes, big sorry. Distilling output again I found - there are problem of 
conjunction of "-finline-function -ftracer". Time ago I report similar 
problem about -ftracer in gcc bugzilla ("make defconfig && make all" 
with -ftracer, in various places in various versions).

BUT: First time (weeks ago) "-ftracer" must be first candidate for me 
to strip. Or I got this error first time without -ftracer or it is some 
kind of my own bug. Just fyi.

But output anymore ;) for first bug only:

make HOSTCC=x86_64-pc-linux-gnu-gcc ARCH=i386 
CROSS_COMPILE=i586-pc-linux-gnu- all
...
  i586-pc-linux-gnu-gcc -Wp,-MD,arch/x86/kvm/.vmx.o.d  -nostdinc 
-isystem /usr/lib/gcc/i586-pc-linux-gnu/4.5.1/include 
-I/var/tmp/portage/sys-kernel/next-sources-9999/work/linux-9999/arch/x86/include 
-Iinclude  -include include/generated/autoconf.h -D__KERNEL__ -Wall 
-Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing 
-fno-common -Werror-implicit-function-declaration -Wno-format-security 
-fno-delete-null-pointer-checks -O2 -finline-functions -ftracer -m32 
-msoft-float -mregparm=3 -freg-struct-return 
-mpreferred-stack-boundary=2 -Wa, -ffreestanding -DCONFIG_AS_CFI=1 
-DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -pipe 
-Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx 
-mno-sse2 -mno-3dnow -Wframe-larger-than=2048 -fno-stack-protector 
-fomit-frame-pointer -Wdeclaration-after-statement -Wno-pointer-sign 
-fno-strict-overflow -fconserve-stack -DCC_HAVE_ASM_GOTO -Ivirt/kvm 
-Iarch/x86/kvm -I.  -DMODULE  -D"KBUILD_STR(s)=#s" 
-D"KBUILD_BASENAME=KBUILD_STR(vmx)"  
-D"KBUILD_MODNAME=KBUILD_STR(kvm_intel)" -c -o arch/x86/kvm/vmx.o 
arch/x86/kvm/vmx.c
arch/x86/kvm/vmx.c: Assembler messages:
arch/x86/kvm/vmx.c:4036: Error: symbol `.Llaunched' is already defined
arch/x86/kvm/vmx.c:4048: Error: symbol `.Lkvm_vmx_return' is already 
defined


> Generally speaking, neither "-O3" or "-finline-functions" seems to be
> passed by default by kbuild, so I am not sure they are meant to be
> supported at all.

I know, -O3 is "uncommon" subject. Just I see "noinline" wide used, 
then sometimes sources adopted to auto-inlining. But -ftracer even more 
ncommon subject? yes & sorry...

>  - Arnaud
>
> > I unsure in precise version boundaries, but first found on release 
> > tree weeks
> > ago and first error only sometimes happened on x86_64 (version 
> > related?). On my
> > own builds I used -fno-inline-functions in local Makefile's, but 
> > this is more
> > local fix.
> >
> > > > --- a/arch/x86/kvm/vmx.c
> > > > +++ b/arch/x86/kvm/vmx.c
> > > > @@ -569,7 +569,7 @@ static inline void ept_sync_individual_a
> > > > Â Â Â}
> > > > Â}
> > > >
> > > > -static unsigned long vmcs_readl(unsigned long field)
> > > > +static noinline unsigned long vmcs_readl(unsigned long field)
> > > > Â{
> > > > Â Â Âunsigned long value = 0;
> > > >
> > > > --- a/drivers/media/radio/radio-aimslab.c
> > > > +++ b/drivers/media/radio/radio-aimslab.c
> > > > @@ -71,7 +71,7 @@ static struct rtrack rtrack_card;
> > > >
> > > > Â/* local things */
> > > >
> > > > -static void sleep_delay(long n)
> > > > +static noinline void sleep_delay(long n)
> > > > Â{
> > > > Â Â Â/* Sleep nicely for 'n' uS */
> > > > Â Â Âint d = n / msecs_to_jiffies(1000);
> > >
> > > A golden rule is that when a programmer reads some code, he should 
> > > be
> > > able to understand why it's there. ÂThere is no way on this little
> > > earth that a programmer will be able to look at this code and say
> > > "ah-hah, that must be a workaround for gcc-4.5 
> > > -finline-functions!".
> > >
> > > We fix that problem this way:
> > >
> > > --- 
> > > a/arch/x86/kvm/vmx.c~fix-miscompiling-with-gcc-45-finline-functions-fix
> > > +++ a/arch/x86/kvm/vmx.c
> > > @@ -569,6 +569,7 @@ static inline void ept_sync_individual_a
> > > Â Â Â }
> > > Â}
> > >
> > > +/* noinline works around gcc-4.5+ build error with 
> > > -finline-functions */
> > > Âstatic noinline unsigned long vmcs_readl(unsigned long field)
> > > Â{
> > > Â Â Â unsigned long value = 0;
> > > --- 
> > > a/drivers/media/radio/radio-aimslab.c~fix-miscompiling-with-gcc-45-finline-functions-fix
> > > +++ a/drivers/media/radio/radio-aimslab.c
> > > @@ -71,6 +71,7 @@ static struct rtrack rtrack_card;
> > >
> > > Â/* local things */
> > >
> > > +/* noinline works around gcc-4.5+ build error with 
> > > -finline-functions */
> > > Âstatic noinline void sleep_delay(long n)
> > > Â{
> > > Â Â Â /* Sleep nicely for 'n' uS */
> > > _

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