[SeaBIOS] Re: [PATCH] build: use -fcf-protection=none when available

[Christian Ehrhardt]

On Fri, Mar 20, 2020 at 12:20 AM Fangrui Song  wrote:
> On 2020-03-19, Christian Ehrhardt wrote:
> > Some hardened gcc v9 compilers (such as the one in Ubuntu)
> > default this option which for seabios leads to emulation errors
> > when running in KVM (does not trigger in TCG) on older intel
> > chips of the Penryn generation (~2006-2008).
> >
> > Symptom in KVM looks like:
> >  KVM internal error. Suberror: 1
> >  emulation failure
> >  EAX=00000000 EBX=00000000 ECX=000086d4 EDX=00000000
> >  ESI=00000000 EDI=00000000 EBP=000086d4 ESP=00006d7c
> >  EIP=00007acf EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
> >  ES =0000 00000000 ffffffff 00809300
> >  CS =f000 000f0000 ffffffff 00809b00
> >  SS =0000 00000000 ffffffff 00809300
> >  DS =0000 00000000 ffffffff 00809300
> >  FS =0000 00000000 ffffffff 00809300
> >  GS =0000 00000000 ffffffff 00809300
> >  LDT=0000 00000000 0000ffff 00008200
> >  TR =0000 00000000 0000ffff 00008b00
> >  GDT=     000f6200 00000037
> >  IDT=     00000000 000003ff
> >  CR0=00000010 CR2=00000000 CR3=00000000 CR4=00000000
> >  DR0=0000000000000000 DR1=0000000000000000
> >  DR2=0000000000000000 DR3=0000000000000000
> >  DR6=00000000ffff0ff0 DR7=0000000000000400
> >  EFER=0000000000000000
> >  Code=b8 90 d9 00 00 66 e8 6b f7 ff ff 66 b8 0a 00 00
> >       00 e9 61 f2 <f3> 0f 1e fb 66 57 66 56 66 53 66 53
> >       66 89 c7 67 66 89 14 24 66 89 ce 66 e8 15 f8 ff ff 88
> >
> > URL: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1866870
> > Signed-off-by: Christian Ehrhardt
> >
> > Makefile | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/Makefile b/Makefile
> > index 5f7d5370..9e8188e5 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -69,6 +69,7 @@ COMMONCFLAGS += $(call
>
> cc-option,$(CC),-fno-stack-protector,)
> > COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
> > COMMONCFLAGS += $(call cc-option,$(CC),-fstack-check=no,)
> > COMMONCFLAGS += $(call cc-option,$(CC),-Wno-address-of-packed-member,)
> > +COMMONCFLAGS += $(call cc-option,$(CC),-fcf-protection=none,)
> > COMMA := ,
> >
> > CFLAGS32FLAT := $(COMMONCFLAGS) -DMODE16=0 -DMODESEGMENT=0
>
> If this is related to endbr32/endbr64 interpretation failures, please
> make it clear in the description.

I didn't know it was related to "endbr32/endbr64 interpretation failures"
when I was writing the patch :-)
I only learned about that when David commented on the LP bug.

But if that helps I can easily add mentioning that in a v2 ...