On Wed, Jul 19, 2017 at 12:45:19PM -0700, Kees Cook wrote:
> > diff --git a/arch/x86/include/asm/refcount.h
> > b/arch/x86/include/asm/refcount.h
> > index 13b91e850a02..e7587db3487c 100644
> > --- a/arch/x86/include/asm/refcount.h
> > +++ b/arch/x86/include/asm/refcount.h
> > @@ -15,6 +15,7 @@
> > ".pushsection .text.unlikely\n" \
> > "111:\tlea %[counter], %%" _ASM_CX "\n" \
> > "112:\t" ASM_UD0 "\n" \
> > + ASM_UNREACHABLE \
> > ".popsection\n" \
> > "113:\n" \
> > _ASM_EXTABLE_REFCOUNT(112b, 113b)
> > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> > index cd4bbe8242bd..85e0b8f42ca0 100644
> > --- a/include/linux/compiler-gcc.h
> > +++ b/include/linux/compiler-gcc.h
> > @@ -202,15 +202,25 @@
> > #endif
> >
> > #ifdef CONFIG_STACK_VALIDATION
> > +
> > #define annotate_unreachable() ({ \
> > asm("%c0:\t\n" \
> > - ".pushsection .discard.unreachable\t\n" \
> > - ".long %c0b - .\t\n" \
> > - ".popsection\t\n" : : "i" (__LINE__)); \
> > + ".pushsection .discard.unreachable\n\t" \
> > + ".long %c0b - .\n\t" \
> > + ".popsection\n\t" : : "i" (__LINE__)); \
>
> Is this just an indentation change?
This was sneaking in a fix to put the tab after the newline instead of
before it. I figured it's not worth its own commit.
> > })
> > +
> > +#define ASM_UNREACHABLE
> > \
> > + "999: .pushsection .discard.unreachable\n\t" \
> > + ".long 999b - .\n\t" \
> > + ".popsection\n\t"
>
> Just so I understand, we'll get a single byte added for each exception
> case, but it'll get discarded during final link?
I think it's four bytes actually, but yeah, the section gets stripped at
vmlinux link time.
--
Josh
