Re: [PATCH v5 00/10] x86/asm: Compile-time asm code validation

Andi Kleen
2015-06-10T15:04:22Z

> > > - duplicate the destination code inside the function
> > > - convert the jump to a call
> >
> > That all won't work for a lot of cases.
>
> Hm, could you give an example?

Just a standard *_user exception handler.

>
> Well, I don't see how that's really a logical conclusion.

What's special about assembler code?

> But we're
> probably being too vague here... Do you have any examples where you
> really need to jump outside of a callable function?

It's not needed, but it's an optimization to optimize icache usage.
It is optional (-freorder-blocks-and-partition)

In this case gcc splits the function into two (hot and cold)

It's actually a nice optimization and it would be sad from stopping
the kernel from using it.

-Andi
--
ak@linux.intel.com -- Speaking for myself only.