Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast path with retpolines on

[Linus Torvalds]

On Fri, Jan 26, 2018 at 10:23 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote:
>
> The issue is that doing it this way gives us, effectively:
>
> long sys_foo(int a, int b)
> {
>   body here;
> }
>
> long SyS_foo(const struct pt_regs *regs)
> {
>   return sys_foo(regs->di, regs->si);
> }
>
> whereas what we want is *static* long sys_foo(...).

How about just marking 'sys_foo()' as being always_inline (but still
not static)? Because the case that _matters_ is that SyS_foo(), thing
when this is enabled.

Sure, you'll get two copies of the code (one in SyS_foo(), the other
being the callable-from C 'sys_foo()' that is exported and almost
never used). But that seems a fairly small price to pay. We could
leave it for later to try to get rid of the unused copies entirely.

             Linus