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Re: [PATCH 1/5] x86: Add -mindirect-branch=
Hi,
On Mon, 8 Jan 2018, H.J. Lu wrote:
> On Mon, Jan 8, 2018 at 4:00 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> > On Mon, Jan 08, 2018 at 03:55:52AM -0800, H.J. Lu wrote:
> >> > I'm wondering whether thunk creation can be a good target-independent generalization? I guess
> >> > we can emit the function declaration without direct writes to asm_out_file? And the emission
> >> > of function body can be potentially a target hook?
> >> >
> >> > What about emitting body of the function with RTL instructions instead of direct assembly write?
> >> > My knowledge of RTL is quite small, but maybe it can bring some generalization and reusability
> >> > for other targets?
> >>
> >> Thunks are x86 specific and they are created the same way as 32-bit PIC thunks.
> >> I don't see how a target hook is used.
> >
> > Talking about PIC thunks, those have I believe . character in their symbols,
> > so that they can't be confused with user functions. Any reason these
> > retpoline thunks aren't?
> >
>
> They used to have '.'. It was changed at the last minute since kernel
> needs to export them as regular symbols.
That can be done via asm aliases or direct assembler use; the kernel
doesn't absolutely have to access them via C compatible symbol names.
Ciao,
Michael.