Messages in this thread | | | Date | Mon, 29 Jan 2018 18:50:34 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 08/24] x86,sme: Annotate indirect call |
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On Mon, Jan 29, 2018 at 06:49:52PM +0100, Peter Zijlstra wrote: > On Fri, Jan 26, 2018 at 10:37:30AM +0000, David Woodhouse wrote: > > On Tue, 2018-01-23 at 16:25 +0100, Peter Zijlstra wrote: > > > This is boot code, we run this _way_ before userspace comes along to > > > poison our branch predictor. > > > > Hm, objtool knows about sections, doesn't it? Why it is whining about > > indirect jumps in inittext anyway? > > > > In fact, why are we even *doing* retpolines in inittext? Not that we > > are; since we flipped the ALTERNATIVE logic around, at that point we > > still have the 'oldinstr' which is a bare jmp anyway. We might as well > > do this: > > > > --- a/include/linux/init.h > > +++ b/include/linux/init.h > > @@ -37,10 +37,15 @@ > > * as gcc otherwise puts the data into the bss section and not into the init > > * section. > > */ > > +#if defined(RETPOLINE) && !defined(MODULE) > > +#define __noretpoline __attribute__((indirect_branch("keep"))) > > +#else > > +#define __noretpoline > > +#endif
Clearly I cannot read...
> > /* These are for everybody (although not all archs will actually > > discard it in modules) */ > > -#define __init __section(.init.text) __cold __inittrace __latent_entropy > > +#define __init __section(.init.text) __cold __inittrace __latent_entropy __noretpoline > > We run module __init text concurrently with userspace.
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