Messages in this thread | | | Subject | Re: [RFC, PATCHv1 15/28] x86: detect 5-level paging support | From | "H. Peter Anvin" <> | Date | Tue, 13 Dec 2016 14:44:06 -0800 |
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On 12/08/16 12:20, Borislav Petkov wrote: > On Thu, Dec 08, 2016 at 12:08:53PM -0800, Linus Torvalds wrote: >> Especially since that's some of the ugliest inline asm ever due to the >> nasty BX handling. > > Yeah, about that: why doesn't gcc handle that for us like it would > handle a clobbered register? I mean, it *should* know that BX is live > when building with -fPIC... The .ifnc thing looks really silly. >
When compiling with -fPIC gcc treats ebx as a "fixed register". A fixed register can't be spilled, and so a clobber of a fixed register is a fatal error.
Like it or not, it's how it works.
-hpa
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