Date: Tue, 7 Feb 2017 17:55:42 +0000 From: Mark Rutland <mark.rutland@....com> To: Peter Zijlstra <peterz@...radead.org> Cc: Kees Cook <keescook@...omium.org>, "Reshetova, Elena" <elena.reshetova@...el.com>, Greg KH <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <h.peter.anvin@...el.com>, Will Deacon <will.deacon@....com>, David Windsor <dwindsor@...il.com>, Hans Liljestrand <ishkamiel@...il.com>, David Howells <dhowells@...hat.com>, LKML <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: Re: [PATCH 4/4] refcount: Report failures through CHECK_DATA_CORRUPTION On Tue, Feb 07, 2017 at 06:30:36PM +0100, Peter Zijlstra wrote: > On Tue, Feb 07, 2017 at 04:03:01PM +0000, Mark Rutland wrote: > > For x86 it's a little painful due to '%' in the register names, but it looks > > possible. The below appears to do the mangling correctly (then screams due to > > the mangled result being nonexistent). > > > asm( > > " .macro reg_to_offset r\n" > > " .irp rs,eax,ebx,ecx,edx\n" > > " .ifc \\r, %\\rs\n" > > " __offset_of_\\rs\n" > > " .endif\n" > > " .endr\n" > > " .endm\n" > > ); > > > > #define asm_sym(var) asm volatile("reg_to_offset %0\n" : : "r" (var)) > > Oh gawd that's a most gnarly hack. :) > Do we want to go do that for all archs or somehow cook a generic > fallback that ends up doing a full function call or something? Given the arch-specific reg->blah mapping is so "fun", I guess a generic fallback would be a good start. I haven't figured out all the plumbing details. It'd be nice to reuse the bug infrastructure so that arches don't have to implement another trap and callback pair, but I guess the reg details need to live in another data structure. Thanks, Mark.
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