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Date: Tue, 26 Jul 2011 20:33:25 +0200 From: Borislav Petkov <bp@...64.org> To: Ingo Molnar <mingo@...e.hu> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>, "Przywara, Andre" <Andre.Przywara@....com>, "Pohlack, Martin" <Martin.Pohlack@....com> Subject: Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue On Sun, Jul 24, 2011 at 09:40:46AM -0400, Borislav Petkov wrote: > > also, the PAGE_ALIGN() complication here looks unnecessary - can the > > vdso 'addr' ever be not 4K aligned above? > > Yeah, it can. I did some trace_printk runs and 'addr' wasn't 4K aligned > in some cases. I think this is because of the stack randomization we do > and we use mm->start_stack to get the vdso base address. Unfortunately, > I can't find those traces anymore but will do some again tomorrow. Better late than never :). So yes, mm->start_stack comes in unaligned from setup_arg_pages() and we use it to generate the vdso VA because the vdso is below the stack: 7fff761f9000-7fff7621a000 rw-p 00000000 00:00 0 [stack] 7fff763ec000-7fff763ed000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall] here's a trace_printk excerpt from vdso_addr() (gets inlined into arch_setup_additional_pages()): <...>-2516 [006] 624.364274: arch_setup_additional_pages: mm->start_stack: 0x7fff7621942a, len: 4096 <...>-2516 [006] 624.364278: arch_setup_additional_pages: randomized: 0x7fff763eb42a <...>-2516 [006] 624.364279: arch_setup_additional_pages: final addr: 0x7fff763eb42a Then, both arch_get_unmapped_area{,_topdown} page-align it. For our case, we PAGE_ALIGN it before randomizing it so that we can control the [14:12] setting. -- Regards/Gruss, Boris. Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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