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Date: Sun, 15 Mar 2015 22:04:53 -0700 From: Yinghai Lu <yinghai@...nel.org> To: Baoquan He <bhe@...hat.com> Cc: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Kees Cook <keescook@...omium.org>, Borislav Petkov <bp@...e.de>, Thomas Gleixner <tglx@...utronix.de>, Jiri Kosina <jkosina@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Matt Fleming <matt.fleming@...el.com> Subject: Re: [PATCH v4] x86, kaslr: Access the correct kaslr_enabled variable On Sun, Mar 15, 2015 at 8:28 PM, Baoquan He <bhe@...hat.com> wrote: > On 03/15/15 at 12:49am, Yinghai Lu wrote: > > It's good to check the ret value as Boris suggested. However it could > fail since early_memremap self fail, e.g slot not found. In this case > making kaslr_enabled true may not be good. It should not fail. we always follow map/access/unmap. and sometime would have two for copying between them. > > As Minfei talked with you kaslr_setup_data is a global variable inside > kernel code, it has been ident mapped. Just derefencing the physical > address which is virtual address too and getting the real stored value > may be safer. No. That ident mapping is set in arch/x86/kernel/head_64.S and it is only for switchover. and it is gone when arch/x86/kernel/head64.c::x86_64_start_kernel/reset_early_page_tables is called. That reset_early_page_tables will only keep kernel high mapping and clear all other. Thanks Yinghai -- 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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