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Date: Tue, 21 Mar 2017 18:59:14 +0300 From: Dmitry Safonov <dsafonov@...tuozzo.com> To: Thomas Gleixner <tglx@...utronix.de>, Adam Borowski <kilobyte@...band.pl> CC: Ingo Molnar <mingo@...nel.org>, Andrei Vagin <avagin@...il.com>, "Ingo Molnar" <mingo@...hat.com>, LKML <linux-kernel@...r.kernel.org>, "Cyrill Gorcunov" <gorcunov@...nvz.org>, Andy Lutomirski <luto@...nel.org>, "Thomas Garnier" <thgarnie@...gle.com>, "H. Peter Anvin" <hpa@...or.com> Subject: Re: linux-next: x86: Unalbe to run x32 processes on the x86_64 kernel On 03/21/2017 03:50 PM, Dmitry Safonov wrote: > On 03/21/2017 03:49 PM, Thomas Gleixner wrote: >> On Tue, 21 Mar 2017, Adam Borowski wrote: >>> On Tue, Mar 21, 2017 at 07:45:39AM +0100, Ingo Molnar wrote: >>>> * Andrei Vagin <avagin@...il.com> wrote: >>>> >>>>> # first bad commit: [45fc8757d1d2128e342b4e7ef39adedf7752faac] x86: >>>>> Make the GDT remapping read-only on 64-bit >>>> >>>> Just wondering, does the following commit fix it: >>>> >>>> 5b781c7e317f x86/tls: Forcibly set the accessed bit in TLS segments >>> >>> It does fix i386 but not x32. >>> >>> By "x32" I mean CONFIG_X86_X32, by "i386" CONFIG_IA32_EMULATION, >>> contrary to >>> Andrei's first report. The naming of the new ABI wasn't too >>> fortunate... >> >> The X32 issue is unrelated to the GDT mapping. >> >> What happens is that the mmap rework from Dmitry switched X32 to use >> 64bit >> mappings, which is wrong. X32 has 64bit instructions and syscalls and >> 32bit >> address space. > > Hmm, in_compat_syscall() checks x32 syscall bit. Which is not set during exec() for x32. So in_compat_syscall() doesn't work there. I've tested this patch on x32-debian port: https://lkml.org/lkml/2017/3/21/489 Though I'm not very happy with the resulting patch :( Maybe one could suggest a better idea.. > I'll take a look, what happens there. > >> Dmitry, can you please have a look and fix that up? For reproduction just >> compile helloworld.c with gcc -mx32. > > Sure, thanks. > -- Dmitry
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