From: Dmitry Safonov <dsafonov@virtuozzo.com>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: <linux-kernel@vger.kernel.org>, <mingo@redhat.com>,
<luto@amacapital.net>, <tglx@linutronix.de>, <hpa@zytor.com>,
<x86@kernel.org>, <0x7f454c46@gmail.com>, <oleg@redhat.com>,
<xemul@virtuozzo.com>, <khorenko@virtuozzo.com>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32)
Date: Fri, 3 Jun 2016 13:27:33 +0300 [thread overview]
Message-ID: <a2937a74-c63c-527d-da26-eb4dd10468a4@virtuozzo.com> (raw)
In-Reply-To: <20160603095748.GC2431@uranus>
On 06/03/2016 12:57 PM, Cyrill Gorcunov wrote:
> On Wed, Jun 01, 2016 at 04:11:36PM +0300, Dmitry Safonov wrote:
>> As the task isn't executing at the moment of {GET,SET}REGS,
>> return regset that corresponds to code selector, rather than
>> value of TIF_IA32 flag.
>> I.e. if we ptrace i386 elf binary that has just changed it's
>> code selector to __USER_CS, than GET_REGS will return
>> full x86_64 register set.
>>
>> Note, that this will work only if application has changed it's CS.
>> If the application does 32-bit syscall with __USER_CS, ptrace
>> will still return 64-bit register set. Which might be still confusing
>> for tools that expect TS_COMPACT to be exposed [1, 2].
>>
>> So this this change should make PTRACE_GETREGSET more reliable and
>> this will be another step to drop TIF_{IA32,X32} flags.
>>
>> [1]: https://sourceforge.net/p/strace/mailman/message/30471411/
>> [2]: https://lkml.org/lkml/2012/1/18/320
>>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: Oleg Nesterov <oleg@redhat.com>
>> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
>
> Looks reasonable! Still if cs has been changed to non-compat
> selector and we now return 64bit registers set, won't it
> cause problems for old tools? I suspect it should not but
> still.
>
Thanks! Hmm, strace works fine - I'll check gdb to be sure.
What else could be bothered by this?
next prev parent reply other threads:[~2016-06-03 10:29 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-01 13:11 [PATCH 0/6] x86: 32-bit compatible C/R on x86_64 Dmitry Safonov
2016-06-01 13:11 ` [PATCH 1/6] x86/vdso: unmap vdso blob on vvar mapping failure Dmitry Safonov
2016-06-01 13:11 ` [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Dmitry Safonov
2016-06-03 9:50 ` Cyrill Gorcunov
2016-06-03 10:03 ` Dmitry Safonov
2016-06-01 13:11 ` [PATCH 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_* Dmitry Safonov
2016-06-01 13:11 ` [PATCH 4/6] x86/coredump: use core regs, rather that TIF_IA32 flag Dmitry Safonov
2016-06-03 9:51 ` Cyrill Gorcunov
2016-06-03 9:56 ` Dmitry Safonov
2016-06-03 10:01 ` Cyrill Gorcunov
2016-06-06 20:45 ` Oleg Nesterov
2016-06-06 22:43 ` Oleg Nesterov
2016-06-08 13:28 ` Dmitry Safonov
2016-06-01 13:11 ` [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Dmitry Safonov
2016-06-03 9:57 ` Cyrill Gorcunov
2016-06-03 10:27 ` Dmitry Safonov [this message]
2016-06-03 10:41 ` Cyrill Gorcunov
2016-06-06 21:19 ` Oleg Nesterov
2016-06-07 11:38 ` Dmitry Safonov
2016-06-09 17:21 ` Andy Lutomirski
2016-06-10 20:07 ` Oleg Nesterov
2016-06-10 20:14 ` Andy Lutomirski
2016-06-13 13:50 ` Oleg Nesterov
2016-06-13 20:40 ` Andy Lutomirski
2016-06-14 14:34 ` Oleg Nesterov
2016-06-14 14:43 ` Dmitry Safonov
2016-06-01 13:11 ` [PATCH 6/6] x86/signal: add SA_{X32,IA32}_ABI sa_flags Dmitry Safonov
2016-06-04 5:08 ` Andy Lutomirski
2016-06-04 15:57 ` Dmitry Safonov
2016-06-01 13:15 ` [PATCH 0/6] x86: 32-bit compatible C/R on x86_64 Dmitry Safonov
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