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Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32)

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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.

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[PATCH 0/6] x86: 32-bit compatible C/R on x86_64 Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-01 15:20 +0200
  [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-01 15:20 +0200
    Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Cyrill Gorcunov <gorcunov@gmail.com> - 2016-06-03 12:00 +0200
      Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Cyrill Gorcunov <gorcunov@gmail.com> - 2016-06-03 12:50 +0200
    Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Oleg Nesterov <oleg@redhat.com> - 2016-06-07 00:30 +0200
      Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-07 13:40 +0200
      Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Andy Lutomirski <luto@amacapital.net> - 2016-06-09 19:30 +0200
        Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Oleg Nesterov <oleg@redhat.com> - 2016-06-10 22:10 +0200
          Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32) Andy Lutomirski <luto@amacapital.net> - 2016-06-10 22:20 +0200
  [PATCH 1/6] x86/vdso: unmap vdso blob on vvar mapping failure Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-01 15:20 +0200
  [PATCH 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_* Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-01 15:20 +0200

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