Commit cc87324b authored Sep 05, 2016 by Dmitry Safonov Committed by Thomas Gleixner Sep 14, 2016

x86/ptrace: Down with test_thread_flag(TIF_IA32)

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



Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: 0x7f454c46@gmail.com
Cc: oleg@redhat.com
Cc: linux-mm@kvack.org
Cc: luto@kernel.org
Cc: Pedro Alves <palves@redhat.com>
Cc: gorcunov@openvz.org
Cc: xemul@virtuozzo.com
Link: http://lkml.kernel.org/r/20160905133308.28234-6-dsafonov@virtuozzo.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 90954e7b

arch/x86/kernel/ptrace.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1358,7 +1358,7 @@ void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
		const struct user_regset_view task_user_regset_view(struct task_struct task)
		{
		#ifdef CONFIG_IA32_EMULATION
		if (test_tsk_thread_flag(task, TIF_IA32))
		if (!user_64bit_mode(task_pt_regs(task)))
		#endif
		#if defined CONFIG_X86_32 \|\| defined CONFIG_IA32_EMULATION
		return &user_x86_32_view;

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