[Devel] [PATCH RHEL7 COMMIT] ms/x86/ptrace: down with test_thread_flag(TIF_IA32)

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.22.2.vz7.16.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.22.2.vz7.16.5
------>
commit 273538cc099711fe9e01c2e01ae5c36264aa7395
Author: Dmitry Safonov <dsafonov at virtuozzo.com>
Date:   Thu Aug 11 13:28:03 2016 +0400

    ms/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
    
    Cc: Oleg Nesterov <oleg at redhat.com>
    Cc: Andy Lutomirski <luto at kernel.org>
    Cc: Ingo Molnar <mingo at redhat.com>
    Cc: Cyrill Gorcunov <gorcunov at openvz.org>
    Cc: Pavel Emelyanov <xemul at virtuozzo.com>
    Cc: x86 at kernel.org
    Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
---
 arch/x86/kernel/ptrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index b7cc6a0..8093633 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1434,7 +1434,7 @@ 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;