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

Submitted by Konstantin Khorenko on Aug. 11, 2016, 9:28 a.m.


Message ID 201608110928.u7B9S3bR002061@finist_cl7.x64_64.work.ct
State New
Series "Compat C/R patches"
Headers show

Commit Message

Konstantin Khorenko Aug. 11, 2016, 9:28 a.m.
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@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@redhat.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Cyrill Gorcunov <gorcunov@openvz.org>
    Cc: Pavel Emelyanov <xemul@virtuozzo.com>
    Cc: x86@kernel.org
    Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
 arch/x86/kernel/ptrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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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)
-	if (test_tsk_thread_flag(task, TIF_IA32))
+	if (!user_64bit_mode(task_pt_regs(task)))
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 		return &user_x86_32_view;