x86 ptrace: unify TIF_SINGLESTEP

This unifies the treatment of TIF_SINGLESTEP on i386 and x86_64.
The bit is now excluded from _TIF_WORK_MASK on i386 as it has been
on x86_64.  This means the do_notify_resume() path using it is never
used, so TIF_SINGLESTEP is not cleared on returning to user mode.

Both now leave TIF_SINGLESTEP set when returning to user, so that
it's already set on an int $0x80 system call entry.  This removes
the need for testing TF on the system_call path.  Doing it this way
fixes the regression for PTRACE_SINGLESTEP into a sigreturn syscall,
introduced by commit 1e2e99f0e4aa6363e8515ed17011c210c8f1b52a.

The clear_TF_reenable case that sets TIF_SINGLESTEP can only happen
on a non-exception kernel entry, i.e. sysenter/syscall instruction.
That will always get to the syscall exit tracing path.

Signed-off-by: Roland McGrath <roland@redhat.com>

1 files changed, 0 insertions, 4 deletions

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 6bc07f0f1202..0ad987d02b72 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -383,10 +383,6 @@ syscall_exit:
                                         # setting need_resched or sigpending
                                         # between sampling and the iret
         TRACE_IRQS_OFF
-        testl $X86_EFLAGS_TF,PT_EFLAGS(%esp)    # If tracing set singlestep flag on exit
-        jz no_singlestep
-        orl $_TIF_SINGLESTEP,TI_flags(%ebp)
-no_singlestep:
         movl TI_flags(%ebp), %ecx
         testw $_TIF_ALLWORK_MASK, %cx   # current->work
         jne syscall_exit_work