x86 single_step: TIF_FORCED_TF
This changes the single-step support to use a new thread_info flag
TIF_FORCED_TF instead of the PT_DTRACE flag in task_struct.ptrace.
This keeps arch implementation uses out of this non-arch field.
This changes the ptrace access to eflags to mask TF and maintain
the TIF_FORCED_TF flag directly if userland sets TF, instead of
relying on ptrace_signal_deliver. The 64-bit and 32-bit kernels
are harmonized on this same behavior. The ptrace_signal_deliver
approach works now, but this change makes the low-level register
access code reliable when called from different contexts than a
ptrace stop, which will be possible in the future.
The 64-bit do_debug exception handler is also changed not to clear TF
from user-mode registers. This matches the 32-bit kernel's behavior.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index 1ac53e9..0a7c812 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -545,14 +545,12 @@
}
/*
- * If TF is set due to a debugger (PT_DTRACE), clear the TF flag so
- * that register information in the sigcontext is correct.
+ * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
+ * flag so that register information in the sigcontext is correct.
*/
- if (unlikely(regs->eflags & TF_MASK)
- && likely(current->ptrace & PT_DTRACE)) {
- current->ptrace &= ~PT_DTRACE;
- regs->eflags &= ~TF_MASK;
- }
+ if (unlikely(regs->eflags & X86_EFLAGS_TF) &&
+ likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
+ regs->eflags &= ~X86_EFLAGS_TF;
/* Set up the stack frame */
if (ka->sa.sa_flags & SA_SIGINFO)