[PATCH] x86_64: Fix interaction of single stepping with debuggers

Ported from i386/Linus

Fix another TF corner case.  Need to do the special TF handling for all
signals to make debuggers happy

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/signal.c b/arch/x86_64/kernel/signal.c
index 4ff0f0117a0..7760224cdfe 100644
--- a/arch/x86_64/kernel/signal.c
+++ b/arch/x86_64/kernel/signal.c
@@ -368,6 +368,18 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
                 }
         }
 
+        /*
+         * If TF is set due to a debugger (PT_DTRACE), clear the TF
+         * flag so that register information in the sigcontext is
+         * correct.
+         */
+        if (unlikely(regs->eflags & TF_MASK)) {
+                if (likely(current->ptrace & PT_DTRACE)) {
+                        current->ptrace &= ~PT_DTRACE;
+                        regs->eflags &= ~TF_MASK;
+                }
+        }
+
 #ifdef CONFIG_IA32_EMULATION
         if (test_thread_flag(TIF_IA32)) {
                 if (ka->sa.sa_flags & SA_SIGINFO)