[RFC,PATCH 03/14] ptrace: introduce user_single_step_siginfo() helper

[Oleg Nesterov <oleg@redhat.com>]

(already in mm: ptrace-introduce-user_single_step_siginfo-helper.patch)

Suggested by Roland.

Currently there is no way to synthesize a single-stepping trap in the
arch-independent manner. This patch adds the default helper which fills
siginfo_t, arch/ can can override it.

Architetures which implement user_enable_single_step() should add
user_single_step_siginfo() also.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
---

 include/linux/ptrace.h |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- V1/include/linux/ptrace.h~3_DEFAULT_HELPER	2009-11-24 19:50:39.000000000 +0100
+++ V1/include/linux/ptrace.h	2009-11-24 19:51:28.000000000 +0100
@@ -273,6 +273,18 @@ static inline void user_enable_block_ste
 }
 #endif	/* arch_has_block_step */
 
+#ifdef ARCH_HAS_USER_SINGLE_STEP_INFO
+extern void user_single_step_siginfo(struct task_struct *tsk,
+				struct pt_regs *regs, siginfo_t *info);
+#else
+static inline void user_single_step_siginfo(struct task_struct *tsk,
+				struct pt_regs *regs, siginfo_t *info)
+{
+	memset(info, 0, sizeof(*info));
+	info->si_signo = SIGTRAP;
+}
+#endif
+
 #ifndef arch_ptrace_stop_needed
 /**
  * arch_ptrace_stop_needed - Decide whether arch_ptrace_stop() should be called