[RFC,PATCH 06/14] ptrace: x86: implement user_single_step_siginfo()

[Oleg Nesterov <oleg@redhat.com>]

(already in mm: ptrace-x86-implement-user_single_step_siginfo.patch)

Suggested by Roland.

Implement user_single_step_siginfo() for x86. Extract this code
from send_sigtrap().

Since x86 calls tracehook_report_syscall_exit(step => 0) the new
helper is not used yet.

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

 arch/x86/include/asm/ptrace.h |    2 ++
 arch/x86/kernel/ptrace.c      |   30 +++++++++++++++++++++---------
 2 files changed, 23 insertions(+), 9 deletions(-)

--- V1/arch/x86/include/asm/ptrace.h~6_X86_HELPER	2009-11-24 19:46:48.000000000 +0100
+++ V1/arch/x86/include/asm/ptrace.h	2009-11-24 19:52:11.000000000 +0100
@@ -230,6 +230,8 @@ extern void user_enable_block_step(struc
 #define arch_has_block_step()	(boot_cpu_data.x86 >= 6)
 #endif
 
+#define ARCH_HAS_USER_SINGLE_STEP_INFO
+
 struct user_desc;
 extern int do_get_thread_area(struct task_struct *p, int idx,
 			      struct user_desc __user *info);
--- V1/arch/x86/kernel/ptrace.c~6_X86_HELPER	2009-11-24 19:46:48.000000000 +0100
+++ V1/arch/x86/kernel/ptrace.c	2009-11-24 19:52:11.000000000 +0100
@@ -1437,21 +1437,33 @@ const struct user_regset_view *task_user
 #endif
 }
 
-void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
-					 int error_code, int si_code)
+static void fill_sigtrap_info(struct task_struct *tsk,
+				struct pt_regs *regs,
+				int error_code, int si_code,
+				struct siginfo *info)
 {
-	struct siginfo info;
-
 	tsk->thread.trap_no = 1;
 	tsk->thread.error_code = error_code;
 
-	memset(&info, 0, sizeof(info));
-	info.si_signo = SIGTRAP;
-	info.si_code = si_code;
+	memset(info, 0, sizeof(*info));
+	info->si_signo = SIGTRAP;
+	info->si_code = si_code;
+	info->si_addr = user_mode_vm(regs) ? (void __user *)regs->ip : NULL;
+}
 
-	/* User-mode ip? */
-	info.si_addr = user_mode_vm(regs) ? (void __user *) regs->ip : NULL;
+void user_single_step_siginfo(struct task_struct *tsk,
+				struct pt_regs *regs,
+				struct siginfo *info)
+{
+	fill_sigtrap_info(tsk, regs, 0, TRAP_BRKPT, info);
+}
 
+void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
+					 int error_code, int si_code)
+{
+	struct siginfo info;
+
+	fill_sigtrap_info(tsk, regs, error_code, si_code, &info);
 	/* Send us the fake SIGTRAP */
 	force_sig_info(SIGTRAP, &info, tsk);
 }