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

[Oleg Nesterov]

(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 <o...@redhat.com>
Acked-by: Roland McGrath <rol...@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);
 }