signals: demultiplexing SIGTRAP signal

Currently a SIGTRAP can denote any one of below reasons.
	- Breakpoint hit
	- H/W debug register hit
	- Single step
	- Signal sent through kill() or rasie()

Architectures like powerpc/parisc provides infrastructure to demultiplex
SIGTRAP signal by passing down the information for receiving SIGTRAP through
si_code of siginfot_t structure. Here is an attempt is generalise this
infrastructure by extending it to x86 and x86_64 archs.

Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: akpm@linux-foundation.org
Cc: paulus@samba.org
Cc: linuxppc-dev@ozlabs.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/ia64/include/asm/siginfo.h

@@ -113,11 +113,6 @@ typedef struct siginfo {
 #undef NSIGSEGV
 #define NSIGSEGV	3
 
-/*
- * SIGTRAP si_codes
- */
-#define TRAP_BRANCH	(__SI_FAULT|3)	/* process taken branch trap */
-#define TRAP_HWBKPT	(__SI_FAULT|4)	/* hardware breakpoint or watchpoint */
 #undef NSIGTRAP
 #define NSIGTRAP	4
 

arch/powerpc/include/asm/siginfo.h

@@ -15,11 +15,6 @@
 
 #include <asm-generic/siginfo.h>
 
-/*
- * SIGTRAP si_codes
- */
-#define TRAP_BRANCH	(__SI_FAULT|3)	/* process taken branch trap */
-#define TRAP_HWBKPT	(__SI_FAULT|4)	/* hardware breakpoint or watchpoint */
 #undef NSIGTRAP
 #define NSIGTRAP	4
 

arch/x86/kernel/ptrace.c

@@ -1358,7 +1358,8 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 #endif
 }
 
-void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
+void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
+					 int error_code, int si_code)
 {
 	struct siginfo info;
 
@@ -1367,7 +1368,7 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
 
 	memset(&info, 0, sizeof(info));
 	info.si_signo = SIGTRAP;
-	info.si_code = TRAP_BRKPT;
+	info.si_code = si_code;
 
 	/* User-mode ip? */
 	info.si_addr = user_mode_vm(regs) ? (void __user *) regs->ip : NULL;
@@ -1454,5 +1455,5 @@ asmregparm void syscall_trace_leave(struct pt_regs *regs)
 	 */
 	if (test_thread_flag(TIF_SINGLESTEP) &&
 	    tracehook_consider_fatal_signal(current, SIGTRAP, SIG_DFL))
-		send_sigtrap(current, regs, 0);
+		send_sigtrap(current, regs, 0, TRAP_BRKPT);
 }

arch/x86/kernel/traps_32.c

@@ -891,6 +891,7 @@ void __kprobes do_debug(struct pt_regs *regs, long error_code)
 {
 	struct task_struct *tsk = current;
 	unsigned int condition;
+	int si_code;
 
 	trace_hardirqs_fixup();
 
@@ -935,8 +936,9 @@ void __kprobes do_debug(struct pt_regs *regs, long error_code)
 			goto clear_TF_reenable;
 	}
 
+	si_code = get_si_code((unsigned long)condition);
 	/* Ok, finally something we can handle */
-	send_sigtrap(tsk, regs, error_code);
+	send_sigtrap(tsk, regs, error_code, si_code);
 
 	/*
 	 * Disable additional traps. They'll be re-enabled when

arch/x86/kernel/traps_64.c

@@ -941,7 +941,7 @@ asmlinkage void __kprobes do_debug(struct pt_regs *regs,
 	tsk->thread.error_code = error_code;
 	info.si_signo = SIGTRAP;
 	info.si_errno = 0;
-	info.si_code = TRAP_BRKPT;
+	info.si_code = get_si_code(condition);
 	info.si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL;
 	force_sig_info(SIGTRAP, &info, tsk);
 

include/asm-generic/siginfo.h

@@ -199,6 +199,8 @@ typedef struct siginfo {
  */
 #define TRAP_BRKPT	(__SI_FAULT|1)	/* process breakpoint */
 #define TRAP_TRACE	(__SI_FAULT|2)	/* process trace trap */
+#define TRAP_BRANCH     (__SI_FAULT|3)  /* process taken branch trap */
+#define TRAP_HWBKPT     (__SI_FAULT|4)  /* hardware breakpoint/watchpoint */
 #define NSIGTRAP	2
 
 /*

include/asm-parisc/siginfo.h

@@ -3,11 +3,6 @@
 
 #include <asm-generic/siginfo.h>
 
-/*
- * SIGTRAP si_codes
- */
-#define TRAP_BRANCH	(__SI_FAULT|3)	/* process taken branch trap */
-#define TRAP_HWBKPT	(__SI_FAULT|4)	/* hardware breakpoint or watchpoint */
 #undef NSIGTRAP
 #define NSIGTRAP	4
 

include/asm-x86/ptrace.h

@@ -143,7 +143,7 @@ convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs);
 
 #ifdef CONFIG_X86_32
 extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
-			 int error_code);
+			 int error_code, int si_code);
 #endif
 
 void signal_fault(struct pt_regs *regs, void __user *frame, char *where);

include/asm-x86/traps.h

@@ -36,6 +36,16 @@ void do_invalid_op(struct pt_regs *, long);
 void do_general_protection(struct pt_regs *, long);
 void do_nmi(struct pt_regs *, long);
 
+static inline int get_si_code(unsigned long condition)
+{
+	if (condition & DR_STEP)
+		return TRAP_TRACE;
+	else if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
+		return TRAP_HWBKPT;
+	else
+		return TRAP_BRKPT;
+}
+
 extern int panic_on_unrecovered_nmi;
 extern int kstack_depth_to_print;