nios2: rework trap handler

Redefine trap handler as below:

 0  N/A        reserved for system calls
 1  SIGUSR1    user-defined signal 1
 2  SIGUSR2    user-defined signal 2
 3  SIGILL     illegal instruction
 4..29         reserved (but implemented to raise SIGILL instead of being undefined)
30  SIGTRAP    KGDB
31  SIGTRAP    trace/breakpoint trap

Signed-off-by: Ley Foon Tan <lftan@altera.com>

arch/nios2/kernel/entry.S

@@ -92,35 +92,35 @@ exception_table:
 
 trap_table:
 	.word	handle_system_call	/* 0  */
-	.word	instruction_trap	/* 1  */
-	.word	instruction_trap	/* 2  */
-	.word	instruction_trap	/* 3  */
-	.word	instruction_trap	/* 4  */
-	.word	instruction_trap	/* 5  */
-	.word	instruction_trap	/* 6  */
-	.word	instruction_trap	/* 7  */
-	.word	instruction_trap	/* 8  */
-	.word	instruction_trap	/* 9  */
-	.word	instruction_trap	/* 10 */
-	.word	instruction_trap	/* 11 */
-	.word	instruction_trap	/* 12 */
-	.word	instruction_trap	/* 13 */
-	.word	instruction_trap	/* 14 */
-	.word	instruction_trap	/* 15 */
-	.word	instruction_trap	/* 16 */
-	.word	instruction_trap	/* 17 */
-	.word	instruction_trap	/* 18 */
-	.word	instruction_trap	/* 19 */
-	.word	instruction_trap	/* 20 */
-	.word	instruction_trap	/* 21 */
-	.word	instruction_trap	/* 22 */
-	.word	instruction_trap	/* 23 */
-	.word	instruction_trap	/* 24 */
-	.word	instruction_trap	/* 25 */
-	.word	instruction_trap	/* 26 */
-	.word	instruction_trap	/* 27 */
-	.word	instruction_trap	/* 28 */
-	.word	instruction_trap	/* 29 */
+	.word	handle_trap_1		/* 1  */
+	.word	handle_trap_2		/* 2  */
+	.word	handle_trap_3		/* 3  */
+	.word	handle_trap_reserved	/* 4  */
+	.word	handle_trap_reserved	/* 5  */
+	.word	handle_trap_reserved	/* 6  */
+	.word	handle_trap_reserved	/* 7  */
+	.word	handle_trap_reserved	/* 8  */
+	.word	handle_trap_reserved	/* 9  */
+	.word	handle_trap_reserved	/* 10 */
+	.word	handle_trap_reserved	/* 11 */
+	.word	handle_trap_reserved	/* 12 */
+	.word	handle_trap_reserved	/* 13 */
+	.word	handle_trap_reserved	/* 14 */
+	.word	handle_trap_reserved	/* 15 */
+	.word	handle_trap_reserved	/* 16 */
+	.word	handle_trap_reserved	/* 17 */
+	.word	handle_trap_reserved	/* 18 */
+	.word	handle_trap_reserved	/* 19 */
+	.word	handle_trap_reserved	/* 20 */
+	.word	handle_trap_reserved	/* 21 */
+	.word	handle_trap_reserved	/* 22 */
+	.word	handle_trap_reserved	/* 23 */
+	.word	handle_trap_reserved	/* 24 */
+	.word	handle_trap_reserved	/* 25 */
+	.word	handle_trap_reserved	/* 26 */
+	.word	handle_trap_reserved	/* 27 */
+	.word	handle_trap_reserved	/* 28 */
+	.word	handle_trap_reserved	/* 29 */
 #ifdef CONFIG_KGDB
 	.word	handle_kgdb_breakpoint	/* 30 KGDB breakpoint */
 #else
@@ -455,6 +455,19 @@ handle_kgdb_breakpoint:
 	br	ret_from_exception
 #endif
 
+handle_trap_1:
+	call	handle_trap_1_c
+	br	ret_from_exception
+
+handle_trap_2:
+	call	handle_trap_2_c
+	br	ret_from_exception
+
+handle_trap_3:
+handle_trap_reserved:
+	call	handle_trap_3_c
+	br	ret_from_exception
+
 /*
  * Beware - when entering resume, prev (the current task) is
  * in r4, next (the new task) is in r5, don't change these

arch/nios2/kernel/traps.c

@@ -23,6 +23,17 @@
 
 static DEFINE_SPINLOCK(die_lock);
 
+static void _send_sig(int signo, int code, unsigned long addr)
+{
+	siginfo_t info;
+
+	info.si_signo = signo;
+	info.si_errno = 0;
+	info.si_code = code;
+	info.si_addr = (void __user *) addr;
+	force_sig_info(signo, &info, current);
+}
+
 void die(const char *str, struct pt_regs *regs, long err)
 {
 	console_verbose();
@@ -39,16 +50,10 @@ void die(const char *str, struct pt_regs *regs, long err)
 
 void _exception(int signo, struct pt_regs *regs, int code, unsigned long addr)
 {
-	siginfo_t info;
-
 	if (!user_mode(regs))
 		die("Exception in kernel mode", regs, signo);
 
-	info.si_signo = signo;
-	info.si_errno = 0;
-	info.si_code = code;
-	info.si_addr = (void __user *) addr;
-	force_sig_info(signo, &info, current);
+	_send_sig(signo, code, addr);
 }
 
 /*
@@ -183,3 +188,18 @@ asmlinkage void unhandled_exception(struct pt_regs *regs, int cause)
 
 	pr_emerg("opcode: 0x%08lx\n", *(unsigned long *)(regs->ea));
 }
+
+asmlinkage void handle_trap_1_c(struct pt_regs *fp)
+{
+	_send_sig(SIGUSR1, 0, fp->ea);
+}
+
+asmlinkage void handle_trap_2_c(struct pt_regs *fp)
+{
+	_send_sig(SIGUSR2, 0, fp->ea);
+}
+
+asmlinkage void handle_trap_3_c(struct pt_regs *fp)
+{
+	_send_sig(SIGILL, ILL_ILLTRP, fp->ea);
+}