nommu ptrace support

The patch below adds ARM ptrace functions to get the process load address.
This is required for useful userspace debugging on mmuless systems.  These
values are obtained by reading magic offsets with PTRACE_PEEKUSR, as on other
nommu targets. I picked arbitrary large values for the offsets.
Signed-off-by: Paul Brook <paul@codesourcery.com>

arch/arm/kernel/ptrace.c

@@ -527,7 +527,13 @@ static int ptrace_read_user(struct task_struct *tsk, unsigned long off,
 		return -EIO;
 
 	tmp = 0;
-	if (off < sizeof(struct pt_regs))
+	if (off == PT_TEXT_ADDR)
+		tmp = tsk->mm->start_code;
+	else if (off == PT_DATA_ADDR)
+		tmp = tsk->mm->start_data;
+	else if (off == PT_TEXT_END_ADDR)
+		tmp = tsk->mm->end_code;
+	else if (off < sizeof(struct pt_regs))
 		tmp = get_user_reg(tsk, off >> 2);
 
 	return put_user(tmp, ret);

include/asm-arm/ptrace.h

@@ -65,6 +65,12 @@
 #define PSR_x		0x0000ff00	/* Extension		*/
 #define PSR_c		0x000000ff	/* Control		*/
 
+/* These are `magic' values for PTRACE_PEEKUSR that return info about where
+   a process is located in memory.  */
+#define PT_TEXT_ADDR		0x10000
+#define PT_DATA_ADDR		0x10004
+#define PT_TEXT_END_ADDR	0x10008
+
 #ifndef __ASSEMBLY__
 
 /*