LoongArch: Fix watchpoint setting error

In the current code, when debugging the following code using gdb,
"invalid argument ..." message will be displayed.

lihui@bogon:~$ cat test.c
  #include <stdio.h>
  int a = 0;
  int main()
  {
	a = 1;
	return 0;
  }
lihui@bogon:~$ gcc -g test.c -o test
lihui@bogon:~$ gdb test
...
(gdb) watch a
Hardware watchpoint 1: a
(gdb) r
...
Invalid argument setting hardware debug registers

There are mainly two types of issues.

1. Some incorrect judgment condition existed in user_watch_state
   argument parsing, causing -EINVAL to be returned.

When setting up a watchpoint, gdb uses the ptrace interface,
ptrace(PTRACE_SETREGSET, tid, NT_LOONGARCH_HW_WATCH, (void *) &iov)).
Register values in user_watch_state as follows:

  addr[0] = 0x0, mask[0] = 0x0, ctrl[0] = 0x0
  addr[1] = 0x0, mask[1] = 0x0, ctrl[1] = 0x0
  addr[2] = 0x0, mask[2] = 0x0, ctrl[2] = 0x0
  addr[3] = 0x0, mask[3] = 0x0, ctrl[3] = 0x0
  addr[4] = 0x0, mask[4] = 0x0, ctrl[4] = 0x0
  addr[5] = 0x0, mask[5] = 0x0, ctrl[5] = 0x0
  addr[6] = 0x0, mask[6] = 0x0, ctrl[6] = 0x0
  addr[7] = 0x12000803c, mask[7] = 0x0, ctrl[7] = 0x610

In arch_bp_generic_fields(), return -EINVAL when ctrl.len is
LOONGARCH_BREAKPOINT_LEN_8(0b00). So delete the incorrect judgment here.

In ptrace_hbp_fill_attr_ctrl(), when note_type is NT_LOONGARCH_HW_WATCH
and ctrl[0] == 0x0, if ((type & HW_BREAKPOINT_RW) != type) will return
-EINVAL. Here ctrl.type should be set based on note_type, and unnecessary
judgments can be removed.

2. The watchpoint argument was not set correctly due to unnecessary
   offset and alignment_mask.

Modify ptrace_hbp_fill_attr_ctrl() and hw_breakpoint_arch_parse(), which
ensure the watchpont argument is set correctly.

All changes according to the LoongArch Reference Manual:
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints

Cc: stable@vger.kernel.org
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/hw_breakpoint.h

@@ -101,7 +101,7 @@ struct perf_event;
 struct perf_event_attr;
 
 extern int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
-				  int *gen_len, int *gen_type, int *offset);
+				  int *gen_len, int *gen_type);
 extern int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw);
 extern int hw_breakpoint_arch_parse(struct perf_event *bp,
 				    const struct perf_event_attr *attr,

arch/loongarch/kernel/hw_breakpoint.c

@@ -283,7 +283,7 @@ int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
  * to generic breakpoint descriptions.
  */
 int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
-			   int *gen_len, int *gen_type, int *offset)
+			   int *gen_len, int *gen_type)
 {
 	/* Type */
 	switch (ctrl.type) {
@@ -303,11 +303,6 @@ int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
 		return -EINVAL;
 	}
 
-	if (!ctrl.len)
-		return -EINVAL;
-
-	*offset = __ffs(ctrl.len);
-
 	/* Len */
 	switch (ctrl.len) {
 	case LOONGARCH_BREAKPOINT_LEN_1:
@@ -386,21 +381,17 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
 			     struct arch_hw_breakpoint *hw)
 {
 	int ret;
-	u64 alignment_mask, offset;
+	u64 alignment_mask;
 
 	/* Build the arch_hw_breakpoint. */
 	ret = arch_build_bp_info(bp, attr, hw);
 	if (ret)
 		return ret;
 
-	if (hw->ctrl.type != LOONGARCH_BREAKPOINT_EXECUTE)
-		alignment_mask = 0x7;
-	else
+	if (hw->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) {
 		alignment_mask = 0x3;
-	offset = hw->address & alignment_mask;
-
-	hw->address &= ~alignment_mask;
-	hw->ctrl.len <<= offset;
+		hw->address &= ~alignment_mask;
+	}
 
 	return 0;
 }

arch/loongarch/kernel/ptrace.c

@@ -494,28 +494,14 @@ static int ptrace_hbp_fill_attr_ctrl(unsigned int note_type,
 				     struct arch_hw_breakpoint_ctrl ctrl,
 				     struct perf_event_attr *attr)
 {
-	int err, len, type, offset;
+	int err, len, type;
 
-	err = arch_bp_generic_fields(ctrl, &len, &type, &offset);
+	err = arch_bp_generic_fields(ctrl, &len, &type);
 	if (err)
 		return err;
 
-	switch (note_type) {
-	case NT_LOONGARCH_HW_BREAK:
-		if ((type & HW_BREAKPOINT_X) != type)
-			return -EINVAL;
-		break;
-	case NT_LOONGARCH_HW_WATCH:
-		if ((type & HW_BREAKPOINT_RW) != type)
-			return -EINVAL;
-		break;
-	default:
-		return -EINVAL;
-	}
-
 	attr->bp_len	= len;
 	attr->bp_type	= type;
-	attr->bp_addr	+= offset;
 
 	return 0;
 }
@@ -609,7 +595,19 @@ static int ptrace_hbp_set_ctrl(unsigned int note_type,
 		return PTR_ERR(bp);
 
 	attr = bp->attr;
-	decode_ctrl_reg(uctrl, &ctrl);
+
+	switch (note_type) {
+	case NT_LOONGARCH_HW_BREAK:
+		ctrl.type = LOONGARCH_BREAKPOINT_EXECUTE;
+		ctrl.len = LOONGARCH_BREAKPOINT_LEN_4;
+		break;
+	case NT_LOONGARCH_HW_WATCH:
+		decode_ctrl_reg(uctrl, &ctrl);
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	err = ptrace_hbp_fill_attr_ctrl(note_type, ctrl, &attr);
 	if (err)
 		return err;