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>

1 files changed, 5 insertions, 14 deletions

diff --git a/arch/loongarch/kernel/hw_breakpoint.c b/arch/loongarch/kernel/hw_breakpoint.c
index fc55c4de2a11..950b2b8a82ee 100644
--- a/arch/loongarch/kernel/hw_breakpoint.c
+++ b/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;
 }