gdb: LoongArch: Add support for hardware watchpoint

LoongArch defines hardware watchpoint functions for load/store
operations. After the software configures the watchpoints for
load/store, the processor hardware will monitor the access
addresses of the load/store operations and trigger watchpoint
exception when the watchpoint setting conditions are met.

After this patch, watch/rwatch/awatch command are supported. Refer to the
following document for hardware watchpoint.
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints

A simple test is as follows:

lihui@bogon:~$ cat test.c
  #include <stdio.h>
  int a = 0;
  int main()
  {
        printf("start test\n");
        a = 1;
        printf("a = %d\n", a);
        printf("end test\n");
        return 0;
  }

lihui@bogon:~$ gcc -g test.c -o test

without this patch:

lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5               printf("start test\n");
(gdb) awatch a
Target does not support this type of hardware watchpoint.
...

with this patch:

lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5               printf("start test\n");
(gdb) awatch a
Hardware access (read/write) watchpoint 2: a
(gdb) c
Continuing.
start test

Hardware access (read/write) watchpoint 2: a

Old value = 0
New value = 1
main () at test.c:7
7               printf("a = %d\n", a);
(gdb) c
Continuing.

Hardware access (read/write) watchpoint 2: a

Value = 1
0x00000001200006e0 in main () at test.c:7
7               printf("a = %d\n", a);
(gdb) c
Continuing.
a = 1
end test
[Inferior 1 (process 22250) exited normally]

Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>

1 files changed, 92 insertions, 0 deletions

diff --git a/gdb/nat/loongarch-hw-point.h b/gdb/nat/loongarch-hw-point.h
new file mode 100644
index 0000000..86e5aa3
--- /dev/null
+++ b/gdb/nat/loongarch-hw-point.h
@@ -0,0 +1,92 @@
+/* Native-dependent code for GNU/Linux on LoongArch processors.
+
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   Contributed by Loongson Ltd.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef NAT_LOONGARCH_HW_POINT_H
+#define NAT_LOONGARCH_HW_POINT_H
+
+/* Macro definitions, data structures, and code for the hardware
+   breakpoint and hardware watchpoint support follow.  We use the
+   following abbreviations throughout the code:
+
+   hw - hardware
+   bp - breakpoint
+   wp - watchpoint  */
+
+/* Maximum number of hardware breakpoint and watchpoint registers.
+   Neither of these values may exceed the width of dr_changed_t
+   measured in bits.  */
+
+#define LOONGARCH_HWP_MAX_NUM 8
+
+
+/* The maximum length of a memory region that can be watched by one
+   hardware watchpoint register.  */
+
+#define LOONGARCH_HWP_MAX_LEN_PER_REG 8
+#define CTRL_PLV3_ENABLE		0x10
+
+#define DR_CONTROL_ENABLED(ctrl)  ((ctrl & CTRL_PLV3_ENABLE) == CTRL_PLV3_ENABLE)
+
+/* Structure for managing the hardware breakpoint/watchpoint resources.
+   DR_ADDR_* stores the address, DR_CTRL_* stores the control register
+   content, and DR_REF_COUNT_* counts the numbers of references to the
+   corresponding bp/wp, by which way the limited hardware resources
+   are not wasted on duplicated bp/wp settings (though so far gdb has
+   done a good job by not sending duplicated bp/wp requests).  */
+
+struct loongarch_debug_reg_state
+{
+  /* hardware watchpoint */
+  CORE_ADDR dr_addr_wp[LOONGARCH_HWP_MAX_NUM];
+  unsigned int dr_ctrl_wp[LOONGARCH_HWP_MAX_NUM];
+  unsigned int dr_ref_count_wp[LOONGARCH_HWP_MAX_NUM];
+};
+
+extern int loongarch_num_wp_regs;
+
+/* Invoked when IDXth breakpoint/watchpoint register pair needs to be
+   updated.  */
+
+void loongarch_notify_debug_reg_change (ptid_t ptid, int is_watchpoint,
+				      unsigned int idx);
+
+
+int loongarch_handle_watchpoint (enum target_hw_bp_type type, CORE_ADDR addr,
+				 int len, int is_insert, ptid_t ptid,
+				 struct loongarch_debug_reg_state *state);
+
+/* Return TRUE if there are any hardware breakpoints.  If WATCHPOINT is TRUE,
+   check hardware watchpoints instead.  */
+
+bool loongarch_any_set_debug_regs_state (loongarch_debug_reg_state *state,
+					 bool watchpoint);
+
+/* Print the values of the cached breakpoint/watchpoint registers.  */
+
+void loongarch_show_debug_reg_state (struct loongarch_debug_reg_state *state,
+				     const char *func, CORE_ADDR addr,
+				     int len, enum target_hw_bp_type type);
+
+/* Return true if we can watch a memory region that starts address
+   ADDR and whose length is LEN in bytes.  */
+
+int loongarch_region_ok_for_watchpoint (CORE_ADDR addr, int len);
+
+#endif /* NAT_LOONGARCH_HW_POINT_H */