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, 2 insertions, 0 deletions

diff --git a/include/elf/common.h b/include/elf/common.h
index 78c85bd..2d18334 100644
--- a/include/elf/common.h
+++ b/include/elf/common.h
@@ -751,6 +751,8 @@
 					/*   note name must be "LINUX".  */
 #define NT_LARCH_LBT    0xa04		/* LoongArch Binary Translation registers */
 					/*   note name must be "CORE".  */
+#define NT_LOONGARCH_HW_WATCH   0xa06	/* LoongArch hardware watchpoint registers */
+					/*   note name must be "LINUX".  */
 #define NT_RISCV_CSR    0x900		/* RISC-V Control and Status Registers */
 					/*   note name must be "LINUX".  */
 #define NT_SIGINFO	0x53494749	/* Fields of siginfo_t.  */