server/gdb_server.c: support unavailable registers

According to gdb documentation, `g` and `p` packets can report a
register being unavailable by a string of 'x' instead of register's
value.

Change-Id: I8ef279f1357c2e612f5d3290eb0022c1b47d9fa7
Signed-off-by: Evgeniy Naydanov <evgeniy.naydanov@syntacore.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7876
Reviewed-by: Marek Vrbka <marek.vrbka@codasip.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Anatoly Parshintsev <kupokupokupopo@gmail.com>
Tested-by: jenkins

diff --git a/src/server/gdb_server.c b/src/server/gdb_server.c
index 4a4ea53dc325162c0de89f48b8a55454f355c18a..497f62c4290dc3663f858041d1ce7dc04973afaf 100644 (file)
--- a/src/server/gdb_server.c
+++ b/src/server/gdb_server.c
@@ -1207,6 +1207,27 @@ static void gdb_target_to_reg(struct target *target,
        }
 }
 
+/* get register value if needed and fill the buffer accordingly */
+static int gdb_get_reg_value_as_str(struct target *target, char *tstr, struct reg *reg)
+{
+       int retval = ERROR_OK;
+
+       if (!reg->valid)
+               retval = reg->type->get(reg);
+
+       const unsigned int len = DIV_ROUND_UP(reg->size, 8) * 2;
+       switch (retval) {
+               case ERROR_OK:
+                       gdb_str_to_target(target, tstr, reg);
+                       return ERROR_OK;
+               case ERROR_TARGET_RESOURCE_NOT_AVAILABLE:
+                       memset(tstr, 'x', len);
+                       tstr[len] = '\0';
+                       return ERROR_OK;
+       }
+       return ERROR_FAIL;
+}
+
 static int gdb_get_registers_packet(struct connection *connection,
                char const *packet, int packet_size)
 {
@@ -1248,16 +1269,11 @@ static int gdb_get_registers_packet(struct connection *connection,
        for (i = 0; i < reg_list_size; i++) {
                if (!reg_list[i] || reg_list[i]->exist == false || reg_list[i]->hidden)
                        continue;
-               if (!reg_list[i]->valid) {
-                       retval = reg_list[i]->type->get(reg_list[i]);
-                       if (retval != ERROR_OK && gdb_report_register_access_error) {
-                               LOG_DEBUG("Couldn't get register %s.", reg_list[i]->name);
-                               free(reg_packet);
-                               free(reg_list);
-                               return gdb_error(connection, retval);
-                       }
+               if (gdb_get_reg_value_as_str(target, reg_packet_p, reg_list[i]) != ERROR_OK) {
+                       free(reg_packet);
+                       free(reg_list);
+                       return gdb_error(connection, retval);
                }
-               gdb_str_to_target(target, reg_packet_p, reg_list[i]);
                reg_packet_p += DIV_ROUND_UP(reg_list[i]->size, 8) * 2;
        }
 
@@ -1369,18 +1385,13 @@ static int gdb_get_register_packet(struct connection *connection,
                return ERROR_SERVER_REMOTE_CLOSED;
        }
 
-       if (!reg_list[reg_num]->valid) {
-               retval = reg_list[reg_num]->type->get(reg_list[reg_num]);
-               if (retval != ERROR_OK && gdb_report_register_access_error) {
-                       LOG_DEBUG("Couldn't get register %s.", reg_list[reg_num]->name);
-                       free(reg_list);
-                       return gdb_error(connection, retval);
-               }
-       }
-
        reg_packet = calloc(DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2 + 1, 1); /* plus one for string termination null */
 
-       gdb_str_to_target(target, reg_packet, reg_list[reg_num]);
+       if (gdb_get_reg_value_as_str(target, reg_packet, reg_list[reg_num]) != ERROR_OK) {
+               free(reg_packet);
+               free(reg_list);
+               return gdb_error(connection, retval);
+       }
 
        gdb_put_packet(connection, reg_packet, DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2);