gdbstub: Check if gdb_regs is NULL

cpu->gdb_regs may be NULL if no coprocessor is registered.

Fixes: 73c392c ("gdbstub: Replace gdb_regs with an array")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-Id: <20231029145033.592566-17-alex.bennee@linaro.org>
Message-Id: <20231019101030.128431-2-akihiko.odaki@daynix.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

gdbstub/gdbstub.c

@@ -385,12 +385,14 @@ static const char *get_feature_xml(const char *p, const char **newp,
                 xml,
                 g_markup_printf_escaped("<xi:include href=\"%s\"/>",
                                         cc->gdb_core_xml_file));
-            for (guint i = 0; i < cpu->gdb_regs->len; i++) {
-                r = &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
-                g_ptr_array_add(
-                    xml,
-                    g_markup_printf_escaped("<xi:include href=\"%s\"/>",
-                                            r->xml));
+            if (cpu->gdb_regs) {
+                for (guint i = 0; i < cpu->gdb_regs->len; i++) {
+                    r = &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
+                    g_ptr_array_add(
+                        xml,
+                        g_markup_printf_escaped("<xi:include href=\"%s\"/>",
+                                                r->xml));
+                }
             }
             g_ptr_array_add(xml, g_strdup("</target>"));
             g_ptr_array_add(xml, NULL);
@@ -430,10 +432,12 @@ static int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg)
         return cc->gdb_read_register(cpu, buf, reg);
     }
 
-    for (guint i = 0; i < cpu->gdb_regs->len; i++) {
-        r = &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
-        if (r->base_reg <= reg && reg < r->base_reg + r->num_regs) {
-            return r->get_reg(env, buf, reg - r->base_reg);
+    if (cpu->gdb_regs) {
+        for (guint i = 0; i < cpu->gdb_regs->len; i++) {
+            r = &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
+            if (r->base_reg <= reg && reg < r->base_reg + r->num_regs) {
+                return r->get_reg(env, buf, reg - r->base_reg);
+            }
         }
     }
     return 0;
@@ -449,10 +453,12 @@ static int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg)
         return cc->gdb_write_register(cpu, mem_buf, reg);
     }
 
-    for (guint i = 0; i < cpu->gdb_regs->len; i++) {
-        r =  &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
-        if (r->base_reg <= reg && reg < r->base_reg + r->num_regs) {
-            return r->set_reg(env, mem_buf, reg - r->base_reg);
+    if (cpu->gdb_regs) {
+        for (guint i = 0; i < cpu->gdb_regs->len; i++) {
+            r =  &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
+            if (r->base_reg <= reg && reg < r->base_reg + r->num_regs) {
+                return r->set_reg(env, mem_buf, reg - r->base_reg);
+            }
         }
     }
     return 0;