gdbstub: replace global gdb_has_xml with a function

Try and make the self reported global hack a little less hackish by
providing a query function instead. As gdb_has_xml was always set if
we negotiated XML we can now use the presence of ->target_xml as the
test instead.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230829161528.2707696-12-alex.bennee@linaro.org>

gdbstub/gdbstub.c

@@ -75,8 +75,6 @@ void gdb_init_gdbserver_state(void)
     gdbserver_state.sstep_flags &= gdbserver_state.supported_sstep_flags;
 }
 
-bool gdb_has_xml;
-
 /* writes 2*len+1 bytes in buf */
 void gdb_memtohex(GString *buf, const uint8_t *mem, int len)
 {
@@ -351,6 +349,11 @@ static CPUState *gdb_get_cpu(uint32_t pid, uint32_t tid)
     }
 }
 
+bool gdb_has_xml(void)
+{
+    return !!gdb_get_cpu_process(gdbserver_state.g_cpu)->target_xml;
+}
+
 static const char *get_feature_xml(const char *p, const char **newp,
                                    GDBProcess *process)
 {
@@ -1084,7 +1087,7 @@ static void handle_set_reg(GArray *params, void *user_ctx)
 {
     int reg_size;
 
-    if (!gdb_has_xml) {
+    if (!gdb_get_cpu_process(gdbserver_state.g_cpu)->target_xml) {
         gdb_put_packet("");
         return;
     }
@@ -1105,7 +1108,7 @@ static void handle_get_reg(GArray *params, void *user_ctx)
 {
     int reg_size;
 
-    if (!gdb_has_xml) {
+    if (!gdb_get_cpu_process(gdbserver_state.g_cpu)->target_xml) {
         gdb_put_packet("");
         return;
     }
@@ -1572,7 +1575,6 @@ static void handle_query_xfer_features(GArray *params, void *user_ctx)
         return;
     }
 
-    gdb_has_xml = true;
     p = get_param(params, 0)->data;
     xml = get_feature_xml(p, &p, process);
     if (!xml) {

gdbstub/internals.h

@@ -33,6 +33,7 @@ typedef struct GDBProcess {
     uint32_t pid;
     bool attached;
 
+    /* If gdb sends qXfer:features:read:target.xml this will be populated */
     char *target_xml;
 } GDBProcess;
 

gdbstub/softmmu.c

@@ -97,7 +97,6 @@ static void gdb_chr_event(void *opaque, QEMUChrEvent event)
 
         vm_stop(RUN_STATE_PAUSED);
         replay_gdb_attached();
-        gdb_has_xml = false;
         break;
     default:
         break;

gdbstub/user.c

@@ -198,7 +198,6 @@ static void gdb_accept_init(int fd)
     gdbserver_state.c_cpu = gdb_first_attached_cpu();
     gdbserver_state.g_cpu = gdbserver_state.c_cpu;
     gdbserver_user_state.fd = fd;
-    gdb_has_xml = false;
 }
 
 static bool gdb_accept_socket(int gdb_fd)

include/exec/gdbstub.h

@@ -31,12 +31,12 @@ int gdbserver_start(const char *port_or_device);
 void gdb_set_stop_cpu(CPUState *cpu);
 
 /**
- * gdb_has_xml:
- * This is an ugly hack to cope with both new and old gdb.
- * If gdb sends qXfer:features:read then assume we're talking to a newish
- * gdb that understands target descriptions.
+ * gdb_has_xml() - report of gdb supports modern target descriptions
+ *
+ * This will report true if the gdb negotiated qXfer:features:read
+ * target descriptions.
  */
-extern bool gdb_has_xml;
+bool gdb_has_xml(void);
 
 /* in gdbstub-xml.c, generated by scripts/feature_to_c.sh */
 extern const char *const xml_builtin[][2];

target/arm/gdbstub.c

@@ -48,7 +48,7 @@ int arm_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
     }
     if (n < 24) {
         /* FPA registers.  */
-        if (gdb_has_xml) {
+        if (gdb_has_xml()) {
             return 0;
         }
         return gdb_get_zeroes(mem_buf, 12);
@@ -56,7 +56,7 @@ int arm_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
     switch (n) {
     case 24:
         /* FPA status register.  */
-        if (gdb_has_xml) {
+        if (gdb_has_xml()) {
             return 0;
         }
         return gdb_get_reg32(mem_buf, 0);
@@ -102,7 +102,7 @@ int arm_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
     }
     if (n < 24) { /* 16-23 */
         /* FPA registers (ignored).  */
-        if (gdb_has_xml) {
+        if (gdb_has_xml()) {
             return 0;
         }
         return 12;
@@ -110,7 +110,7 @@ int arm_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
     switch (n) {
     case 24:
         /* FPA status register (ignored).  */
-        if (gdb_has_xml) {
+        if (gdb_has_xml()) {
             return 0;
         }
         return 4;

target/ppc/gdbstub.c

@@ -56,7 +56,7 @@ static int ppc_gdb_register_len(int n)
         return sizeof(target_ulong);
     case 32 ... 63:
         /* fprs */
-        if (gdb_has_xml) {
+        if (gdb_has_xml()) {
             return 0;
         }
         return 8;
@@ -76,7 +76,7 @@ static int ppc_gdb_register_len(int n)
         return sizeof(target_ulong);
     case 70:
         /* fpscr */
-        if (gdb_has_xml) {
+        if (gdb_has_xml()) {
             return 0;
         }
         return sizeof(target_ulong);