gdbstub: Fix gdb_register_coprocessor() register counting

Commit a0e372f0c49ac01faeaeb73a6e8f50e8ac615f34 reorganized the register
counting for GDB. While it seems correct not to let the total number of
registers skyrocket in an SMP scenario through a static variable, the
distinction between total register count and 'g' packet register count
(last_reg vs. num_g_regs) got lost among the way.

Fix this by introducing CPUState::gdb_num_g_regs and using that in
gdb_handle_packet().

Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org (stable-1.6)
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Tested-by: Max Filippov <jcmvbkbc@gmail.com>
Tested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>

gdbstub.c

@@ -621,6 +621,8 @@ void gdb_register_coprocessor(CPUState *cpu,
         if (g_pos != s->base_reg) {
             fprintf(stderr, "Error: Bad gdb register numbering for '%s'\n"
                     "Expected %d got %d\n", xml, g_pos, s->base_reg);
+        } else {
+            cpu->gdb_num_g_regs = cpu->gdb_num_regs;
         }
     }
 }
@@ -902,7 +904,7 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
     case 'g':
         cpu_synchronize_state(s->g_cpu);
         len = 0;
-        for (addr = 0; addr < s->g_cpu->gdb_num_regs; addr++) {
+        for (addr = 0; addr < s->g_cpu->gdb_num_g_regs; addr++) {
             reg_size = gdb_read_register(s->g_cpu, mem_buf + len, addr);
             len += reg_size;
         }
@@ -914,7 +916,7 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
         registers = mem_buf;
         len = strlen(p) / 2;
         hextomem((uint8_t *)registers, p, len);
-        for (addr = 0; addr < s->g_cpu->gdb_num_regs && len > 0; addr++) {
+        for (addr = 0; addr < s->g_cpu->gdb_num_g_regs && len > 0; addr++) {
             reg_size = gdb_write_register(s->g_cpu, registers, addr);
             len -= reg_size;
             registers += reg_size;

include/qom/cpu.h

@@ -152,6 +152,7 @@ struct kvm_run;
  * @current_tb: Currently executing TB.
  * @gdb_regs: Additional GDB registers.
  * @gdb_num_regs: Number of total registers accessible to GDB.
+ * @gdb_num_g_regs: Number of registers in GDB 'g' packets.
  * @next_cpu: Next CPU sharing TB cache.
  * @kvm_fd: vCPU file descriptor for KVM.
  *
@@ -188,6 +189,7 @@ struct CPUState {
     struct TranslationBlock *current_tb;
     struct GDBRegisterState *gdb_regs;
     int gdb_num_regs;
+    int gdb_num_g_regs;
     CPUState *next_cpu;
 
     int kvm_fd;

qom/cpu.c

@@ -240,7 +240,7 @@ static void cpu_common_initfn(Object *obj)
     CPUState *cpu = CPU(obj);
     CPUClass *cc = CPU_GET_CLASS(obj);
 
-    cpu->gdb_num_regs = cc->gdb_num_core_regs;
+    cpu->gdb_num_regs = cpu->gdb_num_g_regs = cc->gdb_num_core_regs;
 }
 
 static int64_t cpu_common_get_arch_id(CPUState *cpu)