[Qemu-devel] [PATCH -v2] gdbstub: Add vCont support

[Jan Kiszka <jan.kiszka@siemens.com>]

[ Fix signal forwarding, properly handle unknown v-packets. ]

In order to set the VCPU for the next single-step command, you need gdb
6.8 or better - and this patch. It enhances the existing support for
representing VCPUs as threads to the gdb frontend by introducing the
vCont remote gdb command. This is used by gdb to switch the debugging
focus for single-stepping multi-threaded targets.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

 gdbstub.c |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 58 insertions(+), 0 deletions(-)

diff --git a/gdbstub.c b/gdbstub.c
index 0bcd5d5..d9f197f 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1542,6 +1542,64 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
             s->signal = 0;
         gdb_continue(s);
         return RS_IDLE;
+    case 'v':
+        if (strncmp(p, "Cont", 4) == 0) {
+            int res_signal, res_thread;
+
+            p += 4;
+            if (*p == '?') {
+                put_packet(s, "vCont;c;C;s;S");
+                break;
+            }
+            res = 0;
+            res_signal = 0;
+            res_thread = 0;
+            while (*p) {
+                int action, signal;
+
+                if (*p++ != ';') {
+                    res = 0;
+                    break;
+                }
+                action = *p++;
+                signal = 0;
+                if (action == 'C' || action == 'S')
+                    signal = strtoul(p, (char **)&p, 16);
+                else if (action != 'c' && action != 's') {
+                    res = 0;
+                    break;
+                }
+                thread = 0;
+                if (*p == ':')
+                    thread = strtoull(p+1, (char **)&p, 16);
+
+                action = tolower(action);
+                if (res == 0 || (res == 'c' && action == 's')) {
+                    res = action;
+                    res_signal = signal;
+                    res_thread = thread;
+                }
+            }
+            if (res) {
+                if (res_thread != -1 && res_thread != 0) {
+                    for (env = first_cpu; env != NULL; env = env->next_cpu)
+                        if (env->cpu_index + 1 == res_thread)
+                            break;
+                    if (env == NULL) {
+                        put_packet(s, "E22");
+                        break;
+                    }
+                    s->c_cpu = env;
+                }
+                if (res == 's')
+                    cpu_single_step(s->c_cpu, sstep_flags);
+                s->signal = res_signal;
+                gdb_continue(s);
+                return RS_IDLE;
+            }
+            break;
+        } else
+            goto unknown_command;
     case 'k':
         /* Kill the target */
         fprintf(stderr, "\nQEMU: Terminated via GDBstub\n");