[Qemu-devel] [PATCH v2 02/15] gdbstub: add multiprocess support to '?' packets

[Luc Michel <luc.michel@greensocs.com>]

The gdb_get_cpu_pid() function does the PID lookup for the given CPU. It
checks if the CPU is in a QOM container named after the
GDB_CPU_GROUP_NAME macro. If found, it returns the correponding PID,
which is the group ID plus one (group IDs start at 0, GDB PIDs at 1).
When the CPU is not a child of such a container, PID 1 is returned.

The gdb_fmt_thread_id() function generates the string to be used to identify
a given thread, in a response packet for the peer. This function
supports generating thread IDs when multiprocess mode is enabled (in the
form `p<pid>.<tid>').

Use it in the reply to a '?' request.

Signed-off-by: Luc Michel <luc.michel@greensocs.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 gdbstub.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/gdbstub.c b/gdbstub.c
index 5c86218f49..ac9d540fda 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -640,10 +640,37 @@ static int memtox(char *buf, const char *mem, int len)
         }
     }
     return p - buf;
 }
 
+static uint32_t gdb_get_cpu_pid(const GDBState *s, CPUState *cpu)
+{
+    gchar *path;
+    gchar *cont;
+    const char *left;
+    unsigned long pid;
+
+    if (!s->multiprocess || (s->process_num == 1)) {
+        return 1;
+    }
+
+    path = object_get_canonical_path(OBJECT(cpu));
+    cont = g_strrstr(path, "/" GDB_CPU_GROUP_NAME "[");
+
+    if (cont == NULL) {
+        return 1;
+    }
+
+    cont += strlen("/" GDB_CPU_GROUP_NAME "[");
+
+    if (qemu_strtoul(cont, &left, 10, &pid)) {
+        return 1;
+    }
+
+    return pid + 1;
+}
+
 static const char *get_feature_xml(const char *p, const char **newp,
                                    CPUClass *cc)
 {
     size_t len;
     int i;
@@ -909,10 +936,23 @@ static CPUState *find_cpu(uint32_t thread_id)
     }
 
     return NULL;
 }
 
+static char *gdb_fmt_thread_id(const GDBState *s, CPUState *cpu,
+                           char *buf, size_t buf_size)
+{
+    if (s->multiprocess) {
+        snprintf(buf, buf_size, "p%02x.%02x",
+                 gdb_get_cpu_pid(s, cpu), cpu_gdb_index(cpu));
+    } else {
+        snprintf(buf, buf_size, "%02x", cpu_gdb_index(cpu));
+    }
+
+    return buf;
+}
+
 static int is_query_packet(const char *p, const char *query, char separator)
 {
     unsigned int query_len = strlen(query);
 
     return strncmp(p, query, query_len) == 0 &&
@@ -1020,22 +1060,23 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
     const char *p;
     uint32_t thread;
     int ch, reg_size, type, res;
     uint8_t mem_buf[MAX_PACKET_LENGTH];
     char buf[sizeof(mem_buf) + 1 /* trailing NUL */];
+    char thread_id[16];
     uint8_t *registers;
     target_ulong addr, len;
 
     trace_gdbstub_io_command(line_buf);
 
     p = line_buf;
     ch = *p++;
     switch(ch) {
     case '?':
         /* TODO: Make this return the correct value for user-mode.  */
-        snprintf(buf, sizeof(buf), "T%02xthread:%02x;", GDB_SIGNAL_TRAP,
-                 cpu_gdb_index(s->c_cpu));
+        snprintf(buf, sizeof(buf), "T%02xthread:%s;", GDB_SIGNAL_TRAP,
+                 gdb_fmt_thread_id(s, s->c_cpu, thread_id, sizeof(thread_id)));
         put_packet(s, buf);
         /* Remove all the breakpoints when this query is issued,
          * because gdb is doing and initial connect and the state
          * should be cleaned up.
          */
-- 
2.19.0