[PATCH 15/16] gdbserver, btrace: add generic btrace support

[markus dot t dot metzger at intel dot com]

From: Markus Metzger <markus.t.metzger@intel.com>

Add support to gdbserver to understand branch trace related packages.

2012-05-10 Markus Metzger <markus.t.metzger@intel.com>

  gdb/gdbserver/
  * target.h (struct target_ops): Add btrace ops
    (target_supports_btrace): New macro
    (target_btrace_has_changed): New macro
    (target_enable_btrace): New macro
    (target_disable_btrace): New macro
    (target_read_btrace): New macro
  * gdbthread.h (struct thread_info): Add btrace field
  * server.c (handle_btrace_general_set): New function
    (handle_general_set): Call handle_btrace_general_set
    (handle_qxfer_btrace): New function
    (struct qxfer qxfer_packets[]): Add btrace entry
    (handle_btrace_query): New function
    (handle_query): Add btrace to supported query, call handle_btrace_query
  * inferiors.c (remove_thread): Disable btrace


---
 gdb/gdbserver/gdbthread.h |    5 ++
 gdb/gdbserver/inferiors.c |    3 +
 gdb/gdbserver/server.c    |  171 +++++++++++++++++++++++++++++++++++++++++++++
 gdb/gdbserver/target.h    |   38 ++++++++++
 4 files changed, 217 insertions(+), 0 deletions(-)

diff --git a/gdb/gdbserver/gdbthread.h b/gdb/gdbserver/gdbthread.h
index d863ec0..b2b6f62 100644
--- a/gdb/gdbserver/gdbthread.h
+++ b/gdb/gdbserver/gdbthread.h
@@ -22,6 +22,8 @@
 
 #include "server.h"
 
+struct btrace_target_info;
+
 struct thread_info
 {
   struct inferior_list_entry entry;
@@ -58,6 +60,9 @@ struct thread_info
    Each item in the list holds the current step of the while-stepping
    action.  */
   struct wstep_state *while_stepping;
+
+  /* Branch trace target information for this thread.  */
+  struct btrace_target_info *btrace;
 };
 
 extern struct inferior_list all_threads;
diff --git a/gdb/gdbserver/inferiors.c b/gdb/gdbserver/inferiors.c
index 76abaf5..76f5731 100644
--- a/gdb/gdbserver/inferiors.c
+++ b/gdb/gdbserver/inferiors.c
@@ -161,6 +161,9 @@ free_one_thread (struct inferior_list_entry *inf)
 void
 remove_thread (struct thread_info *thread)
 {
+  if (thread->btrace)
+    target_disable_btrace (thread->btrace);
+
   remove_inferior (&all_threads, (struct inferior_list_entry *) thread);
   free_one_thread (&thread->entry);
 }
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index b3d1b41..87613b9 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -446,6 +446,85 @@ write_qxfer_response (char *buf, const void *data, int len, int is_more)
 
 /* Handle all of the extended 'Q' packets.  */
 
+static int
+handle_btrace_general_set (char *own_buf)
+{
+  char *operation = own_buf + strlen ("Qbtrace:");
+
+  if (strncmp ("Qbtrace:", own_buf, strlen ("Qbtrace:")) != 0)
+    return 0;
+
+  if (strncmp ("on:", operation, strlen ("on:")) == 0)
+    {
+      char* ptid_str = operation + strlen ("on:");
+      ptid_t ptid = read_ptid (ptid_str, NULL);
+      struct thread_info *thread = find_thread_ptid (ptid);
+
+      if (!thread)
+        {
+          fprintf (stderr, "No such thread: %s\n", ptid_str);
+          write_enn (own_buf);
+        }
+      else if (thread->btrace)
+        {
+          fprintf (stderr, "Btrace already enabled for %s\n", ptid_str);
+          write_enn (own_buf);
+        }
+      else
+        {
+          thread->btrace = target_enable_btrace (thread->entry.id);
+          if (!thread->btrace)
+          {
+            fprintf (stderr, "Could not enable btrace for %s: %s\n",
+                     ptid_str, strerror (errno));
+            write_enn (own_buf);
+          }
+          else
+            write_ok (own_buf);
+        }
+    }
+  else if (strncmp ("off:", operation, strlen ("off:")) == 0)
+    {
+      char* ptid_str = operation + strlen ("off:");
+      ptid_t ptid = read_ptid (ptid_str, NULL);
+      struct thread_info *thread = find_thread_ptid (ptid);
+
+      if (!thread)
+        {
+          fprintf (stderr, "No such thread: %s\n", ptid_str);
+          write_enn (own_buf);
+        }
+      else if (!thread->btrace)
+        {
+          fprintf (stderr, "Btrace not enabled for %s\n", ptid_str);
+          write_enn (own_buf);
+        }
+      else
+        {
+          int errcode = target_disable_btrace (thread->btrace);
+          if (errcode)
+            {
+              fprintf (stderr, "Could not disable btrace for %s: %s\n",
+                       ptid_str, strerror (errcode));
+              write_enn (own_buf);
+            }
+          else
+            {
+              thread->btrace = NULL;
+              write_ok (own_buf);
+            }
+        }
+    }
+  else
+    {
+      fprintf (stderr, "Unknown btrace operation: %s. Use on or off.\n",
+               own_buf);
+      write_enn (own_buf);
+    }
+
+  return 1;
+}
+
 static void
 handle_general_set (char *own_buf)
 {
@@ -600,6 +679,9 @@ handle_general_set (char *own_buf)
       return;
     }
 
+  if (handle_btrace_general_set (own_buf))
+    return;
+
   /* Otherwise we didn't know what packet it was.  Say we didn't
      understand it.  */
   own_buf[0] = 0;
@@ -1298,6 +1380,57 @@ handle_qxfer_fdpic (const char *annex, gdb_byte *readbuf,
   return (*the_target->read_loadmap) (annex, offset, readbuf, len);
 }
 
+static int
+handle_qxfer_btrace (const char *annex,
+		     gdb_byte *readbuf, const gdb_byte *writebuf,
+		     ULONGEST offset, LONGEST len)
+{
+  static struct buffer cache;
+  struct thread_info *thread;
+  ptid_t ptid;
+  int error;
+
+  if (!the_target->read_btrace || writebuf)
+    return -2;
+
+  if (!target_running () || !annex)
+    return -1;
+
+  ptid = read_ptid ((char *) annex, NULL);
+  thread = find_thread_ptid (ptid);
+  if (!thread)
+    {
+      fprintf (stderr, "No such thread: %s\n", annex);
+      return -1;
+    }
+  else if (!thread->btrace)
+    {
+      fprintf (stderr, "Btrace not enabled for %s\n", annex);
+      return -1;
+    }
+
+  if (!offset)
+    {
+      buffer_free (&cache);
+
+      error = target_read_btrace (thread->btrace, &cache);
+      if (error)
+        return -error;
+    }
+  else if (offset >= cache.used_size)
+    {
+      buffer_free (&cache);
+      return 0;
+    }
+
+  if (len > (cache.used_size - offset))
+    len = cache.used_size - offset;
+
+  memcpy (readbuf, cache.buffer + offset, len);
+
+  return len;
+}
+
 static const struct qxfer qxfer_packets[] =
   {
     { "auxv", handle_qxfer_auxv },
@@ -1311,6 +1444,7 @@ static const struct qxfer qxfer_packets[] =
     { "statictrace", handle_qxfer_statictrace },
     { "threads", handle_qxfer_threads },
     { "traceframe-info", handle_qxfer_traceframe_info },
+    { "btrace", handle_qxfer_btrace },
   };
 
 static int
@@ -1467,6 +1601,33 @@ crc32 (CORE_ADDR base, int len, unsigned int crc)
 
 /* Handle all of the extended 'q' packets.  */
 
+static int
+handle_btrace_query (char *own_buf)
+{
+  if (strncmp ("qbtrace:", own_buf, strlen ("qbtrace:")) == 0)
+    {
+      char *ptid_str = own_buf + strlen ("qbtrace:");
+      ptid_t ptid = read_ptid (ptid_str, NULL);
+      struct thread_info *thread = find_thread_ptid (ptid);
+
+      if (!thread)
+        {
+          fprintf (stderr, "No such thread: %s\n", ptid_str);
+          write_enn (own_buf);
+        }
+      else if (!thread->btrace)
+        {
+          fprintf (stderr, "Btrace not enabled for %s\n", ptid_str);
+          write_enn (own_buf);
+        }
+      else
+        strcpy (own_buf,
+                (target_btrace_has_changed (thread->btrace) ? "yes" : "no"));
+      return 1;
+    }
+  return 0;
+}
+
 void
 handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
 {
@@ -1693,6 +1854,13 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
       if (target_supports_agent ())
 	strcat (own_buf, ";QAgent+");
 
+      if (target_supports_btrace ())
+        {
+          strcat (own_buf, ";qbtrace+");
+          strcat (own_buf, ";Qbtrace+");
+          strcat (own_buf, ";qXfer:btrace:read+");
+        }
+
       return;
     }
 
@@ -1883,6 +2051,9 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
   if (target_supports_tracepoints () && handle_tracepoint_query (own_buf))
     return;
 
+  if (handle_btrace_query (own_buf))
+    return;
+
   /* Otherwise we didn't know what packet it was.  Say we didn't
      understand it.  */
   own_buf[0] = 0;
diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index dcf0230..f89b106 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -22,6 +22,8 @@
 #define TARGET_H
 
 struct emit_ops;
+struct btrace_target_info;
+struct buffer;
 
 /* Ways to "resume" a thread.  */
 
@@ -397,6 +399,23 @@ struct target_ops
 
   /* Return true if target supports debugging agent.  */
   int (*supports_agent) (void);
+
+  /* Check whether the target supports branch tracing.  */
+  int (*supports_btrace) (void);
+
+  /* Enable branch tracing for @ptid and allocate a branch trace target
+     information struct for reading and for disabling branch trace.  */
+  struct btrace_target_info *(*enable_btrace) (ptid_t ptid);
+
+  /* Disable branch tracing.  */
+  int (*disable_btrace) (struct btrace_target_info *tinfo);
+
+  /* Check whether branch trace changed on the target.  */
+  int (*btrace_has_changed) (struct btrace_target_info *);
+
+  /* Read branch trace data into buffer.
+     Returns 0 on success, an error code, otherwise.  */
+  int (*read_btrace) (struct btrace_target_info *, struct buffer *);
 };
 
 extern struct target_ops *the_target;
@@ -521,6 +540,25 @@ void set_target_ops (struct target_ops *);
   (the_target->supports_agent ? \
    (*the_target->supports_agent) () : 0)
 
+#define target_supports_btrace()                                        \
+  (the_target->supports_btrace ? (*the_target->supports_btrace) () : 0)
+
+#define target_enable_btrace(ptid)                                    \
+  (the_target->enable_btrace ?                                        \
+   (*the_target->enable_btrace) (ptid) : (errno = ENOSYS, NULL))
+
+#define target_disable_btrace(tinfo)                              \
+  (the_target->disable_btrace ?                                   \
+   (*the_target->disable_btrace) (tinfo) : (errno = ENOSYS))
+
+#define target_btrace_has_changed(tinfo)                                \
+  (the_target->btrace_has_changed ?                                     \
+   (*the_target->btrace_has_changed) (tinfo) : (errno = ENOSYS, 0))
+
+#define target_read_btrace(tinfo, buffer)                               \
+  (the_target->read_btrace ?                                            \
+   (*the_target->read_btrace) (tinfo, buffer) : (errno = ENOSYS))
+
 /* Start non-stop mode, returns 0 on success, -1 on failure.   */
 
 int start_non_stop (int nonstop);
-- 
1.7.1