Implement qXfer:exec-file:read in gdbserver

From: Gary Benson <gbenson@redhat.com>

This commit implements the "qXfer:exec-file:read" packet in gdbserver.

gdb/gdbserver/ChangeLog:

	* target.h (struct target_ops) <pid_to_exec_file>: New field.

	* linux-low.c (linux_target_ops): Initialize pid_to_exec_file.

	* server.c (handle_qxfer_exec_file): New function.

	(qxfer_packets): Add exec-file entry.

	(handle_query): Report qXfer:exec-file:read as supported packet.

---

 gdb/gdbserver/linux-low.c |   19 +++++++++++++++++++

 gdb/gdbserver/server.c    |   40 ++++++++++++++++++++++++++++++++++++++++

 gdb/gdbserver/target.h    |    7 +++++++

 3 files changed, 66 insertions(+)

Index: gdb-7.6.1/gdb/gdbserver/linux-low.c

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/linux-low.c	2016-03-15 19:04:39.260193747 +0100

+++ gdb-7.6.1/gdb/gdbserver/linux-low.c	2016-03-15 19:04:48.841256052 +0100

@@ -5993,6 +5993,24 @@

 }

 #endif /* HAVE_LINUX_BTRACE */

+// gdb/nat/linux-procfs.c

+static char *

+linux_proc_pid_to_exec_file (int pid)

+{

+  static char buf[PATH_MAX];

+  char name[PATH_MAX];

+  ssize_t len;

+

+  xsnprintf (name, PATH_MAX, "/proc/%d/exe", pid);

+  len = readlink (name, buf, PATH_MAX - 1);

+  if (len <= 0)

+    strcpy (buf, name);

+  else

+    buf[len] = '\0';

+

+  return buf;

+}

+

 static struct target_ops linux_target_ops = {

   linux_create_inferior,

   linux_attach,

@@ -6070,6 +6088,7 @@

   NULL,

   NULL,

 #endif

+  linux_proc_pid_to_exec_file,

 };

 static void

Index: gdb-7.6.1/gdb/gdbserver/server.c

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/server.c	2016-03-15 19:04:39.262193760 +0100

+++ gdb-7.6.1/gdb/gdbserver/server.c	2016-03-15 19:04:48.842256059 +0100

@@ -1006,6 +1006,42 @@

   return (*the_target->read_auxv) (offset, readbuf, len);

 }

+/* Handle qXfer:exec-file:read.  */

+

+static int

+handle_qxfer_exec_file (const char *const_annex,

+			gdb_byte *readbuf, const gdb_byte *writebuf,

+			ULONGEST offset, LONGEST len)

+{

+  char *annex, *file;

+  ULONGEST pid;

+  int total_len;

+

+  if (the_target->pid_to_exec_file == NULL || writebuf != NULL)

+    return -2;

+

+  annex = alloca (strlen (const_annex) + 1);

+  strcpy (annex, const_annex);

+  annex = unpack_varlen_hex (annex, &pid;;

+  if (annex[0] != '\0' || pid == 0)

+    return -1;

+

+  file = (*the_target->pid_to_exec_file) (pid);

+  if (file == NULL)

+    return -1;

+

+  total_len = strlen (file);

+

+  if (offset > total_len)

+    return -1;

+

+  if (offset + len > total_len)

+    len = total_len - offset;

+

+  memcpy (readbuf, file + offset, len);

+  return len;

+}

+

 /* Handle qXfer:features:read.  */

 static int

@@ -1408,6 +1444,7 @@

   {

     { "auxv", handle_qxfer_auxv },

     { "btrace", handle_qxfer_btrace },

+    { "exec-file", handle_qxfer_exec_file},

     { "fdpic", handle_qxfer_fdpic},

     { "features", handle_qxfer_features },

     { "libraries", handle_qxfer_libraries },

@@ -1828,6 +1865,9 @@

       if (target_supports_stopped_by_hw_breakpoint ())

 	strcat (own_buf, ";hwbreak+");

+      if (the_target->pid_to_exec_file != NULL)

+	strcat (own_buf, ";qXfer:exec-file:read+");

+

       return;

     }

Index: gdb-7.6.1/gdb/gdbserver/target.h

===================================================================

--- gdb-7.6.1.orig/gdb/gdbserver/target.h	2016-03-15 19:04:39.262193760 +0100

+++ gdb-7.6.1/gdb/gdbserver/target.h	2016-03-15 19:04:48.842256059 +0100

@@ -421,6 +421,13 @@

      to break a cyclic dependency.  */

   void (*read_btrace) (struct btrace_target_info *, struct buffer *, int type);

+  /* Return the full absolute name of the executable file that was

+     run to create the process PID.  If the executable file cannot

+     be determined, NULL is returned.  Otherwise, a pointer to a

+     character string containing the pathname is returned.  This

+     string should be copied into a buffer by the client if the string

+     will not be immediately used, or if it must persist.  */

+  char *(*pid_to_exec_file) (int pid);

 };

 extern struct target_ops *the_target;