From d50867903fea3ec5cb9a85874aa45a08844952a7 Mon Sep 17 00:00:00 2001
From: Vladimir Prus <vladimir@codesourcery.com>
Date: Thu, 26 Jun 2008 15:10:48 +0000
Subject: [PATCH] 	* target.c (target_read_until_error): New.         *
 target.h (target_read_until_error): Declare.         * mi/mi-main.c
 (mi_cmd_data_read_memory): Use         target_read_until_error.

---
 gdb/ChangeLog                     |  7 ++++
 gdb/mi/mi-main.c                  |  4 +-
 gdb/target.c                      | 66 +++++++++++++++++++++++++++++++
 gdb/target.h                      |  5 +++
 gdb/testsuite/gdb.mi/mi-async.exp |  2 +-
 5 files changed, 81 insertions(+), 3 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 868989ff164..24d6b75c1b2 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2008-06-26  Vladimir Prus  <vladimir@codesourcery.com>
+
+	* target.c (target_read_until_error): New.
+        * target.h (target_read_until_error): Declare.
+        * mi/mi-main.c (mi_cmd_data_read_memory): Use
+        target_read_until_error.
+
 2008-06-25  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	Fix a memory leak found by Hui Zhu <teawater@gmail.com>.
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 5d90c75fdbf..40e6cf548f4 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -782,8 +782,8 @@ mi_cmd_data_read_memory (char *command, char **argv, int argc)
   mbuf = xcalloc (total_bytes, 1);
   make_cleanup (xfree, mbuf);
 
-  nr_bytes = target_read (&current_target, TARGET_OBJECT_MEMORY, NULL,
-			  mbuf, addr, total_bytes);
+  nr_bytes = target_read_until_error (&current_target, TARGET_OBJECT_MEMORY, 
+				      NULL, mbuf, addr, total_bytes);
   if (nr_bytes <= 0)
     error ("Unable to read memory.");
 
diff --git a/gdb/target.c b/gdb/target.c
index 6b009a8e76c..b2f7be7f7f7 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -1451,6 +1451,72 @@ target_read (struct target_ops *ops,
   return len;
 }
 
+LONGEST
+target_read_until_error (struct target_ops *ops,
+			 enum target_object object,
+			 const char *annex, gdb_byte *buf,
+			 ULONGEST offset, LONGEST len)
+{
+  LONGEST xfered = 0;
+  while (xfered < len)
+    {
+      LONGEST xfer = target_read_partial (ops, object, annex,
+					  (gdb_byte *) buf + xfered,
+					  offset + xfered, len - xfered);
+      /* Call an observer, notifying them of the xfer progress?  */
+      if (xfer == 0)
+	return xfered;
+      if (xfer < 0)
+	{
+	  /* We've got an error.  Try to read in smaller blocks.  */
+	  ULONGEST start = offset + xfered;
+	  ULONGEST remaining = len - xfered;
+	  ULONGEST half;
+
+	  /* If an attempt was made to read a random memory address,
+	     it's likely that the very first byte is not accessible.
+	     Try reading the first byte, to avoid doing log N tries
+	     below.  */
+	  xfer = target_read_partial (ops, object, annex, 
+				      (gdb_byte *) buf + xfered, start, 1);
+	  if (xfer <= 0)
+	    return xfered;
+	  start += 1;
+	  remaining -= 1;
+	  half = remaining/2;
+	  
+	  while (half > 0)
+	    {
+	      xfer = target_read_partial (ops, object, annex,
+					  (gdb_byte *) buf + xfered,
+					  start, half);
+	      if (xfer == 0)
+		return xfered;
+	      if (xfer < 0)
+		{
+		  remaining = half;		  
+		}
+	      else
+		{
+		  /* We have successfully read the first half.  So, the
+		     error must be in the second half.  Adjust start and
+		     remaining to point at the second half.  */
+		  xfered += xfer;
+		  start += xfer;
+		  remaining -= xfer;
+		}
+	      half = remaining/2;
+	    }
+
+	  return xfered;
+	}
+      xfered += xfer;
+      QUIT;
+    }
+  return len;
+}
+
+
 /* An alternative to target_write with progress callbacks.  */
 
 LONGEST
diff --git a/gdb/target.h b/gdb/target.h
index 902d4283de5..9641f0d62c8 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -230,6 +230,11 @@ extern LONGEST target_read (struct target_ops *ops,
 			    const char *annex, gdb_byte *buf,
 			    ULONGEST offset, LONGEST len);
 
+extern LONGEST target_read_until_error (struct target_ops *ops,
+					enum target_object object,
+					const char *annex, gdb_byte *buf,
+					ULONGEST offset, LONGEST len);
+  
 extern LONGEST target_write (struct target_ops *ops,
 			     enum target_object object,
 			     const char *annex, const gdb_byte *buf,
diff --git a/gdb/testsuite/gdb.mi/mi-async.exp b/gdb/testsuite/gdb.mi/mi-async.exp
index 9ac91fd7240..a7306988d91 100644
--- a/gdb/testsuite/gdb.mi/mi-async.exp
+++ b/gdb/testsuite/gdb.mi/mi-async.exp
@@ -27,7 +27,7 @@ if { !([isnative] && [istarget *-linux*]) \
 
 # The plan is for async mode to become the default but toggle for now.
 set saved_gdbflags $GDBFLAGS
-set GDBFLAGS [concat $GDBFLAGS " -ex \"maint set linux-async on\""]
+#set GDBFLAGS [concat $GDBFLAGS " -ex \"maint set linux-async on\""]
 
 load_lib mi-support.exp
 
-- 
2.30.2