[PATCH] Include access size in find command error message

["Andrew Burgess" <aburgess at broadcom dot com>]

Currently if a find command can't access memory then we get an error message that looks like this:

  Unable to access target memory at <address>, halting search.

This suggests (to me) that the failed access is immediately at <address>, when the failed access could be some way off, and as (for some targets) we load memory in chunks of 1600 bytes, the failed access could be a surprising distance away. 

The patch below changes the error message to:

  Unable to access <bytes> bytes of target memory at <address>, halting search.

Which I think makes it clearer what gdb was trying to do when it failed.

There's even a test.

OK to commit?

Thanks,
Andrew


2012-09-26  Andrew Burgess  <aburgess@broadcom.com>

	* target.c (simple_search_memory): Include access length in error
	message.

diff --git a/gdb/target.c b/gdb/target.c
index 1fc8802..cea3d10 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -2874,8 +2874,9 @@ simple_search_memory (struct target_ops *ops,
   if (target_read (ops, TARGET_OBJECT_MEMORY, NULL,
 		   search_buf, start_addr, search_buf_size) != search_buf_size)
     {
-      warning (_("Unable to access target memory at %s, halting search."),
-	       hex_string (start_addr));
+      warning (_("Unable to access %s bytes of target "
+		 "memory at %s, halting search."),
+	       plongest (search_buf_size), hex_string (start_addr));
       do_cleanups (old_cleanups);
       return -1;
     }
@@ -2928,8 +2929,9 @@ simple_search_memory (struct target_ops *ops,
 			   search_buf + keep_len, read_addr,
 			   nr_to_read) != nr_to_read)
 	    {
-	      warning (_("Unable to access target "
+	      warning (_("Unable to access %s bytes of target "
 			 "memory at %s, halting search."),
+		       plongest (nr_to_read),
 		       hex_string (read_addr));
 	      do_cleanups (old_cleanups);
 	      return -1;

2012-09-26  Andrew Burgess  <aburgess@broadcom.com>

	Test find command on unmapped memory.
	* gdb.base/find-unmapped.c: New file.
	* gdb.base/find-unmapped.exp: New file.

diff --git a/gdb/testsuite/gdb.base/find-unmapped.c b/gdb/testsuite/gdb.base/find-unmapped.c
new file mode 100644
index 0000000..70059b1
--- /dev/null
+++ b/gdb/testsuite/gdb.base/find-unmapped.c
@@ -0,0 +1,89 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2012 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <string.h>
+
+#define CHUNK_SIZE 16000 /* same as findcmd.c's */
+
+void *global_var_0;
+void *global_var_1;
+void *global_var_2;
+
+void
+breakpt ()
+{
+  /* Nothing. */
+}
+
+int
+main (void)
+{
+  void *p;
+  size_t pg_size;
+  int pg_count;
+  void *unmapped_page, *last_mapped_page, *first_mapped_page;
+
+  /*
+    Map enough pages to cover at least CHUNK_SIZE, and one extra page.  We
+    then unmap the last page.
+
+    From gdb we can then perform find commands into unmapped region, gdb
+    should given an error.
+
+    .----.----.----.----.----.
+    |    |    |    |    |    |
+    '----'----'----'----'----'
+    |<- CHUNK_SIZE ->|
+  */
+
+  pg_size = getpagesize ();
+  /* The +2 gives the extra page.  */
+  pg_count = (CHUNK_SIZE / pg_size) + 2;
+
+  p = mmap (0, (pg_count * pg_size), PROT_READ|PROT_WRITE,
+	    MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+  if (p == MAP_FAILED)
+    {
+      perror ("mmap");
+      return EXIT_FAILURE;
+    }
+
+  memset (p, 0, (pg_count *pg_size));
+
+  if (munmap (p + ((pg_count - 1) * pg_size), pg_size) == -1)
+    {
+      perror ("munmap");
+      return EXIT_FAILURE;
+    }
+
+  first_mapped_page = p;
+  last_mapped_page = p + ((pg_count - 2) * pg_size);
+  unmapped_page = last_mapped_page + pg_size;
+
+  /* Setup global variables we reference from gdb.  */
+  global_var_0 = first_mapped_page;
+  global_var_1 = unmapped_page - 16;
+  global_var_2 = unmapped_page + 16;
+
+  breakpt ();
+
+  return EXIT_SUCCESS;
+}
diff --git a/gdb/testsuite/gdb.base/find-unmapped.exp b/gdb/testsuite/gdb.base/find-unmapped.exp
new file mode 100644
index 0000000..e89be72
--- /dev/null
+++ b/gdb/testsuite/gdb.base/find-unmapped.exp
@@ -0,0 +1,40 @@
+# Copyright 2012 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile
+
+if { [prepare_for_testing ${testfile}.exp ${testfile}] } {
+    return -1
+}
+
+if ![runto breakpt] {
+    return -1
+}
+
+# Basic attempt to read memory from globals.
+gdb_test "x/5w global_var_1" \
+    "$hex:\[ \t\]+0\[ \t\]+0\[ \t\]+0\[ \t\]+0\r\n$hex:\[ \t\]+Cannot access memory at address $hex"
+gdb_test "x/5w global_var_2" \
+    "$hex:\[ \t\]+Cannot access memory at address $hex"
+
+# Now try a find starting from each global.
+gdb_test "find global_var_1, (global_var_2 + 16), 0xff" \
+    "warning: Unable to access $decimal bytes of target memory at $hex, halting search.\r\nPattern not found."
+
+gdb_test "find global_var_2, (global_var_2 + 16), 0xff" \
+    "warning: Unable to access $decimal bytes of target memory at $hex, halting search.\r\nPattern not found."
+
+gdb_test "find global_var_0, (global_var_2 + 16), 0xff" \
+    "warning: Unable to access $decimal bytes of target memory at $hex, halting search.\r\nPattern not found."