[PATCH] Harden tests that deal with memory regions

[Luis Machado <lgustavo@codesourcery.com>]

Exercising aarch64-elf with a custom debug stub i noticed a few failures in
both gdb.base/breakpoint-in-ro-region.exp and gdb.base/memattr.exp:

FAIL: gdb.base/breakpoint-in-ro-region.exp: create read-only mem region covering main
FAIL: gdb.base/breakpoint-in-ro-region.exp: writing to read-only memory fails
FAIL: gdb.base/breakpoint-in-ro-region.exp: inserting software breakpoint in read-only memory fails

FAIL: gdb.base/memattr.exp: create mem region 1
FAIL: gdb.base/memattr.exp: create mem region 2
FAIL: gdb.base/memattr.exp: create mem region 3
FAIL: gdb.base/memattr.exp: create mem region 4
FAIL: gdb.base/memattr.exp: create mem region 5
FAIL: gdb.base/memattr.exp: info mem (1)
FAIL: gdb.base/memattr.exp: mem1 cannot be read
FAIL: gdb.base/memattr.exp: mem2 cannot be written
FAIL: gdb.base/memattr.exp: mem2 can be read
FAIL: gdb.base/memattr.exp: disable mem 1
FAIL: gdb.base/memattr.exp: mem 1 was disabled
FAIL: gdb.base/memattr.exp: enable mem 1
FAIL: gdb.base/memattr.exp: mem 1 was enabled
FAIL: gdb.base/memattr.exp: disable mem 2 4
FAIL: gdb.base/memattr.exp: mem 2 and 4 were disabled
FAIL: gdb.base/memattr.exp: enable mem 2-4
FAIL: gdb.base/memattr.exp: mem 2-4 were enabled
FAIL: gdb.base/memattr.exp: mem 1 to 5 were disabled
FAIL: gdb.base/memattr.exp: mem 1 to 5 were enabled
FAIL: gdb.base/memattr.exp: delete mem 1
FAIL: gdb.base/memattr.exp: mem 1 was deleted
FAIL: gdb.base/memattr.exp: delete mem 2 4
FAIL: gdb.base/memattr.exp: mem 2 and 4 were deleted
FAIL: gdb.base/memattr.exp: mem 2-4 were deleted

These failures don't show up with gdbserver or native gdb on Linux because
they don't export any memory maps, therefore the vector of memory regions is
empty.

Outside of that scenario, we can't guarantee the absence of memory regions
reported by the target upon a connection. In our particular target, we
provide a memory map and the memory regions vector ceases to be empty.

With a non-empty memory regions vector, manipulating memory regions will cause
gdb to be more verbose and output text. For example:

memattr.c:require_user_regions

  /* Otherwise, let the user know how to get back.  */
  if (from_tty)
    warning (_("Switching to manual control of memory regions; use "
	       "\"mem auto\" to fetch regions from the target again."));

memattr.c:create_mem_region

      if ((lo >= n->lo && (lo < n->hi || n->hi == 0))
	  || (hi > n->lo && (hi <= n->hi || n->hi == 0))
	  || (lo <= n->lo && ((hi >= n->hi && n->hi != 0) || hi == 0)))
	{
	  printf_unfiltered (_("overlapping memory region\n"));
	  return;
	}

In my particular case i got both of the above messages.

In order to fix this, i've moved the delete_memory proc from
gdb.base/memattr.exp to a new file lib/gdb-memory.exp and made lib/gdb.exp
load that file.

For both gdb.base/breakpoint-in-ro-region.exp and gdb.base/memattr.exp the
patch clears all existing memory regions after running to main. That way we
are guaranteed to have a clean state for memory regions so the tests can
exercise whatever they want and have an expected output pattern.

Regression checked on x86-64/Ubuntu 16.04.

OK?

gdb/testsuite/ChangeLog:

2017-01-23  Luis Machado  <lgustavo@codesourcery.com>

	* lib/gdb-memory.exp: New file.
	* lib/gdb.exp: Load gdb-memory.exp
	* gdb.base/memattr.exp (delete_memory): Move proc to
	lib/gdb-memory.exp and rename to delete_memory_regions.
	Replace delete_memory with delete_memory_regions.
	Cleanup memory regions before tests.
	* gdb.base/breakpoint-in-ro-region.exp: Cleanup memory regions
	before tests.
---
 gdb/testsuite/gdb.base/breakpoint-in-ro-region.exp |  3 ++
 gdb/testsuite/gdb.base/memattr.exp                 | 19 +++--------
 gdb/testsuite/lib/gdb-memory.exp                   | 38 ++++++++++++++++++++++
 gdb/testsuite/lib/gdb.exp                          |  1 +
 4 files changed, 47 insertions(+), 14 deletions(-)
 create mode 100644 gdb/testsuite/lib/gdb-memory.exp

diff --git a/gdb/testsuite/gdb.base/breakpoint-in-ro-region.exp b/gdb/testsuite/gdb.base/breakpoint-in-ro-region.exp
index 7c3bd46..e0c1a37 100644
--- a/gdb/testsuite/gdb.base/breakpoint-in-ro-region.exp
+++ b/gdb/testsuite/gdb.base/breakpoint-in-ro-region.exp
@@ -137,6 +137,9 @@ if ![get_function_bounds "main" main_lo main_hi] {
     return -1
 }
 
+# Delete all memory regions.
+delete_memory_regions
+
 # Manually create a read-only memory region that covers 'main'.
 gdb_test_no_output "mem $main_lo $main_hi ro" \
     "create read-only mem region covering main"
diff --git a/gdb/testsuite/gdb.base/memattr.exp b/gdb/testsuite/gdb.base/memattr.exp
index 5e37187..74f5ce6 100644
--- a/gdb/testsuite/gdb.base/memattr.exp
+++ b/gdb/testsuite/gdb.base/memattr.exp
@@ -25,6 +25,9 @@ if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
 
 runto main
 
+# Delete all memory regions.
+delete_memory_regions
+
 set mem1start -1
 set mem2start -1
 set mem3start -1
@@ -487,18 +490,6 @@ gdb_test "delete mem 8" "No memory region number 8." \
 # Test overlapping checking
 #
 
-proc delete_memory {} {
-    global gdb_prompt
-
-    gdb_test_multiple "delete mem" "delete mem" {
-       -re "Delete all memory regions.*y or n.*$" {
-           send_gdb "y\n"
-           exp_continue
-       }
-       -re "$gdb_prompt $" { }
-    }
-}
-
 # Create a region that doesn't overlap (a PASS in the table).
 
 proc region_pass { region } {
@@ -530,7 +521,7 @@ proc region_fail { region } {
 #                  |--|       PASS
 #                        |--- PASS
 
-delete_memory
+delete_memory_regions
 gdb_test_no_output "mem 0x30 0x60 ro"
 with_test_prefix "0x30 0x60" {
     region_fail "0x20 0x40"
@@ -562,7 +553,7 @@ with_test_prefix "0x30 0x60" {
 #         |--|                PASS
 #   |--|                      PASS
 
-delete_memory
+delete_memory_regions
 gdb_test_no_output "mem 0x30 0x0 ro"
 with_test_prefix "0x30 0x0" {
     region_fail "0x20 0x50"
diff --git a/gdb/testsuite/lib/gdb-memory.exp b/gdb/testsuite/lib/gdb-memory.exp
new file mode 100644
index 0000000..3377011
--- /dev/null
+++ b/gdb/testsuite/lib/gdb-memory.exp
@@ -0,0 +1,38 @@
+# Copyright 2017 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/>.
+
+# This file was written by Fred Fish. (fnf@cygnus.com)
+
+# Generic gdb subroutines that should work for any target.  If these
+# need to be modified for any target, it can be done with a variable
+# or by passing arguments.
+
+# This file holds functions and data dealing with memory regions manipulation.
+
+# Deletes all the memory regions GDB currently knows about.
+
+proc delete_memory_regions {} {
+    global gdb_prompt
+
+    gdb_test_multiple "delete mem" "delete mem" {
+       -re "Delete all memory regions.*y or n.*$" {
+           send_gdb "y\n"
+           exp_continue
+       }
+       -re "$gdb_prompt $" { }
+    }
+}
+
+
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 2ff5c22..8c64a28 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -28,6 +28,7 @@ if {$tool == ""} {
 load_lib libgloss.exp
 load_lib cache.exp
 load_lib gdb-utils.exp
+load_lib gdb-memory.exp
 
 global GDB
 
-- 
2.7.4