gdb: new command 'maint flush dcache'

Add a new command to flush the dcache.

gdb/ChangeLog:

	* NEWS: Mention new commands.
	* target-dcache.c: Add 'cli/cli-cmds.h' include.
	(maint_flush_dcache_command): New function.
	(_initialize_target_dcache): Create new 'maint flush dcache'
	command.

gdb/doc/ChangeLog:

	* gdb.texinfo (Caching Target Data): Document 'maint flush
	dcache'.

gdb/testsuite/ChangeLog:

	* gdb.base/dcache-flush.c: New file.
	* gdb.base/dcache-flush.exp: New file.

8 files changed, 143 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f7ca2c9..80dc1e0 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,13 @@
 2020-12-13  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* NEWS: Mention new commands.
+	* target-dcache.c: Add 'cli/cli-cmds.h' include.
+	(maint_flush_dcache_command): New function.
+	(_initialize_target_dcache): Create new 'maint flush dcache'
+	command.
+
+2020-12-13  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	* NEWS: Mention new commands, and that the old commands are now
 	deprecated.
 	* cli/cli-cmds.c (maintenanceflushlist): Define.
diff --git a/gdb/NEWS b/gdb/NEWS
index 4d96388..66702862 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -44,6 +44,9 @@ maintenance flush register-cache
   These new commands are equivalent to the already existing commands
   'maintenance flush-symbol-cache' and 'flushregs' respectively.
 
+maintenance flush dcache
+  A new command to flush the dcache.
+
 * Changed commands
 
 break [PROBE_MODIFIER] [LOCATION] [thread THREADNUM]
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 6ad728e..5650974 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,5 +1,10 @@
 2020-12-13  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* gdb.texinfo (Caching Target Data): Document 'maint flush
+	dcache'.
+
+2020-12-13  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	* gdb.texinfo (Symbols): Document 'maint flush symbol-cache'.
 	(Maintenance Commands): Document 'maint flush register-cache'.
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 5bafb9d..5b6ac854 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -13494,6 +13494,12 @@ Show maximum number of dcache entries.  @xref{Caching Target Data, info dcache}.
 @kindex show dcache line-size
 Show default size of dcache lines.
 
+@item maint flush dcache
+@cindex dcache, flushing
+@kindex maint flush dcache
+Flush the contents (if any) of the dcache.  This maintainer command is
+useful when debugging the dcache implementation.
+
 @end table
 
 @node Searching Memory
diff --git a/gdb/target-dcache.c b/gdb/target-dcache.c
index 0226d67..90b60f6 100644
--- a/gdb/target-dcache.c
+++ b/gdb/target-dcache.c
@@ -19,6 +19,7 @@
 #include "target-dcache.h"
 #include "gdbcmd.h"
 #include "progspace.h"
+#include "cli/cli-cmds.h"
 
 /* The target dcache is kept per-address-space.  This key lets us
    associate the cache with the address space.  */
@@ -152,6 +153,16 @@ code_cache_enabled_p (void)
   return code_cache_enabled;
 }
 
+/* Implement the 'maint flush dcache' command.  */
+
+static void
+maint_flush_dcache_command (const char *command, int from_tty)
+{
+  target_dcache_invalidate ();
+  if (from_tty)
+    printf_filtered (_("The dcache was flushed.\n"));
+}
+
 void _initialize_target_dcache ();
 void
 _initialize_target_dcache ()
@@ -178,4 +189,12 @@ access is on."),
 			   set_code_cache,
 			   show_code_cache,
 			   &setlist, &showlist);
+
+  add_cmd ("dcache", class_maintenance, maint_flush_dcache_command,
+	   _("\
+Force gdb to flush its target memory data cache.\n\
+\n\
+The dcache caches all target memory accesses where possible, this\n\
+includes the stack-cache and the code-cache."),
+	   &maintenanceflushlist);
 }
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 130de8a..3411f6c 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2020-12-13  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* gdb.base/dcache-flush.c: New file.
+	* gdb.base/dcache-flush.exp: New file.
+
+2020-12-13  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	* gdb.base/c-linkage-name.exp: Update to use new 'maint flush ...'
 	commands.
 	* gdb.base/killed-outside.exp: Likewise.
diff --git a/gdb/testsuite/gdb.base/dcache-flush.c b/gdb/testsuite/gdb.base/dcache-flush.c
new file mode 100644
index 0000000..b512ea3
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dcache-flush.c
@@ -0,0 +1,33 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2020 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/>.  */
+
+int __attribute__((noinline))
+func (int *v1, int *v2)
+{
+  return *v1 - *v2 - 1;
+}
+
+int
+main ()
+{
+  int var1 = 4;
+  int var2 = 3;
+  int res;
+
+  res = func (&var1, &var2);
+  return res;
+}
diff --git a/gdb/testsuite/gdb.base/dcache-flush.exp b/gdb/testsuite/gdb.base/dcache-flush.exp
new file mode 100644
index 0000000..6c7d2f4
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dcache-flush.exp
@@ -0,0 +1,64 @@
+# Copyright 2020 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/>.
+
+# Test that the dcache can be flushed.
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" ${testfile}] } {
+    return -1
+}
+
+if ![runto func] {
+    return -1
+}
+
+gdb_test "up" ".* main .*"
+gdb_test "p var1" " = 4"
+gdb_test "p var2" " = 3"
+
+# By reading var1 and var2 we should have at least one line in the
+# dcache.
+gdb_test "info dcache" \
+    [multi_line \
+	 "Dcache $decimal lines of $decimal bytes each." \
+	 "Contains data for process $decimal" \
+	 "Line 0: address $hex \[$decimal hits\].*" \
+	 "Cache state: $decimal active lines, $decimal hits" ] \
+    "check dcache before flushing"
+
+# Flush the dcache.
+gdb_test "maint flush dcache" "The dcache was flushed\."
+
+# Check the dcache is now empty.
+gdb_test "info dcache" \
+    [multi_line  "Dcache $decimal lines of $decimal bytes each." \
+	 "No data cache available." ] \
+    "check dcache after flushing"
+
+# Read the stack variables again, refilling the dcache.
+with_test_prefix "refilling" {
+    gdb_test "p var1" " = 4"
+    gdb_test "p var2" " = 3"
+}
+
+# And check we have some content back in the dcache.
+gdb_test "info dcache" \
+    [multi_line \
+	 "Dcache $decimal lines of $decimal bytes each." \
+	 "Contains data for process $decimal" \
+	 "Line 0: address $hex \[$decimal hits\].*" \
+	 "Cache state: $decimal active lines, $decimal hits" ] \
+    "check dcache before refilling"