Re: [PATCH 2/2] gdb: new command 'maint flush dcache'

Luis Machado via Gdb-patches
2020-11-23T16:28:13Z

On 11/23/20 7:39 AM, Andrew Burgess wrote:
> 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.
> ---
> gdb/ChangeLog | 8 ++++
> gdb/NEWS | 3 ++
> gdb/doc/ChangeLog | 5 ++
> gdb/doc/gdb.texinfo | 6 +++
> gdb/target-dcache.c | 19 ++++++++
> gdb/testsuite/ChangeLog | 5 ++
> gdb/testsuite/gdb.base/dcache-flush.c | 33 +++++++++++++
> gdb/testsuite/gdb.base/dcache-flush.exp | 64 +++++++++++++++++++++++++
> 8 files changed, 143 insertions(+)
> create mode 100644 gdb/testsuite/gdb.base/dcache-flush.c
> create mode 100644 gdb/testsuite/gdb.base/dcache-flush.exp
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index b07b054223f..ef59c7c1e69 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -32,6 +32,9 @@ 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/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 3745aa52973..7017823ef75 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -13494,6 +13494,12 @@
> @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 0226d672780..90b60f62f2e 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/gdb.base/dcache-flush.c b/gdb/testsuite/gdb.base/dcache-flush.c
> new file mode 100644
> index 00000000000..b512ea31760
> --- /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 00000000000..6c7d2f4bef8
> --- /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"
>

LGTM