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[patchv4] Workaround gdbserver<7.7 for setfs
- From: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: gdb-patches at sourceware dot org, Gary Benson <gbenson at redhat dot com>
- Date: Wed, 6 Apr 2016 15:49:11 +0200
- Subject: [patchv4] Workaround gdbserver<7.7 for setfs
- Authentication-results: sourceware.org; auth=none
- References: <20160319201842 dot GA16540 at host1 dot jankratochvil dot net> <56F13963 dot 9040204 at redhat dot com> <20160322131604 dot GA24312 at host1 dot jankratochvil dot net> <56F14F1E dot 5010606 at redhat dot com> <20160323211547 dot GA17400 at host1 dot jankratochvil dot net> <20160324220933 dot GA27445 at host1 dot jankratochvil dot net> <20160324223241 dot GB2548 at host1 dot jankratochvil dot net> <56FBDFE7 dot 90203 at redhat dot com> <20160404211406 dot GA32241 at host1 dot jankratochvil dot net> <5703E7FF dot 6060304 at redhat dot com>
On Tue, 05 Apr 2016 18:29:51 +0200, Pedro Alves wrote:
> MustReplyEmpty is actually not a useful probe packet, because
> that's actually an M (write memory) packet, which is then
> misinterpreted and fails the write. So not an unknown packet.
Oops, OK.
> Try qMustReplyEmpty or something like that instead.
With these requirements on this workaround I have followed the gdbserver-7.6
sources and the bug was in function handle_notif_ack which is called only from
handle_v_requests, therefore for any packets /^v/.
OK to check in this one?
Thanks,
Jan
gdb/gdbserver/ChangeLog
2016-04-05 Jan Kratochvil <jan.kratochvil@redhat.com>
* remote.c (unknown_v_replies_ok): New variable.
(packet_config_support): Read it.
(remote_start_remote): Set it.
diff --git a/gdb/remote.c b/gdb/remote.c
index 5c407b6..a88f4cd 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1496,6 +1496,15 @@ enum {
static struct packet_config remote_protocol_packets[PACKET_MAX];
+/* gdbserver < 7.7 (before its fix from 2013-12-11) did reply to any
+ unknown 'v' packet with string "OK". "OK" gets interpreted by GDB
+ as a reply to known packet. For packet "vFile:setfs:" it is an
+ invalid reply and GDB would return error in
+ remote_hostio_set_filesystem, making remote files access impossible.
+ If this variable is non-zero it means the remote gdbserver is buggy
+ and any not yet detected packets are assumed as unsupported. */
+static int unknown_v_replies_ok;
+
/* Returns the packet's corresponding "set remote foo-packet" command
state. See struct packet_config for more details. */
@@ -1519,6 +1528,9 @@ packet_config_support (struct packet_config *config)
case AUTO_BOOLEAN_FALSE:
return PACKET_DISABLE;
case AUTO_BOOLEAN_AUTO:
+ if (unknown_v_replies_ok && config->name != NULL
+ && config->name[0] == 'v')
+ return PACKET_DISABLE;
return config->support;
default:
gdb_assert_not_reached (_("bad switch"));
@@ -4023,6 +4035,21 @@ remote_start_remote (int from_tty, struct target_ops *target, int extended_p)
if (packet_support (PACKET_QAllow) != PACKET_DISABLE)
remote_set_permissions (target);
+ /* See unknown_v_replies_ok description. */
+ {
+ const char v_mustreplyempty[] = "vMustReplyEmpty";
+
+ putpkt (v_mustreplyempty);
+ getpkt (&rs->buf, &rs->buf_size, 0);
+ if (strcmp (rs->buf, "OK") == 0)
+ unknown_v_replies_ok = 1;
+ else if (strcmp (rs->buf, "") == 0)
+ unknown_v_replies_ok = 0;
+ else
+ error (_("Remote replied unexpectedly to '%s': %s"), v_mustreplyempty,
+ rs->buf);
+ }
+
/* Next, we possibly activate noack mode.
If the QStartNoAckMode packet configuration is set to AUTO,