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[patchv5] 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: Tue, 26 Apr 2016 23:29:23 +0200
- Subject: [patchv5] Workaround gdbserver<7.7 for setfs
- Authentication-results: sourceware.org; auth=none
- References: <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> <20160406134911 dot GA30545 at host1 dot jankratochvil dot net> <57051DAB dot 7000008 at redhat dot com> <20160406151925 dot GA17174 at host1 dot jankratochvil dot net> <20160406190905 dot GA16036 at host1 dot jankratochvil dot net>
Hi Pedro,
On Wed, 06 Apr 2016 21:09:05 +0200, Jan Kratochvil wrote:
> it no longer transferred any files with old gdbserver after this commit.
> (I do not have setup a regression testsuite for old gdbserver.)
>
> Therefore reverting it
posting a new implementation based on Pedro's off-list comment:
hmm. guess we could still salvage it, by 1) still doing the detection
early; 2) accept OK as "unsupported" in setfs only?
OK for check-in?
Thanks,
Jan
With current FSF GDB HEAD and old FSF gdbserver I expected I could do:
gdb -ex 'file target:/root/redhat/threadit' -ex 'target remote :1234'
(supplying that unsupported qXfer:exec-file:read by "file")
But that does not work because:
Sending packet: $vFile:setfs:0#bf...Packet received: OK
Packet vFile:setfs (hostio-setfs) is supported
...
Sending packet: $vFile:setfs:104#24...Packet received: OK
"target:/root/redhat/threadit": could not open as an executable file: Invalid argument
GDB documentation says:
The valid responses to Host I/O packets are:
An empty response indicates that this operation is not recognized.
This "empty response" vs. "OK" was a bug in gdbserver < 7.7. It was fixed by:
commit e7f0d979dd5cc4f8b658df892e93db69d6d660b7
Author: Yao Qi <yao@codesourcery.com>
Date: Tue Dec 10 21:59:20 2013 +0800
Fix a bug in matching notifications.
Message-ID: <1386684626-11415-1-git-send-email-yao@codesourcery.com>
https://sourceware.org/ml/gdb-patches/2013-12/msg00373.html
2013-12-10 Yao Qi <yao@codesourcery.com>
* notif.c (handle_notif_ack): Return 0 if no notification
matches.
with unpatched old FSF gdbserver and patched FSF GDB HEAD:
gdb -ex 'file target:/root/redhat/threadit' -ex 'target remote :1234'
Sending packet: $vFile:setfs:0#bf...Packet received: OK
Packet vFile:setfs (hostio-setfs) is NOT supported
...
(gdb) info sharedlibrary
From To Syms Read Shared Object Library
0x00007ffff7ddbae0 0x00007ffff7df627a Yes (*) target:/lib64/ld-linux-x86-64.so.2
0x00007ffff7bc48a0 0x00007ffff7bcf514 Yes (*) target:/lib64/libpthread.so.0
gdb/ChangeLog
2016-04-26 Jan Kratochvil <jan.kratochvil@redhat.com>
* remote.c (remote_start_remote): Detect PACKET_vFile_setfs.support.
diff --git a/gdb/remote.c b/gdb/remote.c
index e5bf15d..a9b7201 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -4031,6 +4031,25 @@ remote_start_remote (int from_tty, struct target_ops *target, int extended_p)
if (packet_support (PACKET_QAllow) != PACKET_DISABLE)
remote_set_permissions (target);
+ /* 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.
+ Disable "vFile:setfs:" in such case. Do not disable other 'v' packets as
+ other "vFile" packets get correctly detected even on gdbserver < 7.7. */
+ {
+ const char v_mustreplyempty[] = "vMustReplyEmpty";
+
+ putpkt (v_mustreplyempty);
+ getpkt (&rs->buf, &rs->buf_size, 0);
+ if (strcmp (rs->buf, "OK") == 0)
+ remote_protocol_packets[PACKET_vFile_setfs].support = PACKET_DISABLE;
+ else if (strcmp (rs->buf, "") != 0)
+ 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,