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Workaround gdbserver<7.7 for setfs

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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 e7f0d979dd
	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
2016-04-06  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* remote.c (struct remote_state): New field unknown_v_replies_ok.
	(packet_config_support): Read it.
	(remote_start_remote): Set it.
This commit is contained in:
Jan Kratochvil
2016-04-06 17:13:12 +02:00
parent 927f2d25ef
commit 319cb5d0cf
2 changed files with 37 additions and 0 deletions
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31
gdb/remote.c
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@@ -426,6 +426,15 @@ struct remote_state
request/reply nature of the RSP. We only cache data for a single
file descriptor at a time. */
struct readahead_cache readahead_cache;
/* 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. */
int unknown_v_replies_ok;
};
/* Private data that we'll store in (struct thread_info)->private. */
@@ -1519,6 +1528,13 @@ packet_config_support (struct packet_config *config)
case AUTO_BOOLEAN_FALSE:
return PACKET_DISABLE;
case AUTO_BOOLEAN_AUTO:
{
struct remote_state *rs = get_remote_state ();
if (rs->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 +4039,21 @@ 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)
rs->unknown_v_replies_ok = 1;
else if (strcmp (rs->buf, "") == 0)
rs->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,