[patch] Workaround gdbserver<7.7 for setfs [Re: [patch] Suggest newer gdbserver if it has no qXfer:exec-file:read]

[Jan Kratochvil <jan.kratochvil@redhat.com>]

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On Wed, 23 Mar 2016 22:15:47 +0100, Jan Kratochvil wrote:
> 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.
> 
> OT: I do not see why "empty response" is response "OK" but apparently it is.

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.

But I would prefer to make gdb compatible with gdbserver-7.6.1.

OK for check-in?


Thanks,
Jan

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gdb/ChangeLog
2016-03-24  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* remote.c (packet_ok): Add workaround for vFile:setfs.

diff --git a/gdb/remote.c b/gdb/remote.c
index af0a08a..be5cc09 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1311,7 +1311,14 @@ packet_ok (const char *buf, struct packet_config *config)
     internal_error (__FILE__, __LINE__,
 		    _("packet_ok: attempt to use a disabled packet"));
 
-  result = packet_check_result (buf);
+  if (strcmp (config->name, "vFile:setfs") == 0 && strcmp (buf, "OK") == 0)
+    {
+      /* Workaround gdbserver < 7.7 before its fix from 2013-12-11.  */
+      result = PACKET_UNKNOWN;
+    }
+  else
+    result = packet_check_result (buf);
+
   switch (result)
     {
     case PACKET_OK: