Workaround gdbserver<7.7 for setfs
authorJan Kratochvil <jan.kratochvil@redhat.com>
Wed, 27 Apr 2016 19:27:40 +0000 (21:27 +0200)
committerJan Kratochvil <jan.kratochvil@redhat.com>
Wed, 27 Apr 2016 19:27:40 +0000 (21:27 +0200)
commit57809e5e5a506664eb54433ded81ab0785168a83
treeb182387a6aaa5528d584b75b36b60f730f9c77a5
parent91f8bf69a526912f86da81070407bba6a050e27f
Workaround gdbserver<7.7 for setfs

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.
gdb/ChangeLog
gdb/remote.c