Never got a response to this, did I miss it somehow? If not, please see below.
---------- Forwarded message ---------- From: jw4...@gmail.com <jw4...@gmail.com> Date: Fri, Dec 2, 2016 at 9:21 PM Subject: GDB Remote target descriptions To: lldb-dev@lists.llvm.org Hi all, I've been adding support for the qXfer:features:read:target.xml message for our tools at $WORK and have run into a couple hiccups to puzzle over. First off, the request message as defined at https://sourceware.org/gdb/ onlinedocs/gdb/General-Query-Packets.html#qXfer%20target% 20description%20read is in the form qXfer:features:read:annex:offset,size. When talking to GDB it works to respond with a 'l' or 'm' message smaller than size, then GDB proceeds to request the next chunk, and so on until the debug server says there is no more data. I believe there is a bug in lldb's handling of this message in that if the response is shorter than 'size' while also being incomplete, lldb requests the next chunk with a giant offset. This patch fixes the behavior: Index: source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp =================================================================== --- source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp (revision 288181) +++ source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp (working copy) @@ -3342,7 +3342,7 @@ case ('m'): if (str.length() > 1) output << &str[1]; - offset += size; + offset += str.length() - 1; break; // unknown chunk Secondly, it appears that lldb only processes a single <feature> element per "file" when discovering the register descriptions, the workaround seems to be to put each individual feature in an <xi:include> file or conglomerate everything under a single feature in target.xml, but that has an unfortunate side effect of not working right when talking to GDB. This one I didn't dig too far into that code but it looks like ProcessGDBRemote::GetGDBServerRegisterInfo only extracts a single <feature> node (the last one) from the target description. In any case, these are both able to be worked around in my environment without too much work but it would be nice to get at least that first item fixed.
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