[Bug remote/25702] New: GDB may send qSupported packet which larger than possible packet size of stub.

[Bug remote/25702] New: GDB may send qSupported packet which larger than possible packet size of stub.

[sergey.belyashov at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25702

            Bug ID: 25702
           Summary: GDB may send qSupported packet which larger than
                    possible packet size of stub.
           Product: gdb
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: remote
          Assignee: unassigned at sourceware dot org
          Reporter: sergey.belyashov at gmail dot com
  Target Milestone: ---

Quote from
https://sourceware.org/gdb/current/onlinedocs/gdb/General-Query-Packets.html#qSupported
:
> The remote stub can accept packets up to at least bytes in length. GDB will
> send packets up to this size for bulk transfers, and will never send larger
> packets. This is a limit on the data characters in the packet, including the
> frame and checksum. There is no trailing NUL byte in a remote protocol packet;
> if the stub stores packets in a NUL-terminated format, it should allow an extra
> byte in its buffer for the NUL. If this stub feature is not supported, GDB
> guesses based on the size of the ‘g’ packet response.

For example, Z80 (GDB support is developing) CPU has 13 16-bit register pairs,
so 26 bytes total. It is 52 hex digits. Plus '$', 'G', '#' and CSUM. Total 56
bytes. But first request from gdb looks like:
$qSupported:multiprocess+;swbreak+;hwbreak+;qRelocInsn+;fork-events+;vfork-events+;exec-events+;vContSupported+;QThreadEvents+;no-resumed+#df

It is naked by stub. GDB totally request 4 times with same result.

I suggest to initially send qSupported with maximum packet size not larger than
G command request for particular target. And after receiving answer resend full
size (if needed).

-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug remote/25702] GDB may send qSupported packet which larger than possible packet size of stub.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25702

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2020-08-09

-- 
You are receiving this mail because:
You are on the CC list for the bug.