[Qemu-devel] [PATCH] Parsing problem of gdb 'M' packet

[Thomas Petazzoni]

Hello,

I've found a problem in the code parsing the gdb 'M' packet. During gdb 
remote sessions, I saw strange things when writing to memory :

============================================================
(gdb) print addr
$1 = 0
(gdb) set addr=12
(gdb) print addr
$2 = 49152
============================================================

So, I went into Qemu code, and found a problem in gdbstub.c. The format 
of a 'M' packet is Maddr,length:XX... as stated on [1]. So the addr is 
separated from the length using a comma, and the length from the data 
using a colon.

However, the Qemu code assumed that all fields were seperated with a 
comma, leading to wrong analysis of the data field.

The included one-line patch fixes the problem :

=============================================================
(gdb) print addr
$1 = 0
(gdb) set addr=12
(gdb) print addr
$2 = 12
=============================================================

Thomas

[1] http://sources.redhat.com/gdb/current/onlinedocs/gdb_33.html#SEC664
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Index: gdbstub.c
===================================================================
RCS file: /cvsroot/qemu/qemu/gdbstub.c,v
retrieving revision 1.22
diff -u -u -r1.22 gdbstub.c
--- gdbstub.c   3 Jan 2005 23:34:06 -0000       1.22
+++ gdbstub.c   15 Jan 2005 16:06:09 -0000
@@ -420,7 +420,7 @@
         if (*p == ',')
             p++;
         len = strtoul(p, (char **)&p, 16);
-        if (*p == ',')
+        if (*p == ':')
             p++;
         hextomem(mem_buf, p, len);
         if (cpu_memory_rw_debug(env, addr, mem_buf, len, 1) != 0)

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