Nate Lawson writes:
> I've put together a patch that enables a kernel on the target machine to
> detect a GDB packet and automatically enter GDB mode. When the debugger
> detaches, it also continues execution. This speeds up debugging,
> especially when the target is in a remote location. The patch plus more
> explanation is at:
>
> http://www.root.org/~nate/freebsd/
Neat. A couple of comments:
1. I think a better abstraction of the GDB packet protocol would
be something like this:
struct gdb_parse {
int state; /* opaque state value */
u_int len; /* current packet length */
u_int maxlen; /* maximum packet length */
u_char data[0]; /* packet data */
};
extern void gdb_parse_init(struct gdb_parse *p);
extern int gdb_parse_byte(struct gdb_parse *p);
That is, if you're doing the state machine, why not go ahead
and decode the packet data as well?
2. You need to handle the escape mechanism for packets containing
"raw" data.: '$', '#', and '~' are escaped with '~' characters
in case the the 'X' command is used.
3. I think GDB_AUTO_DETACH should be mandatory, i.e., the current
state of affairs is a bug IMHO.
4. Does FreeBSD use the 'O' command to send ordinary serial port output
when GDB mode is active? Haven't looked but this would be nice to
have if it's not already there.
5. Receipt of a '$' character should always reset the state, no?
(modulo the '~' escape mechanism mentioned above).
-Archie
__________________________________________________________________________
Archie Cobbs * Packet Design * http://www.packetdesign.com
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