|Subject:||Problems debugging multithreaded program wirh gdbserver via serial port|
|From:||"Yoni Rabinovitch" <Yoni.Rabinovich@Teledata-Networks.com>|
|Date:||Mon, 8 Nov 2004 16:11:32 +0200|
|Thread-topic:||Problems debugging multithreaded program wirh gdbserver via se rial port|
I am trying to debug a multithreaded program running on an embedded MIPS 5Kc using gdb and gdbserver, connected via
a serial port.
My environment is as follows:
MIPS kernel based on 2.4.18
gdb : 6.2.1, configured with --host=i686-pc-linux-gnu --target=mips-hardhat-linux --disable-sim --disable-tcl --enable-threads --enable-shared
gdbserver: 6.2.1, configured with --target=mips-linux --enable-threads --enable-shared
gcc : 3.2.3, }
binutils : 2.13 } Built using crosstool
glibc: 2.2.5 }
My problems are as follows:
1) If I try to run the program from gdbserver (i.e. gdbserver /dev/ttyS0 wlsd), I get "readchar: Input/output error" messages,
and nothing works. See attached file gdb_fail.
What is going on here ?
2) If I first run the program, and then attach gdbserver to it (i.e. gdbserver /dev/ttyS0 --attach 80), I can debug it.
However, debugging is amazingly slow !!
For example, it can take 10 minutes for the "backtrace" (bt) command to complete !!!
Also, I get messages saying "Cannot access memory at address 0x2c" whnever I try to look at the stack.
See attached file gdb_trace.
Why is it going so slow ?
What is the cause of the "Cannot access memory at address 0x2c" messages ?
3) If I repeat the scenario described in 2), but with "set debug remote 1", it seems to work somewhat faster
(e.g. bt takes about 1 minute to complete).
I am seeing alot of "Packet instead of Ack, ignoring it" messages.
See attached file gdb_trace_debug.
What do these messages mean ?
In general, what to I need to do to get gdb <-> gdbserver debugging working properly over a serial port?
Thanks in advance for any tips !!
<<gdb_fail>> <<gdb_trace_debug>> <<gdb_trace>>
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