On Mon, Nov 08, 2004 at 04:11:32PM +0200, Yoni Rabinovitch wrote: > Hi, > > 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 ? It sounds like your serial port is messed up. > 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 ? GDB is confused by glibc's syscall stubs. In general, don't worry about errors at the end of backtraces. > 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 ? Try "set debug serial 1" in addition - it's very verbose but maybe it will tell you what the "packet" is. -- Daniel Jacobowitz
