Debugging an L4 task

[Derick Swanepoel]

Hi,

I am trying to debug an L4 task that double pagefaults before reaching
the main function. How should one use the debugger to run a task so it
can be debugged without having to break into the debugger later? The
backtrace doesn't seem very useful because it looks like a stack
overflow due to infinite recursion.

Here is the loader output:

exec    | testtask: Loading
exec    | testtask: Has no dynamic info
exec    | testtask: Saved 50936 bytes of symbols
exec    | testtask: "libloader.s.so" not in library list
loader  | testtask: Starting sigma0-style application
exec    | testtask: Packed 37981 bytes of symbols
exec    | testtask: Packed 60324 bytes of lines
loader  | testtask,#11: Entry at 00009c7c => 01600000
loader  | testtask,#11: Started
loader  | testtask,#11: Double PF (w) at 0c776bec eip 016290bf (11.00)


Here is the backtrace:

backtrace (thread 11.00, fp=01629068, pc=016290bf):
#1  016290bf : capdigits + 0x12
#2  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#3  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#4  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#5  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#6  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#7  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#8  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#9  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#10  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#11  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#12  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#13  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#14  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#15  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#16  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#17  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#18  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#19  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#20  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#21  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#22  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#23  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#24  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#25  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#26  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#27  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#28  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#29  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#30  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#31  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#32  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#33  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#34  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#35  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148
#36  01604dca : outs + 0x2a
      /home/derick/DROPS/l4/pkg/log/lib/src/logliblinux.c:22
#37  01604970 : flush + 0x20
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:47
#38  01604a4f : printchar + 0xcf
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:71
#39  01604c56 : LOG_fputs + 0x26
      /home/derick/DROPS/l4/pkg/log/lib/src/log_printf.c:148

 --kernel-bt-follows-- (don't trust w/o frame pointer!!)
#1  f0005950
#2  f0004c7e
#3  f0009e01
#4  f0009e01
#5  f00053ee
#6  f0009a65
#7  f000b3fa
#8  f00049ce
#9  f000b767
#10  f00086e3
#11  f0004084
#12  f0006931
#13  f00253a2


Thanks in advance,
Derick