Debugging

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GDB Interface

coreboot has an easy to use interface to the GNU debugger gdb. To enable it, add the following two lines to your mainboard's config.-lb:

uses CONFIG_GDB_STUB
default CONFIG_GDB_STUB=1

Then you will not get exceptions like this:

Unexpected Exception: 0 @ 10:0012724b - Halting
Code: 0 eflags: 00010046
eax: 00000001 ebx: 00000061 ecx: 00000004 edx: 00000000
edi: 00000000 esi: 00000061 ebp: 00163abc esp: 00163a98

But instead you will be able to connect to the machine using gdb over a serial line in case of an exception:

(gdb) file coreboot-v2/coreboot-builds/kontron_986lcd-m/fallback/coreboot_ram
Reading symbols from coreboot-v2/coreboot-builds/kontron_986lcd-m/fallback/coreboot_ram...done.
(gdb) set remotebaud 115200
(gdb) target remote /dev/ttyUSB0
Remote debugging using /dev/ttyUSB0
0x0012824b in __udivdi3 (n=17082841390, d=0) at ...
...
(gdb) bt
#0  0x0012824b in __udivdi3 (n=17082841390, d=0)
    at /usr/lib/gcc/gcc- 4.3.2/libgcc/../gcc/libgcc2.c:899 
#1  0x0011efa2 in handle_port_61h ()
#2  0x0011fbc3 in my_inb ()
#3  0x001189f5 in x86emuOp_in_byte_AL_IMM ()
#4  0x001092f1 in X86EMU_exec ()
#5  0x0010a06f in biosemu ()
#6  0x0011fcfb in run_bios ()
#7  0x0010cbcb in pci_dev_init ()
#8  0x00103d9b in dev_initialize ()
#9  0x0010f8b5 in hardwaremain ()
#10 0x00100099 in _text ()