file vmlinux
load
set $r0 = 0
set $r1 = 0
set $r2 = 0
set $r3 = 0
set $r4 = 0
set $r5 = 0
set $r6 = 0
set $r7 = 0
set $r8 = 0
set $r9 = 0
set $r10 = 0
set $r11 = 0
set $r12 = 0
set $r13 = 0
set $r14 = 0
set $r15 = 0
set $r16 = 0
set $r17 = 0
set $r18 = 0
set $r19 = 0
set $r20 = 0
set $r21 = 0
set $r22 = 0
set $r23 = 0
set $r24 = 0
set $r25 = 0
set $r26 = 0
set $r27 = 0
set $r28 = 0
set $r29 = 0
set $r30 = 0
set $r31 = 0
set $sr = 0
break *0x00000110
break *0x0043a20c
break *0x0043a088
break *0x0043a0b0
break *0x0043a0f0
break *0x0043a104
break *0x0043a118
break *0x0043a15c
break *0x0043a188
jump *0x100


kernel jumps to the _start function in head.S file
.
.
.
... I kept continuing until the jump to or32_early_setup at the end of _start function

c0440a20 T setup_cpuinfo
c0440d74 T or32_early_setup
c0440de0 T detect_unit_config


(gdb) disas 0x0043a188-0x20, +0x40
Dump of assembler code from 0x43a168 to 0x43a1a8:
   0x0043a168:    l.ori r4,r4,0xfeed
   0x0043a16c:    l.sfeq r3,r4
   0x0043a170:    l.bf 0x43a17c
   0x0043a174:    l.nop 0x0
   0x0043a178:    l.or r25,r0,r0
   0x0043a17c:    l.or r3,r0,r25
   0x0043a180:    l.movhi r24,0xc044
   0x0043a184:    l.ori r24,r24,0xd74
=> 0x0043a188:    l.jalr r24
   0x0043a18c:    l.nop 0x0
   0x0043a190:    l.movhi r2,0x0
   0x0043a194:    l.movhi r3,0x0
   0x0043a198:    l.movhi r4,0x0
   0x0043a19c:    l.movhi r5,0x0
   0x0043a1a0:    l.movhi r6,0x0
   0x0043a1a4:    l.movhi r7,0x0
End of assembler dump.

End of assembler dump.
(gdb) si
0x0043a18c in ?? ()
(gdb) info registers
r0             0x0                 0
r1             0xc041e000          0xc041e000 <mmlist_lock>
r2             0x0                 0x0
r3             0x0                 0
r4             0xd00dfeed          -804389139
r5             0x400               1024
r6             0x8009              32777
r7             0x0                 0
r8             0x0                 0
r9             0x43a190            0x43a190
r10            0xc041c000          -1069432832
r11            0x0                 0
r12            0x0                 0
r13            0x0                 0
r14            0x10                16
r15            0x0                 0
r16            0x40                64
r17            0x0                 0
r18            0x0                 0
r19            0x0                 0
r20            0x0                 0
r21            0x0                 0
r22            0x0                 0
---Type <return> to continue, or q <return> to quit---
r23            0x0                 0
r24            0xc0440d74          -1069281932
r25            0x0                 0
r26            0x30                48
r27            0x0                 0
r28            0x60                96
r29            0x0                 0
r30            0xa069              41065
r31            0x41c000            4308992
ppc            0x43a188            0x43a188
npc            0x43a18c            0x43a18c
sr             0x8009              [ SM DCE FO CID=0 ]

------------------------
(gdb) disas 0xc0440d74
Dump of assembler code for function or32_early_setup:
   0xc0440d74 <+0>:    l.mtspr r3,r1,0x574
   0xc0440d78 <+4>:    l.mtspr r3,r1,0x574
   0xc0440d7c <+8>:    l.mtspr r3,r1,0x574
   0xc0440d80 <+12>:    l.mtspr r3,r1,0x574
   0xc0440d84 <+16>:    l.mtspr r3,r1,0x574
   0xc0440d88 <+20>:    l.mtspr r3,r1,0x574
   0xc0440d8c <+24>:    l.mtspr r3,r1,0x574
   0xc0440d90 <+28>:    l.mtspr r3,r1,0x574
   0xc0440d94 <+32>:    l.mtspr r3,r1,0x574
   0xc0440d98 <+36>:    l.mtspr r3,r1,0x574
   0xc0440d9c <+40>:    l.mtspr r3,r1,0x574
   0xc0440da0 <+44>:    l.mtspr r3,r1,0x574
   0xc0440da4 <+48>:    l.mtspr r3,r1,0x574
   0xc0440da8 <+52>:    l.mtspr r3,r1,0x574
   0xc0440dac <+56>:    l.mtspr r3,r1,0x574
   0xc0440db0 <+60>:    l.mtspr r3,r1,0x574
   0xc0440db4 <+64>:    l.mtspr r3,r1,0x574
   0xc0440db8 <+68>:    l.mtspr r3,r1,0x574
   0xc0440dbc <+72>:    l.mtspr r3,r1,0x574
   0xc0440dc0 <+76>:    l.mtspr r3,r1,0x574
   0xc0440dc4 <+80>:    l.mtspr r3,r1,0x574
   0xc0440dc8 <+84>:    l.mtspr r3,r1,0x574
---Type <return> to continue, or q <return> to quit---q
Quit
(gdb) disas 0x440d74, +0x20
Dump of assembler code from 0x440d74 to 0x440d94:
   0x00440d74:    l.sw -8(r1),r2
   0x00440d78:    l.sw -4(r1),r9
   0x00440d7c:    l.sw -12(r1),r16
   0x00440d80:    l.ori r2,r1,0x0
   0x00440d84:    l.sfeqi r3,0
   0x00440d88:    l.bf 0x440dac
   0x00440d8c:    l.addi r1,r1,-16
   0x00440d90:    l.ori r16,r3,0x0
End of assembler dump.
(gdb) break *0x200
Breakpoint 10 at 0x200
(gdb) si
0xc0440d74 in or32_early_setup ()
(gdb) si

Breakpoint 10, 0x00000200 in ?? ()
(gdb) si
0x00000204 in ?? ()
(gdb) si
0x00000208 in ?? ()
(gdb) si
0x00000208 in ?? ()
(gdb) si
0x0000020c in ?? ()
(gdb) si
0x00000210 in ?? ()
(gdb) si
0x00000214 in ?? ()
(gdb) si
0x00000218 in ?? ()
(gdb) si
0x0000021c in ?? ()
(gdb) si
0x00000220 in ?? ()
(gdb) si
0x00000224 in ?? ()
(gdb) si
0x00000228 in ?? ()
(gdb) si
0x0000022c in ?? ()
(gdb) si
0x00000230 in ?? ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063104 in kmsg_dump_rewind_nolock ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063104 in kmsg_dump_rewind_nolock ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) si
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) si
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) si
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb) si
0xc0063108 in kmsg_dump_rewind_nolock ()
(gdb)