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[Qemu-devel] Single stepping MIPS in GDB
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From: |
Dirk Behme |
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Subject: |
[Qemu-devel] Single stepping MIPS in GDB |
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Date: |
Mon, 27 Mar 2006 19:53:01 +0200 |
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User-agent: |
Mozilla Thunderbird 1.0.7 (X11/20050923) |
Hi,
now, after ARM, I try to debug some low level system init
code on MIPS as well. For this, I use
qemu-snapshot-2006-03-21_23 because this already includes
little endian MIPS (--target-list=mipsel-softmmu). I can
load my program to MIPS default start address 0x80010000,
use mipsel-linux-gdb to attach to it and load symbols. Start
address is set correctly. But seems that I have trouble
single stepping (si). I would assume that with first si
system should jump to 0x80010400 (please find some debug
output below). Instead, PC is set to 0x0.
If I start program with 'continue' in gdb, seems that
program starts to run correctly. After stop at random
location with ctrl-c in gdb, the following single steps seem
to fail as well (please see below as well).
Any hints what I'm making wrong here?
Many thanks
Dirk
*1* Debug output for single step at startup. PC is set to
0x0 instead to next command at 0x80010400
_start ()
at uboot/u-boot-1.1.4/cpu/mips/start.S:43
43 RVECENT(reset,0) /* U-boot entry point */
(gdb) p/x $pc
$1 = 0x80010000
(gdb) x/2i $pc
0x80010000 <_start>: b 0x80010400 <reset>
0x80010004 <_start+4>: nop
(gdb) si
0x00000000 in ?? ()
(gdb) p/x $pc
$2 = 0x0
(gdb)
/tmp> cat qemu.log
pc=0x80010000 HI=0x00000000 LO=0x00000000 ds 0002 00000000 0
GPR00: r0 00000000 at 00000000 v0 00000000 v1 00000000
GPR04: a0 00000000 a1 00000000 a2 00000000 a3 00000000
GPR08: t0 00000000 t1 00000000 t2 00000000 t3 00000000
GPR12: t4 00000000 t5 00000000 t6 00000000 t7 00000000
GPR16: s0 00000000 s1 00000000 s2 00000000 s3 00000000
GPR20: s4 00000000 s5 00000000 s6 00000000 s7 00000000
GPR24: t8 00000000 t9 00000000 k0 00000000 k1 00000000
GPR28: gp 00000000 sp 00000000 s8 00000000 ra 00000000
CP0 Status 0x10400004 Cause 0x00000400 EPC 0x00000000
Config0 0x80008090 Config1 0x1e190c8a LLAddr 0x00000000
cpu_mips_handle_mmu_fault pc 80010000 ad 80010000 rw 2
is_user 0 smmu 1
cpu_mips_handle_mmu_fault address=80010000 ret 0 physical
00010000 prot 3
------------------------------------------------
pc=0x80010000 HI=0x00000000 LO=0x00000000 ds 0002 00000000 0
GPR00: r0 00000000 at 00000000 v0 00000000 v1 00000000
GPR04: a0 00000000 a1 00000000 a2 00000000 a3 00000000
GPR08: t0 00000000 t1 00000000 t2 00000000 t3 00000000
GPR12: t4 00000000 t5 00000000 t6 00000000 t7 00000000
GPR16: s0 00000000 s1 00000000 s2 00000000 s3 00000000
GPR20: s4 00000000 s5 00000000 s6 00000000 s7 00000000
GPR24: t8 00000000 t9 00000000 k0 00000000 k1 00000000
GPR28: gp 00000000 sp 00000000 s8 00000000 ra 00000000
CP0 Status 0x10400004 Cause 0x00000400 EPC 0x00000000
Config0 0x80008090 Config1 0x1e190c8a LLAddr 0x00000000
IN:
0x80010000: b 0x80010400
0x80010004: nop
OP:
0x0000: goto_tb0
0x0001: save_pc 0x80010400
0x0002: set_T0 0x829ce00
0x0003: exit_tb
0x0004: reset_T0
0x0005: exit_tb
0x0006: end
---------------- 2 00000002
OUT: [size=24]
0x08a9ce00: jmp 0xa4ab0b4
0x08a9ce05: movl $0x80010400,0x80(%ebp)
0x08a9ce0f: mov $0x829ce00,%ebx
0x08a9ce14: ret
0x08a9ce15: xor %ebx,%ebx
0x08a9ce17: ret
Trace 0x08a9ce00 [80010000]
pc=0x80010400 HI=0x00000000 LO=0x00000000 ds 0002 00000000 0
GPR00: r0 00000000 at 00000000 v0 00000000 v1 00000000
GPR04: a0 00000000 a1 00000000 a2 00000000 a3 00000000
GPR08: t0 00000000 t1 00000000 t2 00000000 t3 00000000
GPR12: t4 00000000 t5 00000000 t6 00000000 t7 00000000
GPR16: s0 00000000 s1 00000000 s2 00000000 s3 00000000
GPR20: s4 00000000 s5 00000000 s6 00000000 s7 00000000
GPR24: t8 00000000 t9 00000000 k0 00000000 k1 00000000
GPR28: gp 00000000 sp 00000000 s8 00000000 ra 00000000
CP0 Status 0x10400004 Cause 0x00000400 EPC 0x00000000
Config0 0x80008090 Config1 0x1e190c8a LLAddr 0x00000000
------------------------------------------------
pc=0x80010400 HI=0x00000000 LO=0x00000000 ds 0002 00000000 0
GPR00: r0 00000000 at 00000000 v0 00000000 v1 00000000
GPR04: a0 00000000 a1 00000000 a2 00000000 a3 00000000
GPR08: t0 00000000 t1 00000000 t2 00000000 t3 00000000
GPR12: t4 00000000 t5 00000000 t6 00000000 t7 00000000
GPR16: s0 00000000 s1 00000000 s2 00000000 s3 00000000
GPR20: s4 00000000 s5 00000000 s6 00000000 s7 00000000
GPR24: t8 00000000 t9 00000000 k0 00000000 k1 00000000
GPR28: gp 00000000 sp 00000000 s8 00000000 ra 00000000
CP0 Status 0x10400004 Cause 0x00000400 EPC 0x00000000
Config0 0x80008090 Config1 0x1e190c8a LLAddr 0x00000000
IN:
OP:
0x0000: save_pc 0x80010400
0x0001: debug
0x0002: end
---------------- 2 00000002
OUT: [size=21]
0x08a9ce20: movl $0x80010400,0x80(%ebp)
0x08a9ce2a: push $0x10002
0x08a9ce2f: call 0x80866c0
0x08a9ce34: pop %eax
Trace 0x08a9ce20 [80010400]
search pc 1
------------------------------------------------
pc=0x80010400 HI=0x00000000 LO=0x00000000 ds 0002 00000000 0
GPR00: r0 00000000 at 00000000 v0 00000000 v1 00000000
GPR04: a0 00000000 a1 00000000 a2 00000000 a3 00000000
GPR08: t0 00000000 t1 00000000 t2 00000000 t3 00000000
GPR12: t4 00000000 t5 00000000 t6 00000000 t7 00000000
GPR16: s0 00000000 s1 00000000 s2 00000000 s3 00000000
GPR20: s4 00000000 s5 00000000 s6 00000000 s7 00000000
GPR24: t8 00000000 t9 00000000 k0 00000000 k1 00000000
GPR28: gp 00000000 sp 00000000 s8 00000000 ra 00000000
CP0 Status 0x10400004 Cause 0x00000400 EPC 0x00000000
Config0 0x80008090 Config1 0x1e190c8a LLAddr 0x00000000
IN:
OP:
0x0000: save_pc 0x80010400
0x0001: debug
0x0002: end
---------------- 2 00000002
/tmp >
Debug output from debug enabled in gdbserver:
command='m80010000,4'
reply='ff000010'
command='m80010004,4'
reply='00000000'
command='m80010000,4'
reply='ff000010'
command='m80010004,4'
reply='00000000'
command='m80010000,4'
reply='ff000010'
command='Z0,80010400,4'
reply='OK'
command='vCont?'
reply=''
command='Hc0'
reply=''
command='c'
Foo #B ret: 0
reply='S05'
command='g'
reply='0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040100000000000000000000000000004000000000000'
command='z0,80010400,4'
reply='OK'
command='m0,4'
reply='00000000'
command='mfffffffc,4'
reply='E14'
command='m0,4'
reply='00000000'
command='mfffffffc,4'
reply='E14'
command='m0,4'
reply='00000000'
command='mfffffffc,4'
reply='E14'
command='m0,4'
reply='00000000'
command='mfffffffc,4'
reply='E14'
command='m0,4'
reply='00000000'
command='m4,4'
reply='00000000'
*2* Start program with 'continue', stop somewhere with
ctrl-c, then single step:
(gdb) p/x $pc
$3 = 0x800108cc
(gdb) si
143 2: sw zero, 0(a0)
(gdb) si
143 2: sw zero, 0(a0)
(gdb) si
143 2: sw zero, 0(a0)
(gdb) p/x $pc
$4 = 0x800108cc
(gdb) x/3i $pc
0x800108cc <mips_cache_reset+28>: sw zero,0(a0)
0x800108d0 <mips_cache_reset+32>: sw zero,4(a0)
0x800108d4 <mips_cache_reset+36>: sw zero,8(a0)
(gdb)
- [Qemu-devel] Single stepping MIPS in GDB,
Dirk Behme <=