title: 驱动调试(四)oops确定调用树
date: 2019/1/14 19:30:32
toc: true
驱动调试(四)oops确定调用树
内核开启调用树
如果内核开启调用信息的打印
# 这个需要配置内核
#│ Symbol: FRAME_POINTER [=y] │
#│ Prompt: Compile the kernel with frame pointers │
#│ Defined at lib/Kconfig.debug:357 │
#│ Depends on: DEBUG_KERNEL && ............... │
#│ Location: │
#│ -> Kernel hacking │
#│ -> Kernel debugging (DEBUG_KERNEL [=y])
为什么这个选项叫做FRAME_POINTER,因为实际上使用了ARM中的fp寄存器,在A函数调用B函数时,B在开头保存了fb,ip,lr,pc等到栈中,一般情况下就是倒数第4个是fp,这个栈里面的fp也就是父函数的栈底
所以,在栈里面通过寻找fp,倒数第二个就能依次找到LR,依次找到调用树了
能显示出调用关系在oops中
Backtrace:
[<bf000000>] (first_drv_open+0x0/0x3c [first_drv]) from [<c008d888>] (chrdev_open+0x14c/0x164)
[<c008d73c>] (chrdev_open+0x0/0x164) from [<c0089e48>] (__dentry_open+0x100/0x1e8)
r8:c2ca741c r7:c0474d20 r6:c008d73c r5:c04b2e5c r4:c3e9b700
[<c0089d48>] (__dentry_open+0x0/0x1e8) from [<c0089f64>] (nameidata_to_filp+0x34/0x48)
[<c0089f30>] (nameidata_to_filp+0x0/0x48) from [<c0089fb8>] (do_filp_open+0x40/0x48)
r4:00000002
[<c0089f78>] (do_filp_open+0x0/0x48) from [<c008a2f4>] (do_sys_open+0x54/0xe4)
r5:be848ee0 r4:00000002
[<c008a2a0>] (do_sys_open+0x0/0xe4) from [<c008a3a8>] (sys_open+0x24/0x28)
[<c008a384>] (sys_open+0x0/0x28) from [<c002bea0>] (ret_fast_syscall+0x0/0x2c)
Code: e24cb004 e59f1024 e3a00000 e5912000 (e5923000)
Segmentation fault
调用关系如下
ret_fast_syscall
sys_open
do_filp_open
nameidata_to_filp
__dentry_open
chrdev_open
first_drv_open
栈指针分析
原理
在C函数的调用中,会先保存返回地址(LR)到栈中,也就是说LR的值是调用者的PC值.我们依次找到栈底,找到lr即可.
A()
B()
C()
{
//B的LR存到C分配的栈中
}
寄存器别名
- r15 PC The Program Counter.
- r14 LR The Link Register.
- r12 IP The Intra-Procedure-call scratch register. （可简单的认为暂存SP）
- r11 frame pointer
基础解释
-
栈底指的是堆栈指针sp所指的起始位置
-
STMDB 先存储,后做减法,也就是sp指向的位置是栈有效的数据,寄存器高地址存高字节
！：表示最后的地址写回到Rn中 stmdb sp!, {fp, ip, lr, pc}
例子分析
找到PC地址的位置
可以看下上一个章节,这里使用模块装载的例子
pc : [<bf000018>]
栈分析
可以看出来栈中的fp指向了父函数的栈底,最后一个函数的fb为0,也就是一个中断函数了图片这里可能看不清,左键拖动可以查看原图(高清)
这里有具体的txt分析,还是excel的图片好看,拖动放大
r15 PC The Program Counter.
r14 LR The Link Register.
r13 SP The Stack Pointer.
r12 IP The Intra-Procedure-call scratch register. （可简单的认为暂存SP）
r11 frame pointer。
栈底指的是堆栈指针sp所指的起始位置
stmdb sp!, {fp, ip, lr, pc}
# 高地址存高字节
也就是存储如下
-------------------------------------------------------------------------------
r15 PC The Program Counter.
r14 LR The Link Register.
r12 IP The Intra-Procedure-call scratch register. （可简单的认为暂存SP）
r11 frame pointer。
-------------------------------------------------------------------------------
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
00000000 <first_drv_open>:
0: e1a0c00d mov ip, sp
4: e92dd800 stmdb sp!, {fp, ip, lr, pc}
8: e24cb004 sub fp, ip, #4 ; 0x4 #这里是fp运算后是 c2c81e94
c: e59f1024 ldr r1, [pc, #36] ; 38 <__mod_vermagic5>
10: e3a00000 mov r0, #0 ; 0x0
14: e5912000 ldr r2, [r1]
18: e5923000 ldr r3, [r2] // 在这里出错 r2=56000050
#****************************************************************************
sp : c2c81e88 ip : c2c81e98 fp : c2c81e94
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: xxxxxxxx xxxxxxxx c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC ---↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
#****************************************************************************
>>>>>>>c008d888
c008d73c <chrdev_open>:
c008d73c: e1a0c00d mov ip, sp
c008d740: e92dd9f0 stmdb sp!, {r4, r5, r6, r7, r8, fp, ip, lr, pc}
c008d744: e24cb004 sub fp, ip, #4 ; 0x4
c008d748: e24dd004 sub sp, sp, #4 ; 0x4
...
c008d888: e2507000 subs r7, r0, #0 ; 0x0
#****************************************************************************
0 4 8 C 10 14 18 1C
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC --↑↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
fp(old) IP LR pc ↑--------这个位置正好是上面那个被调用函数存储在栈中的fp,也是这里的栈底(起始位置)
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
1ee0: c0089f64 c0089d58 00000000 00000002 c2c81f68 c2c81f00 c0089fb8 c0089f40
1f00: c2c81f04 c2c8e3c0 c0474e20 00000000 00000000 c2cd9000 00000101 00000001
1f20: 00000000 c2c80000 c046dec8 c046dec0 ffffffe8 c070b000 c2c81f68 c2c81f48
#****************************************************************************
这里sp存储了r4, r5, r6, r7, r8, fp, ip, lr, pc,然后再减去4,也就是存储了10个32位数据
这里我们看到
lr=c0089e48
fp(old)=c2c81ee4 上一级函数的栈底
>>>c0089e48
c0089d48 <__dentry_open>:
c0089d48: e1a0c00d mov ip, sp
c0089d4c: e92dddf0 stmdb sp!, {r4, r5, r6, r7, r8, sl, fp, ip, lr, pc}
....
c0089e38: e1a00005 mov r0, r5
c0089e3c: e1a01004 mov r1, r4
c0089e40: e1a0e00f mov lr, pc
c0089e44: e1a0f006 mov pc, r6
c0089e48: e250a000 subs sl, r0, #0 ; 0x0
#****************************************************************************
0 4 8 C 10 14 18 1C
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC --↑↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
fp(old) IP LR pc ↑--------这个位置正好是上面那个被调用函数存储在栈中的fp,也是这里的栈底(起始位置)
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
↑ fp(old) ip
1ee0: c0089f64 c0089d58 00000000 00000002 c2c81f68 c2c81f00 c0089fb8 c0089f40
lr pc ↑
这个地址是 c2c81ee4
正好是上一级的存在栈中的fp
1f00: c2c81f04 c2c8e3c0 c0474e20 00000000 00000000 c2cd9000 00000101 00000001
1f20: 00000000 c2c80000 c046dec8 c046dec0 ffffffe8 c070b000 c2c81f68 c2c81f48
#****************************************************************************
lr=c0089f64
fp(old)=c2c81efc
c0089f30 <nameidata_to_filp>:
c0089f30: e1a0c00d mov ip, sp
c0089f34: e92dd810 stmdb sp!, {r4, fp, ip, lr, pc}
c0089f38: e24cb004 sub fp, ip, #4 ; 0x4
c0089f3c: e24dd004 sub sp, sp, #4 ; 0x4 ;sp=sp-4 也就是再多4个字节
...
c0089f5c: e58de000 str lr, [sp]
c0089f60: ebffff78 bl c0089d48 <__dentry_open>
c0089f64: e1a04000 mov r4, r0
#****************************************************************************
0 4 8 C 10 14 18 1C
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC --↑↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
fp(old) IP LR pc ↑--------这个位置正好是上面那个被调用函数存储在栈中的fp,也是这里的栈底(起始位置)
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
↑ fp(old) ip
1ee0: c0089f64 c0089d58 00000000 00000002 c2c81f68 c2c81f00 c0089fb8 c0089f40
lr pc ↑ fp(old) ip lr pc这个地址是被调用的存在栈中的fp
这个地址是 c2c81ee4
正好是上一级的存在栈中的fp
1f00: c2c81f04 c2c8e3c0 c0474e20 00000000 00000000 c2cd9000 00000101 00000001
1f20: 00000000 c2c80000 c046dec8 c046dec0 ffffffe8 c070b000 c2c81f68 c2c81f48
lr=c0089fb8
fp(old)=c2c81f68
c0089f78 <do_filp_open>:
c0089f78: e1a0c00d mov ip, sp
c0089f7c: e92dd830 stmdb sp!, {r4, r5, fp, ip, lr, pc} ;6个
c0089f80: e24cb004 sub fp, ip, #4 ; 0x4
c0089f84: e24dd054 sub sp, sp, #84 ; 0x54 #84/4=21个 21+6=27个
.....
c0089fb4: 0bffffdd bleq c0089f30 <nameidata_to_filp>
c0089fb8: e24bd014 sub sp, fp, #20 ; 0x14
#****************************************************************************
0 4 8 C 10 14 18 1C
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC --↑↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
fp(old) IP LR pc ↑--------这个位置正好是上面那个被调用函数存储在栈中的fp,也是这里的栈底(起始位置)
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
↑ fp(old) ip
1ee0: c0089f64 c0089d58 00000000 00000002 c2c81f68 c2c81f00 c0089fb8 c0089f40
lr pc ↑ fp(old) ip lr pc这个地址是被调用的存在栈中的fp
这个地址是 c2c81ee4
正好是上一级的存在栈中的fp
1f00: c2c81f04 c2c8e3c0 c0474e20 00000000 00000000 c2cd9000 00000101 00000001
1f20: 00000000 c2c80000 c046dec8 c046dec0 ffffffe8 c070b000 c2c81f68 c2c81f48
1f40: c008a16c c009fc70 00000003 00000000 c3e38be0 00000002 bedd1edc c2c81f94
fp(old)
1f60: c2c81f6c c008a2f4 c0089f88 00008520 bedd1ed4 0000860c 00008670 00000005
Ip LR PC↑刚好也是(fp_old)
1f80: c002c044 4013365c c2c81fa4 c2c81f98 c008a3a8 c008a2b0 00000000 c2c81fa8
1fa0: c002bea0 c008a394 bedd1ed4 0000860c 00008720 00000002 bedd1edc 00000001
1fc0: bedd1ed4 0000860c 00008670 00000001 00008520 00000000 4013365c bedd1ea8
1fe0: 00000000 bedd1e84 0000266c 400c98e0 60000010 00008720 00000000 00000000
fp(old)=c2c81f94
lr=c008a2f4
c008a2a0 <do_sys_open>:
c008a2a0: e1a0c00d mov ip, sp
c008a2a4: e92dddf0 stmdb sp!, {r4, r5, r6, r7, r8, sl, fp, ip, lr, pc}
c008a2a8: e24cb004 sub fp, ip, #4 ; 0x4
c008a2ac: e24dd004 sub sp, sp, #4 ; 0x4 ;10+1=11
.....
c008a2ec: ba00001d blt c008a368 <do_sys_open+0xc8>
c008a2f0: ebffff20 bl c0089f78 <do_filp_open>
c008a2f4: e1a08000 mov r8, r0
#****************************************************************************
0 4 8 C 10 14 18 1C
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC --↑↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
fp(old) IP LR pc ↑--------这个位置正好是上面那个被调用函数存储在栈中的fp,也是这里的栈底(起始位置)
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
↑ fp(old) ip
1ee0: c0089f64 c0089d58 00000000 00000002 c2c81f68 c2c81f00 c0089fb8 c0089f40
lr pc ↑ fp(old) ip lr pc这个地址是被调用的存在栈中的fp
这个地址是 c2c81ee4
正好是上一级的存在栈中的fp
1f00: c2c81f04 c2c8e3c0 c0474e20 00000000 00000000 c2cd9000 00000101 00000001
1f20: 00000000 c2c80000 c046dec8 c046dec0 ffffffe8 c070b000 c2c81f68 c2c81f48
1f40: c008a16c c009fc70 00000003 00000000 c3e38be0 00000002 bedd1edc c2c81f94
fp(old)
1f60: c2c81f6c c008a2f4 c0089f88 00008520 bedd1ed4 0000860c 00008670 00000005
Ip LR PC↑刚好也是(fp_old)
1f80: c002c044 4013365c c2c81fa4 c2c81f98 c008a3a8 c008a2b0 00000000 c2c81fa8
fp_old ip lr pc ↑
1fa0: c002bea0 c008a394 bedd1ed4 0000860c 00008720 00000002 bedd1edc 00000001
1fc0: bedd1ed4 0000860c 00008670 00000001 00008520 00000000 4013365c bedd1ea8
1fe0: 00000000 bedd1e84 0000266c 400c98e0 60000010 00008720 00000000 00000000
lr=c008a3a8
fp_old=c2c81fa4
c008a384 <sys_open>:
c008a384: e1a0c00d mov ip, sp
c008a388: e92dd800 stmdb sp!, {fp, ip, lr, pc}
...
c008a3a4: ebffffbd bl c008a2a0 <do_sys_open>
c008a3a8: e89da800 ldmia sp, {fp, sp, pc}
#****************************************************************************
0 4 8 C 10 14 18 1C
Stack: (0xc2c81e88 to 0xc2c82000)
1e80: c2c81ebc c2c81e98 c008d888 bf000010 00000000 c3e38be0
fp(now) ↑--fp(old) ip LR PC --↑↑
1ea0: c2c3b100 c008d73c c0474e20 c2c8e3c0 c2c81ee4 c2c81ec0 c0089e48 c008d74c
fp(old) IP LR pc ↑--------这个位置正好是上面那个被调用函数存储在栈中的fp,也是这里的栈底(起始位置)
1ec0: c3e38be0 c2c81f04 00000003 ffffff9c c002c044 c070b000 c2c81efc c2c81ee8
↑ fp(old) ip
1ee0: c0089f64 c0089d58 00000000 00000002 c2c81f68 c2c81f00 c0089fb8 c0089f40
lr pc ↑ fp(old) ip lr pc这个地址是被调用的存在栈中的fp
这个地址是 c2c81ee4
正好是上一级的存在栈中的fp
1f00: c2c81f04 c2c8e3c0 c0474e20 00000000 00000000 c2cd9000 00000101 00000001
1f20: 00000000 c2c80000 c046dec8 c046dec0 ffffffe8 c070b000 c2c81f68 c2c81f48
1f40: c008a16c c009fc70 00000003 00000000 c3e38be0 00000002 bedd1edc c2c81f94
fp(old)
1f60: c2c81f6c c008a2f4 c0089f88 00008520 bedd1ed4 0000860c 00008670 00000005
Ip LR PC↑刚好也是(fp_old)
1f80: c002c044 4013365c c2c81fa4 c2c81f98 c008a3a8 c008a2b0 00000000 c2c81fa8
fp_old ip lr pc ↑ fp(old) ip
1fa0: c002bea0 c008a394 bedd1ed4 0000860c 00008720 00000002 bedd1edc 00000001
lr pc ↑
1fc0: bedd1ed4 0000860c 00008670 00000001 00008520 00000000 4013365c bedd1ea8
1fe0: 00000000 bedd1e84 0000266c 400c98e0 60000010 00008720 00000000 00000000
lr=c008a3a8
fp(old)=00000000 这里没有了,从下面来看 确实没有了,没有再操作fp了
ret_fast_syscall 软中断了
c002bea0 <ret_fast_syscall>:
c002bea0: e321f093 msr CPSR_c, #147 ; 0x93
c002bea4: e5991000 ldr r1, [r9]
c002bea8: e31100ff tst r1, #255 ; 0xff
c002beac: 1a000006 bne c002becc <fast_work_pending>
c002beb0: e59d1048 ldr r1, [sp, #72]
c002beb4: e5bde044 ldr lr, [sp, #68]!
c002beb8: e16ff001 msr SPSR_fsxc, r1
c002bebc: e95d7ffe ldmdb sp, {r1, r2, r3, r4, r5, r6, r7, r8, r9, sl, fp, ip, sp, lr}^
c002bec0: e1a00000 nop (mov r0,r0)
c002bec4: e28dd00c add sp, sp, #12 ; 0xc
c002bec8: e1b0f00e movs pc, lr