• arm栈推导

    按照栈生长方向分：可以分为递增栈（向高地址生长）；递减栈（向低地址生长）

    按照sp执行位置来分：满栈（sp指向栈顶元素的位置）；空栈（sp指向即将入栈的元素位置）

    我这个环境是满减栈

     其实通过函数栈推导函数调用过程主要就是结合sp的位置以及汇编代码的压栈信息。找到LR寄存器的位置。

    代码示例

    起了一个内核线程，在函数f3里面会访问空指针，然后进入kdb

    1. void f3(void ) {
    2.   int i     = 0;
    3.   int* addr = NULL; 
    4.   for (i = 0; i < 10; ++i)
    5.   {
    6.      printk("%d\n", i);
    7.   }
    8.   *addr = 0x123;
    9.   return;
    10. }
    11. void f2(int a, int b) {
    12.   int d = 0;
    13.   int *addr = 0;
    14.   f3();
    15.   d = a + b;
    16.   printk("%d, %p\n", d, addr);
    17.   return;
    18. }
    19.  
    20. void f1(int a, int b) {
    21.   int c = 0;
    22.   c = a + b;
    23.   f2(c,20);
    24.   while (c > 0)
    25.   {  
    26. 	printk("%d\n", c);
    27. 	--c;
    28.   }
    29.   return;
    30. }
    31. struct timer_list timer;
    32. spinlock_t mylock;
    33. static struct task_struct *test_task;
    34. int test_thread(void* a)
    35. {
    36. 	unsigned long flags;
    37. 	printk(KERN_EMERG "\r\n softlockup simulate, in_interrupt %u in_softirq %u, cpu id %d\n", in_interrupt(), in_softirq(), smp_processor_id());
    38. 	
    39. 	/*local_irq_disable();
    40. 	while (1){}*/
    41. 	f1(10, 20);
    42. 	return 0;
    43. }

    对应的汇编代码如下 

    1. void f3(void ) {
    2.     3ed0:	e92d4010 	push	{r4, lr}
    3.   int i     = 0;
    4.   int* addr = NULL; 
    5.   for (i = 0; i < 10; ++i)
    6.     3ed4:	e3a04000 	mov	r4, #0
    7.   {
    8.      printk("%d\n", i);
    9.     3ed8:	e1a01004 	mov	r1, r4
    10.     3edc:	e59f001c 	ldr	r0, [pc, #28]	; 3f00 0x30>
    11. 	dev->dev_addr[5] = (u8)(mac_high16 >> 8);
    12. }
    13. void f3(void ) {
    14.   int i     = 0;
    15.   int* addr = NULL; 
    16.   for (i = 0; i < 10; ++i)
    17.     3ee0:	e2844001 	add	r4, r4, #1
    18.   {
    19.      printk("%d\n", i);
    20.     3ee4:	ebfffffe 	bl	0 
    21. 	dev->dev_addr[5] = (u8)(mac_high16 >> 8);
    22. }
    23. void f3(void ) {
    24.   int i     = 0;
    25.   int* addr = NULL; 
    26.   for (i = 0; i < 10; ++i)
    27.     3ee8:	e354000a 	cmp	r4, #10
    28.     3eec:	1afffff9 	bne	3ed8 0x8>
    29.   {
    30.      printk("%d\n", i);
    31.   }
    32.   *addr = 0x123;
    33.     3ef0:	e3a03000 	mov	r3, #0
    34.     3ef4:	e3002123 	movw	r2, #291	; 0x123
    35.     3ef8:	e5832000 	str	r2, [r3]
    36.     3efc:	e8bd8010 	pop	{r4, pc}
    37.     3f00:	0000034c 	.word	0x0000034c
    38.  
    39. 00003f04 :
    40.   return;
    41. }
    42. void f2(int a, int b) {
    43.     3f04:	e92d4038 	push	{r3, r4, r5, lr}
    44.     3f08:	e1a04000 	mov	r4, r0
    45.     3f0c:	e1a05001 	mov	r5, r1
    46.   int d = 0;
    47.   int *addr = 0;
    48.   f3();
    49.     3f10:	ebfffffe 	bl	3ed0 
    50.   d = a + b;
    51.   printk("%d, %p\n", d, addr);
    52.     3f14:	e0841005 	add	r1, r4, r5
    53.     3f18:	e3000000 	movw	r0, #0
    54.     3f1c:	e3a02000 	mov	r2, #0
    55.     3f20:	e3400000 	movt	r0, #0
    56.   return;
    57. }
    58.     3f24:	e8bd4038 	pop	{r3, r4, r5, lr}
    59. void f2(int a, int b) {
    60.   int d = 0;
    61.   int *addr = 0;
    62.   f3();
    63.   d = a + b;
    64.   printk("%d, %p\n", d, addr);
    65.     3f28:	eafffffe 	b	0 
    66.  
    67. 00003f2c :
    68.   return;
    69. }
    70.  
    71. void f1(int a, int b) {
    72.     3f2c:	e92d4010 	push	{r4, lr}
    73.   int c = 0;
    74.   c = a + b;
    75.     3f30:	e0804001 	add	r4, r0, r1
    76.   f2(c,20);
    77.     3f34:	e3a01014 	mov	r1, #20
    78.     3f38:	e1a00004 	mov	r0, r4
    79.     3f3c:	ebfffffe 	bl	3f04 
    80.   while (c > 0)
    81.     3f40:	e3540000 	cmp	r4, #0
    82.     3f44:	d8bd8010 	pople	{r4, pc}
    83.   {  
    84. 	printk("%d\n", c);
    85.     3f48:	e1a01004 	mov	r1, r4
    86.     3f4c:	e59f000c 	ldr	r0, [pc, #12]	; 3f60 0x34>
    87.     3f50:	ebfffffe 	bl	0 
    88.  
    89. void f1(int a, int b) {
    90.   int c = 0;
    91.   c = a + b;
    92.   f2(c,20);
    93.   while (c > 0)
    94.     3f54:	e2544001 	subs	r4, r4, #1
    95.     3f58:	1afffffa 	bne	3f48 0x1c>
    96.     3f5c:	e8bd8010 	pop	{r4, pc}
    97.     3f60:	0000034c 	.word	0x0000034c
    98.  
    99. 00003f64 :
    100. }
    101. struct timer_list timer;
    102. spinlock_t mylock;
    103. static struct task_struct *test_task;
    104. int test_thread(void* a)
    105. {
    106.     3f64:	e92d4008 	push	{r3, lr}
    107.     3f68:	e1a0200d 	mov	r2, sp
    108.     3f6c:	e3c23d7f 	bic	r3, r2, #8128	; 0x1fc0
    109. 	unsigned long flags;
    110. 	printk(KERN_EMERG "\r\n softlockup simulate, in_interrupt %u in_softirq %u, cpu id %d\n", in_interrupt(), in_softirq(), smp_processor_id());
    111.     3f70:	e3a01cff 	mov	r1, #65280	; 0xff00
    112.     3f74:	e3c3303f 	bic	r3, r3, #63	; 0x3f
    113.     3f78:	e340101f 	movt	r1, #31
    114.     3f7c:	e3000000 	movw	r0, #0
    115.     3f80:	e3400000 	movt	r0, #0
    116.     3f84:	e5932004 	ldr	r2, [r3, #4]
    117.     3f88:	e5933014 	ldr	r3, [r3, #20]
    118.     3f8c:	e0021001 	and	r1, r2, r1
    119.     3f90:	e2022cff 	and	r2, r2, #65280	; 0xff00
    120.     3f94:	ebfffffe 	bl	0 
    121. 	
    122. 	/*local_irq_disable();
    123. 	while (1){}*/
    124. 	f1(10, 20);
    125.     3f98:	e3a0000a 	mov	r0, #10
    126.     3f9c:	e3a01014 	mov	r1, #20
    127.     3fa0:	ebfffffe 	bl	3f2c 
    128. 	return 0;
    129. }
    130.     3fa4:	e3a00000 	mov	r0, #0
    131.     3fa8:	e8bd8008 	pop	{r3, pc}

    从上面的汇编代码可以看到每个函数的入栈信息如下。假设函数f3里面的栈顶指针为 sp_f3

    完整的异常log如下： 

    1. Unable to handle kernel NULL pointer dereference at virtual address 00000000
    2. pgd = c0004000
    3. [00000000] *pgd=00000000
    4. Internal error: Oops: 817 [#1] SMP ARM
    5.  
    6. Entering kdb (current=0xeea2e880, pid 649) on processor 3 Oops: (null)
    7. due to oops @ 0xc03087a8
    8.  
    9. dCPU: 3 PID: 649 Comm: test_task Not tainted 3.16.0 #65
    10. dtask: eea2e880 ti: ee226000 task.ti: ee226000
    11. PC is at f3+0x28/0x34
    12. LR is at f3+0x18/0x34
    13. pc : []    lr : []    psr: 60000013
    14. sp : ee227f40  ip : 00000001  fp : 00000000
    15. r10: 00000000  r9 : 00000000  r8 : 00000000
    16. r7 : c0308814  r6 : 00000000  r5 : 00000014  r4 : 0000000a
    17. r3 : 00000000  r2 : 00000123  r1 : 20000093  r0 : 00000001
    18. Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
    19. Control: 10c53c7d  Table: 8e30006a  DAC: 00000015
    20. dCPU: 3 PID: 649 Comm: test_task Not tainted 3.16.0 #65
    21. [] (unwind_backtrace) from [] (show_stack+0x10/0x14)
    22. [] (show_stack) from [] (dump_stack+0x74/0x90)
    23. [] (dump_stack) from [] (kdb_dumpregs+0x30/0x50)
    24. [] (kdb_dumpregs) from [] (kdb_main_loop+0x31c/0x70c)
    25. [] (kdb_main_loop) from [] (kdb_stub+0x1e0/0x44c)
    26. [] (kdb_stub) from [] (kgdb_cpu_enter+0x3c4/0x6e0)
    27. [] (kgdb_cpu_enter) from [] (kgdb_handle_exception+0x168/0x1d0)
    28. [] (kgdb_handle_exception) from [] (kgdb_notify+0x24/0x3c)
    29. [] (kgdb_notify) from [] (notifier_call_chain+0x44/0x84)
    30. [] (notifier_call_chain) from [] (__atomic_notifier_call_chain+0x18/0x20)
    31. [] (__atomic_notifier_call_chain) from [] (atomic_notifier_call_chain+0x18/0x20)
    32. [] (atomic_notifier_call_chain) from [] (notify_die+0x3c/0x44)
    33. [] (notify_die) from [] (die+0xe8/0x2c8)
    34. [] (die) from [] (__do_kernel_fault.part.8+0x54/0x74)
    35. [] (__do_kernel_fault.part.8) from [] (do_page_fault+0x1a8/0x3a4)
    36. [] (do_page_fault) from [] (do_DataAbort+0x34/0x98)
    37. [] (do_DataAbort) from [] (__dabt_svc+0x38/0x60)
    38. Exception stack(0xee227ef8 to 0xee227f40)
    39. 7ee0:                                                       00000001 20000093
    40. 7f00: 00000123 00000000 0000000a 00000014 00000000 c0308814 00000000 00000000
    41. 7f20: 00000000 00000000 00000001 ee227f40 c0308798 c03087a8 60000013 ffffffff
    42. [] (__dabt_svc) from [] (f3+0x28/0x34)
    43. [] (f3) from [] (f2+0x10/0x28)
    44. [] (f2) from [] (f1+0x14/0x38)
    45. [] (f1) from [] (test_thread+0x40/0x48)
    46. [] (test_thread) from [] (kthread+0xcc/0xe8)
    47. [] (kthread) from [] (ret_from_fork+0x14/0x3c)

     

    从异常log我们可以知道f3的栈顶指针为 sp : ee227f40

    f2的返回地址为ee227f40 + 4指向的地址里面的内容

    同理一级一级往上推

     

     

     c03087c4 = 0xc03087c4 (f2+0x10)

    c03087f0 = 0xc03087f0 (f1+0x14)
    c0308854 = 0xc0308854 (test_thread+0x40)
    c003c4fc = 0xc003c4fc (kthread+0xcc)

    和异常log里面的一样
    [] (f3) from [] (f2+0x10/0x28)
    [] (f2) from [] (f1+0x14/0x38)
    [] (f1) from [] (test_thread+0x40/0x48)
    [] (test_thread) from [] (kthread+0xcc/0xe8)
    [] (kthread) from [] (ret_from_fork+0x14/0x3c)

    另外也可以用命令mds直接查看 

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  • 原文地址：https://blog.csdn.net/qq_42693685/article/details/132818903