调试 – 观察Linux内核中的变量(内存地址)更改,并在更改时打印堆栈跟踪？【转】

> debugging – Linux kernel hardware break points – Stack Overflow
> Hardware Breakpoint (or watchpoint) – The Linux Kernel Archives

…我可以用它来开发我在这里发布的示例,testhrarr.c内核模块/驱动程序和Makefile(下面).它表明硬件观察点跟踪可以通过两种方式实现：使用perf程序,它可以不变地探测驱动程序;或者通过向驱动程序添加一些硬件断点代码(在示例中,由HWDEBUG_STACK定义变量包含).

本质上,调试像int这样的标准原子变量类型(如runco??unt变量)的内容很简单,只要它们被定义为内核模块中的全局变量,因此它们最终全局显示为内核符号.因此,下面的代码将testhrarr_添加为变量的前缀(以避免命名冲突).但是,由于需要解除引用,调试数组的内容可能有点棘手 – 这就是本文演示的内容,调试testhrarr_arr数组的第一个字节.它完成于：

1. $echo `cat /etc/lsb-release`
2. DISTRIB_ID=Ubuntu DISTRIB_RELEASE=11.04 DISTRIB_CODENAME=natty DISTRIB_DESCRIPTION="Ubuntu 11.04"
3. $uname -a
4. Linux mypc 2.6.38-16-generic #67-Ubuntu SMP Thu Sep 6 18:00:43 UTC 2012 i686 i686 i386 GNU/Linux
5. $cat /proc/cpuinfo | grep "model name"
6. model name : Intel(R) Atom(TM) CPU N450 @ 1.66GHz
7. model name : Intel(R) Atom(TM) CPU N450 @ 1.66GHz

testhrarr模块基本上在模块初始化时为小数组分配内存,设置定时器函数,并公开/ proc / testhrarr_proc文件(使用较新的proc_create接口).然后,尝试从/ proc / testhrarr_proc文件(例如,使用cat)读取将触发计时器功能,该功能将修改testhrarr_arr数组值,并将消息转储到/ var / log / syslog.我们期望testhrarr_arr [0]在操作期间会改变三次;一次在testhrarr_startup中,两次在testhrarr_timer_function中(由于换行).

使用perf

使用make构建模块后,您可以使用以下命令加载它：

1. sudo insmod ./testhrarr.ko

此时,/ var / log / syslog将包含：

1. kernel: [40277.199913] Init testhrarr: 0 ; HZ: 250 ; 1/HZ (ms): 4 ; hrres: 0.000000001
2. kernel: [40277.199930] Addresses: _runcount 0xf84be22c ; _arr 0xf84be2a0 ; _arr[0] 0xed182a80 (0xed182a80) ; _timer_function 0xf84bc1c3 ; my_hrtimer 0xf84be260; my_hrt.f 0xf84be27c
3. kernel: [40277.220329] HW Breakpoint for testhrarr_arr write installed (0xf84be2a0)

注意,只是将testhrarr_arr作为硬件观察点的符号传递,扫描该变量的地址(0xf84be2a0),而不是数组的第一个元素的地址(0xed182a80)！因此,硬件断点不会触发 – 因此行为就好像硬件断点代码根本不存在(可以通过取消定义HWDEBUG_STACK来实现)！

因此,即使没有通过内核模块代码设置的硬件断点,我们仍然可以使用perf来观察内存地址的变化 – 在perf中,我们指定我们要监视的地址(这里是testhrarr_arr的第一个元素的地址,0xed182a80),以及应该运行的进程：这里我们运行bash,所以我们可以执行cat / proc / testhrarr_proc,它将触发内核模块定时器,然后是sleep 0.5,这将允许定时器完成. -a参数也是必需的,否则可能会遗漏一些事件：

1. $sudo perf record -a --call-graph --event=mem:0xed182a80:w bash -c ‘cat /proc/testhrarr_proc ; sleep 0.5‘
2. testhrarr proc: startup
3. [ perf record: Woken up 1 times to write data ]
4. [ perf record: Captured and wrote 0.485 MB perf.data (~21172 samples) ]

此时,/ var / log / syslog还包含以下内容：

2. ^{[40822.114964] testhrarr_timer_function: testhrarr_runcount 0}
3. ^{[40822.114980] testhrarr jiffies 10130528 ; ret: 1 ; ktnsec: 40822114975062}
4. ^{[40822.118956] testhrarr_timer_function: testhrarr_runcount 1}
5. ^{[40822.118977] testhrarr jiffies 10130529 ; ret: 1 ; ktnsec: 40822118973195}
6. ^{[40822.122940] testhrarr_timer_function: testhrarr_runcount 2}
7. ^{[40822.122956] testhrarr jiffies 10130530 ; ret: 1 ; ktnsec: 40822122951143}
8. ^{[40822.126962] testhrarr_timer_function: testhrarr_runcount 3}
9. ^{[40822.126978] testhrarr jiffies 10130531 ; ret: 1 ; ktnsec: 40822126973583}
10. ^{[40822.130941] testhrarr_timer_function: testhrarr_runcount 4}
11. ^{[40822.130961] testhrarr jiffies 10130532 ; ret: 1 ; ktnsec: 40822130955167}
12. ^{[40822.134940] testhrarr_timer_function: testhrarr_runcount 5}
13. ^{[40822.134962] testhrarr jiffies 10130533 ; ret: 1 ; ktnsec: 40822134958888}
14. ^{[40822.138936] testhrarr_timer_function: testhrarr_runcount 6}
15. ^{[40822.138958] testhrarr jiffies 10130534 ; ret: 1 ; ktnsec: 40822138955693}
16. ^{[40822.142940] testhrarr_timer_function: testhrarr_runcount 7}
17. ^{[40822.142962] testhrarr jiffies 10130535 ; ret: 1 ; ktnsec: 40822142959345}
18. ^{[40822.146936] testhrarr_timer_function: testhrarr_runcount 8}
19. ^{[40822.146957] testhrarr jiffies 10130536 ; ret: 1 ; ktnsec: 40822146954479}
20. ^{[40822.150949] testhrarr_timer_function: testhrarr_runcount 9}
21. ^{[40822.150970] testhrarr jiffies 10130537 ; ret: 1 ; ktnsec: 40822150963438}
22. ^{[40822.154974] testhrarr_timer_function: testhrarr_runcount 10}
23. ^{[40822.154988] testhrarr [ 5,7,9,11,13,]}

要读取perf(一个名为perf.data的文件)的捕获,我们可以使用：

1. $sudo perf report --call-graph flat --stdio
2. ^{No kallsyms or vmlinux with build-id 5031df4d8668bcc45a7bdb4023909c6f8e2d3d34 was found}
3. ^{[testhrarr] with build id 5031df4d8668bcc45a7bdb4023909c6f8e2d3d34 not found,continuing without symbols}
4. ^{Failed to open /bin/cat,continuing without symbols}
5. ^{Failed to open /usr/lib/libpixman-1.so.0.20.2,continuing without symbols}
6. ^{Failed to open /usr/lib/xorg/modules/drivers/intel_drv.so,continuing without symbols}
7. ^{Failed to open /usr/bin/Xorg,continuing without symbols}
8. ^{# Events: 5 unknown}
9. ^#
10. ^{# Overhead Command Shared Object Symbol}
11. ^{# ........ ....... ............. ....................................}
12. ^#
13. ^{87.50% Xorg [testhrarr] [k] testhrarr_timer_function}
14. ^87.50%
15. ^{testhrarr_timer_function}
16. ^{__run_hrtimer}
17. ^{hrtimer_interrupt}
18. ^{smp_apic_timer_interrupt}
19. ^{apic_timer_interrupt}
20. ^0x30185d
21. ^0x2ed701
22. ^0x2ed8cc
23. ^0x2edba0
24. ^0x9d0386
25. ^0x8126fc8
26. ^0x81217a1
27. ^0x811bdd3
28. ^0x8070aa7
29. ^0x806281c
30. ^{__libc_start_main}
31. ^0x8062411
33. ^{6.25% cat [testhrarr] [k] testhrarr_timer_function}
34. ^6.25%
35. ^{testhrarr_timer_function}
36. ^{testhrarr_proc_show}
37. ^seq_read
38. ^{proc_reg_read}
39. ^vfs_read
40. ^sys_read
41. ^syscall_call
42. ^0xaa2416
43. ^0x8049f4d
44. ^{__libc_start_main}
45. ^0x8049081
47. ^{3.12% swapper [testhrarr] [k] testhrarr_timer_function}
48. ^3.12%
49. ^{testhrarr_timer_function}
50. ^{__run_hrtimer}
51. ^{hrtimer_interrupt}
52. ^{smp_apic_timer_interrupt}
53. ^{apic_timer_interrupt}
54. ^{cpuidle_idle_call}
55. ^cpu_idle
56. ^{start_secondary}
58. ^{3.12% cat [testhrarr] [k] 0x356}
59. ^3.12%
60. ^0xf84bc356
61. ^0xf84bc3a7
62. ^seq_read
63. ^{proc_reg_read}
64. ^vfs_read
65. ^sys_read
66. ^syscall_call
67. ^0xaa2416
68. ^0x8049f4d
69. ^{__libc_start_main}
70. ^0x8049081
74. ^#
75. ^{# (For a higher level overview,try: perf report --sort comm,dso)}
76. ^#

因此,由于我们正在使用调试on(Makefile中的-g)构建内核模块,所以即使实时内核不是调试内核,perf也不能找到该模块的符号.所以它在大多数时候正确地将testhrarr_timer_function解释为setter,虽然它没有报告testhrarr_startup(但它报告了testhrarr_proc_show调用它).还有对0xf84bc3a7和0xf84bc356的引用无法解析;但请注意,模块加载为0xf84bc000：

1. $sudo cat /proc/modules | grep testhr
2. testhrarr 13433 0 - Live 0xf84bc000

……并且该条目也以…开头[k] 0x356;如果我们查看内核模块的objdump：

1. $objdump -S testhrarr.ko | less
2. ^...
3. ^{00000323 :}
5. ^{static void testhrarr_startup(void)}
6. ^{
7. ^...
8. ^{testhrarr_arr[0] = 0; //just the first element}
9. ^{34b: a1 80 00 00 00 mov 0x80,%eax}
10. ^{350: c7 00 00 00 00 00 movl $0x0,(%eax)}
11. ^{hrtimer_start(&my_hrtimer,ktime_period_ns,HRTIMER_MODE_REL);}
12. ^{356: c7 04 24 01 00 00 00 movl $0x1,(%esp) **********}
13. ^{35d: 8b 15 1c 00 00 00 mov 0x1c,%edx}
14. ^...
15. ^{00000375 :}
18. ^{static int testhrarr_proc_show(struct seq_file *m,void *v) {}
19. ^...
20. ^{seq_printf(m,"testhrarr proc: startup\n");}
21. ^{38f: c7 44 24 04 79 00 00 movl $0x79,0x4(%esp)}
22. ^{396: 00}
23. ^{397: 8b 45 fc mov -0x4(%ebp),%eax}
24. ^{39a: 89 04 24 mov %eax,(%esp)}
25. ^{39d: e8 fc ff ff ff call 39e}
26. ^{testhrarr_startup();}
27. ^{3a2: e8 7c ff ff ff call 323}
28. ^{3a7: eb 1c jmp 3c5 **********}
29. ^{} else {}
30. ^{seq_printf(m,"testhrarr proc: (is running,%d)\n",testhrarr_runcount);}
31. ^{3a9: a1 0c 00 00 00 mov 0xc,%eax}
32. ^...

…所以0xf84bc356显然是指hrtimer_start;和0xf84bc3a7 – > 3a7指其调用testhrarr_proc_show函数;值得庆幸的是. (请注意,我已经体验过不同版本的驱动程序,_start可以显示,而timer_function由纯粹的地址表示;不确定是什么原因).

然而,perf的一个问题是,它给了我这些函数的统计“开销”(不确定是什么意思 – 可能是在函数的进入和退出之间花费的时间？) – 但我真正想要的是堆栈跟踪的日志是顺序的.不确定是否可以为此设置perf – 但绝对可以使用内核模块代码来完成硬件断点.

使用内核模块HW断点

HWDEBUG_STACK中的代码实现了HW断点的设置和处理.如上所述,符号ksym_name(如果未指定)的默认设置是testhrarr_arr,它根本不触发硬件断点.在insmod期间,可以在命令行中指定ksym_name参数;在这里我们可以注意到：

1. $sudo rmmod testhrarr # remove module if still loaded
2. $sudo insmod ./testhrarr.ko ksym=testhrarr_arr[0]

…在/ var / log / syslog中安装了HW Breakpoint for testhrarr_arr [0]的结果(0x(null)); – 这意味着我们不能使用带括号表示法的符号进行数组访问;谢天谢地,这里的空指针只是意味着HW断点将再次不会触发;它不会完全崩溃操作系统:)

但是,有一个全局变量用于引用testhrarr_arr数组的第一个元素,称为testhrarr_arr_first – 注意如何在代码中专门处理此全局变量,并且需要取消引用,以便获得正确的地址.所以我们这样做：

1. $sudo rmmod testhrarr # remove module if still loaded
2. $sudo insmod ./testhrarr.ko ksym=testhrarr_arr_first

…并且syslog通知：

1. kernel: [43910.509726] Init testhrarr: 0 ; HZ: 250 ; 1/HZ (ms): 4 ; hrres: 0.000000001
2. kernel: [43910.509765] Addresses: _runcount 0xf84be22c ; _arr 0xf84be2a0 ; _arr[0] 0xedf6c5c0 (0xedf6c5c0) ; _timer_function 0xf84bc1c3 ; my_hrtimer 0xf84be260; my_hrt.f 0xf84be27c
3. kernel: [43910.538535] HW Breakpoint for testhrarr_arr_first write installed (0xedf6c5c0)

…我们可以看到HW断点设置为0xedf6c5c0,这是testhrarr_arr [0]的地址.现在,如果我们通过/ proc文件触发驱动程序：

1. $cat /proc/testhrarr_proc
2. testhrarr proc: startup

…我们在syslog中获取：

1. ^{kernel: [44069.735695] testhrarr_arr_first value is changed}
2. ^{[44069.735711] Pid: 29320,comm: cat Not tainted 2.6.38-16-generic #67-Ubuntu}
3. ^{[44069.735719] Call Trace:}
4. ^{[44069.735737] [] ? sample_hbp_handler+0x2d/0x3b [testhrarr]}
5. ^{[44069.735755] [] ? __perf_event_overflow+0x90/0x240}
6. ^{[44069.735768] [] ? proc_alloc_inode+0x23/0x90}
7. ^{[44069.735778] [] ? proc_alloc_inode+0x23/0x90}
8. ^{[44069.735790] [] ? perf_swevent_event+0x136/0x140}
9. ^{[44069.735801] [] ? perf_bp_event+0x70/0x80}
10. ^{[44069.735812] [] ? prep_new_page+0x110/0x1a0}
11. ^{[44069.735824] [] ? get_page_from_freelist+0x12e/0x320}
12. ^{[44069.735836] [] ? seq_open+0x3d/0xa0}
13. ^{[44069.735848] [] ? hw_breakpoint_handler.clone.0+0x102/0x130}
14. ^{[44069.735861] [] ? hw_breakpoint_exceptions_notify+0x22/0x30}
15. ^{[44069.735872] [] ? notifier_call_chain+0x45/0x60}
16. ^{[44069.735883] [] ? atomic_notifier_call_chain+0x22/0x30}
17. ^{[44069.735894] [] ? notify_die+0x2d/0x30}
18. ^{[44069.735904] [] ? do_debug+0x88/0x180}
19. ^{[44069.735915] [] ? debug_stack_correct+0x30/0x38}
20. ^{[44069.735928] [] ? testhrarr_startup+0x33/0x52 [testhrarr]}
21. ^{[44069.735940] [] ? testhrarr_proc_show+0x32/0x57 [testhrarr]}
22. ^{[44069.735952] [] ? seq_read+0x145/0x390}
23. ^{[44069.735963] [] ? seq_read+0x0/0x390}
24. ^{[44069.735973] [] ? proc_reg_read+0x64/0xa0}
25. ^{[44069.735985] [] ? vfs_read+0x9f/0x160}
26. ^{[44069.735995] [] ? proc_reg_read+0x0/0xa0}
27. ^{[44069.736003] [] ? sys_read+0x42/0x70}
28. ^{[44069.736013] [] ? syscall_call+0x7/0xb}
29. ^{[44069.736019] Dump stack from sample_hbp_handler}
30. ^{[44069.740132] testhrarr_timer_function: testhrarr_runcount 0}
31. ^{[44069.740146] testhrarr jiffies 10942435 ; ret: 1 ; ktnsec: 44069740142485}
32. ^{[44069.740159] testhrarr_arr_first value is changed}
33. ^{[44069.740169] Pid: 4302,comm: gnome-terminal Not tainted 2.6.38-16-generic #67-Ubuntu}
34. ^{[44069.740176] Call Trace:}
35. ^{[44069.740195] [] ? sample_hbp_handler+0x2d/0x3b [testhrarr]}
36. ^{[44069.740213] [] ? __perf_event_overflow+0x90/0x240}
37. ^{[44069.740227] [] ? perf_swevent_event+0x136/0x140}
38. ^{[44069.740239] [] ? perf_bp_event+0x70/0x80}
39. ^{[44069.740253] [] ? sched_clock_local+0xd3/0x1c0}
40. ^{[44069.740267] [] ? format_decode+0x323/0x380}
41. ^{[44069.740280] [] ? hw_breakpoint_handler.clone.0+0x102/0x130}
42. ^{[44069.740292] [] ? hw_breakpoint_exceptions_notify+0x22/0x30}
43. ^{[44069.740302] [] ? notifier_call_chain+0x45/0x60}
44. ^{[44069.740313] [] ? atomic_notifier_call_chain+0x22/0x30}
45. ^{[44069.740324] [] ? notify_die+0x2d/0x30}
46. ^{[44069.740335] [] ? do_debug+0x88/0x180}
47. ^{[44069.740345] [] ? debug_stack_correct+0x30/0x38}
48. ^{[44069.740364] [] ? init_intel_cacheinfo+0x103/0x394}
49. ^{[44069.740379] [] ? testhrarr_timer_function+0xed/0x160 [testhrarr]}
50. ^{[44069.740391] [] ? __run_hrtimer+0x6f/0x190}
51. ^{[44069.740404] [] ? testhrarr_timer_function+0x0/0x160 [testhrarr]}
52. ^{[44069.740416] [] ? hrtimer_interrupt+0x108/0x240}
53. ^{[44069.740430] [] ? smp_apic_timer_interrupt+0x56/0x8a}
54. ^{[44069.740441] [] ? apic_timer_interrupt+0x31/0x38}
55. ^{[44069.740453] [] ? _raw_spin_unlock_irqrestore+0x15/0x20}
56. ^{[44069.740465] [] ? try_to_del_timer_sync+0x67/0xb0}
57. ^{[44069.740476] [] ? del_timer_sync+0x29/0x50}
58. ^{[44069.740486] [] ? flush_delayed_work+0x13/0x40}
59. ^{[44069.740500] [] ? tty_flush_to_ldisc+0x12/0x20}
60. ^{[44069.740510] [] ? n_tty_poll+0x4f/0x190}
61. ^{[44069.740523] [] ? tty_poll+0x6d/0x90}
62. ^{[44069.740531] [] ? n_tty_poll+0x0/0x190}
63. ^{[44069.740542] [] ? do_poll.clone.3+0xd0/0x210}
64. ^{[44069.740553] [] ? do_sys_poll+0x134/0x1e0}
65. ^{[44069.740563] [] ? __pollwait+0x0/0xd0}
66. ^{[44069.740572] [] ? pollwake+0x0/0x60}
67. ^...
68. ^{[44069.740742] [] ? pollwake+0x0/0x60}
69. ^{[44069.740757] [] ? rw_verify_area+0x6c/0x130}
70. ^{[44069.740770] [] ? ktime_get_ts+0xf8/0x120}
71. ^{[44069.740781] [] ? poll_select_set_timeout+0x64/0x70}
72. ^{[44069.740793] [] ? sys_poll+0x5a/0xd0}
73. ^{[44069.740804] [] ? syscall_call+0x7/0xb}
74. ^{[44069.740815] [] ? init_intel_cacheinfo+0x23/0x394}
75. ^{[44069.740822] Dump stack from sample_hbp_handler}
76. ^{[44069.744130] testhrarr_timer_function: testhrarr_runcount 1}
77. ^{[44069.744143] testhrarr jiffies 10942436 ; ret: 1 ; ktnsec: 44069744140055}
78. ^{[44069.748132] testhrarr_timer_function: testhrarr_runcount 2}
79. ^{[44069.748145] testhrarr jiffies 10942437 ; ret: 1 ; ktnsec: 44069748141271}
80. ^{[44069.752131] testhrarr_timer_function: testhrarr_runcount 3}
81. ^{[44069.752145] testhrarr jiffies 10942438 ; ret: 1 ; ktnsec: 44069752141164}
82. ^{[44069.756131] testhrarr_timer_function: testhrarr_runcount 4}
83. ^{[44069.756141] testhrarr jiffies 10942439 ; ret: 1 ; ktnsec: 44069756138318}
84. ^{[44069.760130] testhrarr_timer_function: testhrarr_runcount 5}
85. ^{[44069.760141] testhrarr jiffies 10942440 ; ret: 1 ; ktnsec: 44069760138469}
86. ^{[44069.760154] testhrarr_arr_first value is changed}
87. ^{[44069.760164] Pid: 4302,comm: gnome-terminal Not tainted 2.6.38-16-generic #67-Ubuntu}
88. ^{[44069.760170] Call Trace:}
89. ^{[44069.760187] [] ? sample_hbp_handler+0x2d/0x3b [testhrarr]}
90. ^{[44069.760202] [] ? __perf_event_overflow+0x90/0x240}
91. ^{[44069.760213] [] ? perf_swevent_event+0x136/0x140}
92. ^{[44069.760224] [] ? perf_bp_event+0x70/0x80}
93. ^{[44069.760235] [] ? sched_clock_local+0xd3/0x1c0}
94. ^{[44069.760247] [] ? format_decode+0x323/0x380}
95. ^{[44069.760258] [] ? hw_breakpoint_handler.clone.0+0x102/0x130}
96. ^{[44069.760269] [] ? hw_breakpoint_exceptions_notify+0x22/0x30}
97. ^{[44069.760279] [] ? notifier_call_chain+0x45/0x60}
98. ^{[44069.760289] [] ? atomic_notifier_call_chain+0x22/0x30}
99. ^{[44069.760299] [] ? notify_die+0x2d/0x30}
100. ^{[44069.760308] [] ? do_debug+0x88/0x180}
101. ^{[44069.760318] [] ? debug_stack_correct+0x30/0x38}
102. ^{[44069.760334] [] ? init_intel_cacheinfo+0x103/0x394}
103. ^{[44069.760345] [] ? testhrarr_timer_function+0xed/0x160 [testhrarr]}
104. ^{[44069.760356] [] ? __run_hrtimer+0x6f/0x190}
105. ^{[44069.760366] [] ? send_to_group.clone.1+0xf8/0x150}
106. ^{[44069.760376] [] ? testhrarr_timer_function+0x0/0x160 [testhrarr]}
107. ^{[44069.760387] [] ? hrtimer_interrupt+0x108/0x240}
108. ^{[44069.760396] [] ? fsnotify+0x1a5/0x290}
109. ^{[44069.760407] [] ? smp_apic_timer_interrupt+0x56/0x8a}
110. ^{[44069.760416] [] ? apic_timer_interrupt+0x31/0x38}
111. ^{[44069.760428] [] ? mem_cgroup_resize_limit+0x108/0x1c0}
112. ^{[44069.760437] [] ? fput+0x0/0x30}
113. ^{[44069.760446] [] ? sys_write+0x67/0x70}
114. ^{[44069.760455] [] ? syscall_call+0x7/0xb}
115. ^{[44069.760464] [] ? init_intel_cacheinfo+0x23/0x394}
116. ^{[44069.760470] Dump stack from sample_hbp_handler}
117. ^{[44069.764134] testhrarr_timer_function: testhrarr_runcount 6}
118. ^{[44069.764147] testhrarr jiffies 10942441 ; ret: 1 ; ktnsec: 44069764144141}
119. ^{[44069.768133] testhrarr_timer_function: testhrarr_runcount 7}
120. ^{[44069.768146] testhrarr jiffies 10942442 ; ret: 1 ; ktnsec: 44069768142976}
121. ^{[44069.772134] testhrarr_timer_function: testhrarr_runcount 8}
122. ^{[44069.772148] testhrarr jiffies 10942443 ; ret: 1 ; ktnsec: 44069772144121}
123. ^{[44069.776132] testhrarr_timer_function: testhrarr_runcount 9}
124. ^{[44069.776145] testhrarr jiffies 10942444 ; ret: 1 ; ktnsec: 44069776141971}
125. ^{[44069.780133] testhrarr_timer_function: testhrarr_runcount 10}
126. ^{[44069.780141] testhrarr [ 5,]}

…我们得到一个堆栈跟踪正好三次 – 一次在testhrarr_startup期间,两次在testhrarr_timer_function中：一次用于runco??unt == 0,一次用于runco??unt == 5,如预期的那样.

嗯,希望这有助于某人,
干杯!

Makefile文件

1. CONFIG_MODULE_FORCE_UNLOAD=y
2.  
3. # debug build:
4. # "CFLAGS was changed ... Fix it to use EXTRA_CFLAGS."
5. override EXTRA_CFLAGS+=-g -O0
6.  
7. obj-m += testhrarr.o
8. #testhrarr-objs := testhrarr.o
9.  
10. all:
11. @echo EXTRA_CFLAGS = $(EXTRA_CFLAGS)
12. make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
13.  
14. clean:
15. make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

testhrarr.c

1. /*
2. * [http://www.tldp.org/LDP/lkmpg/2.6/html/lkmpg.html#AEN189 The Linux Kernel Module Programming Guide]
3. * https://stackoverflow.com/questions/16920238/reliability-of-linux-kernel-add-timer-at-resolution-of-one-jiffy/17055867#17055867
4. * https://stackoverflow.com/questions/8516021/proc-create-example-for-kernel-module/18924359#18924359
5. * http://lxr.free-electrons.com/source/samples/hw_breakpoint/data_breakpoint.c
6. */
7.  
8.  
9. #include <linux/module.h> /* Needed by all modules */
10. #include <linux/kernel.h> /* Needed for KERN_INFO */
11. #include <linux/init.h> /* Needed for the macros */
12. #include <linux/jiffies.h>
13. #include <linux/time.h>
14. #include <linux/proc_fs.h> /* /proc entry */
15. #include <linux/seq_file.h> /* /proc entry */
16. #define ARRSIZE 5
17. #define MAXRUNS 2*ARRSIZE
18.  
19. #include <linux/hrtimer.h>
20.  
21. #define HWDEBUG_STACK 1
22.  
23. #if (HWDEBUG_STACK == 1)
24. #include <linux/perf_event.h>
25. #include <linux/hw_breakpoint.h>
26.  
27. struct perf_event * __percpu *sample_hbp;
28. static char ksym_name[KSYM_NAME_LEN] = "testhrarr_arr";
29. module_param_string(ksym,ksym_name,KSYM_NAME_LEN,S_IRUGO);
30. MODULE_PARM_DESC(ksym,"Kernel symbol to monitor; this module will report any"
31. " write operations on the kernel symbol");
32. #endif
33.  
34. static volatile int testhrarr_runcount = 0;
35. static volatile int testhrarr_isRunning = 0;
36.  
37. static unsigned long period_ms;
38. static unsigned long period_ns;
39. static ktime_t ktime_period_ns;
40. static struct hrtimer my_hrtimer;
41.  
42. static int* testhrarr_arr;
43. static int* testhrarr_arr_first;
44.  
45. static enum hrtimer_restart testhrarr_timer_function(struct hrtimer *timer)
46. {
47. unsigned long tjnow;
48. ktime_t kt_now;
49. int ret_overrun;
50.  
51. printk(KERN_INFO
52. " %s: testhrarr_runcount %d \n",__func__,testhrarr_runcount);
53.  
54. if (testhrarr_runcount < MAXRUNS) {
55. tjnow = jiffies;
56. kt_now = hrtimer_cb_get_time(&my_hrtimer);
57. ret_overrun = hrtimer_forward(&my_hrtimer,kt_now,ktime_period_ns);
58. printk(KERN_INFO
59. " testhrarr jiffies %lu ; ret: %d ; ktnsec: %lld\n",tjnow,ret_overrun,ktime_to_ns(kt_now));
60. testhrarr_arr[(testhrarr_runcount % ARRSIZE)] += testhrarr_runcount;
61. testhrarr_runcount++;
62. return HRTIMER_RESTART;
63. }
64. else {
65. int i;
66. testhrarr_isRunning = 0;
67. // do not use KERN_DEBUG etc,if printk buffering until newline is desired!
68. printk("testhrarr_arr [ ");
69. for(i=0; i<ARRSIZE; i++) {
70. printk("%d,",testhrarr_arr[i]);
71. }
72. printk("]\n");
73. return HRTIMER_NORESTART;
74. }
75. }
76.  
77. static void testhrarr_startup(void)
78. {
79. if (testhrarr_isRunning == 0) {
80. testhrarr_isRunning = 1;
81. testhrarr_runcount = 0;
82. testhrarr_arr[0] = 0; //just the first element
83. hrtimer_start(&my_hrtimer,HRTIMER_MODE_REL);
84. }
85. }
86.  
87.  
88. static int testhrarr_proc_show(struct seq_file *m,void *v) {
89. if (testhrarr_isRunning == 0) {
90. seq_printf(m,"testhrarr proc: startup\n");
91. testhrarr_startup();
92. } else {
93. seq_printf(m,testhrarr_runcount);
94. }
95. return 0;
96. }
97.  
98. static int testhrarr_proc_open(struct inode *inode,struct file *file) {
99. return single_open(file,testhrarr_proc_show,NULL);
100. }
101.  
102. static const struct file_operations testhrarr_proc_fops = {
103. .owner = THIS_MODULE,.open = testhrarr_proc_open,.read = seq_read,.llseek = seq_lseek,.release = single_release,};
104.  
105.  
106. #if (HWDEBUG_STACK == 1)
107. static void sample_hbp_handler(struct perf_event *bp,struct perf_sample_data *data,struct pt_regs *regs)
108. {
109. printk(KERN_INFO "%s value is changed\n",ksym_name);
110. dump_stack();
111. printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
112. }
113. #endif
114.  
115. static int __init testhrarr_init(void)
116. {
117. struct timespec tp_hr_res;
118. #if (HWDEBUG_STACK == 1)
119. struct perf_event_attr attr;
120. #endif
121.  
122. period_ms = 1000/HZ;
123. hrtimer_get_res(CLOCK_MONOTONIC,&tp_hr_res);
124. printk(KERN_INFO
125. "Init testhrarr: %d ; HZ: %d ; 1/HZ (ms): %ld ; hrres: %lld.%.9ld\n",testhrarr_runcount,HZ,period_ms,(long long)tp_hr_res.tv_sec,tp_hr_res.tv_nsec );
126.  
127. testhrarr_arr = (int*)kcalloc(ARRSIZE,sizeof(int),GFP_ATOMIC);
128. testhrarr_arr_first = &testhrarr_arr[0];
129.  
130. hrtimer_init(&my_hrtimer,CLOCK_MONOTONIC,HRTIMER_MODE_REL);
131. my_hrtimer.function = &testhrarr_timer_function;
132. period_ns = period_ms*( (unsigned long)1E6L );
133. ktime_period_ns = ktime_set(0,period_ns);
134.  
135. printk(KERN_INFO
136. " Addresses: _runcount 0x%p ; _arr 0x%p ; _arr[0] 0x%p (0x%p) ; _timer_function 0x%p ; my_hrtimer 0x%p; my_hrt.f 0x%p\n",&testhrarr_runcount,&testhrarr_arr,&(testhrarr_arr[0]),testhrarr_arr_first,&testhrarr_timer_function,&my_hrtimer,&my_hrtimer.function);
137.  
138.  
139. proc_create("testhrarr_proc",NULL,&testhrarr_proc_fops);
140.  
141.  
142. #if (HWDEBUG_STACK == 1)
143. hw_breakpoint_init(&attr);
144. if (strcmp(ksym_name,"testhrarr_arr_first") == 0) {
145. // just for testhrarr_arr_first - interpret the found symbol address
146. // as int*,and dereference it to get the "real" address it points to
147. attr.bp_addr = *((int*)kallsyms_lookup_name(ksym_name));
148. } else {
149. // the usual - address is kallsyms_lookup_name result
150. attr.bp_addr = kallsyms_lookup_name(ksym_name);
151. }
152. attr.bp_len = HW_BREAKPOINT_LEN_1;
153. attr.bp_type = HW_BREAKPOINT_W ; //| HW_BREAKPOINT_R;
154.  
155. sample_hbp = register_wide_hw_breakpoint(&attr,(perf_overflow_handler_t)sample_hbp_handler);
156. if (IS_ERR((void __force *)sample_hbp)) {
157. int ret = PTR_ERR((void __force *)sample_hbp);
158. printk(KERN_INFO "Breakpoint registration failed\n");
159. return ret;
160. }
161.  
162. // explicit cast needed to show 64-bit bp_addr as 32-bit address
163. // https://stackoverflow.com/questions/11796909/how-to-resolve-cast-to-pointer-from-integer-of-different-size-warning-in-c-co/11797103#11797103
164. printk(KERN_INFO "HW Breakpoint for %s write installed (0x%p)\n",(void*)(uintptr_t)attr.bp_addr);
165. #endif
166.  
167. return 0;
168. }
169.  
170. static void __exit testhrarr_exit(void)
171. {
172. int ret_cancel = 0;
173. kfree(testhrarr_arr);
174. while( hrtimer_callback_running(&my_hrtimer) ) {
175. ret_cancel++;
176. }
177. if (ret_cancel != 0) {
178. printk(KERN_INFO " testhrarr Waited for hrtimer callback to finish (%d)\n",ret_cancel);
179. }
180. if (hrtimer_active(&my_hrtimer) != 0) {
181. ret_cancel = hrtimer_cancel(&my_hrtimer);
182. printk(KERN_INFO " testhrarr active hrtimer cancelled: %d (%d)\n",ret_cancel,testhrarr_runcount);
183. }
184. if (hrtimer_is_queued(&my_hrtimer) != 0) {
185. ret_cancel = hrtimer_cancel(&my_hrtimer);
186. printk(KERN_INFO " testhrarr queued hrtimer cancelled: %d (%d)\n",testhrarr_runcount);
187. }
188. remove_proc_entry("testhrarr_proc",NULL);
189. #if (HWDEBUG_STACK == 1)
190. unregister_wide_hw_breakpoint(sample_hbp);
191. printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n",ksym_name);
192. #endif
193. printk(KERN_INFO "Exit testhrarr\n");
194. }
195.  
196. module_init(testhrarr_init);
197. module_exit(testhrarr_exit);
198.  
199. MODULE_LICENSE("GPL");