我想以某种方式“监视”
Linux内核中的变量(或内存地址)(确切地说是内核模块/驱动程序);并找出改变它的原因 – 基本上,当变量改变时打印出堆栈跟踪.
例如,在this answer年末列出的内核模块testjiffy-hr.c中,我想在每次runcount变量更改时打印出堆栈跟踪;希望堆栈跟踪然后会提到testjiffy_timer_function,这确实是改变该变量的函数.
现在,我知道我可以使用kgdb连接到在虚拟机中运行的调试Linux内核,甚至可以设置断点(所以希望也是观察点) – 但问题是我实际上想要调试ALSA驱动程序,特别是播放dma_area缓冲区(我得到了一些意想不到的数据) – 这对时间非常敏感;并且运行调试内核本身会弄乱时间(更不用说在虚拟机中运行它)了.
这里更大的问题是回放dma_area指针仅在回放操作期间(或者换句话说,在_start和_stop处理程序之间)存在 – 所以我必须在每个_start回调中记录dma_area地址,然后以某种方式“在播放操作期间安排“用于”观看“.
所以我希望有一种方法可以直接在驱动程序代码中执行此类操作 – 例如,在此_start回调中添加一些代码来记录dma_area指针,并将其用作启动“watch”的命令的参数改变;从相应的回调函数打印堆栈跟踪. (我知道这也会影响时间,但我希望它能够“轻松”,不会过多地影响“实时”驱动程序操作).
所以我的问题是：在Linux内核中进行调试的这种技术是否存在？
如果不是：是否可以设置硬件(或软件)中断,该中断会对特定内存地址的更改做出反应？然后,我可以设置这样的中断处理程序,可以打印出堆栈跟踪吗？ (虽然,我认为整个上下文在IRQ处理程序运行时会发生变化,因此可能会出现堆栈跟踪错误)？
如果没有：是否还有其他技术,这将允许我打印进程的堆栈跟踪,该跟踪更改存储在内核中给定内存位置的值(希望在实时的非调试内核中)？
解决方法
非常感谢
@CosminRatiu和
Eugene的回复;多亏了那些,我发现：
> 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runcount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：
$echo `cat /etc/lsb-release` DISTRIB_ID=Ubuntu DISTRIB_RELEASE=11.04 DISTRIB_CODENAME=natty DISTRIB_DESCRIPTION="Ubuntu 11.04" $uname -a Linux mypc 2.6.38-16-generic #67-Ubuntu SMP Thu Sep 6 18:00:43 UTC 2012 i686 i686 i386 GNU/Linux $cat /proc/cpuinfo | grep "model name" model name : Intel(R) Atom(TM) CPU N450 @ 1.66GHz 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：
sudo insmod ./testhrarr.ko
此时,/ var / log / syslog将包含：
kernel: [40277.199913] Init testhrarr: 0 ; HZ: 250 ; 1/HZ (ms): 4 ; hrres: 0.000000001 kernel: [40277.199930] Addresses: _runcount 0xf84be22c ; _arr 0xf84be2a0 ; _arr[0] 0xed182a80 (0xed182a80) ; _timer_function 0xf84bc1c3 ; my_hrtimer 0xf84be260; my_hrt.f 0xf84be27c 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：
$sudo perf record -a --call-graph --event=mem:0xed182a80:w bash -c 'cat /proc/testhrarr_proc ; sleep 0.5' testhrarr proc: startup [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.485 MB perf.data (~21172 samples) ]
此时,/ var / log / syslog还包含以下内容：
[40822.114964] testhrarr_timer_function: testhrarr_runcount 0 [40822.114980] testhrarr jiffies 10130528 ; ret: 1 ; ktnsec: 40822114975062 [40822.118956] testhrarr_timer_function: testhrarr_runcount 1 [40822.118977] testhrarr jiffies 10130529 ; ret: 1 ; ktnsec: 40822118973195 [40822.122940] testhrarr_timer_function: testhrarr_runcount 2 [40822.122956] testhrarr jiffies 10130530 ; ret: 1 ; ktnsec: 40822122951143 [40822.126962] testhrarr_timer_function: testhrarr_runcount 3 [40822.126978] testhrarr jiffies 10130531 ; ret: 1 ; ktnsec: 40822126973583 [40822.130941] testhrarr_timer_function: testhrarr_runcount 4 [40822.130961] testhrarr jiffies 10130532 ; ret: 1 ; ktnsec: 40822130955167 [40822.134940] testhrarr_timer_function: testhrarr_runcount 5 [40822.134962] testhrarr jiffies 10130533 ; ret: 1 ; ktnsec: 40822134958888 [40822.138936] testhrarr_timer_function: testhrarr_runcount 6 [40822.138958] testhrarr jiffies 10130534 ; ret: 1 ; ktnsec: 40822138955693 [40822.142940] testhrarr_timer_function: testhrarr_runcount 7 [40822.142962] testhrarr jiffies 10130535 ; ret: 1 ; ktnsec: 40822142959345 [40822.146936] testhrarr_timer_function: testhrarr_runcount 8 [40822.146957] testhrarr jiffies 10130536 ; ret: 1 ; ktnsec: 40822146954479 [40822.150949] testhrarr_timer_function: testhrarr_runcount 9 [40822.150970] testhrarr jiffies 10130537 ; ret: 1 ; ktnsec: 40822150963438 [40822.154974] testhrarr_timer_function: testhrarr_runcount 10 [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：
$sudo perf report --call-graph flat --stdio
No kallsyms or vmlinux with build-id 5031df4d8668bcc45a7bdb4023909c6f8e2d3d34 was found
[testhrarr] with build id 5031df4d8668bcc45a7bdb4023909c6f8e2d3d34 not found,continuing without symbols
Failed to open /bin/cat,continuing without symbols
Failed to open /usr/lib/libpixman-1.so.0.20.2,continuing without symbols
Failed to open /usr/lib/xorg/modules/drivers/intel_drv.so,continuing without symbols
Failed to open /usr/bin/Xorg,continuing without symbols
# Events: 5 unknown
#
# Overhead Command Shared Object Symbol
# ........ ....... ............. ....................................
#
87.50% Xorg [testhrarr] [k] testhrarr_timer_function
87.50%
testhrarr_timer_function
__run_hrtimer
hrtimer_interrupt
smp_apic_timer_interrupt
apic_timer_interrupt
0x30185d
0x2ed701
0x2ed8cc
0x2edba0
0x9d0386
0x8126fc8
0x81217a1
0x811bdd3
0x8070aa7
0x806281c
__libc_start_main
0x8062411
6.25% cat [testhrarr] [k] testhrarr_timer_function
6.25%
testhrarr_timer_function
testhrarr_proc_show
seq_read
proc_reg_read
vfs_read
sys_read
syscall_call
0xaa2416
0x8049f4d
__libc_start_main
0x8049081
3.12% swapper [testhrarr] [k] testhrarr_timer_function
3.12%
testhrarr_timer_function
__run_hrtimer
hrtimer_interrupt
smp_apic_timer_interrupt
apic_timer_interrupt
cpuidle_idle_call
cpu_idle
start_secondary
3.12% cat [testhrarr] [k] 0x356
3.12%
0xf84bc356
0xf84bc3a7
seq_read
proc_reg_read
vfs_read
sys_read
syscall_call
0xaa2416
0x8049f4d
__libc_start_main
0x8049081
#
# (For a higher level overview,try: perf report --sort comm,dso)
#
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：
$sudo cat /proc/modules | grep testhr 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：
$objdump -S testhrarr.ko | less
...
00000323 :
static void testhrarr_startup(void)
{
...
testhrarr_arr[0] = 0; //just the first element
34b: a1 80 00 00 00 mov 0x80,%eax
350: c7 00 00 00 00 00 movl $0x0,(%eax)
hrtimer_start(&my_hrtimer,ktime_period_ns,HRTIMER_MODE_REL);
356: c7 04 24 01 00 00 00 movl $0x1,(%esp) **********
35d: 8b 15 1c 00 00 00 mov 0x1c,%edx
...
00000375 :
static int testhrarr_proc_show(struct seq_file *m,void *v) {
...
seq_printf(m,"testhrarr proc: startup\n");
38f: c7 44 24 04 79 00 00 movl $0x79,0x4(%esp)
396: 00
397: 8b 45 fc mov -0x4(%ebp),%eax
39a: 89 04 24 mov %eax,(%esp)
39d: e8 fc ff ff ff call 39e
testhrarr_startup();
3a2: e8 7c ff ff ff call 323
3a7: eb 1c jmp 3c5 **********
} else {
seq_printf(m,"testhrarr proc: (is running,%d)\n",testhrarr_runcount);
3a9: a1 0c 00 00 00 mov 0xc,%eax
...
…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：
$sudo rmmod testhrarr # remove module if still loaded $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：
$sudo rmmod testhrarr # remove module if still loaded $sudo insmod ./testhrarr.ko ksym=testhrarr_arr_first
…并且syslog通知：
kernel: [43910.509726] Init testhrarr: 0 ; HZ: 250 ; 1/HZ (ms): 4 ; hrres: 0.000000001 kernel: [43910.509765] Addresses: _runcount 0xf84be22c ; _arr 0xf84be2a0 ; _arr[0] 0xedf6c5c0 (0xedf6c5c0) ; _timer_function 0xf84bc1c3 ; my_hrtimer 0xf84be260; my_hrt.f 0xf84be27c 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：
$cat /proc/testhrarr_proc testhrarr proc: startup
…我们在syslog中获取：
kernel: [44069.735695] testhrarr_arr_first value is changed [44069.735711] Pid: 29320,comm: cat Not tainted 2.6.38-16-generic #67-Ubuntu [44069.735719] Call Trace: [44069.735737] [] ? sample_hbp_handler+0x2d/0x3b [testhrarr] [44069.735755] [] ? __perf_event_overflow+0x90/0x240 [44069.735768] [] ? proc_alloc_inode+0x23/0x90 [44069.735778] [] ? proc_alloc_inode+0x23/0x90 [44069.735790] [] ? perf_swevent_event+0x136/0x140 [44069.735801] [] ? perf_bp_event+0x70/0x80 [44069.735812] [] ? prep_new_page+0x110/0x1a0 [44069.735824] [] ? get_page_from_freelist+0x12e/0x320 [44069.735836] [] ? seq_open+0x3d/0xa0 [44069.735848] [] ? hw_breakpoint_handler.clone.0+0x102/0x130 [44069.735861] [] ? hw_breakpoint_exceptions_notify+0x22/0x30 [44069.735872] [] ? notifier_call_chain+0x45/0x60 [44069.735883] [] ? atomic_notifier_call_chain+0x22/0x30 [44069.735894] [] ? notify_die+0x2d/0x30 [44069.735904] [] ? do_debug+0x88/0x180 [44069.735915] [] ? debug_stack_correct+0x30/0x38 [44069.735928] [] ? testhrarr_startup+0x33/0x52 [testhrarr] [44069.735940] [] ? testhrarr_proc_show+0x32/0x57 [testhrarr] [44069.735952] [] ? seq_read+0x145/0x390 [44069.735963] [] ? seq_read+0x0/0x390 [44069.735973] [] ? proc_reg_read+0x64/0xa0 [44069.735985] [] ? vfs_read+0x9f/0x160 [44069.735995] [] ? proc_reg_read+0x0/0xa0 [44069.736003] [] ? sys_read+0x42/0x70 [44069.736013] [] ? syscall_call+0x7/0xb [44069.736019] Dump stack from sample_hbp_handler [44069.740132] testhrarr_timer_function: testhrarr_runcount 0 [44069.740146] testhrarr jiffies 10942435 ; ret: 1 ; ktnsec: 44069740142485 [44069.740159] testhrarr_arr_first value is changed [44069.740169] Pid: 4302,comm: gnome-terminal Not tainted 2.6.38-16-generic #67-Ubuntu [44069.740176] Call Trace: [44069.740195] [] ? sample_hbp_handler+0x2d/0x3b [testhrarr] [44069.740213] [] ? __perf_event_overflow+0x90/0x240 [44069.740227] [] ? perf_swevent_event+0x136/0x140 [44069.740239] [] ? perf_bp_event+0x70/0x80 [44069.740253] [] ? sched_clock_local+0xd3/0x1c0 [44069.740267] [] ? format_decode+0x323/0x380 [44069.740280] [] ? hw_breakpoint_handler.clone.0+0x102/0x130 [44069.740292] [] ? hw_breakpoint_exceptions_notify+0x22/0x30 [44069.740302] [] ? notifier_call_chain+0x45/0x60 [44069.740313] [] ? atomic_notifier_call_chain+0x22/0x30 [44069.740324] [] ? notify_die+0x2d/0x30 [44069.740335] [] ? do_debug+0x88/0x180 [44069.740345] [] ? debug_stack_correct+0x30/0x38 [44069.740364] [] ? init_intel_cacheinfo+0x103/0x394 [44069.740379] [] ? testhrarr_timer_function+0xed/0x160 [testhrarr] [44069.740391] [] ? __run_hrtimer+0x6f/0x190 [44069.740404] [] ? testhrarr_timer_function+0x0/0x160 [testhrarr] [44069.740416] [] ? hrtimer_interrupt+0x108/0x240 [44069.740430] [] ? smp_apic_timer_interrupt+0x56/0x8a [44069.740441] [] ? apic_timer_interrupt+0x31/0x38 [44069.740453] [] ? _raw_spin_unlock_irqrestore+0x15/0x20 [44069.740465] [] ? try_to_del_timer_sync+0x67/0xb0 [44069.740476] [] ? del_timer_sync+0x29/0x50 [44069.740486] [] ? flush_delayed_work+0x13/0x40 [44069.740500] [] ? tty_flush_to_ldisc+0x12/0x20 [44069.740510] [] ? n_tty_poll+0x4f/0x190 [44069.740523] [] ? tty_poll+0x6d/0x90 [44069.740531] [] ? n_tty_poll+0x0/0x190 [44069.740542] [] ? do_poll.clone.3+0xd0/0x210 [44069.740553] [] ? do_sys_poll+0x134/0x1e0 [44069.740563] [] ? __pollwait+0x0/0xd0 [44069.740572] [] ? pollwake+0x0/0x60 ... [44069.740742] [] ? pollwake+0x0/0x60 [44069.740757] [] ? rw_verify_area+0x6c/0x130 [44069.740770] [] ? ktime_get_ts+0xf8/0x120 [44069.740781] [] ? poll_select_set_timeout+0x64/0x70 [44069.740793] [] ? sys_poll+0x5a/0xd0 [44069.740804] [] ? syscall_call+0x7/0xb [44069.740815] [] ? init_intel_cacheinfo+0x23/0x394 [44069.740822] Dump stack from sample_hbp_handler [44069.744130] testhrarr_timer_function: testhrarr_runcount 1 [44069.744143] testhrarr jiffies 10942436 ; ret: 1 ; ktnsec: 44069744140055 [44069.748132] testhrarr_timer_function: testhrarr_runcount 2 [44069.748145] testhrarr jiffies 10942437 ; ret: 1 ; ktnsec: 44069748141271 [44069.752131] testhrarr_timer_function: testhrarr_runcount 3 [44069.752145] testhrarr jiffies 10942438 ; ret: 1 ; ktnsec: 44069752141164 [44069.756131] testhrarr_timer_function: testhrarr_runcount 4 [44069.756141] testhrarr jiffies 10942439 ; ret: 1 ; ktnsec: 44069756138318 [44069.760130] testhrarr_timer_function: testhrarr_runcount 5 [44069.760141] testhrarr jiffies 10942440 ; ret: 1 ; ktnsec: 44069760138469 [44069.760154] testhrarr_arr_first value is changed [44069.760164] Pid: 4302,comm: gnome-terminal Not tainted 2.6.38-16-generic #67-Ubuntu [44069.760170] Call Trace: [44069.760187] [] ? sample_hbp_handler+0x2d/0x3b [testhrarr] [44069.760202] [] ? __perf_event_overflow+0x90/0x240 [44069.760213] [] ? perf_swevent_event+0x136/0x140 [44069.760224] [] ? perf_bp_event+0x70/0x80 [44069.760235] [] ? sched_clock_local+0xd3/0x1c0 [44069.760247] [] ? format_decode+0x323/0x380 [44069.760258] [] ? hw_breakpoint_handler.clone.0+0x102/0x130 [44069.760269] [] ? hw_breakpoint_exceptions_notify+0x22/0x30 [44069.760279] [] ? notifier_call_chain+0x45/0x60 [44069.760289] [] ? atomic_notifier_call_chain+0x22/0x30 [44069.760299] [] ? notify_die+0x2d/0x30 [44069.760308] [] ? do_debug+0x88/0x180 [44069.760318] [] ? debug_stack_correct+0x30/0x38 [44069.760334] [] ? init_intel_cacheinfo+0x103/0x394 [44069.760345] [] ? testhrarr_timer_function+0xed/0x160 [testhrarr] [44069.760356] [] ? __run_hrtimer+0x6f/0x190 [44069.760366] [] ? send_to_group.clone.1+0xf8/0x150 [44069.760376] [] ? testhrarr_timer_function+0x0/0x160 [testhrarr] [44069.760387] [] ? hrtimer_interrupt+0x108/0x240 [44069.760396] [] ? fsnotify+0x1a5/0x290 [44069.760407] [] ? smp_apic_timer_interrupt+0x56/0x8a [44069.760416] [] ? apic_timer_interrupt+0x31/0x38 [44069.760428] [] ? mem_cgroup_resize_limit+0x108/0x1c0 [44069.760437] [] ? fput+0x0/0x30 [44069.760446] [] ? sys_write+0x67/0x70 [44069.760455] [] ? syscall_call+0x7/0xb [44069.760464] [] ? init_intel_cacheinfo+0x23/0x394 [44069.760470] Dump stack from sample_hbp_handler [44069.764134] testhrarr_timer_function: testhrarr_runcount 6 [44069.764147] testhrarr jiffies 10942441 ; ret: 1 ; ktnsec: 44069764144141 [44069.768133] testhrarr_timer_function: testhrarr_runcount 7 [44069.768146] testhrarr jiffies 10942442 ; ret: 1 ; ktnsec: 44069768142976 [44069.772134] testhrarr_timer_function: testhrarr_runcount 8 [44069.772148] testhrarr jiffies 10942443 ; ret: 1 ; ktnsec: 44069772144121 [44069.776132] testhrarr_timer_function: testhrarr_runcount 9 [44069.776145] testhrarr jiffies 10942444 ; ret: 1 ; ktnsec: 44069776141971 [44069.780133] testhrarr_timer_function: testhrarr_runcount 10 [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runcount == 0,一次用于runcount == 5,如预期的那样.
嗯,希望这有助于某人,
干杯!
Makefile文件
CONFIG_MODULE_FORCE_UNLOAD=y
# debug build:
# "CFLAGS was changed ... Fix it to use EXTRA_CFLAGS."
override EXTRA_CFLAGS+=-g -O0
obj-m += testhrarr.o
#testhrarr-objs := testhrarr.o
all:
@echo EXTRA_CFLAGS = $(EXTRA_CFLAGS)
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
testhrarr.c
/*
* [http://www.tldp.org/LDP/lkmpg/2.6/html/lkmpg.html#AEN189 The Linux Kernel Module Programming Guide]
* https://stackoverflow.com/questions/16920238/reliability-of-linux-kernel-add-timer-at-resolution-of-one-jiffy/17055867#17055867
* https://stackoverflow.com/questions/8516021/proc-create-example-for-kernel-module/18924359#18924359
* http://lxr.free-electrons.com/source/samples/hw_breakpoint/data_breakpoint.c
*/
#include <linux/module.h> /* Needed by all modules */
#include <linux/kernel.h> /* Needed for KERN_INFO */
#include <linux/init.h> /* Needed for the macros */
#include <linux/jiffies.h>
#include <linux/time.h>
#include <linux/proc_fs.h> /* /proc entry */
#include <linux/seq_file.h> /* /proc entry */
#define ARRSIZE 5
#define MAXRUNS 2*ARRSIZE
#include <linux/hrtimer.h>
#define HWDEBUG_STACK 1
#if (HWDEBUG_STACK == 1)
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
struct perf_event * __percpu *sample_hbp;
static char ksym_name[KSYM_NAME_LEN] = "testhrarr_arr";
module_param_string(ksym,ksym_name,KSYM_NAME_LEN,S_IRUGO);
MODULE_PARM_DESC(ksym,"Kernel symbol to monitor; this module will report any"
" write operations on the kernel symbol");
#endif
static volatile int testhrarr_runcount = 0;
static volatile int testhrarr_isRunning = 0;
static unsigned long period_ms;
static unsigned long period_ns;
static ktime_t ktime_period_ns;
static struct hrtimer my_hrtimer;
static int* testhrarr_arr;
static int* testhrarr_arr_first;
static enum hrtimer_restart testhrarr_timer_function(struct hrtimer *timer)
{
unsigned long tjnow;
ktime_t kt_now;
int ret_overrun;
printk(KERN_INFO
" %s: testhrarr_runcount %d \n",__func__,testhrarr_runcount);
if (testhrarr_runcount < MAXRUNS) {
tjnow = jiffies;
kt_now = hrtimer_cb_get_time(&my_hrtimer);
ret_overrun = hrtimer_forward(&my_hrtimer,kt_now,ktime_period_ns);
printk(KERN_INFO
" testhrarr jiffies %lu ; ret: %d ; ktnsec: %lld\n",tjnow,ret_overrun,ktime_to_ns(kt_now));
testhrarr_arr[(testhrarr_runcount % ARRSIZE)] += testhrarr_runcount;
testhrarr_runcount++;
return HRTIMER_RESTART;
}
else {
int i;
testhrarr_isRunning = 0;
// do not use KERN_DEBUG etc,if printk buffering until newline is desired!
printk("testhrarr_arr [ ");
for(i=0; i<ARRSIZE; i++) {
printk("%d,",testhrarr_arr[i]);
}
printk("]\n");
return HRTIMER_NORESTART;
}
}
static void testhrarr_startup(void)
{
if (testhrarr_isRunning == 0) {
testhrarr_isRunning = 1;
testhrarr_runcount = 0;
testhrarr_arr[0] = 0; //just the first element
hrtimer_start(&my_hrtimer,HRTIMER_MODE_REL);
}
}
static int testhrarr_proc_show(struct seq_file *m,void *v) {
if (testhrarr_isRunning == 0) {
seq_printf(m,"testhrarr proc: startup\n");
testhrarr_startup();
} else {
seq_printf(m,testhrarr_runcount);
}
return 0;
}
static int testhrarr_proc_open(struct inode *inode,struct file *file) {
return single_open(file,testhrarr_proc_show,NULL);
}
static const struct file_operations testhrarr_proc_fops = {
.owner = THIS_MODULE,.open = testhrarr_proc_open,.read = seq_read,.llseek = seq_lseek,.release = single_release,};
#if (HWDEBUG_STACK == 1)
static void sample_hbp_handler(struct perf_event *bp,struct perf_sample_data *data,struct pt_regs *regs)
{
printk(KERN_INFO "%s value is changed\n",ksym_name);
dump_stack();
printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
}
#endif
static int __init testhrarr_init(void)
{
struct timespec tp_hr_res;
#if (HWDEBUG_STACK == 1)
struct perf_event_attr attr;
#endif
period_ms = 1000/HZ;
hrtimer_get_res(CLOCK_MONOTONIC,&tp_hr_res);
printk(KERN_INFO
"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 );
testhrarr_arr = (int*)kcalloc(ARRSIZE,sizeof(int),GFP_ATOMIC);
testhrarr_arr_first = &testhrarr_arr[0];
hrtimer_init(&my_hrtimer,CLOCK_MONOTONIC,HRTIMER_MODE_REL);
my_hrtimer.function = &testhrarr_timer_function;
period_ns = period_ms*( (unsigned long)1E6L );
ktime_period_ns = ktime_set(0,period_ns);
printk(KERN_INFO
" 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);
proc_create("testhrarr_proc",NULL,&testhrarr_proc_fops);
#if (HWDEBUG_STACK == 1)
hw_breakpoint_init(&attr);
if (strcmp(ksym_name,"testhrarr_arr_first") == 0) {
// just for testhrarr_arr_first - interpret the found symbol address
// as int*,and dereference it to get the "real" address it points to
attr.bp_addr = *((int*)kallsyms_lookup_name(ksym_name));
} else {
// the usual - address is kallsyms_lookup_name result
attr.bp_addr = kallsyms_lookup_name(ksym_name);
}
attr.bp_len = HW_BREAKPOINT_LEN_1;
attr.bp_type = HW_BREAKPOINT_W ; //| HW_BREAKPOINT_R;
sample_hbp = register_wide_hw_breakpoint(&attr,(perf_overflow_handler_t)sample_hbp_handler);
if (IS_ERR((void __force *)sample_hbp)) {
int ret = PTR_ERR((void __force *)sample_hbp);
printk(KERN_INFO "Breakpoint registration failed\n");
return ret;
}
// explicit cast needed to show 64-bit bp_addr as 32-bit address
// https://stackoverflow.com/questions/11796909/how-to-resolve-cast-to-pointer-from-integer-of-different-size-warning-in-c-co/11797103#11797103
printk(KERN_INFO "HW Breakpoint for %s write installed (0x%p)\n",(void*)(uintptr_t)attr.bp_addr);
#endif
return 0;
}
static void __exit testhrarr_exit(void)
{
int ret_cancel = 0;
kfree(testhrarr_arr);
while( hrtimer_callback_running(&my_hrtimer) ) {
ret_cancel++;
}
if (ret_cancel != 0) {
printk(KERN_INFO " testhrarr Waited for hrtimer callback to finish (%d)\n",ret_cancel);
}
if (hrtimer_active(&my_hrtimer) != 0) {
ret_cancel = hrtimer_cancel(&my_hrtimer);
printk(KERN_INFO " testhrarr active hrtimer cancelled: %d (%d)\n",ret_cancel,testhrarr_runcount);
}
if (hrtimer_is_queued(&my_hrtimer) != 0) {
ret_cancel = hrtimer_cancel(&my_hrtimer);
printk(KERN_INFO " testhrarr queued hrtimer cancelled: %d (%d)\n",testhrarr_runcount);
}
remove_proc_entry("testhrarr_proc",NULL);
#if (HWDEBUG_STACK == 1)
unregister_wide_hw_breakpoint(sample_hbp);
printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n",ksym_name);
#endif
printk(KERN_INFO "Exit testhrarr\n");
}
module_init(testhrarr_init);
module_exit(testhrarr_exit);
MODULE_LICENSE("GPL");
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