cregit-Linux how code gets into the kernel

Release 4.7 samples/kprobes/kprobe_example.c

Directory: samples/kprobes
/*
 * NOTE: This example is works on x86 and powerpc.
 * Here's a sample kernel module showing the use of kprobes to dump a
 * stack trace and selected registers when _do_fork() is called.
 *
 * For more information on theory of operation of kprobes, see
 * Documentation/kprobes.txt
 *
 * You will see the trace data in /var/log/messages and on the console
 * whenever _do_fork() is invoked to create a new process.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kprobes.h>


#define MAX_SYMBOL_LEN	64

static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
module_param_string(symbol, symbol, sizeof(symbol), 0644);

/* For each probe you need to allocate a kprobe structure */

static struct kprobe kp = {
	.symbol_name	= symbol,
};

/* kprobe pre_handler: called just before the probed instruction is executed */

static int handler_pre(struct kprobe *p, struct pt_regs *regs) { #ifdef CONFIG_X86 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, ip = %lx," " flags = 0x%lx\n", p->symbol_name, p->addr, regs->ip, regs->flags); #endif #ifdef CONFIG_PPC printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx," " msr = 0x%lx\n", p->symbol_name, p->addr, regs->nip, regs->msr); #endif #ifdef CONFIG_MIPS printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx," " status = 0x%lx\n", p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status); #endif #ifdef CONFIG_TILEGX printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx," " ex1 = 0x%lx\n", p->symbol_name, p->addr, regs->pc, regs->ex1); #endif /* A dump_stack() here will give a stack backtrace */ return 0; }

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ananth n. mavinakayanahalliananth n. mavinakayanahalli6650.00%125.00%
tony lutony lu2317.42%125.00%
david daneydavid daney2317.42%125.00%
huang shijiehuang shijie2015.15%125.00%
Total132100.00%4100.00%

/* kprobe post_handler: called after the probed instruction is executed */
static void handler_post(struct kprobe *p, struct pt_regs *regs, unsigned long flags) { #ifdef CONFIG_X86 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n", p->symbol_name, p->addr, regs->flags); #endif #ifdef CONFIG_PPC printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n", p->symbol_name, p->addr, regs->msr); #endif #ifdef CONFIG_MIPS printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n", p->symbol_name, p->addr, regs->cp0_status); #endif #ifdef CONFIG_TILEGX printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, ex1 = 0x%lx\n", p->symbol_name, p->addr, regs->ex1); #endif }

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ananth n. mavinakayanahalliananth n. mavinakayanahalli5650.00%125.00%
huang shijiehuang shijie2017.86%125.00%
tony lutony lu1816.07%125.00%
david daneydavid daney1816.07%125.00%
Total112100.00%4100.00%

/* * fault_handler: this is called if an exception is generated for any * instruction within the pre- or post-handler, or when Kprobes * single-steps the probed instruction. */
static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr) { printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr); /* Return 0 because we don't handle the fault. */ return 0; }

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Total35100.00%1100.00%


static int __init kprobe_init(void) { int ret; kp.pre_handler = handler_pre; kp.post_handler = handler_post; kp.fault_handler = handler_fault; ret = register_kprobe(&kp); if (ret < 0) { printk(KERN_INFO "register_kprobe failed, returned %d\n", ret); return ret; } printk(KERN_INFO "Planted kprobe at %p\n", kp.addr); return 0; }

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ananth n. mavinakayanahalliananth n. mavinakayanahalli70100.00%1100.00%
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static void __exit kprobe_exit(void) { unregister_kprobe(&kp); printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr); }

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module_init(kprobe_init) module_exit(kprobe_exit) MODULE_LICENSE("GPL");

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ananth n. mavinakayanahalliananth n. mavinakayanahalli28965.68%116.67%
huang shijiehuang shijie6815.45%233.33%
david daneydavid daney419.32%116.67%
tony lutony lu419.32%116.67%
petr mladekpetr mladek10.23%116.67%
Total440100.00%6100.00%
Directory: samples/kprobes
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