Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 | // SPDX-License-Identifier: GPL-2.0-only /* * 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 pr_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 pr_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 pr_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_ARM64 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx," " pstate = 0x%lx\n", p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate); #endif #ifdef CONFIG_S390 pr_info("<%s> pre_handler: p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n", p->symbol_name, p->addr, regs->psw.addr, regs->flags); #endif /* A dump_stack() here will give a stack backtrace */ return 0; } /* 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 pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n", p->symbol_name, p->addr, regs->flags); #endif #ifdef CONFIG_PPC pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n", p->symbol_name, p->addr, regs->msr); #endif #ifdef CONFIG_MIPS pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n", p->symbol_name, p->addr, regs->cp0_status); #endif #ifdef CONFIG_ARM64 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n", p->symbol_name, p->addr, (long)regs->pstate); #endif #ifdef CONFIG_S390 pr_info("<%s> pre_handler: p->addr, 0x%p, flags = 0x%lx\n", p->symbol_name, p->addr, regs->flags); #endif } /* * 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) { pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr); /* Return 0 because we don't handle the fault. */ return 0; } 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) { pr_err("register_kprobe failed, returned %d\n", ret); return ret; } pr_info("Planted kprobe at %p\n", kp.addr); return 0; } static void __exit kprobe_exit(void) { unregister_kprobe(&kp); pr_info("kprobe at %p unregistered\n", kp.addr); } module_init(kprobe_init) module_exit(kprobe_exit) MODULE_LICENSE("GPL"); |