1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Here's a sample kernel module showing the use of kprobes to dump a 4 * stack trace and selected registers when kernel_clone() is called. 5 * 6 * For more information on theory of operation of kprobes, see 7 * Documentation/trace/kprobes.rst 8 * 9 * You will see the trace data in /var/log/messages and on the console 10 * whenever kernel_clone() is invoked to create a new process. 11 */ 12 13 #define pr_fmt(fmt) "%s: " fmt, __func__ 14 15 #include <linux/kernel.h> 16 #include <linux/module.h> 17 #include <linux/kprobes.h> 18 19 static char symbol[KSYM_NAME_LEN] = "kernel_clone"; 20 module_param_string(symbol, symbol, KSYM_NAME_LEN, 0644); 21 22 /* For each probe you need to allocate a kprobe structure */ 23 static struct kprobe kp = { 24 .symbol_name = symbol, 25 }; 26 27 /* kprobe pre_handler: called just before the probed instruction is executed */ 28 static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs) 29 { 30 #ifdef CONFIG_X86 31 pr_info("<%s> p->addr = 0x%p, ip = %lx, flags = 0x%lx\n", 32 p->symbol_name, p->addr, regs->ip, regs->flags); 33 #endif 34 #ifdef CONFIG_PPC 35 pr_info("<%s> p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n", 36 p->symbol_name, p->addr, regs->nip, regs->msr); 37 #endif 38 #ifdef CONFIG_MIPS 39 pr_info("<%s> p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n", 40 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status); 41 #endif 42 #ifdef CONFIG_ARM64 43 pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, pstate = 0x%lx\n", 44 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate); 45 #endif 46 #ifdef CONFIG_ARM 47 pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, cpsr = 0x%lx\n", 48 p->symbol_name, p->addr, (long)regs->ARM_pc, (long)regs->ARM_cpsr); 49 #endif 50 #ifdef CONFIG_RISCV 51 pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, status = 0x%lx\n", 52 p->symbol_name, p->addr, regs->epc, regs->status); 53 #endif 54 #ifdef CONFIG_S390 55 pr_info("<%s> p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n", 56 p->symbol_name, p->addr, regs->psw.addr, regs->flags); 57 #endif 58 59 /* A dump_stack() here will give a stack backtrace */ 60 return 0; 61 } 62 63 /* kprobe post_handler: called after the probed instruction is executed */ 64 static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs, 65 unsigned long flags) 66 { 67 #ifdef CONFIG_X86 68 pr_info("<%s> p->addr = 0x%p, flags = 0x%lx\n", 69 p->symbol_name, p->addr, regs->flags); 70 #endif 71 #ifdef CONFIG_PPC 72 pr_info("<%s> p->addr = 0x%p, msr = 0x%lx\n", 73 p->symbol_name, p->addr, regs->msr); 74 #endif 75 #ifdef CONFIG_MIPS 76 pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n", 77 p->symbol_name, p->addr, regs->cp0_status); 78 #endif 79 #ifdef CONFIG_ARM64 80 pr_info("<%s> p->addr = 0x%p, pstate = 0x%lx\n", 81 p->symbol_name, p->addr, (long)regs->pstate); 82 #endif 83 #ifdef CONFIG_ARM 84 pr_info("<%s> p->addr = 0x%p, cpsr = 0x%lx\n", 85 p->symbol_name, p->addr, (long)regs->ARM_cpsr); 86 #endif 87 #ifdef CONFIG_RISCV 88 pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n", 89 p->symbol_name, p->addr, regs->status); 90 #endif 91 #ifdef CONFIG_S390 92 pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n", 93 p->symbol_name, p->addr, regs->flags); 94 #endif 95 } 96 97 static int __init kprobe_init(void) 98 { 99 int ret; 100 kp.pre_handler = handler_pre; 101 kp.post_handler = handler_post; 102 103 ret = register_kprobe(&kp); 104 if (ret < 0) { 105 pr_err("register_kprobe failed, returned %d\n", ret); 106 return ret; 107 } 108 pr_info("Planted kprobe at %p\n", kp.addr); 109 return 0; 110 } 111 112 static void __exit kprobe_exit(void) 113 { 114 unregister_kprobe(&kp); 115 pr_info("kprobe at %p unregistered\n", kp.addr); 116 } 117 118 module_init(kprobe_init) 119 module_exit(kprobe_exit) 120 MODULE_LICENSE("GPL"); 121