| // 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/staging/kprobes.rst |
| * |
| * 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 __kprobes 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 __kprobes 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; |
| } |
| /* NOKPROBE_SYMBOL() is also available */ |
| NOKPROBE_SYMBOL(handler_fault); |
| |
| 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"); |