119 lines
3.5 KiB
C
119 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* NOTE: This example is works on x86 and powerpc.
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* Here's a sample kernel module showing the use of kprobes to dump a
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* stack trace and selected registers when _do_fork() is called.
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*
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* For more information on theory of operation of kprobes, see
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* Documentation/kprobes.txt
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*
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* You will see the trace data in /var/log/messages and on the console
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* whenever _do_fork() is invoked to create a new process.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#define MAX_SYMBOL_LEN 64
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static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
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module_param_string(symbol, symbol, sizeof(symbol), 0644);
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/* For each probe you need to allocate a kprobe structure */
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static struct kprobe kp = {
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.symbol_name = symbol,
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};
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/* kprobe pre_handler: called just before the probed instruction is executed */
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static int handler_pre(struct kprobe *p, struct pt_regs *regs)
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{
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#ifdef CONFIG_X86
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pr_info("<%s> pre_handler: p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
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p->symbol_name, p->addr, regs->ip, regs->flags);
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#endif
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#ifdef CONFIG_PPC
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pr_info("<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
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p->symbol_name, p->addr, regs->nip, regs->msr);
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#endif
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#ifdef CONFIG_MIPS
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pr_info("<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
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p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
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#endif
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#ifdef CONFIG_ARM64
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pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
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" pstate = 0x%lx\n",
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p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
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#endif
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#ifdef CONFIG_S390
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pr_info("<%s> pre_handler: p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
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p->symbol_name, p->addr, regs->psw.addr, regs->flags);
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#endif
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/* A dump_stack() here will give a stack backtrace */
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return 0;
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}
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/* kprobe post_handler: called after the probed instruction is executed */
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static void handler_post(struct kprobe *p, struct pt_regs *regs,
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unsigned long flags)
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{
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#ifdef CONFIG_X86
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pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
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p->symbol_name, p->addr, regs->flags);
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#endif
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#ifdef CONFIG_PPC
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pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
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p->symbol_name, p->addr, regs->msr);
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#endif
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#ifdef CONFIG_MIPS
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pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
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p->symbol_name, p->addr, regs->cp0_status);
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#endif
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#ifdef CONFIG_ARM64
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pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
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p->symbol_name, p->addr, (long)regs->pstate);
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#endif
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#ifdef CONFIG_S390
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pr_info("<%s> pre_handler: p->addr, 0x%p, flags = 0x%lx\n",
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p->symbol_name, p->addr, regs->flags);
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#endif
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}
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/*
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* fault_handler: this is called if an exception is generated for any
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* instruction within the pre- or post-handler, or when Kprobes
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* single-steps the probed instruction.
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*/
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static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
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{
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pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr);
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/* Return 0 because we don't handle the fault. */
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return 0;
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}
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static int __init kprobe_init(void)
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{
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int ret;
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kp.pre_handler = handler_pre;
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kp.post_handler = handler_post;
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kp.fault_handler = handler_fault;
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ret = register_kprobe(&kp);
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if (ret < 0) {
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pr_err("register_kprobe failed, returned %d\n", ret);
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return ret;
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}
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pr_info("Planted kprobe at %p\n", kp.addr);
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return 0;
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}
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static void __exit kprobe_exit(void)
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{
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unregister_kprobe(&kp);
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pr_info("kprobe at %p unregistered\n", kp.addr);
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}
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module_init(kprobe_init)
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module_exit(kprobe_exit)
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MODULE_LICENSE("GPL");
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