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linux-next/samples/kprobes/kprobe_example.c
Linus Torvalds 612e7a4c16 kernel-clone-v5.9
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Merge tag 'kernel-clone-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull kernel_clone() updates from Christian Brauner:
 "During the v5.9 merge window we reworked the process creation
  codepaths across multiple architectures. After this work we were only
  left with the _do_fork() helper based on the struct kernel_clone_args
  calling convention. As was pointed out _do_fork() isn't valid
  kernelese especially for a helper that isn't just static.

  This series removes the _do_fork() helper and introduces the new
  kernel_clone() helper. The process creation cleanup didn't change the
  name to something more reasonable mainly because _do_fork() was used
  in quite a few places. So sending this as a separate series seemed the
  better strategy.

  I originally intended to send this early in the v5.9 development cycle
  after the merge window had closed but given that this was touching
  quite a few places I decided to defer this until the v5.10 merge
  window"

* tag 'kernel-clone-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  sched: remove _do_fork()
  tracing: switch to kernel_clone()
  kgdbts: switch to kernel_clone()
  kprobes: switch to kernel_clone()
  x86: switch to kernel_clone()
  sparc: switch to kernel_clone()
  nios2: switch to kernel_clone()
  m68k: switch to kernel_clone()
  ia64: switch to kernel_clone()
  h8300: switch to kernel_clone()
  fork: introduce kernel_clone()
2020-10-14 14:32:52 -07:00

121 lines
3.6 KiB
C

// 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 kernel_clone() is called.
*
* For more information on theory of operation of kprobes, see
* Documentation/trace/kprobes.rst
*
* You will see the trace data in /var/log/messages and on the console
* whenever kernel_clone() 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] = "kernel_clone";
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");