path: root/kernel/trace/trace_kprobe.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Kprobes-based tracing events
 *
 * Created by Masami Hiramatsu <mhiramat@redhat.com>
 *
 */
#define pr_fmt(fmt)	"trace_kprobe: " fmt

#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/rculist.h>
#include <linux/error-injection.h>

#include "trace_kprobe_selftest.h"
#include "trace_probe.h"
#include "trace_probe_tmpl.h"

#define KPROBE_EVENT_SYSTEM "kprobes"
#define KRETPROBE_MAXACTIVE_MAX 4096

/**
 * Kprobe event core functions
 */
struct trace_kprobe {
	struct list_head	list;
	struct kretprobe	rp;	/* Use rp.kp for kprobe use */
	unsigned long __percpu *nhit;
	const char		*symbol;	/* symbol name */
	struct trace_probe	tp;
};

#define SIZEOF_TRACE_KPROBE(n)				\
	(offsetof(struct trace_kprobe, tp.args) +	\
	(sizeof(struct probe_arg) * (n)))

static nokprobe_inline bool trace_kprobe_is_return(struct trace_kprobe *tk)
{
	return tk->rp.handler != NULL;
}

static nokprobe_inline const char *trace_kprobe_symbol(struct trace_kprobe *tk)
{
	return tk->symbol ? tk->symbol : "unknown";
}

static nokprobe_inline unsigned long trace_kprobe_offset(struct trace_kprobe *tk)
{
	return tk->rp.kp.offset;
}

static nokprobe_inline bool trace_kprobe_has_gone(struct trace_kprobe *tk)
{
	return !!(kprobe_gone(&tk->rp.kp));
}

static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
						 struct module *mod)
{
	int len = strlen(mod->name);
	const char *name = trace_kprobe_symbol(tk);
	return strncmp(mod->name, name, len) == 0 && name[len] == ':';
}

static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
{
	char *p;
	bool ret;

	if (!tk->symbol)
		return false;
	p = strchr(tk->symbol, ':');
	if (!p)
		return true;
	*p = '\0';
	mutex_lock(&module_mutex);
	ret = !!find_module(tk->symbol);
	mutex_unlock(&module_mutex);
	*p = ':';

	return ret;
}

static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
{
	unsigned long nhit = 0;
	int cpu;

	for_each_possible_cpu(cpu)
		nhit += *per_cpu_ptr(tk->nhit, cpu);

	return nhit;
}

/* Return 0 if it fails to find the symbol address */
static nokprobe_inline
unsigned long trace_kprobe_address(struct trace_kprobe *tk)
{
	unsigned long addr;

	if (tk->symbol) {
		addr = (unsigned long)
			kallsyms_lookup_name(trace_kprobe_symbol(tk));
		if (addr)
			addr += tk->rp.kp.offset;
	} else {
		addr = (unsigned long)tk->rp.kp.addr;
	}
	return addr;
}

bool trace_kprobe_on_func_entry(struct trace_event_call *call)
{
	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;

	return kprobe_on_func_entry(tk->rp.kp.addr,
			tk->rp.kp.addr ? NULL : tk->rp.kp.symbol_name,
			tk->rp.kp.addr ? 0 : tk->rp.kp.offset);
}

bool trace_kprobe_error_injectable(struct trace_event_call *call)
{
	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;

	return within_error_injection_list(trace_kprobe_address(tk));
}

static int register_kprobe_event(struct trace_kprobe *tk);
static int unregister_kprobe_event(struct trace_kprobe *tk);

static DEFINE_MUTEX(probe_lock);