path: root/kernel/trace/trace_kprobe.c

/*
 * Kprobes-based tracing events
 *
 * Created by Masami Hiramatsu <mhiramat@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#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_probe.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_is_on_module(struct trace_kprobe *tk)
{
	return !!strchr(trace_kprobe_symbol(tk), ':');
}

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;
}

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;
	unsigned long addr;

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

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

static DEFINE_MUTEX(probe_lock);
static LIST_HEAD(probe_list);

static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
static int kretprobe_dispatcher(struct kretprobe_instance *ri,
				struct pt_regs *regs);

/* Memory fetching by symbol */
struct symbol_cache {
	char		*symbol;
	long		offset;
	unsigned long	addr;
};

unsigned long update_symbol_cache(struct symbol_cache *sc)
{
	sc->addr = (unsigned long)kallsyms_lookup_name(sc->symbol);

	if (sc->addr)
		sc->addr += sc->offset;

	return sc->addr;
}

void free_symbol_cache(struct symbol_cache *sc)
{
	kfree(sc->symbol);
	kfree(sc);
}

struct symbol_cache *alloc_symbol_cache(const char *sym, long offset)
{
	struct symbol_cache *sc;

	if (!sym || strlen(sym) == 0)
		return NULL;

	sc = kzalloc(sizeof(struct symbol_cache), GFP_KERNEL);
	if (!sc)
		return NULL;

	sc->symbol = kstrdup(sym, GFP_KERNEL);
	if (!sc->symbol) {
		kfree(sc);
		return NULL;
	}
	sc->offset = offset;
	update_symbol_cache(sc);

	return sc;
}

/*
 * Kprobes-specific fetch functions
 */
#define DEFINE_FETCH_stack(type)					\
static void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,		\
					  void *offset, void *dest)	\
{									\
	*(type *)dest = (type)regs_get_kernel_stack_nth(regs,		\
				(unsigned int)((unsigned long)offset));	\
}									\
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(stack, type));

DEFINE_BASIC_FETCH_FUNCS(stack)
/* No string on the stack entry */
#define fetch_stack_string	NULL
#define fetch_stack_string_size	NULL

#define DEFINE_FETCH_memory(type)					\
static void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,		\
					  void *addr, void *dest)	\
{									\
	type retval;							\
	if (probe_kernel_address(