kernel/trace/trace_kprobe.c



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/*
 * 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
 */

#include <linux/module.h>
#include <linux/uaccess.h>

#include "trace_probe.h"

#define KPROBE_EVENT_SYSTEM "kprobes"

/**
 * Kprobe event core functions
 */

struct trace_probe {
	struct list_head	list;
	struct kretprobe	rp;	/* Use rp.kp for kprobe use */
	unsigned long 		nhit;
	unsigned int		flags;	/* For TP_FLAG_* */
	const char		*symbol;	/* symbol name */
	struct ftrace_event_class	class;
	struct ftrace_event_call	call;
	ssize_t			size;		/* trace entry size */
	unsigned int		nr_args;
	struct probe_arg	args[];
};

#define SIZEOF_TRACE_PROBE(n)			\
	(offsetof(struct trace_probe, args) +	\
	(sizeof(struct probe_arg) * (n)))


static __kprobes int trace_probe_is_return(struct trace_probe *tp)
{
	return tp->rp.handler != NULL;
}

static __kprobes const char *trace_probe_symbol(struct trace_probe *tp)
{
	return tp->symbol ? tp->symbol : "unknown";
}

static __kprobes unsigned long trace_probe_offset(struct trace_probe *tp)
{
	return tp->rp.kp.offset;
}

static __kprobes bool trace_probe_is_enabled(struct trace_probe *tp)
{
	return !!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE));
}

static __kprobes bool trace_probe_is_registered(struct trace_probe *tp)
{
	return !!(tp->flags & TP_FLAG_REGISTERED);
}

static __kprobes bool trace_probe_has_gone(struct trace_probe *tp)
{
	return !!(kprobe_gone(&tp->rp.kp));
}

static __kprobes bool trace_probe_within_module(struct trace_probe *tp,
						struct module *mod)
{
	int len = strlen(mod->name);
	const char *name = trace_probe_symbol(tp);
	return strncmp(mod->name, name, len) == 0 && name[len] == ':';
}

static __kprobes bool trace_probe_is_on_module(struct trace_probe *tp)
{
	return !!strchr(trace_probe_symbol(tp), ':');
}

static int register_probe_event(struct trace_probe *tp);
static void unregister_probe_event(struct trace_probe *tp);

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);

/*
 * Allocate new trace_probe and initialize it (including kprobes).
 */
static struct trace_probe *alloc_trace_probe(const char *group,
					     const char *event,
					     void *addr,
					     const char *symbol,
					     unsigned long offs,
					     int nargs, bool is_return)
{
	struct trace_probe *tp;
	int ret = -ENOMEM;

	tp = kzalloc(SIZEOF_TRACE_PROBE(nargs), GFP_KERNEL);
	if (!tp)
		return ERR_PTR(ret);

	if (symbol) {
		tp->symbol = kstrdup(symbol, GFP_KERNEL);
		if (!tp->symbol)
			goto error;
		tp->rp.kp.symbol_name = tp->symbol;
		tp->rp.kp.offset = offs;
	} else
		tp->rp.kp.addr = addr;

	if (is_return)
		tp->rp.handler = kretprobe_dispatcher;
	else
		tp->rp.kp.pre_handler = kprobe_dispatcher;

	if (!event || !is_good_name(event)) {
		ret = -EINVAL;
		goto error;
	}

	tp->call.class = &tp->class;
	tp->call.name = kstrdup(event, GFP_KERNEL);
	if (!tp->call.name)
		goto error;

	if (!group || !is_good_name(group)) {
		ret = -EINVAL;
		goto error;
	}

	tp->class.system = kstrdup(group, GFP_KERNEL);
	if (!tp->class.system)
		goto error;

	INIT_LIST_HEAD(&tp->list);
	return tp;
error:
	kfree(tp->call.name);
	kfree(tp->symbol);
	kfree(tp);
	return ERR_PTR(ret);
}

static void free_trace_probe(struct trace_probe *tp)
{
	int i;

	for (i = 0; i < tp->nr_args; i++)
		traceprobe_free_probe_arg(&tp->args[i]);

	kfree(tp->call.class->system);
	kfree(tp->call.name);
	kfree(tp->symbol);
	kfree(tp);
}

static struct trace_probe *find_trace_probe(const char *event,
					    const char *group)
{
	struct trace_probe *tp;

	list_for_each_entry(tp, &probe_list, list)
		if (strcmp(tp->call.name, event) == 0 &&
		    strcmp(tp->call.class->system, group) == 0)
			return tp;
	return NULL;
}

/* Enable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
static int enable_trace_probe(struct trace_probe *tp, int flag)
{
	int ret = 0;

	tp->flags |= flag;
	if (trace_probe_is_enabled(tp) && trace_probe_is_registered(tp) &&
	    !trace_probe_has_gone(tp)) {
		if (trace_probe_is_return(tp))
			ret = enable_kretprobe(&tp->rp);
		else
			ret = enable_kprobe(&tp->rp.kp);
	}

	return ret;
}

/* Disable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
static void disable_trace_probe(struct trace_probe *tp, int flag)
{
	tp->flags &= ~flag;
	if (!trace_probe_is_enabled(tp) && trace_probe_is_registered(tp)) {
		if (trace_probe_is_return(tp))
			disable_kretprobe(&tp->rp);
		else
			disable_kprobe(&tp->rp.kp);
	}
}

/* Internal register function - just handle k*probes and flags */
static int __register_trace_probe(struct trace_probe *tp)
{
	int i, ret;

	if (trace_probe_is_registered(tp))
		return -EINVAL;

	for (i = 0; i < tp->nr_args; i++)
		traceprobe_update_arg(&tp->args[i]);

	/* Set/clear disabled flag according to tp->flag */
	if (trace_probe_is_enabled(tp))
		tp->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
	else
		tp->rp.kp.flags |= KPROBE_FLAG_DISABLED;

	if (trace_probe_is_return(tp))
		ret = register_kretprobe(&tp->rp);
	else
		ret = register_kprobe(&tp->rp.kp);

	if (ret == 0)
		tp->flags |= TP_FLAG_REGISTERED;
	else {
		pr_warning("Could not insert probe at %s+%lu: %d\n",
			   trace_probe_symbol(tp), trace_probe_offset(tp), ret);
		if (ret == -ENOENT && trace_probe_is_on_module(tp)) {
			pr_warning("This probe might be able to register after"
				   "target module is loaded. Continue.\n");
			ret = 0;
		} else if (ret == -EILSEQ) {
			pr_warning("Probing address(0x%p) is not an "
				   "instruction boundary.\n",
				   tp->rp.kp.addr);
			ret = -EINVAL;
		}
	}

	return ret;
}

/* Internal unregister function - just handle k*probes and flags */
static void __unregister_trace_probe(struct trace_probe *tp)
{
	if (trace_probe_is_registered(tp)) {
		if (trace_probe_is_return(tp))
			unregister_kretprobe(&tp->rp);
		else
			unregister_kprobe(&tp->rp.kp);
		tp->flags &= ~TP_FLAG_REGISTERED;
		/* Cleanup kprobe for reuse */
		if (tp->rp.kp.symbol_name)
			tp->rp.kp.addr = NULL;
	}
}

/* Unregister a trace_probe and probe_event: call with locking probe_lock */
static int unregister_trace_probe(struct trace_probe *tp)
{
	/* Enabled event can not be unregistered */
	if (trace_probe_is_enabled(tp))
		return -EBUSY;

	__unregister_trace_probe(tp);
	list_del(&tp->list);
	unregister_probe_event(tp);

	return 0;
}

/* Register a trace_probe and probe_event */
static int register_trace_probe(struct trace_probe *tp)
{
	struct trace_probe *old_tp;
	int ret;

	mutex_lock(&probe_lock);

	/* Delete old (same name) event if exist */
	old_tp = find_trace_probe(tp->call.name, tp->call.class->system);
	if (old_tp) {
		ret = unregister_trace_probe(old_tp);
		if (ret < 0)
			goto end;
		free_trace_probe(old_tp);
	}

	/* Register new event */
	ret = register_probe_event(tp);
	if (ret) {
		pr_warning("Failed to register probe event(%d)\n", ret);
		goto end;
	}

	/* Register k*probe */
	ret = __register_trace_probe(tp);
	if (ret < 0)
		unregister_probe_event(tp);
	else
		list_add_tail(&tp->list, &probe_list);

end:
	mutex_unlock(&probe_lock);
	return ret;
}

/* Module notifier call back, checking event on the module */
static int trace_probe_module_callback(struct notifier_block *nb,
				       unsigned long val, void *data)
{
	struct module *mod = data;
	struct trace_probe *tp;
	int ret;

	if (val != MODULE_STATE_COMING)
		return NOTIFY_DONE;

	/* Update probes on coming module */
	mutex_lock(&probe_lock);
	list_for_each_entry(tp, &probe_list, list) {
		if (trace_probe_within_module(tp, mod)) {
			/* Don't need to check busy - this should have gone. */
			__unregister_trace_probe(tp);
			ret = __register_trace_probe(tp);
			if (ret)
				pr_warning("Failed to re-register probe %s on"
					   "%s: %d\n",
					   tp->call.name, mod->name, ret);
		}
	}
	mutex_unlock(&probe_lock);

	return NOTIFY_DONE;
}

static struct notifier_block trace_probe_module_nb = {
	.notifier_call = trace_probe_module_callback,
	.priority = 1	/* Invoked after kprobe module callback */
};

static int create_trace_probe(int argc, char **argv)
{
	/*
	 * Argument syntax:
	 *  - Add kprobe: p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS]
	 *  - Add kretprobe: r[:[GRP/]EVENT] [MOD:]KSYM[+0] [FETCHARGS]
	 * Fetch args:
	 *  $retval	: fetch return value
	 *  $stack	: fetch stack address
	 *  $stackN	: fetch Nth of stack (N:0-)
	 *  @ADDR	: fetch memory at ADDR (ADDR should be in kernel)
	 *  @SYM[+|-offs] : fetch memory at SYM +|- offs (SYM is a data symbol)
	 *  %REG	: fetch register REG
	 * Dereferencing memory fetch:
	 *  +|-offs(ARG) : fetch memory at ARG +|- offs address.
	 * Alias name of args:
	 *  NAME=FETCHARG : set NAME as alias of FETCHARG.
	 * Type of args:
	 *  FETCHARG:TYPE : use TYPE instead of unsigned long.
	 */
	struct trace_probe *tp;
	int i, ret = 0;
	bool is_return = false, is_delete = false;
	char *symbol = NULL, *event = NULL, *group = NULL;
	char *arg;
	unsigned long offset = 0;
	void *addr = NULL;
	char buf[MAX_EVENT_NAME_LEN];

	/* argc must be >= 1 */
	if (argv[0][0] == 'p')
		is_return = false;
	else if (argv[0][0] == 'r')
		is_return = true;
	else if (argv[0][0] == '-')
		is_delete = true;
	else {
		pr_info("Probe definition must be started with 'p', 'r' or"
			" '-'.\n");
		return -EINVAL;
	}

	if (argv[0][1] == ':') {
		event = &argv[0][2];
		if (strchr(event, '/')) {
			group = event;
			event = strchr(group, '/') + 1;
			event[-1] = '\0';
			if (strlen(group) == 0) {
				pr_info("Group name is not specified\n");
				return -EINVAL;
			}
		}
		if (strlen(event) == 0) {
			pr_info("Event name is not specified\n");
			return -EINVAL;
		}
	}
	if (!group)
		group = KPROBE_EVENT_SYSTEM;

	if (is_delete) {
		if (!event) {
			pr_info("Delete command needs an event name.\n");
			return -EINVAL;
		}
		mutex_lock(&probe_lock);
		tp = find_trace_probe(event, group);
		if (!tp) {
			mutex_unlock(&probe_lock);
			pr_info("Event %s/%s doesn't exist.\n", group, event);
			return -ENOENT;
		}
		/* delete an event */
		ret = unregister_trace_probe(tp);
		if (ret == 0)
			free_trace_probe(tp);
		mutex_unlock(&probe_lock);
		return ret;
	}

	if (argc < 2) {
		pr_info("Probe point is not specified.\n");
		return -EINVAL;
	}
	if (isdigit(argv[1][0])) {
		if (is_return) {
			pr_info("Return probe point must be a symbol.\n");
			return -EINVAL;
		}
		/* an address specified */
		ret = strict_strtoul(&argv[1][0], 0, (unsigned long *)&addr);
		if (ret) {
			pr_info("Failed to parse address.\n");
			return ret;
		}
	} else {
		/* a symbol specified */
		symbol = argv[1];
		/* TODO: support .init module functions */
		ret = traceprobe_split_symbol_offset(symbol, &offset);
		if (ret) {
			pr_info("Failed to parse symbol.\n");
			return ret;
		}
		if (offset && is_return) {
			pr_info("Return probe must be used without offset.\n");
			return -EINVAL;
		}
	}
	argc -= 2; argv += 2;

	/* setup a probe */
	if (!event) {
		/* Make a new event name */
		if (symbol)
			snprintf(buf, MAX_EVENT_NAME_LEN, "%c_%s_%ld",
				 is_return ? 'r' : 'p', symbol, offset);
		else
			snprintf(buf, MAX_EVENT_NAME_LEN, "%c_0x%p",
				 is_return ? 'r' : 'p', addr);
		event = buf;
	}
	tp = alloc_trace_probe(group, event, addr, symbol, offset, argc,
			       is_return);
	if (IS_ERR(tp)) {
		pr_info("Failed to allocate trace_probe.(%d)\n",
			(int)PTR_ERR(tp));
		return PTR_ERR(tp);
	}

	/* parse arguments */
	ret = 0;
	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
		/* Increment count for freeing args in error case */
		tp->nr_args++;

		/* Parse argument name */
		arg = strchr(argv[i], '=');
		if (arg) {
			*arg++ = '\0';
			tp->args[i].name = kstrdup(argv[i], GFP_KERNEL);
		} else {
			arg = argv[i];
			/* If argument name is omitted, set "argN" */
			snprintf(buf, MAX_EVENT_NAME_LEN, "arg%d", i + 1);
			tp->args[i].name = kstrdup(buf, GFP_KERNEL);
		}

		if (!tp->args[i].name) {
			pr_info("Failed to allocate argument[%d] name.\n", i);
			ret = -ENOMEM;
			goto error;
		}

		if (!is_good_name(tp->args[i].name)) {
			pr_info("Invalid argument[%d] name: %s\n",
				i, tp->args[i].name);
			ret = -EINVAL;
			goto error;
		}

		if (traceprobe_conflict_field_name(tp->args[i].name,
							tp->args, i)) {
			pr_info("Argument[%d] name '%s' conflicts with "
				"another field.\n", i, argv[i]);
			ret = -EINVAL;
			goto error;
		}

		/* Parse fetch argument */
		ret = traceprobe_parse_probe_arg(arg, &tp->size, &tp->args[i],
						is_return, true);
		if (ret) {
			pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
			goto error;
		}
	}

	ret = register_trace_probe(tp);
	if (ret)
		goto error;
	return 0;

error:
	free_trace_probe(tp);
	return ret;
}

static int release_all_trace_probes(void)
{
	struct trace_probe *tp;
	int ret = 0;

	mutex_lock(&probe_lock);
	/* Ensure no probe is in use. */
	list_for_each_entry(tp, &probe_list, list)
		if (trace_probe_is_enabled(tp)) {
			ret = -EBUSY;
			goto end;
		}
	/* TODO: Use batch unregistration */
	while (!list_empty(&probe_list)) {
		tp = list_entry(probe_list.next, struct trace_probe, list);
		unregister_trace_probe(tp);
		free_trace_probe(tp);
	}

end:
	mutex_unlock(&probe_lock);

	return ret;
}

/* Probes listing interfaces */
static void *probes_seq_start(struct seq_file *m, loff_t *pos)
{
	mutex_lock(&probe_lock);
	return seq_list_start(&probe_list, *pos);
}

static void *probes_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
	return seq_list_next(v, &probe_list, pos);
}

static void probes_seq_stop(struct seq_file *m, void *v)
{
	mutex_unlock(&probe_lock);
}

static int probes_seq_show(struct seq_file *m, void *v)
{
	struct trace_probe *tp = v;
	int i;

	seq_printf(m, "%c", trace_probe_is_return(tp) ? 'r' : 'p');
	seq_printf(m, ":%s/%s", tp->call.class->system, tp->call.name);

	if (!tp->symbol)
		seq_printf(m, " 0x%p", tp->rp.kp.addr);
	else if (tp->rp.kp.offset)
		seq_printf(m, " %s+%u", trace_probe_symbol(tp),
			   tp->rp.kp.offset);
	else
		seq_printf(m, " %s", trace_probe_symbol(tp));

	for (i = 0; i < tp->nr_args; i++)
		seq_printf(m, " %s=%s", tp->args[i].name, tp->args[i].comm);
	seq_printf(m, "\n");

	return 0;
}

static const struct seq_operations probes_seq_op = {
	.start  = probes_seq_start,
	.next   = probes_seq_next,
	.stop   = probes_seq_stop,
	.show   = probes_seq_show
};

static int probes_open(struct inode *inode, struct file *file)
{
	int ret;

	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
		ret = release_all_trace_probes();
		if (ret < 0)
			return ret;
	}

	return seq_open(file, &probes_seq_op);
}

static ssize_t probes_write(struct file *file, const char __user *buffer,
			    size_t count, loff_t *ppos)
{
	return traceprobe_probes_write(file, buffer, count, ppos,
			create_trace_probe);
}

static const struct file_operations kprobe_events_ops = {
	.owner          = THIS_MODULE,
	.open           = probes_open,
	.read           = seq_read,
	.llseek         = seq_lseek,
	.release        = seq_release,
	.write		= probes_write,
};

/* Probes profiling interfaces */
static int probes_profile_seq_show(struct seq_file *m, void *v)
{
	struct trace_probe *tp = v;

	seq_printf(m, "  %-44s %15lu %15lu\n", tp->call.name, tp->nhit,
		   tp->rp.kp.nmissed);

	return 0;
}

static const struct seq_operations profile_seq_op = {
	.start  = probes_seq_start,
	.next   = probes_seq_next,
	.stop   = probes_seq_stop,
	.show   = probes_profile_seq_show
};

static int profile_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &profile_seq_op);
}

static const struct file_operations kprobe_profile_ops = {
	.owner          = THIS_MODULE,
	.open           = profile_open,
	.read           = seq_read,
	.llseek         = seq_lseek,
	.release        = seq_release,
};

/* Sum up total data length for dynamic arraies (strings) */
static __kprobes int __get_data_size(struct trace_probe *tp,
				     struct pt_regs *regs)
{
	int i, ret = 0;
	u32 len;

	for (i = 0; i < tp->nr_args; i++)
		if (unlikely(tp->args[i].fetch_size.fn)) {
			call_fetch(&tp->args[i].fetch_size, regs, &len);
			ret += len;
		}

	return ret;
}

/* Store the value of each argument */
static __kprobes void store_trace_args(int ent_size, struct trace_probe *tp,
				       struct pt_regs *regs,
				       u8 *data, int maxlen)
{
	int i;
	u32 end = tp->size;
	u32 *dl;	/* Data (relative) location */

	for (i = 0; i < tp->nr_args; i++) {
		if (unlikely(tp->args[i].fetch_size.fn)) {
			/*
			 * First, we set the relative location and
			 * maximum data length to *dl
			 */
			dl = (u32 *)(data + tp->args[i].offset);
			*dl = make_data_rloc(maxlen, end - tp->args[i].offset);
			/* Then try to fetch string or dynamic array data */
			call_fetch(&tp->args[i].fetch, regs, dl);
			/* Reduce maximum length */
			end += get_rloc_len(*dl);
			maxlen -= get_rloc_len(*dl);
			/* Trick here, convert data_rloc to data_loc */
			*dl = convert_rloc_to_loc(*dl,
				 ent_size + tp->args[i].offset);
		} else
			/* Just fetching data normally */
			call_fetch(&tp->args[i].fetch, regs,
				   data + tp->args[i].offset);
	}
}

/* Kprobe handler */
static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
{
	struct trace_probe *tp = container_of(kp, struct trace_probe, rp.kp);
	struct kprobe_trace_entry_head *entry;
	struct ring_buffer_event *event;
	struct ring_buffer *buffer;
	int size, dsize, pc;
	unsigned long irq_flags;
	struct ftrace_event_call *call = &tp->call;

	tp->nhit++;

	local_save_flags(irq_flags);