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Commit 9aaf5a5f authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
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perf probe: Check kprobes blacklist when adding new events 



Recent linux kernel provides a blacklist of the functions which can not
be probed. perf probe can now check this blacklist before setting new
events and indicate better error message for users.

Without this patch,
  ----
  # perf probe --add vmalloc_fault
  Added new event:
  Failed to write event: Invalid argument
    Error: Failed to add events.
  ----
With this patch
  ----
  # perf probe --add vmalloc_fault
  Added new event:
  Warning: Skipped probing on blacklisted function: vmalloc_fault
  ----

Reported-by: default avatarArnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150219143113.14434.5387.stgit@localhost.localdomain


Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 55d43bca

tools/perf/util/probe-event.c

+108 −1
Original line number Diff line number Diff line
@@ -1903,6 +1903,95 @@ static struct strlist *get_probe_trace_command_rawlist(int fd) 
	return sl;

}



struct kprobe_blacklist_node {

	struct list_head list;

	unsigned long start;

	unsigned long end;

	char *symbol;

};



static void kprobe_blacklist__delete(struct list_head *blacklist)

{

	struct kprobe_blacklist_node *node;



	while (!list_empty(blacklist)) {

		node = list_first_entry(blacklist,

					struct kprobe_blacklist_node, list);

		list_del(&node->list);

		free(node->symbol);

		free(node);

	}

}



static int kprobe_blacklist__load(struct list_head *blacklist)

{

	struct kprobe_blacklist_node *node;

	const char *__debugfs = debugfs_find_mountpoint();

	char buf[PATH_MAX], *p;

	FILE *fp;

	int ret;



	if (__debugfs == NULL)

		return -ENOTSUP;



	ret = e_snprintf(buf, PATH_MAX, "%s/kprobes/blacklist", __debugfs);

	if (ret < 0)

		return ret;



	fp = fopen(buf, "r");

	if (!fp)

		return -errno;



	ret = 0;

	while (fgets(buf, PATH_MAX, fp)) {

		node = zalloc(sizeof(*node));

		if (!node) {

			ret = -ENOMEM;

			break;

		}

		INIT_LIST_HEAD(&node->list);

		list_add_tail(&node->list, blacklist);

		if (sscanf(buf, "0x%lx-0x%lx", &node->start, &node->end) != 2) {

			ret = -EINVAL;

			break;

		}

		p = strchr(buf, '\t');

		if (p) {

			p++;

			if (p[strlen(p) - 1] == '\n')

				p[strlen(p) - 1] = '\0';

		} else

			p = (char *)"unknown";

		node->symbol = strdup(p);

		if (!node->symbol) {

			ret = -ENOMEM;

			break;

		}

		pr_debug2("Blacklist: 0x%lx-0x%lx, %s\n",

			  node->start, node->end, node->symbol);

		ret++;

	}

	if (ret < 0)

		kprobe_blacklist__delete(blacklist);

	fclose(fp);



	return ret;

}



static struct kprobe_blacklist_node *

kprobe_blacklist__find_by_address(struct list_head *blacklist,

				  unsigned long address)

{

	struct kprobe_blacklist_node *node;



	list_for_each_entry(node, blacklist, list) {

		if (node->start <= address && address <= node->end)

			return node;

	}



	return NULL;

}



/* Show an event */

static int show_perf_probe_event(struct perf_probe_event *pev,

				 const char *module)
@@ -2117,6 +2206,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev, 
	char buf[64];

	const char *event, *group;

	struct strlist *namelist;

	LIST_HEAD(blacklist);

	struct kprobe_blacklist_node *node;



	if (pev->uprobes)

		fd = open_uprobe_events(true);
@@ -2134,11 +2225,25 @@ static int __add_probe_trace_events(struct perf_probe_event *pev, 
		pr_debug("Failed to get current event list.\n");

		return -EIO;

	}

	/* Get kprobe blacklist if exists */

	if (!pev->uprobes) {

		ret = kprobe_blacklist__load(&blacklist);

		if (ret < 0)

			pr_debug("No kprobe blacklist support, ignored\n");

	}



	ret = 0;

	pr_info("Added new event%s\n", (ntevs > 1) ? "s:" : ":");

	for (i = 0; i < ntevs; i++) {

		tev = &tevs[i];

		/* Ensure that the address is NOT blacklisted */

		node = kprobe_blacklist__find_by_address(&blacklist,

							 tev->point.address);

		if (node) {

			pr_warning("Warning: Skipped probing on blacklisted function: %s\n", node->symbol);

			continue;

		}



		if (pev->event)

			event = pev->event;

		else
@@ -2189,13 +2294,15 @@ static int __add_probe_trace_events(struct perf_probe_event *pev, 
		allow_suffix = true;

	}



	if (ret >= 0) {

	/* Note that it is possible to skip all events because of blacklist */

	if (ret >= 0 && tev->event) {

		/* Show how to use the event. */

		pr_info("\nYou can now use it in all perf tools, such as:\n\n");

		pr_info("\tperf record -e %s:%s -aR sleep 1\n\n", tev->group,

			 tev->event);

	}



	kprobe_blacklist__delete(&blacklist);

	strlist__delete(namelist);

	close(fd);

	return ret;