kdebug_trigger.c   [plain text]

/*
 * Copyright (c) 2016 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 * kperf's kdebug trigger is a precise mechanism for taking samples of the
 * thread tracing a kdebug event.
 *
 * The filter used by kperf differs from kdebug's typefilter. kperf's filter
 * is small -- only around 140 bytes, as opposed to kdebug's 8KB filter.  It
 * can also target precise debug IDs, instead of only being able to specify
 * an entire subclass in a kdebug typefilter.  Function specifiers can be
 * provided to match against along with a class or subclass.  For instance, this
 * allows the kperf filter to only trigger a sample if an ending syscall event
 * (DBG_BSD, DBG_BSD_EXCP_SC) occurs.
 *
 * The tradeoff for this flexibility is that only KPERF_KDEBUG_DEBUGIDS_MAX (32)
 * classes, subclasses, or exact debug IDs can be filtered at one time.
 *
 * The filter consists of up to 32 debug IDs and an array of 2-bit type codes
 * packed into a 64-bit value.  To determine if a given debug ID should trigger
 * a kperf sample, each debug ID is checked.  The type code is unpacked from the
 * 64-bit value to apply a mask to the debug ID.  Then, a sample occurs if the
 * masked debug ID is equal to the debug ID in the filter's list.
 */

#include <kern/kalloc.h>
#include <kperf/action.h>
#include <kperf/buffer.h>
#include <kperf/context.h>
#include <kperf/kdebug_trigger.h>
#include <kperf/kperf.h>
#include <sys/errno.h>

boolean_t kperf_kdebug_active = FALSE;
static void kperf_kdebug_update(void);

static uint8_t kperf_kdebug_action = 0;

static struct kperf_kdebug_filter {
	uint64_t types[2];
	uint32_t debugids[KPERF_KDEBUG_DEBUGIDS_MAX];
	uint8_t n_debugids;
} __attribute__((packed)) *kperf_kdebug_filter = NULL;

enum kperf_kdebug_filter_type {
	KPERF_KDEBUG_FILTER_CLASS,
	KPERF_KDEBUG_FILTER_CLASS_FN,
	KPERF_KDEBUG_FILTER_CSC,
	KPERF_KDEBUG_FILTER_CSC_FN,
	KPERF_KDEBUG_FILTER_DEBUGID,
	KPERF_KDEBUG_FILTER_DEBUGID_FN
};

const static uint32_t debugid_masks[] = {
	[KPERF_KDEBUG_FILTER_CLASS] = KDBG_CLASS_MASK,
	[KPERF_KDEBUG_FILTER_CLASS_FN] = KDBG_CLASS_MASK | KDBG_FUNC_MASK,
	[KPERF_KDEBUG_FILTER_CSC] = KDBG_CSC_MASK,
	[KPERF_KDEBUG_FILTER_CSC_FN] = KDBG_CSC_MASK | KDBG_FUNC_MASK,
	[KPERF_KDEBUG_FILTER_DEBUGID] = KDBG_EVENTID_MASK,
	[KPERF_KDEBUG_FILTER_DEBUGID_FN] = UINT32_MAX,
};

/*
 * Types are packed into 2 64-bit fields in the filter, with 4-bits for each
 * type.  Only 3 bits are strictly necessary, but using 4 simplifies the
 * unpacking.
 */

/* UNSAFE */
#define DECODE_TYPE(TYPES, I) ((((uint8_t *)(TYPES))[(I) / 2] >> ((I) % 2) * 4) & 0xf)

int
kperf_kdebug_init(void)
{
	kperf_kdebug_filter = kalloc_tag(sizeof(*kperf_kdebug_filter),
	                                 VM_KERN_MEMORY_DIAG);
	if (kperf_kdebug_filter == NULL) {
		return ENOMEM;
	}
	bzero(kperf_kdebug_filter, sizeof(*kperf_kdebug_filter));

	return 0;
}

void
kperf_kdebug_reset(void)
{
	int err;

	if ((err = kperf_init())) {
		return;
	}

	kperf_kdebug_action = 0;
	bzero(kperf_kdebug_filter, sizeof(*kperf_kdebug_filter));
	kperf_kdebug_update();
}

boolean_t
kperf_kdebug_should_trigger(uint32_t debugid)
{
	/* ignore kperf events */
	if (KDBG_EXTRACT_CLASS(debugid) == DBG_PERF) {
		return FALSE;
	}

	/*
	 * Search linearly through list of debugids and masks.  If the filter
	 * gets larger than 128 bytes, change this to either a binary search or
	 * a sparse bitmap on the uint32_t range, depending on the new size.
	 */
	for (uint8_t i = 0; i < kperf_kdebug_filter->n_debugids; i++) {
		uint32_t check_debugid =
			kperf_kdebug_filter->debugids[i];
		uint32_t mask = debugid_masks[DECODE_TYPE(kperf_kdebug_filter->types, i)];

		if ((debugid & mask) == check_debugid) {
			return TRUE;
		}
	}

	return FALSE;
}

int
kperf_kdebug_set_filter(user_addr_t user_filter, uint32_t user_size)
{
	uint32_t n_debugids_provided = 0;
	int err = 0;

	if ((err = kperf_init())) {
		return err;
	}

	/* detect disabling the filter completely */
	if (user_filter == USER_ADDR_NULL || user_size == 0) {
		bzero(kperf_kdebug_filter, sizeof(*kperf_kdebug_filter));
		goto out;
	}

	n_debugids_provided = (uint32_t)KPERF_KDEBUG_N_DEBUGIDS(user_size);

	if ((err = kperf_kdebug_set_n_debugids(n_debugids_provided))) {
		goto out;
	}

	if ((err = copyin(user_filter, (char *)kperf_kdebug_filter,
	                  KPERF_KDEBUG_FILTER_SIZE(n_debugids_provided))))
	{
		bzero(kperf_kdebug_filter, sizeof(*kperf_kdebug_filter));
		goto out;
	}

out:
	kperf_kdebug_update();

	return err;
}

uint32_t
kperf_kdebug_get_filter(struct kperf_kdebug_filter **filter)
{
	int err;

	if ((err = kperf_init())) {
		return 0;
	}

	assert(filter != NULL);

	*filter = kperf_kdebug_filter;
	return kperf_kdebug_filter->n_debugids;
}

int
kperf_kdebug_set_n_debugids(uint32_t n_debugids_in)
{
	int err;

	if ((err = kperf_init())) {
		return EINVAL;
	}

	if (n_debugids_in > KPERF_KDEBUG_DEBUGIDS_MAX) {
		return EINVAL;
	}

	kperf_kdebug_filter->n_debugids = n_debugids_in;

	return 0;
}

int
kperf_kdebug_set_action(int action_id)
{
	if (action_id < 0 || (unsigned int)action_id > kperf_action_get_count()) {
		return EINVAL;
	}

	kperf_kdebug_action = action_id;
	kperf_kdebug_update();

	return 0;
}

int
kperf_kdebug_get_action(void)
{
	return kperf_kdebug_action;
}

static void
kperf_kdebug_update(void)
{
	int err;

	if ((err = kperf_init())) {
		return;
	}

	if (kperf_kdebug_action != 0 &&
	    kperf_kdebug_filter->n_debugids != 0)
	{
		kperf_kdebug_active = TRUE;
	} else {
		kperf_kdebug_active = FALSE;
	}
}