tipc: simplify print buffer handling in tipc_printf

[deliverable/linux.git] / net / tipc / log.c

/*
 * net/tipc/log.c: TIPC print buffer routines for debugging
 *
 * Copyright (c) 1996-2006, Ericsson AB
 * Copyright (c) 2005-2007, Wind River Systems
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the names of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "core.h"
#include "config.h"
#include "log.h"

/*
 * TIPC pre-defines the following print buffers:
 *
 * TIPC_NULL : null buffer (i.e. print nowhere)
 * TIPC_CONS : system console
 * TIPC_LOG  : TIPC log buffer
 *
 * Additional user-defined print buffers are also permitted.
 */
static struct print_buf null_buf = { NULL, 0, NULL, 0 };
struct print_buf *const TIPC_NULL = &null_buf;

static struct print_buf cons_buf = { NULL, 0, NULL, 1 };
struct print_buf *const TIPC_CONS = &cons_buf;

static struct print_buf log_buf = { NULL, 0, NULL, 1 };
struct print_buf *const TIPC_LOG = &log_buf;

/*
 * Locking policy when using print buffers.
 *
 * 1) tipc_printf() uses 'print_lock' to protect against concurrent access to
 * 'print_string' when writing to a print buffer. This also protects against
 * concurrent writes to the print buffer being written to.
 *
 * 2) tipc_log_XXX() leverages the aforementioned use of 'print_lock' to
 * protect against all types of concurrent operations on their associated
 * print buffer (not just write operations).
 *
 * Note: All routines of the form tipc_printbuf_XXX() are lock-free, and rely
 * on the caller to prevent simultaneous use of the print buffer(s) being
 * manipulated.
 */
static DEFINE_SPINLOCK(print_lock);

static void tipc_printbuf_move(struct print_buf *pb_to,
			       struct print_buf *pb_from);

/**
 * tipc_printbuf_init - initialize print buffer to empty
 * @pb: pointer to print buffer structure
 * @raw: pointer to character array used by print buffer
 * @size: size of character array
 *
 * Note: If the character array is too small (or absent), the print buffer
 * becomes a null device that discards anything written to it.
 */
void tipc_printbuf_init(struct print_buf *pb, char *raw, u32 size)
{
	pb->buf = raw;
	pb->crs = raw;
	pb->size = size;
	pb->echo = 0;

	if (size < TIPC_PB_MIN_SIZE) {
		pb->buf = NULL;
	} else if (raw) {
		pb->buf[0] = 0;
		pb->buf[size - 1] = ~0;
	}
}

/**
 * tipc_printbuf_reset - reinitialize print buffer to empty state
 * @pb: pointer to print buffer structure
 */
static void tipc_printbuf_reset(struct print_buf *pb)
{
	if (pb->buf) {
		pb->crs = pb->buf;
		pb->buf[0] = 0;
		pb->buf[pb->size - 1] = ~0;
	}
}

/**
 * tipc_printbuf_empty - test if print buffer is in empty state
 * @pb: pointer to print buffer structure
 *
 * Returns non-zero if print buffer is empty.
 */
static int tipc_printbuf_empty(struct print_buf *pb)
{
	return !pb->buf || (pb->crs == pb->buf);
}

/**
 * tipc_printbuf_validate - check for print buffer overflow
 * @pb: pointer to print buffer structure
 *
 * Verifies that a print buffer has captured all data written to it.
 * If data has been lost, linearize buffer and prepend an error message
 *
 * Returns length of print buffer data string (including trailing NUL)
 */
int tipc_printbuf_validate(struct print_buf *pb)
{
	char *err = "\n\n*** PRINT BUFFER OVERFLOW ***\n\n";
	char *cp_buf;
	struct print_buf cb;

	if (!pb->buf)
		return 0;

	if (pb->buf[pb->size - 1] == 0) {
		cp_buf = kmalloc(pb->size, GFP_ATOMIC);
		if (cp_buf) {
			tipc_printbuf_init(&cb, cp_buf, pb->size);
			tipc_printbuf_move(&cb, pb);
			tipc_printbuf_move(pb, &cb);
			kfree(cp_buf);
			memcpy(pb->buf, err, strlen(err));
		} else {
			tipc_printbuf_reset(pb);
			tipc_printf(pb, err);
		}
	}
	return pb->crs - pb->buf + 1;
}

/**
 * tipc_printbuf_move - move print buffer contents to another print buffer
 * @pb_to: pointer to destination print buffer structure
 * @pb_from: pointer to source print buffer structure
 *
 * Current contents of destination print buffer (if any) are discarded.
 * Source print buffer becomes empty if a successful move occurs.
 */
static void tipc_printbuf_move(struct print_buf *pb_to,
			       struct print_buf *pb_from)
{
	int len;

	/* Handle the cases where contents can't be moved */
	if (!pb_to->buf)
		return;

	if (!pb_from->buf) {
		tipc_printbuf_reset(pb_to);
		return;
	}

	if (pb_to->size < pb_from->size) {
		strcpy(pb_to->buf, "*** PRINT BUFFER MOVE ERROR ***");
		pb_to->buf[pb_to->size - 1] = ~0;
		pb_to->crs = strchr(pb_to->buf, 0);
		return;
	}

	/* Copy data from char after cursor to end (if used) */
	len = pb_from->buf + pb_from->size - pb_from->crs - 2;
	if ((pb_from->buf[pb_from->size - 1] == 0) && (len > 0)) {
		strcpy(pb_to->buf, pb_from->crs + 1);
		pb_to->crs = pb_to->buf + len;
	} else
		pb_to->crs = pb_to->buf;

	/* Copy data from start to cursor (always) */
	len = pb_from->crs - pb_from->buf;
	strcpy(pb_to->crs, pb_from->buf);
	pb_to->crs += len;

	tipc_printbuf_reset(pb_from);
}

/**
 * tipc_printf - append formatted output to print buffer
 * @pb: pointer to print buffer
 * @fmt: formatted info to be printed
 */
void tipc_printf(struct print_buf *pb, const char *fmt, ...)
{
	int i;
	va_list args;
	char *buf;
	int len;

	buf = pb->crs;
	len = pb->buf + pb->size - pb->crs;
	va_start(args, fmt);
	i = vscnprintf(buf, len, fmt, args);
	va_end(args);
	pb->crs += i;
}

/**
 * tipc_log_resize - change the size of the TIPC log buffer
 * @log_size: print buffer size to use
 */
int tipc_log_resize(int log_size)
{
	int res = 0;

	spin_lock_bh(&print_lock);
	kfree(TIPC_LOG->buf);
	TIPC_LOG->buf = NULL;
	if (log_size) {
		if (log_size < TIPC_PB_MIN_SIZE)
			log_size = TIPC_PB_MIN_SIZE;
		res = TIPC_LOG->echo;
		tipc_printbuf_init(TIPC_LOG, kmalloc(log_size, GFP_ATOMIC),
				   log_size);
		TIPC_LOG->echo = res;
		res = !TIPC_LOG->buf;
	}
	spin_unlock_bh(&print_lock);

	return res;
}

/**
 * tipc_log_resize_cmd - reconfigure size of TIPC log buffer
 */
struct sk_buff *tipc_log_resize_cmd(const void *req_tlv_area, int req_tlv_space)
{
	u32 value;

	if (!TLV_CHECK(req_tlv_area, req_tlv_space, TIPC_TLV_UNSIGNED))
		return tipc_cfg_reply_error_string(TIPC_CFG_TLV_ERROR);

	value = ntohl(*(__be32 *)TLV_DATA(req_tlv_area));
	if (value > 32768)
		return tipc_cfg_reply_error_string(TIPC_CFG_INVALID_VALUE
						   " (log size must be 0-32768)");
	if (tipc_log_resize(value))
		return tipc_cfg_reply_error_string(
			"unable to create specified log (log size is now 0)");
	return tipc_cfg_reply_none();
}

/**
 * tipc_log_dump - capture TIPC log buffer contents in configuration message
 */
struct sk_buff *tipc_log_dump(void)
{
	struct sk_buff *reply;

	spin_lock_bh(&print_lock);
	if (!TIPC_LOG->buf) {
		spin_unlock_bh(&print_lock);
		reply = tipc_cfg_reply_ultra_string("log not activated\n");
	} else if (tipc_printbuf_empty(TIPC_LOG)) {
		spin_unlock_bh(&print_lock);
		reply = tipc_cfg_reply_ultra_string("log is empty\n");
	} else {
		struct tlv_desc *rep_tlv;
		struct print_buf pb;
		int str_len;

		str_len = min(TIPC_LOG->size, 32768u);
		spin_unlock_bh(&print_lock);
		reply = tipc_cfg_reply_alloc(TLV_SPACE(str_len));
		if (reply) {
			rep_tlv = (struct tlv_desc *)reply->data;
			tipc_printbuf_init(&pb, TLV_DATA(rep_tlv), str_len);
			spin_lock_bh(&print_lock);
			tipc_printbuf_move(&pb, TIPC_LOG);
			spin_unlock_bh(&print_lock);
			str_len = strlen(TLV_DATA(rep_tlv)) + 1;
			skb_put(reply, TLV_SPACE(str_len));
			TLV_SET(rep_tlv, TIPC_TLV_ULTRA_STRING, NULL, str_len);
		}
	}
	return reply;
}