cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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length.c (2735B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* Copyright (C) 2012, 2020 Oliver Hartkopp <socketcan@hartkopp.net>
      3 */
      4
      5#include <linux/can/dev.h>
      6
      7/* CAN DLC to real data length conversion helpers */
      8
      9static const u8 dlc2len[] = {
     10	0, 1, 2, 3, 4, 5, 6, 7,
     11	8, 12, 16, 20, 24, 32, 48, 64
     12};
     13
     14/* get data length from raw data length code (DLC) */
     15u8 can_fd_dlc2len(u8 dlc)
     16{
     17	return dlc2len[dlc & 0x0F];
     18}
     19EXPORT_SYMBOL_GPL(can_fd_dlc2len);
     20
     21static const u8 len2dlc[] = {
     22	0, 1, 2, 3, 4, 5, 6, 7, 8,	/* 0 - 8 */
     23	9, 9, 9, 9,			/* 9 - 12 */
     24	10, 10, 10, 10,			/* 13 - 16 */
     25	11, 11, 11, 11,			/* 17 - 20 */
     26	12, 12, 12, 12,			/* 21 - 24 */
     27	13, 13, 13, 13, 13, 13, 13, 13,	/* 25 - 32 */
     28	14, 14, 14, 14, 14, 14, 14, 14,	/* 33 - 40 */
     29	14, 14, 14, 14, 14, 14, 14, 14,	/* 41 - 48 */
     30	15, 15, 15, 15, 15, 15, 15, 15,	/* 49 - 56 */
     31	15, 15, 15, 15, 15, 15, 15, 15	/* 57 - 64 */
     32};
     33
     34/* map the sanitized data length to an appropriate data length code */
     35u8 can_fd_len2dlc(u8 len)
     36{
     37	/* check for length mapping table size at build time */
     38	BUILD_BUG_ON(ARRAY_SIZE(len2dlc) != CANFD_MAX_DLEN + 1);
     39
     40	if (unlikely(len > CANFD_MAX_DLEN))
     41		return CANFD_MAX_DLC;
     42
     43	return len2dlc[len];
     44}
     45EXPORT_SYMBOL_GPL(can_fd_len2dlc);
     46
     47/**
     48 * can_skb_get_frame_len() - Calculate the CAN Frame length in bytes
     49 * 	of a given skb.
     50 * @skb: socket buffer of a CAN message.
     51 *
     52 * Do a rough calculation: bit stuffing is ignored and length in bits
     53 * is rounded up to a length in bytes.
     54 *
     55 * Rationale: this function is to be used for the BQL functions
     56 * (netdev_sent_queue() and netdev_completed_queue()) which expect a
     57 * value in bytes. Just using skb->len is insufficient because it will
     58 * return the constant value of CAN(FD)_MTU. Doing the bit stuffing
     59 * calculation would be too expensive in term of computing resources
     60 * for no noticeable gain.
     61 *
     62 * Remarks: The payload of CAN FD frames with BRS flag are sent at a
     63 * different bitrate. Currently, the can-utils canbusload tool does
     64 * not support CAN-FD yet and so we could not run any benchmark to
     65 * measure the impact. There might be possible improvement here.
     66 *
     67 * Return: length in bytes.
     68 */
     69unsigned int can_skb_get_frame_len(const struct sk_buff *skb)
     70{
     71	const struct canfd_frame *cf = (const struct canfd_frame *)skb->data;
     72	u8 len;
     73
     74	if (can_is_canfd_skb(skb))
     75		len = canfd_sanitize_len(cf->len);
     76	else if (cf->can_id & CAN_RTR_FLAG)
     77		len = 0;
     78	else
     79		len = cf->len;
     80
     81	if (can_is_canfd_skb(skb)) {
     82		if (cf->can_id & CAN_EFF_FLAG)
     83			len += CANFD_FRAME_OVERHEAD_EFF;
     84		else
     85			len += CANFD_FRAME_OVERHEAD_SFF;
     86	} else {
     87		if (cf->can_id & CAN_EFF_FLAG)
     88			len += CAN_FRAME_OVERHEAD_EFF;
     89		else
     90			len += CAN_FRAME_OVERHEAD_SFF;
     91	}
     92
     93	return len;
     94}
     95EXPORT_SYMBOL_GPL(can_skb_get_frame_len);