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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cfserl.c (4453B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Copyright (C) ST-Ericsson AB 2010
      4 * Author:	Sjur Brendeland
      5 */
      6
      7#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
      8
      9#include <linux/stddef.h>
     10#include <linux/spinlock.h>
     11#include <linux/slab.h>
     12#include <net/caif/caif_layer.h>
     13#include <net/caif/cfpkt.h>
     14#include <net/caif/cfserl.h>
     15
     16#define container_obj(layr) ((struct cfserl *) layr)
     17
     18#define CFSERL_STX 0x02
     19#define SERIAL_MINIUM_PACKET_SIZE 4
     20#define SERIAL_MAX_FRAMESIZE 4096
     21struct cfserl {
     22	struct cflayer layer;
     23	struct cfpkt *incomplete_frm;
     24	/* Protects parallel processing of incoming packets */
     25	spinlock_t sync;
     26	bool usestx;
     27};
     28
     29static int cfserl_receive(struct cflayer *layr, struct cfpkt *pkt);
     30static int cfserl_transmit(struct cflayer *layr, struct cfpkt *pkt);
     31static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
     32			   int phyid);
     33
     34void cfserl_release(struct cflayer *layer)
     35{
     36	kfree(layer);
     37}
     38
     39struct cflayer *cfserl_create(int instance, bool use_stx)
     40{
     41	struct cfserl *this = kzalloc(sizeof(struct cfserl), GFP_ATOMIC);
     42	if (!this)
     43		return NULL;
     44	caif_assert(offsetof(struct cfserl, layer) == 0);
     45	this->layer.receive = cfserl_receive;
     46	this->layer.transmit = cfserl_transmit;
     47	this->layer.ctrlcmd = cfserl_ctrlcmd;
     48	this->usestx = use_stx;
     49	spin_lock_init(&this->sync);
     50	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
     51	return &this->layer;
     52}
     53
     54static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
     55{
     56	struct cfserl *layr = container_obj(l);
     57	u16 pkt_len;
     58	struct cfpkt *pkt = NULL;
     59	struct cfpkt *tail_pkt = NULL;
     60	u8 tmp8;
     61	u16 tmp;
     62	u8 stx = CFSERL_STX;
     63	int ret;
     64	u16 expectlen = 0;
     65
     66	caif_assert(newpkt != NULL);
     67	spin_lock(&layr->sync);
     68
     69	if (layr->incomplete_frm != NULL) {
     70		layr->incomplete_frm =
     71		    cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
     72		pkt = layr->incomplete_frm;
     73		if (pkt == NULL) {
     74			spin_unlock(&layr->sync);
     75			return -ENOMEM;
     76		}
     77	} else {
     78		pkt = newpkt;
     79	}
     80	layr->incomplete_frm = NULL;
     81
     82	do {
     83		/* Search for STX at start of pkt if STX is used */
     84		if (layr->usestx) {
     85			cfpkt_extr_head(pkt, &tmp8, 1);
     86			if (tmp8 != CFSERL_STX) {
     87				while (cfpkt_more(pkt)
     88				       && tmp8 != CFSERL_STX) {
     89					cfpkt_extr_head(pkt, &tmp8, 1);
     90				}
     91				if (!cfpkt_more(pkt)) {
     92					cfpkt_destroy(pkt);
     93					layr->incomplete_frm = NULL;
     94					spin_unlock(&layr->sync);
     95					return -EPROTO;
     96				}
     97			}
     98		}
     99
    100		pkt_len = cfpkt_getlen(pkt);
    101
    102		/*
    103		 *  pkt_len is the accumulated length of the packet data
    104		 *  we have received so far.
    105		 *  Exit if frame doesn't hold length.
    106		 */
    107
    108		if (pkt_len < 2) {
    109			if (layr->usestx)
    110				cfpkt_add_head(pkt, &stx, 1);
    111			layr->incomplete_frm = pkt;
    112			spin_unlock(&layr->sync);
    113			return 0;
    114		}
    115
    116		/*
    117		 *  Find length of frame.
    118		 *  expectlen is the length we need for a full frame.
    119		 */
    120		cfpkt_peek_head(pkt, &tmp, 2);
    121		expectlen = le16_to_cpu(tmp) + 2;
    122		/*
    123		 * Frame error handling
    124		 */
    125		if (expectlen < SERIAL_MINIUM_PACKET_SIZE
    126		    || expectlen > SERIAL_MAX_FRAMESIZE) {
    127			if (!layr->usestx) {
    128				if (pkt != NULL)
    129					cfpkt_destroy(pkt);
    130				layr->incomplete_frm = NULL;
    131				spin_unlock(&layr->sync);
    132				return -EPROTO;
    133			}
    134			continue;
    135		}
    136
    137		if (pkt_len < expectlen) {
    138			/* Too little received data */
    139			if (layr->usestx)
    140				cfpkt_add_head(pkt, &stx, 1);
    141			layr->incomplete_frm = pkt;
    142			spin_unlock(&layr->sync);
    143			return 0;
    144		}
    145
    146		/*
    147		 * Enough data for at least one frame.
    148		 * Split the frame, if too long
    149		 */
    150		if (pkt_len > expectlen)
    151			tail_pkt = cfpkt_split(pkt, expectlen);
    152		else
    153			tail_pkt = NULL;
    154
    155		/* Send the first part of packet upwards.*/
    156		spin_unlock(&layr->sync);
    157		ret = layr->layer.up->receive(layr->layer.up, pkt);
    158		spin_lock(&layr->sync);
    159		if (ret == -EILSEQ) {
    160			if (layr->usestx) {
    161				if (tail_pkt != NULL)
    162					pkt = cfpkt_append(pkt, tail_pkt, 0);
    163				/* Start search for next STX if frame failed */
    164				continue;
    165			} else {
    166				cfpkt_destroy(pkt);
    167				pkt = NULL;
    168			}
    169		}
    170
    171		pkt = tail_pkt;
    172
    173	} while (pkt != NULL);
    174
    175	spin_unlock(&layr->sync);
    176	return 0;
    177}
    178
    179static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
    180{
    181	struct cfserl *layr = container_obj(layer);
    182	u8 tmp8 = CFSERL_STX;
    183	if (layr->usestx)
    184		cfpkt_add_head(newpkt, &tmp8, 1);
    185	return layer->dn->transmit(layer->dn, newpkt);
    186}
    187
    188static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
    189			   int phyid)
    190{
    191	layr->up->ctrlcmd(layr->up, ctrl, phyid);
    192}