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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drm_displayid.c (2897B)

      1// SPDX-License-Identifier: MIT
      2/*
      3 * Copyright © 2021 Intel Corporation
      4 */
      5
      6#include <drm/drm_displayid.h>
      7#include <drm/drm_edid.h>
      8#include <drm/drm_print.h>
      9
     10static int validate_displayid(const u8 *displayid, int length, int idx)
     11{
     12	int i, dispid_length;
     13	u8 csum = 0;
     14	const struct displayid_header *base;
     15
     16	base = (const struct displayid_header *)&displayid[idx];
     17
     18	DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
     19		      base->rev, base->bytes, base->prod_id, base->ext_count);
     20
     21	/* +1 for DispID checksum */
     22	dispid_length = sizeof(*base) + base->bytes + 1;
     23	if (dispid_length > length - idx)
     24		return -EINVAL;
     25
     26	for (i = 0; i < dispid_length; i++)
     27		csum += displayid[idx + i];
     28	if (csum) {
     29		DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
     30		return -EINVAL;
     31	}
     32
     33	return 0;
     34}
     35
     36static const u8 *drm_find_displayid_extension(const struct edid *edid,
     37					      int *length, int *idx,
     38					      int *ext_index)
     39{
     40	const u8 *displayid = drm_find_edid_extension(edid, DISPLAYID_EXT, ext_index);
     41	const struct displayid_header *base;
     42	int ret;
     43
     44	if (!displayid)
     45		return NULL;
     46
     47	/* EDID extensions block checksum isn't for us */
     48	*length = EDID_LENGTH - 1;
     49	*idx = 1;
     50
     51	ret = validate_displayid(displayid, *length, *idx);
     52	if (ret)
     53		return NULL;
     54
     55	base = (const struct displayid_header *)&displayid[*idx];
     56	*length = *idx + sizeof(*base) + base->bytes;
     57
     58	return displayid;
     59}
     60
     61void displayid_iter_edid_begin(const struct edid *edid,
     62			       struct displayid_iter *iter)
     63{
     64	memset(iter, 0, sizeof(*iter));
     65
     66	iter->edid = edid;
     67}
     68
     69static const struct displayid_block *
     70displayid_iter_block(const struct displayid_iter *iter)
     71{
     72	const struct displayid_block *block;
     73
     74	if (!iter->section)
     75		return NULL;
     76
     77	block = (const struct displayid_block *)&iter->section[iter->idx];
     78
     79	if (iter->idx + sizeof(*block) <= iter->length &&
     80	    iter->idx + sizeof(*block) + block->num_bytes <= iter->length)
     81		return block;
     82
     83	return NULL;
     84}
     85
     86const struct displayid_block *
     87__displayid_iter_next(struct displayid_iter *iter)
     88{
     89	const struct displayid_block *block;
     90
     91	if (!iter->edid)
     92		return NULL;
     93
     94	if (iter->section) {
     95		/* current block should always be valid */
     96		block = displayid_iter_block(iter);
     97		if (WARN_ON(!block)) {
     98			iter->section = NULL;
     99			iter->edid = NULL;
    100			return NULL;
    101		}
    102
    103		/* next block in section */
    104		iter->idx += sizeof(*block) + block->num_bytes;
    105
    106		block = displayid_iter_block(iter);
    107		if (block)
    108			return block;
    109	}
    110
    111	for (;;) {
    112		iter->section = drm_find_displayid_extension(iter->edid,
    113							     &iter->length,
    114							     &iter->idx,
    115							     &iter->ext_index);
    116		if (!iter->section) {
    117			iter->edid = NULL;
    118			return NULL;
    119		}
    120
    121		iter->idx += sizeof(struct displayid_header);
    122
    123		block = displayid_iter_block(iter);
    124		if (block)
    125			return block;
    126	}
    127}
    128
    129void displayid_iter_end(struct displayid_iter *iter)
    130{
    131	memset(iter, 0, sizeof(*iter));
    132}