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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edd.c (4132B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* -*- linux-c -*- ------------------------------------------------------- *
      3 *
      4 *   Copyright (C) 1991, 1992 Linus Torvalds
      5 *   Copyright 2007 rPath, Inc. - All Rights Reserved
      6 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
      7 *
      8 * ----------------------------------------------------------------------- */
      9
     10/*
     11 * Get EDD BIOS disk information
     12 */
     13
     14#include "boot.h"
     15#include <linux/edd.h>
     16#include "string.h"
     17
     18#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
     19
     20/*
     21 * Read the MBR (first sector) from a specific device.
     22 */
     23static int read_mbr(u8 devno, void *buf)
     24{
     25	struct biosregs ireg, oreg;
     26
     27	initregs(&ireg);
     28	ireg.ax = 0x0201;		/* Legacy Read, one sector */
     29	ireg.cx = 0x0001;		/* Sector 0-0-1 */
     30	ireg.dl = devno;
     31	ireg.bx = (size_t)buf;
     32
     33	intcall(0x13, &ireg, &oreg);
     34
     35	return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */
     36}
     37
     38static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
     39{
     40	int sector_size;
     41	char *mbrbuf_ptr, *mbrbuf_end;
     42	u32 buf_base, mbr_base;
     43	extern char _end[];
     44	u16 mbr_magic;
     45
     46	sector_size = ei->params.bytes_per_sector;
     47	if (!sector_size)
     48		sector_size = 512; /* Best available guess */
     49
     50	/* Produce a naturally aligned buffer on the heap */
     51	buf_base = (ds() << 4) + (u32)&_end;
     52	mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
     53	mbrbuf_ptr = _end + (mbr_base-buf_base);
     54	mbrbuf_end = mbrbuf_ptr + sector_size;
     55
     56	/* Make sure we actually have space on the heap... */
     57	if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
     58		return -1;
     59	if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
     60		return -1;
     61
     62	memset(mbrbuf_ptr, 0, sector_size);
     63	if (read_mbr(devno, mbrbuf_ptr))
     64		return -1;
     65
     66	*mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
     67	mbr_magic = *(u16 *)&mbrbuf_ptr[510];
     68
     69	/* check for valid MBR magic */
     70	return mbr_magic == 0xAA55 ? 0 : -1;
     71}
     72
     73static int get_edd_info(u8 devno, struct edd_info *ei)
     74{
     75	struct biosregs ireg, oreg;
     76
     77	memset(ei, 0, sizeof(*ei));
     78
     79	/* Check Extensions Present */
     80
     81	initregs(&ireg);
     82	ireg.ah = 0x41;
     83	ireg.bx = EDDMAGIC1;
     84	ireg.dl = devno;
     85	intcall(0x13, &ireg, &oreg);
     86
     87	if (oreg.eflags & X86_EFLAGS_CF)
     88		return -1;	/* No extended information */
     89
     90	if (oreg.bx != EDDMAGIC2)
     91		return -1;
     92
     93	ei->device  = devno;
     94	ei->version = oreg.ah;		 /* EDD version number */
     95	ei->interface_support = oreg.cx; /* EDD functionality subsets */
     96
     97	/* Extended Get Device Parameters */
     98
     99	ei->params.length = sizeof(ei->params);
    100	ireg.ah = 0x48;
    101	ireg.si = (size_t)&ei->params;
    102	intcall(0x13, &ireg, &oreg);
    103
    104	/* Get legacy CHS parameters */
    105
    106	/* Ralf Brown recommends setting ES:DI to 0:0 */
    107	ireg.ah = 0x08;
    108	ireg.es = 0;
    109	intcall(0x13, &ireg, &oreg);
    110
    111	if (!(oreg.eflags & X86_EFLAGS_CF)) {
    112		ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2);
    113		ei->legacy_max_head = oreg.dh;
    114		ei->legacy_sectors_per_track = oreg.cl & 0x3f;
    115	}
    116
    117	return 0;
    118}
    119
    120void query_edd(void)
    121{
    122	char eddarg[8];
    123	int do_mbr = 1;
    124#ifdef CONFIG_EDD_OFF
    125	int do_edd = 0;
    126#else
    127	int do_edd = 1;
    128#endif
    129	int be_quiet;
    130	int devno;
    131	struct edd_info ei, *edp;
    132	u32 *mbrptr;
    133
    134	if (cmdline_find_option("edd", eddarg, sizeof(eddarg)) > 0) {
    135		if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
    136			do_edd = 1;
    137			do_mbr = 0;
    138		}
    139		else if (!strcmp(eddarg, "off"))
    140			do_edd = 0;
    141		else if (!strcmp(eddarg, "on"))
    142			do_edd = 1;
    143	}
    144
    145	be_quiet = cmdline_find_option_bool("quiet");
    146
    147	edp    = boot_params.eddbuf;
    148	mbrptr = boot_params.edd_mbr_sig_buffer;
    149
    150	if (!do_edd)
    151		return;
    152
    153	/* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
    154	 * so give a hint if this happens.
    155	 */
    156
    157	if (!be_quiet)
    158		printf("Probing EDD (edd=off to disable)... ");
    159
    160	for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
    161		/*
    162		 * Scan the BIOS-supported hard disks and query EDD
    163		 * information...
    164		 */
    165		if (!get_edd_info(devno, &ei)
    166		    && boot_params.eddbuf_entries < EDDMAXNR) {
    167			memcpy(edp, &ei, sizeof(ei));
    168			edp++;
    169			boot_params.eddbuf_entries++;
    170		}
    171
    172		if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++))
    173			boot_params.edd_mbr_sig_buf_entries = devno-0x80+1;
    174	}
    175
    176	if (!be_quiet)
    177		printf("ok\n");
    178}
    179
    180#endif