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