1 /* -*- linux-c -*- ------------------------------------------------------- * 2 * 3 * Copyright (C) 1991, 1992 Linus Torvalds 4 * Copyright 2007 rPath, Inc. - All Rights Reserved 5 * 6 * This file is part of the Linux kernel, and is made available under 7 * the terms of the GNU General Public License version 2. 8 * 9 * ----------------------------------------------------------------------- */ 10 11 /* 12 * Get EDD BIOS disk information 13 */ 14 15 #include "boot.h" 16 #include <linux/edd.h> 17 18 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE) 19 20 /* 21 * Read the MBR (first sector) from a specific device. 22 */ 23 static int read_mbr(u8 devno, void *buf) 24 { 25 u16 ax, bx, cx, dx; 26 27 ax = 0x0201; /* Legacy Read, one sector */ 28 cx = 0x0001; /* Sector 0-0-1 */ 29 dx = devno; 30 bx = (size_t)buf; 31 asm volatile("pushfl; stc; int $0x13; setc %%al; popfl" 32 : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx) 33 : : "esi", "edi", "memory"); 34 35 return -(u8)ax; /* 0 or -1 */ 36 } 37 38 static 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 73 static int get_edd_info(u8 devno, struct edd_info *ei) 74 { 75 u16 ax, bx, cx, dx, di; 76 77 memset(ei, 0, sizeof *ei); 78 79 /* Check Extensions Present */ 80 81 ax = 0x4100; 82 bx = EDDMAGIC1; 83 dx = devno; 84 asm("pushfl; stc; int $0x13; setc %%al; popfl" 85 : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx) 86 : : "esi", "edi"); 87 88 if ((u8)ax) 89 return -1; /* No extended information */ 90 91 if (bx != EDDMAGIC2) 92 return -1; 93 94 ei->device = devno; 95 ei->version = ax >> 8; /* EDD version number */ 96 ei->interface_support = cx; /* EDD functionality subsets */ 97 98 /* Extended Get Device Parameters */ 99 100 ei->params.length = sizeof(ei->params); 101 ax = 0x4800; 102 dx = devno; 103 asm("pushfl; int $0x13; popfl" 104 : "+a" (ax), "+d" (dx), "=m" (ei->params) 105 : "S" (&ei->params) 106 : "ebx", "ecx", "edi"); 107 108 /* Get legacy CHS parameters */ 109 110 /* Ralf Brown recommends setting ES:DI to 0:0 */ 111 ax = 0x0800; 112 dx = devno; 113 di = 0; 114 asm("pushw %%es; " 115 "movw %%di,%%es; " 116 "pushfl; stc; int $0x13; setc %%al; popfl; " 117 "popw %%es" 118 : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di) 119 : : "esi"); 120 121 if ((u8)ax == 0) { 122 ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2); 123 ei->legacy_max_head = dx >> 8; 124 ei->legacy_sectors_per_track = cx & 0x3f; 125 } 126 127 return 0; 128 } 129 130 void query_edd(void) 131 { 132 char eddarg[8]; 133 int do_mbr = 1; 134 #ifdef CONFIG_EDD_OFF 135 int do_edd = 0; 136 #else 137 int do_edd = 1; 138 #endif 139 int be_quiet; 140 int devno; 141 struct edd_info ei, *edp; 142 u32 *mbrptr; 143 144 if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) { 145 if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) { 146 do_edd = 1; 147 do_mbr = 0; 148 } 149 else if (!strcmp(eddarg, "off")) 150 do_edd = 0; 151 else if (!strcmp(eddarg, "on")) 152 do_edd = 1; 153 } 154 155 be_quiet = cmdline_find_option_bool("quiet"); 156 157 edp = boot_params.eddbuf; 158 mbrptr = boot_params.edd_mbr_sig_buffer; 159 160 if (!do_edd) 161 return; 162 163 /* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe, 164 * so give a hint if this happens. 165 */ 166 167 if (!be_quiet) 168 printf("Probing EDD (edd=off to disable)... "); 169 170 for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) { 171 /* 172 * Scan the BIOS-supported hard disks and query EDD 173 * information... 174 */ 175 if (!get_edd_info(devno, &ei) 176 && boot_params.eddbuf_entries < EDDMAXNR) { 177 memcpy(edp, &ei, sizeof ei); 178 edp++; 179 boot_params.eddbuf_entries++; 180 } 181 182 if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++)) 183 boot_params.edd_mbr_sig_buf_entries = devno-0x80+1; 184 } 185 186 if (!be_quiet) 187 printf("ok\n"); 188 } 189 190 #endif 191