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 * arch/i386/boot/edd.c 13 * 14 * Get EDD BIOS disk information 15 */ 16 17 #include "boot.h" 18 #include <linux/edd.h> 19 20 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE) 21 22 /* 23 * Read the MBR (first sector) from a specific device. 24 */ 25 static int read_mbr(u8 devno, void *buf) 26 { 27 u16 ax, bx, cx, dx; 28 29 ax = 0x0201; /* Legacy Read, one sector */ 30 cx = 0x0001; /* Sector 0-0-1 */ 31 dx = devno; 32 bx = (size_t)buf; 33 asm volatile("pushfl; stc; int $0x13; setc %%al; popfl" 34 : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx) 35 : : "esi", "edi", "memory"); 36 37 return -(u8)ax; /* 0 or -1 */ 38 } 39 40 static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig) 41 { 42 int sector_size; 43 char *mbrbuf_ptr, *mbrbuf_end; 44 u32 buf_base, mbr_base; 45 extern char _end[]; 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 if (read_mbr(devno, mbrbuf_ptr)) 64 return -1; 65 66 *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET]; 67 return 0; 68 } 69 70 static int get_edd_info(u8 devno, struct edd_info *ei) 71 { 72 u16 ax, bx, cx, dx, di; 73 74 memset(ei, 0, sizeof *ei); 75 76 /* Check Extensions Present */ 77 78 ax = 0x4100; 79 bx = EDDMAGIC1; 80 dx = devno; 81 asm("pushfl; stc; int $0x13; setc %%al; popfl" 82 : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx) 83 : : "esi", "edi"); 84 85 if ((u8)ax) 86 return -1; /* No extended information */ 87 88 if (bx != EDDMAGIC2) 89 return -1; 90 91 ei->device = devno; 92 ei->version = ax >> 8; /* EDD version number */ 93 ei->interface_support = cx; /* EDD functionality subsets */ 94 95 /* Extended Get Device Parameters */ 96 97 ei->params.length = sizeof(ei->params); 98 ax = 0x4800; 99 dx = devno; 100 asm("pushfl; int $0x13; popfl" 101 : "+a" (ax), "+d" (dx), "=m" (ei->params) 102 : "S" (&ei->params) 103 : "ebx", "ecx", "edi"); 104 105 /* Get legacy CHS parameters */ 106 107 /* Ralf Brown recommends setting ES:DI to 0:0 */ 108 ax = 0x0800; 109 dx = devno; 110 di = 0; 111 asm("pushw %%es; " 112 "movw %%di,%%es; " 113 "pushfl; stc; int $0x13; setc %%al; popfl; " 114 "popw %%es" 115 : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di) 116 : : "esi"); 117 118 if ((u8)ax == 0) { 119 ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2); 120 ei->legacy_max_head = dx >> 8; 121 ei->legacy_sectors_per_track = cx & 0x3f; 122 } 123 124 return 0; 125 } 126 127 void query_edd(void) 128 { 129 char eddarg[8]; 130 int do_mbr = 1; 131 int do_edd = 1; 132 int devno; 133 struct edd_info ei, *edp; 134 u32 *mbrptr; 135 136 if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) { 137 if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) 138 do_mbr = 0; 139 else if (!strcmp(eddarg, "off")) 140 do_edd = 0; 141 } 142 143 edp = boot_params.eddbuf; 144 mbrptr = boot_params.edd_mbr_sig_buffer; 145 146 if (!do_edd) 147 return; 148 149 for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) { 150 /* 151 * Scan the BIOS-supported hard disks and query EDD 152 * information... 153 */ 154 get_edd_info(devno, &ei); 155 156 if (boot_params.eddbuf_entries < EDDMAXNR) { 157 memcpy(edp, &ei, sizeof ei); 158 edp++; 159 boot_params.eddbuf_entries++; 160 } 161 162 if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++)) 163 boot_params.edd_mbr_sig_buf_entries = devno-0x80+1; 164 } 165 } 166 167 #endif 168