diff options
Diffstat (limited to 'arch/x86/boot/edd.c')
| -rw-r--r-- | arch/x86/boot/edd.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/arch/x86/boot/edd.c b/arch/x86/boot/edd.c new file mode 100644 index 00000000000..bd138e442ec --- /dev/null +++ b/arch/x86/boot/edd.c @@ -0,0 +1,167 @@ +/* -*- linux-c -*- ------------------------------------------------------- * + * + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright 2007 rPath, Inc. - All Rights Reserved + * + * This file is part of the Linux kernel, and is made available under + * the terms of the GNU General Public License version 2. + * + * ----------------------------------------------------------------------- */ + +/* + * arch/i386/boot/edd.c + * + * Get EDD BIOS disk information + */ + +#include "boot.h" +#include <linux/edd.h> + +#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE) + +/* + * Read the MBR (first sector) from a specific device. + */ +static int read_mbr(u8 devno, void *buf) +{ + u16 ax, bx, cx, dx; + + ax = 0x0201; /* Legacy Read, one sector */ + cx = 0x0001; /* Sector 0-0-1 */ + dx = devno; + bx = (size_t)buf; + asm volatile("pushfl; stc; int $0x13; setc %%al; popfl" + : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx) + : : "esi", "edi", "memory"); + + return -(u8)ax; /* 0 or -1 */ +} + +static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig) +{ + int sector_size; + char *mbrbuf_ptr, *mbrbuf_end; + u32 buf_base, mbr_base; + extern char _end[]; + + sector_size = ei->params.bytes_per_sector; + if (!sector_size) + sector_size = 512; /* Best available guess */ + + /* Produce a naturally aligned buffer on the heap */ + buf_base = (ds() << 4) + (u32)&_end; + mbr_base = (buf_base+sector_size-1) & ~(sector_size-1); + mbrbuf_ptr = _end + (mbr_base-buf_base); + mbrbuf_end = mbrbuf_ptr + sector_size; + + /* Make sure we actually have space on the heap... */ + if (!(boot_params.hdr.loadflags & CAN_USE_HEAP)) + return -1; + if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr) + return -1; + + if (read_mbr(devno, mbrbuf_ptr)) + return -1; + + *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET]; + return 0; +} + +static int get_edd_info(u8 devno, struct edd_info *ei) +{ + u16 ax, bx, cx, dx, di; + + memset(ei, 0, sizeof *ei); + + /* Check Extensions Present */ + + ax = 0x4100; + bx = EDDMAGIC1; + dx = devno; + asm("pushfl; stc; int $0x13; setc %%al; popfl" + : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx) + : : "esi", "edi"); + + if ((u8)ax) + return -1; /* No extended information */ + + if (bx != EDDMAGIC2) + return -1; + + ei->device = devno; + ei->version = ax >> 8; /* EDD version number */ + ei->interface_support = cx; /* EDD functionality subsets */ + + /* Extended Get Device Parameters */ + + ei->params.length = sizeof(ei->params); + ax = 0x4800; + dx = devno; + asm("pushfl; int $0x13; popfl" + : "+a" (ax), "+d" (dx), "=m" (ei->params) + : "S" (&ei->params) + : "ebx", "ecx", "edi"); + + /* Get legacy CHS parameters */ + + /* Ralf Brown recommends setting ES:DI to 0:0 */ + ax = 0x0800; + dx = devno; + di = 0; + asm("pushw %%es; " + "movw %%di,%%es; " + "pushfl; stc; int $0x13; setc %%al; popfl; " + "popw %%es" + : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di) + : : "esi"); + + if ((u8)ax == 0) { + ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2); + ei->legacy_max_head = dx >> 8; + ei->legacy_sectors_per_track = cx & 0x3f; + } + + return 0; +} + +void query_edd(void) +{ + char eddarg[8]; + int do_mbr = 1; + int do_edd = 1; + int devno; + struct edd_info ei, *edp; + u32 *mbrptr; + + if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) { + if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) + do_mbr = 0; + else if (!strcmp(eddarg, "off")) + do_edd = 0; + } + + edp = boot_params.eddbuf; + mbrptr = boot_params.edd_mbr_sig_buffer; + + if (!do_edd) + return; + + for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) { + /* + * Scan the BIOS-supported hard disks and query EDD + * information... + */ + get_edd_info(devno, &ei); + + if (boot_params.eddbuf_entries < EDDMAXNR) { + memcpy(edp, &ei, sizeof ei); + edp++; + boot_params.eddbuf_entries++; + } + + if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++)) + boot_params.edd_mbr_sig_buf_entries = devno-0x80+1; + } +} + +#endif |