/* -*- 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
