Commit d13444a5 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by Linus Torvalds

EDD probing code for the new x86 setup code

Probe EDD and MBR signatures, in order to make it easier to map
physical hard drives to BIOS drives.
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 31b54f40
/* -*- 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)
struct edd_dapa {
u8 pkt_size;
u8 rsvd;
u16 sector_cnt;
u16 buf_off, buf_seg;
u64 lba;
u64 buf_lin_addr;
};
/*
* Read the MBR (first sector) from a specific device.
*/
static int read_mbr(u8 devno, void *buf)
{
struct edd_dapa dapa;
u16 ax, bx, cx, dx, si;
memset(&dapa, 0, sizeof dapa);
dapa.pkt_size = sizeof(dapa);
dapa.sector_cnt = 1;
dapa.buf_off = (size_t)buf;
dapa.buf_seg = ds();
/* dapa.lba = 0; */
ax = 0x4200; /* Extended Read */
si = (size_t)&dapa;
dx = devno;
asm("pushfl; stc; int $0x13; setc %%al; popfl"
: "+a" (ax), "+S" (si), "+d" (dx)
: "m" (dapa)
: "ebx", "ecx", "edi", "memory");
if (!(u8)ax)
return 0; /* OK */
ax = 0x0201; /* Legacy Read, one sector */
cx = 0x0001; /* Sector 0-0-1 */
dx = devno;
bx = (size_t)buf;
asm("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)
{
int sector_size;
char *mbrbuf_ptr, *mbrbuf_end;
u32 mbrsig;
u32 buf_base, mbr_base;
extern char _end[];
static char mbr_buf[1024];
sector_size = ei->params.bytes_per_sector;
if (!sector_size)
sector_size = 512; /* Best available guess */
buf_base = (ds() << 4) + (u32)&_end;
mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
mbrbuf_ptr = mbr_buf + (mbr_base-buf_base);
mbrbuf_end = mbrbuf_ptr + sector_size;
if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
return 0;
if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
return 0;
if (read_mbr(devno, mbrbuf_ptr))
return 0;
mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
return mbrsig;
}
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)
: "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;
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 = (struct edd_info *)boot_params.eddbuf;
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) {
u32 mbr_sig;
mbr_sig = read_mbr_sig(devno, &ei);
boot_params.edd_mbr_sig_buffer[devno-0x80] = mbr_sig;
}
}
}
#endif
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