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// SPDX-License-Identifier: GPL-2.0-only
/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
* Copyright 2009 Intel Corporation; author H. Peter Anvin
*
* ----------------------------------------------------------------------- */
/*
* Get EDD BIOS disk information
*/
#include "boot.h"
#include <linux/edd.h>
#include "string.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)
{
struct biosregs ireg, oreg;
initregs(&ireg);
ireg.ax = 0x0201; /* Legacy Read, one sector */
ireg.cx = 0x0001; /* Sector 0-0-1 */
ireg.dl = devno;
ireg.bx = (size_t)buf;
intcall(0x13, &ireg, &oreg);
return -(oreg.eflags & X86_EFLAGS_CF); /* 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[];
u16 mbr_magic;
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;
memset(mbrbuf_ptr, 0, sector_size);
if (read_mbr(devno, mbrbuf_ptr))
return -1;
*mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
mbr_magic = *(u16 *)&mbrbuf_ptr[510];
/* check for valid MBR magic */
return mbr_magic == 0xAA55 ? 0 : -1;
}
static int get_edd_info(u8 devno, struct edd_info *ei)
{
struct biosregs ireg, oreg;
memset(ei, 0, sizeof(*ei));
/* Check Extensions Present */
initregs(&ireg);
ireg.ah = 0x41;
ireg.bx = EDDMAGIC1;
ireg.dl = devno;
intcall(0x13, &ireg, &oreg);
if (oreg.eflags & X86_EFLAGS_CF)
return -1; /* No extended information */
if (oreg.bx != EDDMAGIC2)
return -1;
ei->device = devno;
ei->version = oreg.ah; /* EDD version number */
ei->interface_support = oreg.cx; /* EDD functionality subsets */
/* Extended Get Device Parameters */
ei->params.length = sizeof(ei->params);
ireg.ah = 0x48;
ireg.si = (size_t)&ei->params;
intcall(0x13, &ireg, &oreg);
/* Get legacy CHS parameters */
/* Ralf Brown recommends setting ES:DI to 0:0 */
ireg.ah = 0x08;
ireg.es = 0;
intcall(0x13, &ireg, &oreg);
if (!(oreg.eflags & X86_EFLAGS_CF)) {
ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2);
ei->legacy_max_head = oreg.dh;
ei->legacy_sectors_per_track = oreg.cl & 0x3f;
}
return 0;
}
void query_edd(void)
{
char eddarg[8];
int do_mbr = 1;
#ifdef CONFIG_EDD_OFF
int do_edd = 0;
#else
int do_edd = 1;
#endif
int be_quiet;
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_edd = 1;
do_mbr = 0;
}
else if (!strcmp(eddarg, "off"))
do_edd = 0;
else if (!strcmp(eddarg, "on"))
do_edd = 1;
}
be_quiet = cmdline_find_option_bool("quiet");
edp = boot_params.eddbuf;
mbrptr = boot_params.edd_mbr_sig_buffer;
if (!do_edd)
return;
/* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
* so give a hint if this happens.
*/
if (!be_quiet)
printf("Probing EDD (edd=off to disable)... ");
for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
/*
* Scan the BIOS-supported hard disks and query EDD
* information...
*/
if (!get_edd_info(devno, &ei)
&& 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;
}
if (!be_quiet)
printf("ok\n");
}
#endif
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