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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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3435d3476c
Impact: BIOS proofing "Glove box" off BIOS interrupts in the EDD code. LKML-Reference: <49DE7F79.4030106@zytor.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
182 lines
4.1 KiB
C
182 lines
4.1 KiB
C
/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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* Copyright 2009 Intel Corporation; author H. Peter Anvin
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* Get EDD BIOS disk information
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*/
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#include "boot.h"
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#include <linux/edd.h>
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#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
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/*
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* Read the MBR (first sector) from a specific device.
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*/
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static int read_mbr(u8 devno, void *buf)
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{
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struct biosregs ireg, oreg;
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initregs(&ireg);
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ireg.ax = 0x0201; /* Legacy Read, one sector */
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ireg.cx = 0x0001; /* Sector 0-0-1 */
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ireg.dl = devno;
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ireg.bx = (size_t)buf;
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intcall(0x13, &ireg, &oreg);
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return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */
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}
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static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
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{
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int sector_size;
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char *mbrbuf_ptr, *mbrbuf_end;
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u32 buf_base, mbr_base;
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extern char _end[];
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u16 mbr_magic;
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sector_size = ei->params.bytes_per_sector;
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if (!sector_size)
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sector_size = 512; /* Best available guess */
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/* Produce a naturally aligned buffer on the heap */
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buf_base = (ds() << 4) + (u32)&_end;
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mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
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mbrbuf_ptr = _end + (mbr_base-buf_base);
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mbrbuf_end = mbrbuf_ptr + sector_size;
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/* Make sure we actually have space on the heap... */
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if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
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return -1;
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if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
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return -1;
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memset(mbrbuf_ptr, 0, sector_size);
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if (read_mbr(devno, mbrbuf_ptr))
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return -1;
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*mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
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mbr_magic = *(u16 *)&mbrbuf_ptr[510];
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/* check for valid MBR magic */
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return mbr_magic == 0xAA55 ? 0 : -1;
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}
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static int get_edd_info(u8 devno, struct edd_info *ei)
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{
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struct biosregs ireg, oreg;
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memset(ei, 0, sizeof *ei);
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/* Check Extensions Present */
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initregs(&ireg);
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ireg.ah = 0x41;
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ireg.bx = EDDMAGIC1;
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ireg.dl = devno;
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intcall(0x13, &ireg, &oreg);
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if (oreg.eflags & X86_EFLAGS_CF)
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return -1; /* No extended information */
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if (oreg.bx != EDDMAGIC2)
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return -1;
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ei->device = devno;
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ei->version = oreg.ah; /* EDD version number */
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ei->interface_support = oreg.cx; /* EDD functionality subsets */
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/* Extended Get Device Parameters */
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ei->params.length = sizeof(ei->params);
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ireg.ah = 0x48;
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ireg.si = (size_t)&ei->params;
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intcall(0x13, &ireg, &oreg);
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/* Get legacy CHS parameters */
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/* Ralf Brown recommends setting ES:DI to 0:0 */
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ireg.ah = 0x08;
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ireg.es = 0;
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intcall(0x13, &ireg, &oreg);
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if (!(oreg.eflags & X86_EFLAGS_CF)) {
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ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2);
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ei->legacy_max_head = oreg.dh;
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ei->legacy_sectors_per_track = oreg.cl & 0x3f;
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}
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return 0;
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}
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void query_edd(void)
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{
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char eddarg[8];
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int do_mbr = 1;
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#ifdef CONFIG_EDD_OFF
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int do_edd = 0;
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#else
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int do_edd = 1;
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#endif
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int be_quiet;
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int devno;
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struct edd_info ei, *edp;
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u32 *mbrptr;
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if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
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if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
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do_edd = 1;
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do_mbr = 0;
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}
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else if (!strcmp(eddarg, "off"))
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do_edd = 0;
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else if (!strcmp(eddarg, "on"))
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do_edd = 1;
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}
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be_quiet = cmdline_find_option_bool("quiet");
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edp = boot_params.eddbuf;
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mbrptr = boot_params.edd_mbr_sig_buffer;
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if (!do_edd)
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return;
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/* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
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* so give a hint if this happens.
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*/
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if (!be_quiet)
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printf("Probing EDD (edd=off to disable)... ");
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for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
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/*
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* Scan the BIOS-supported hard disks and query EDD
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* information...
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*/
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if (!get_edd_info(devno, &ei)
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&& boot_params.eddbuf_entries < EDDMAXNR) {
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memcpy(edp, &ei, sizeof ei);
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edp++;
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boot_params.eddbuf_entries++;
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}
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if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++))
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boot_params.edd_mbr_sig_buf_entries = devno-0x80+1;
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}
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if (!be_quiet)
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printf("ok\n");
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}
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#endif
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