![H. Peter Anvin](/assets/img/avatar_default.png)
When filling in the MBR signature array, the setup code failed to advance boot_params.edd_mbr_sig_buf_entries, which resulted in the valid data being ignored. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
168 lines
3.8 KiB
C
168 lines
3.8 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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*
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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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* arch/i386/boot/edd.c
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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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u16 ax, bx, cx, dx;
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ax = 0x0201; /* Legacy Read, one sector */
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cx = 0x0001; /* Sector 0-0-1 */
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dx = devno;
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bx = (size_t)buf;
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asm("pushfl; stc; int $0x13; setc %%al; popfl"
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: "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)
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: : "esi", "edi", "memory");
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return -(u8)ax; /* 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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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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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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return 0;
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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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u16 ax, bx, cx, dx, di;
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memset(ei, 0, sizeof *ei);
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/* Check Extensions Present */
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ax = 0x4100;
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bx = EDDMAGIC1;
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dx = devno;
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asm("pushfl; stc; int $0x13; setc %%al; popfl"
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: "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)
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: : "esi", "edi");
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if ((u8)ax)
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return -1; /* No extended information */
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if (bx != EDDMAGIC2)
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return -1;
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ei->device = devno;
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ei->version = ax >> 8; /* EDD version number */
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ei->interface_support = 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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ax = 0x4800;
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dx = devno;
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asm("pushfl; int $0x13; popfl"
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: "+a" (ax), "+d" (dx), "=m" (ei->params)
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: "S" (&ei->params)
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: "ebx", "ecx", "edi");
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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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ax = 0x0800;
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dx = devno;
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di = 0;
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asm("pushw %%es; "
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"movw %%di,%%es; "
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"pushfl; stc; int $0x13; setc %%al; popfl; "
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"popw %%es"
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: "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)
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: : "esi");
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if ((u8)ax == 0) {
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ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);
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ei->legacy_max_head = dx >> 8;
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ei->legacy_sectors_per_track = cx & 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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int do_edd = 1;
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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_mbr = 0;
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else if (!strcmp(eddarg, "off"))
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do_edd = 0;
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}
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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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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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get_edd_info(devno, &ei);
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if (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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}
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#endif
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