The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/bios.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 1997 Michael Smith
    5  * Copyright (c) 1998 Jonathan Lemon
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 #include <sys/cdefs.h>
   31 __FBSDID("$FreeBSD: releng/12.0/sys/amd64/amd64/bios.c 326257 2017-11-27 15:03:07Z pfg $");
   32 
   33 /*
   34  * Subset of the i386 bios support code.  We cannot make bios16 nor bios32
   35  * calls, so we can leave that out.  However, searching for bios rom
   36  * signatures can be useful for locating tables, eg: powernow settings.
   37  */
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/kernel.h>
   42 #include <vm/vm.h>
   43 #include <vm/pmap.h>
   44 #include <machine/vmparam.h>
   45 #include <machine/pc/bios.h>
   46 
   47 #define BIOS_START      0xe0000
   48 #define BIOS_SIZE       0x20000
   49 
   50 /*
   51  * bios_sigsearch
   52  *
   53  * Search some or all of the BIOS region for a signature string.
   54  *
   55  * (start)      Optional offset returned from this function 
   56  *              (for searching for multiple matches), or NULL
   57  *              to start the search from the base of the BIOS.
   58  *              Note that this will be a _physical_ address in
   59  *              the range 0xe0000 - 0xfffff.
   60  * (sig)        is a pointer to the byte(s) of the signature.
   61  * (siglen)     number of bytes in the signature.
   62  * (paralen)    signature paragraph (alignment) size.
   63  * (sigofs)     offset of the signature within the paragraph.
   64  *
   65  * Returns the _physical_ address of the found signature, 0 if the
   66  * signature was not found.
   67  */
   68 
   69 u_int32_t
   70 bios_sigsearch(u_int32_t start, u_char *sig, int siglen, int paralen, int sigofs)
   71 {
   72     u_char      *sp, *end;
   73     
   74     /* compute the starting address */
   75     if ((start >= BIOS_START) && (start <= (BIOS_START + BIOS_SIZE))) {
   76         sp = (char *)BIOS_PADDRTOVADDR(start);
   77     } else if (start == 0) {
   78         sp = (char *)BIOS_PADDRTOVADDR(BIOS_START);
   79     } else {
   80         return 0;                               /* bogus start address */
   81     }
   82 
   83     /* compute the end address */
   84     end = (u_char *)BIOS_PADDRTOVADDR(BIOS_START + BIOS_SIZE);
   85 
   86     /* loop searching */
   87     while ((sp + sigofs + siglen) < end) {
   88         
   89         /* compare here */
   90         if (!bcmp(sp + sigofs, sig, siglen)) {
   91             /* convert back to physical address */
   92             return((u_int32_t)(uintptr_t)BIOS_VADDRTOPADDR(sp));
   93         }
   94         sp += paralen;
   95     }
   96     return(0);
   97 }

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