Date: Sat, 10 Aug 2002 00:52:37 +0200 From: hal@telefonica.net To: freebsd-questions@freebsd.org Subject: Memory below 1 MB Message-ID: <E17dIcF-0000X0-00@ash.drims.net>
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Hello,
As I explained in another message, I am writing some graphics code (both for fun and educational purposes) and need to access memory below 1 MB. I have tried it by opening /dev/mem, calling mmap, i386_vm86 and even opening /dev/io to change permission levels. However, the program (and actually the physical terminal) hangs when doing the interruption call.
I attach the test program within this mail. If attachments are not part of this list's etiquette, sorry, it will not happen again. Compile with "gcc -o whatever vesainfo.c" if you want to have a look (you will need root privileges to execute it).
Well, I am completely desperate. I tried everything I could, but for some magical reasons, this low-level access does not work. Any ideas?
Thank you in advance,
Alex
vesastructs.h:
#ifndef __VESASTRUCTS_H
#define __VESASTRUCTS_H
typedef unsigned char byte;
typedef unsigned short word;
typedef unsigned int dword;
struct VesaInfo
{
byte signature[4];
word version;
char *oemName;
dword capabilities;
word *suppModes;
word total64kBlocks;
word oemSoftVersion;
byte *vendorName;
byte *productName;
byte *productRev;
word VBEAFVersion;
word *accelSuppModes;
byte reserved[216];
byte oemStrings[256];
};
#endif
vesainfo.c:
#include <sys/types.h>
#include <sys/mman.h>
#include <machine/sysarch.h>
#include <machine/vm86.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include "vesastructs.h"
int main (void)
{
struct vm86_init_args vm86init;
struct vm86_intcall_args intargs;
struct VesaInfo *vbeInfo;
char c;
int f, io;
unsigned int len=0x400;
int ioperm=0;
f=open("/dev/mem", O_RDWR);
if (f==-1)
{
printf("Could Not Access Memory\n");
return -1;
}
vbeInfo=(struct VesaInfo*)mmap((void*)0x10000, 0x1000,
PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_FIXED|MAP_SHARED,
f, 0x10000);
if (vbeInfo==MAP_FAILED)
{
printf("Peta mmap\n");
return -1;
}
memset(&vm86init, 0, sizeof(struct vm86_init_args));
memset(&intargs, 0, sizeof(struct vm86_intcall_args));
memset(vbeInfo, 0, sizeof(struct VesaInfo));
printf("vbeInfo = %p\n", vbeInfo);
vbeInfo->signature[0]='V';
vbeInfo->signature[1]='B';
vbeInfo->signature[2]='E';
vbeInfo->signature[3]='2';
printf("vbeSig = %c%c%c%c\n",
vbeInfo->signature[0],
vbeInfo->signature[1],
vbeInfo->signature[2],
vbeInfo->signature[3]);
// sleep(1);
if (!i386_vm86(VM86_INIT, &vm86init))
{
printf("VM86_INIT successful\n");
}
intargs.intnum=0x10;
intargs.vmf.vmf_ax=0x4f00;
intargs.vmf.vmf_es=(((dword)vbeInfo)&0xf0000)>>4; /*0x1000;*/
intargs.vmf.vmf_di=((dword)vbeInfo)&0xffff; /*0x0000;*/
i386_set_ioperm(0, 0x400, 1);
i386_get_ioperm(0, &len, &ioperm);
printf("len=%x perm=%x\n", len, ioperm);
// return -1;
io=open("/dev/io", 0);
if (io==-1)
{
printf("io pef\n");
return -1;
}
// sleep(1);
printf("INTCALL (0x%x, ax=0x%.04x, es:di=%.04x:%.04x)\n",
intargs.intnum, intargs.vmf.vmf_ax,
intargs.vmf.vmf_es, intargs.vmf.edi.r_ex);
if (!i386_vm86(VM86_INTCALL, &intargs))
{
printf("VM86_INTCALL successful (ax=%.04x)\n", intargs.vmf.vmf_ax);
}
// sleep(1);
printf("vbeVer\n");
// sleep(1);
printf("VESA signature: %c%c%c%c\nVESA Version: 0x%.04x\n",
vbeInfo->signature[0],
vbeInfo->signature[1],
vbeInfo->signature[2],
vbeInfo->signature[3],
vbeInfo->version);
return 0;
}
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