| Код | #include <stdio.h> // for printf(), perror()
#include <fcntl.h> // for open()
#include <stdlib.h> // for exit()
#include <unistd.h> // for lseek(), read()
#include <sys/mman.h> // for mmap()
#include <asm/vm86.h> // for struct vm86_struct
#include <linux/linkage.h> // for asmlinkage attribute
#define ELF_LOAD_ADDRESS 0x08048000 // where Linux puts this
asmlinkage void blue( void ); // no C++ "name-mangling"
asm(" .code16 "); // generate 16-bit codes
asm(" .align 16 "); // "paragraph" alignment
asm("blue: "); // label procedure entry
asm(" movw $0xB800, %ax "); // address screen memory
asm(" movw %ax, %es "); // using ES register
asm(" xorw %di, %di "); // point es:di to screen
asm(" movb $0x17, %al "); // white-upon-blue color
asm(" movw $0x4000, %cx "); // number of screen elts
asm("nxpel: "); // main loop begins here
asm(" movb %al, %es:1(%di) "); // write color attribute
asm(" addw $2, %di "); // point to next element
asm(" loop nxpel "); // process entire screen
asm(" hlt "); // exit Virtual8086 mode
asm(" .code32 "); // generate 32-bit codes
int vm86( struct vm86_struct *vm )
{
int retval;
asm(" movl $113, %eax "); // system-call ID-number
asm(" movl %0, %%ebx " : : "m" (vm) ); // struct address
asm(" int $0x80 "); // enter the Linux kernel
asm(" movl %%eax, %0 " : "=m" (retval) ); // store retval
return retval; // return function status
}
struct vm86_struct vm; // virtual machine struct
int main( int argc, char **argv )
{
int fd, prot, flag;
// setup a memory-mapping for accessing video display memory
void *vram = (void*)0x000B8000; // address of 32KB window
prot = PROT_READ | PROT_WRITE; // read-write access is needed
flag = MAP_FIXED | MAP_SHARED; // with a fixed-shared mapping
if ( ( fd = open( "/dev/mem", O_RDWR ) ) < 0 )
{ perror( "open /dev/mem" ); exit(1); }
if ( mmap( vram, 0x8000, prot, flag, fd, (int)vram ) == MAP_FAILED )
{ perror( "mmap /dev/mem" ); exit(1); }
// setup 64KB memory-mapping for access to VM86 code and stack
void *prog = (void*)0x00010000; // address of 64KB region
prot = PROT_READ | PROT_WRITE; // read-write access is needed
flag = MAP_FIXED | MAP_SHARED; // with a fixed-shared mapping
if ( ( fd = open( "/dev/zero", O_RDWR ) ) < 0 )
{ perror( "open /dev/zero" ); exit(1); }
if ( mmap( prog, 0x10000, prot, flag, fd, 0 ) == MAP_FAILED )
{ perror( "mmap /dev/zero" ); exit(1); }
// now "load" our program code into this memory-mapped region
if ( ( fd = open( argv[0], O_RDONLY ) ) < 0 )
{ perror( argv[0] ); exit(1); }
int progsize = lseek( fd, 0, SEEK_END );
if ( lseek( fd, 0, SEEK_SET ) != 0 ) { perror( "lseek" ); exit(1); }
if ( read( fd, prog, progsize ) != progsize )
{ perror( "read" ); exit(1); }
// compute offset-address for the 16-bit code's entry-point
int initial_IP = (int)blue - ELF_LOAD_ADDRESS;
int initial_CS = ((int)prog) >> 4; // segment-address
// initialize data-structure for entering to Virtual-8086 Mode
vm.regs.eip = initial_IP; // initial instruction offset
vm.regs.cs = initial_CS; // segment-address for code
vm.regs.eflags = (1<<9); // IF=1, IOPL=0
vm.regs.ss = initial_CS; // segment-address for stack
vm.regs.esp = 0x10000; // initial stacktop offset
vm.cpu_type = CPU_386; // specify required processor
// execute in Virtual-8086 Mode (until 'hlt' is encountered)
vm86( &vm ); // execute the 'blue' routine
printf( "\nReturned successfully from Virtual-8086 Mode\n\n" );
} |
Человек говорит, что программа в любом случае завершается сегфолтом. |