Gives Bus errory in memcpy() in coping /dev/fb0 to a file.

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hello,

I am trying to get the snapshot of the screen through a c program by mmaping
the framebuffer device /dev/fb0 .
For this i compiled kernel with virtual framebuffer support and passing
vga=791 as boot line argument.

Though i am able to get snapshot by
[root@tw pcapp]# cat /dev/fb0 > frame

and see it on the screen by
[root@tw pcapp]# cat frame > /dev/fb0

When i try to capture the frame buffer using the below c code, It gives bus
error @ memcpy()

Output :::::::::

[root@tw pcapp]# ./pcapp
1024x768, 16bpp
framebuffer device mapped to memory @ 0xb7db3000.
FB_FRAME mapped to memory @ 0xb7c33000.
Bus error
[root@tw pcapp]#



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#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

#define FB_FILE "/dev/fb0"
#define FB_FRAME "fb_frame"

int main (int argc, char *argv[])
{
int fdin = -1;
int fdout = -1;
char *src = NULL;
char *dst = NULL;
struct fb_var_screeninfo vinfo;
long int screensize = 0;

if ((fdin = open (FB_FILE, O_RDONLY)) < 0) {
printf ("Faile to open %s file", FB_FILE);
return 0;
}

/* open/create the output file */
if ((fdout = open (FB_FRAME, O_RDWR | O_CREAT | O_TRUNC, S_IRWXU)) < 0) {
printf ("faile to open %s for writing", FB_FRAME);
return -1;
}

// Get variable screen information
if (ioctl(fdin, FBIOGET_VSCREENINFO, &vinfo)) {
printf("Error reading variable information.\n");
return -1;
}

printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );

// Calculate the size of the screen in bytes
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

// Map the device to memory
src = (char *)mmap(0, screensize, PROT_READ, MAP_SHARED, fdin, 0);
if ((int)src == -1) {
printf("Error: failed to map framebuffer device to memory.\n");
return -1;
}

/* mmap the FB_FRAME file */
dst = mmap (0, screensize, PROT_READ | PROT_WRITE, MAP_PRIVATE, fdout, 0);
if ((int)dst == -1) {
printf("FB_FRAME:: mmap error ");
return -1;
}

printf("framebuffer device mapped to memory @ %p.\n", src);
printf("FB_FRAME mapped to memory @ %p.\n", dst);
/* copy /dev/fb0 to fb_frame file */
memcpy (dst, src, screensize);
close(fdin);
close(fdout);
return 0;
}

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