Date: Wed, 26 Oct 2005 16:25:01 +0800 From: Xin LI <delphij@frontfree.net> To: freebsd-hackers@FreeBSD.org Cc: zhuyan@staff.sina.com.cn, LI Xin <delphij@delphij.net> Subject: Is it possible to mmap() raw disk device? Message-ID: <1130315101.810.5.camel@spirit>
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Dear folks,
When we were trying to make a userland FS application we have
encountered "Invalid Argument" when doing mmap() over an open descriptor
to a disk device. The program goes here:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h> /* mmap() */
#include <fcntl.h>
#include <errno.h>
#include <assert.h>
int
main(int argc, char *argv[])
{
int fd;
char *src, *dst;
struct stat statbuf;
dst =3D strdup("abcdefghijklmn");
if (dst =3D=3D NULL) {
printf("Can not allocate memory\n");
exit(-1);
}
if ((fd =3D open("/dev/da2s1", O_RDWR | O_DIRECT)) < 0)
printf("can't open for read/write");
if ((src =3D mmap(0, 10, PROT_WRITE | PROT_READ,
MAP_SHARED, fd, 0)) =3D=3D (caddr_t) -1) {
perror("mmap error for input");
return -1;
}
memcpy(dst, src, 10); /* does the file copy */
exit(0);
}
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
Do we need some special prerequisite before doing mmap()? According to
the vm_mmap.c it seems that we should map a DTYPE_VNODE object, which
looks somewhat confusing...
Thanks in advance!
Cheers,
--=20
Xin LI <delphij delphij net> http://www.delphij.net/
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