{
virtual_addr1 = kmalloc(0x20, GFP_USER);
phy_addr1 = __pa(virtual_addr1 );
virtual_addr2 = ioremap(phy_addr1, 0x20 );
}
I noticed that virtual_addr1 is not equal to virtual_addr2. And if i
dereference virtual_addr2 ( *virtual_addr2 ),
kernel crash. What is wrong here ?
-Ratheesh
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Il giorno 15/ott/2011, alle ore 09.01, ratheesh kannoth ha scritto:
> {
> virtual_addr1 = kmalloc(0x20, GFP_USER);
> phy_addr1 = __pa(virtual_addr1 );
> virtual_addr2 = ioremap(phy_addr1, 0x20 );
>
> }
>
>
> I noticed that virtual_addr1 is not equal to virtual_addr2. And if i
> dereference virtual_addr2 ( *virtual_addr2 ),
> kernel crash. What is wrong here ?
>
Obviously virtual_addr1 and virtual_addr2 are not equals! kmalloc returns a logical address (in fact you can simply calc the relative physical address with macro __pa) and ioremap returns a virtual address in the range [VMALLOC_START - VMALLOC_END]. However usually ioremap is used to deal with iomem and you shouldn't dereference the returned pointer directly: you should use instead ioread{8,16,32} or iowrite{8,16,32} family functions in order to make code portable. However i try to write a simple LKM with your code and i can dereference the pointer returned by ioremap correctly. Can you post some detailed code?
Mirko
- --
Mirko Banchi
e-mail: mk.banchi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
id-jabber: mk.banchi-/eSpBmjxGS4dnm+yROfE0A@public.gmane.org
PGP key fingerprint:
308F BFB1 4E67 2522 C88E
DC69 7631 52ED 32A5 6456
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Darwin)
iEYEARECAAYFAk6ZyZAACgkQdjFS7TKlZFaeIACfY5w9Z12jBkIUFvdreBPI QBcC
CasAn1cAjnoWc/743741GREIDOa6zj9I
=nkdk
-----END PGP SIGNATURE-----