Handle kernel page faults using task gate

[eliad lubovsky <eliadl@013.net>]

I am trying to handle page faults exceptions in the kernel using the
task gate mechanism. I succeeded to transfer the execution to my page
fault handler using a new TSS and updates to the GDT and IDT tables
(similar to the double fault mechanism in 2.6). After handling the fault
and allocating the physical page I use the iret instruction to switch
back to the previous task. The problem is that I got a double fault with
the same address that cause the fault (although the physical page is
allocated and mapped). Any clues?

The new page fault TSS:
struct tss_struct pagefault_tss __cacheline_aligned = {
        .esp0           = STACK_START,
        .ss0            = __KERNEL_DS,
        .ldt            = 0,
        .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
                                                     
        .eip            = (unsigned long) pagefault_fn,
        .eflags         = X86_EFLAGS_SF|0x2,/* 0x2 bit is always set */
        .esp            = STACK_START,
        .es             = __USER_DS,
        .cs             = __KERNEL_CS,
        .ss             = __KERNEL_DS,
        .ds             = __USER_DS,
                                                      
        .__cr3          = __pa(swapper_pg_dir)
};