On 07/06/2012 05:05 PM, Catalin Marinas wrote:
> +/*
> + * PAGE_OFFSET - the virtual address of the start of the kernel image.
> + * VA_BITS - the maximum number of bits for virtual addresses.
> + * TASK_SIZE - the maximum size of a user space task.
> + * TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area.
> + * The module space lives between the addresses given by TASK_SIZE
> + * and PAGE_OFFSET - it must be within 128MB of the kernel text.
> + */
> +#define PAGE_OFFSET UL(0xffffffc000000000)
> +#define MODULES_END (PAGE_OFFSET)
> +#define MODULES_VADDR (MODULES_END - SZ_64M)
> +#define VA_BITS (39)
> +#define TASK_SIZE_64 (UL(1) << VA_BITS)
Pedantic nit pick. Shouldn't that "it must be within 128MB of the kernel
text" be "within 128MB of the *end* of the kernel text"? The point being
that on AArch64 unconditional branches are encoded as imm26+1 (27 bits)
and so you're going with -64MB to ensure that you're within the range.
Jon.
On Tue, Oct 02, 2012 at 01:43:04AM +0100, Jon Masters wrote:
> On 07/06/2012 05:05 PM, Catalin Marinas wrote:
>
> > +/*
> > + * PAGE_OFFSET - the virtual address of the start of the kernel image.
> > + * VA_BITS - the maximum number of bits for virtual addresses.
> > + * TASK_SIZE - the maximum size of a user space task.
> > + * TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area.
> > + * The module space lives between the addresses given by TASK_SIZE
> > + * and PAGE_OFFSET - it must be within 128MB of the kernel text.
> > + */
> > +#define PAGE_OFFSET UL(0xffffffc000000000)
> > +#define MODULES_END (PAGE_OFFSET)
> > +#define MODULES_VADDR (MODULES_END - SZ_64M)
> > +#define VA_BITS (39)
> > +#define TASK_SIZE_64 (UL(1) << VA_BITS)
>
> Pedantic nit pick. Shouldn't that "it must be within 128MB of the kernel
> text" be "within 128MB of the *end* of the kernel text"? The point being
> that on AArch64 unconditional branches are encoded as imm26+1 (27 bits)
> and so you're going with -64MB to ensure that you're within the range.
I read it to be within 128MB of any part of the kernel text but I can
change it to "end of" if that's clearer.
--
Catalin