On Thu, Dec 04, 2014 at 12:03:05PM +0000, Catalin Marinas wrote:
> On Mon, Sep 15, 2014 at 12:33:25PM +0100, Russell King - ARM Linux wrote:
> > On Mon, Sep 15, 2014 at 07:07:20PM +0800, Wang, Yalin wrote:
> > > @@ -636,6 +646,11 @@ static int keep_initrd;
> > > void free_initrd_mem(unsigned long start, unsigned long end)
> > > {
> > > if (!keep_initrd) {
> > > + if (start == initrd_start)
> > > + start = round_down(start, PAGE_SIZE);
> > > + if (end == initrd_end)
> > > + end = round_up(end, PAGE_SIZE);
> > > +
> > > poison_init_mem((void *)start, PAGE_ALIGN(end) - start);
> > > free_reserved_area((void *)start, (void *)end, -1, "initrd");
> > > }
> >
> > is the only bit of code you likely need to achieve your goal.
> >
> > Thinking about this, I think that you are quite right to align these.
> > The memory around the initrd is defined to be system memory, and we
> > already free the pages around it, so it *is* wrong not to free the
> > partial initrd pages.
>
> Actually, I think we have a problem, at least on arm64 (raised by Peter
> Maydell). There is no guarantee that the page around start/end of initrd
> is free, it may contain the dtb for example. This is even more obvious
> when we have a 64KB page kernel (the boot loader doesn't know the page
> size that the kernel is going to use).
>
> The bug was there before as we had poison_init_mem() already (not it
> disappeared since free_reserved_area does the poisoning).
>
> So as a quick fix I think we need the rounding the other way (and in the
> general case we probably lose a page at the end of initrd):
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 494297c698ca..39fd080683e7 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -335,9 +335,9 @@ void free_initrd_mem(unsigned long start, unsigned long end)
> {
> if (!keep_initrd) {
> if (start == initrd_start)
> - start = round_down(start, PAGE_SIZE);
> + start = round_up(start, PAGE_SIZE);
> if (end == initrd_end)
> - end = round_up(end, PAGE_SIZE);
> + end = round_down(end, PAGE_SIZE);
>
> free_reserved_area((void *)start, (void *)end, 0, "initrd");
> }
>
> A better fix would be to check what else is around the start/end of
> initrd.
Care to submit this as a proper patch? We should at least fix Peter's issue
before doing things like extending headers, which won't work for older
kernels anyway.
Will
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