Subject: [linux-next PATCH] arm64: fix kernel crash with 48-bit VA and 64KB granule

From: [email-masked] (Dennis Chen)
Date: Wed, 6 Jan 2016 14:14:09 +0800

On Tue, Jan 05, 2016 at 09:56:03AM +0000, Catalin Marinas wrote:
> On Tue, Jan 05, 2016 at 04:40:44PM +0800, Dennis Chen wrote:
> > On Tue, Jan 05, 2016 at 09:38:11AM +0100, Ard Biesheuvel wrote:
> > > >> On 5 January 2016 at 03:18, Dennis Chen <[email-masked]> wrote:
> > > >> > The commit 3400749b5a22 ("arm64/efi: refactor EFI init and runtime
> > > >> > code for reuse by 32-bit ARM") uses pgd_alloc() to allocate space for
> > > >> > efi_mm.pgd while not the static efi_pgd[], since this function will be
> > > >> > called with early_initcall, which results in the pgd_cache used by
> > > >> > pgd_alloc() has not been initialized yet, kernel will hang in this
> > > >> > case. This patch is trying to make the pgd_cache_init() called before
> > > >> > arm_enable_runtime_services() by changing its core_initcall to
> > > >> > early_initcall.
> > > >> >
> > > >> > Signed-off-by: Dennis Chen <[email-masked]>
> > > >> > Tested-by: Sudeep Holla <[email-masked]>
> > > >> >
> > > >> > Cc: Will Deacon <[email-masked]>
> > > >> > Cc: Catalin Marinas <[email-masked]>
> > > >> > Cc: Ard Biesheuvel <[email-masked]>
> > > >> > Cc: Sudeep Holla <[email-masked]>
> > > >> > ---
> > > >> >  arch/arm64/mm/pgd.c | 2 +-
> > > >> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >> >
> > > >> > diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c
> > > >> > index cb3ba1b..859a788 100644
> > > >> > --- a/arch/arm64/mm/pgd.c
> > > >> > +++ b/arch/arm64/mm/pgd.c
> > > >> > @@ -56,4 +56,4 @@ static int __init pgd_cache_init(void)
> > > >> >                                               SLAB_PANIC, NULL);
> > > >> >         return 0;
> > > >> >  }
> > > >> > -core_initcall(pgd_cache_init);
> > > >> > +early_initcall(pgd_cache_init);
> [...]
> > > Well, since arm_enable_runtime_services() is an early_initcall()
> > > itself, how are you guaranteeing the ordering between the two? Link
> > > order?
> >
> > Link order.
>
> And can you explain how this works, what guarantees it gives?
>
You can take a look at include/asm-generic/vmlinux.ldx.h: INIT_CALLS macro,
for the init call section, early_initcall is the first chuck in the section,
followed by LEVEL[0-7]. For the same level, the layout order is determined
by the link order, ARCH is always precedence over the drivers. Catalin, are
you giving me a kernel examination? :)

>
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>
> BTW, please sort out the legal disclaimer (raise an IT ticket).
>
Hmm, the ticket has been raised.
> --
> Catalin
>
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