Messages in this thread | | | Date | Fri, 08 Jan 2016 10:17:02 +0000 | From | James Morse <> | Subject | Re: [PATCH v2 12/13] arm64: add support for relocatable kernel |
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Hi Ard!
On 30/12/15 15:26, Ard Biesheuvel wrote: > This adds support for runtime relocation of the kernel Image, by > building it as a PIE (ET_DYN) executable and applying the dynamic > relocations in the early boot code. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > ---
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 01a33e42ed70..ab582ee58b58 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -243,6 +253,16 @@ ENDPROC(stext) > preserve_boot_args: > mov x21, x0 // x21=FDT > > +#ifdef CONFIG_ARM64_RELOCATABLE_KERNEL > + /* > + * Mask off the bits of the random value supplied in x1 so it can serve > + * as a KASLR displacement value which will move the kernel image to a > + * random offset in the lower half of the VMALLOC area. > + */ > + mov x23, #(1 << (VA_BITS - 2)) - 1 > + and x23, x23, x1, lsl #SWAPPER_BLOCK_SHIFT > +#endif
I've managed to make this fail to boot by providing a seed that caused the kernel to overlap a 1G boundary on a 4K system.
(It looks like your v3 may have the same issue - but I haven't tested it.)
> + > adr_l x0, boot_args // record the contents of > stp x21, x1, [x0] // x0 .. x3 at kernel entry > stp x2, x3, [x0, #16]
Thanks!
James
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