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Commit 884143f6 authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Will Deacon
Browse files

arm64: kexec_file: add kaslr support 



Adding "kaslr-seed" to dtb enables triggering kaslr, or kernel virtual
address randomization, at secondary kernel boot. We always do this as
it will have no harm on kaslr-incapable kernel.

We don't have any "switch" to turn off this feature directly, but still
can suppress it by passing "nokaslr" as a kernel boot argument.

Signed-off-by: default avatarAKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
[will: Use rng_is_initialized()]
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 732b7b93

arch/arm64/kernel/machine_kexec_file.c

+18 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/libfdt.h>

#include <linux/memblock.h>

#include <linux/of_fdt.h>

#include <linux/random.h>

#include <linux/string.h>

#include <linux/types.h>

#include <asm/byteorder.h>
@@ -24,6 +25,7 @@ 
#define FDT_PSTR_INITRD_STA	"linux,initrd-start"

#define FDT_PSTR_INITRD_END	"linux,initrd-end"

#define FDT_PSTR_BOOTARGS	"bootargs"

#define FDT_PSTR_KASLR_SEED	"kaslr-seed"



const struct kexec_file_ops * const kexec_file_loaders[] = {

	&kexec_image_ops,
@@ -82,11 +84,26 @@ static int setup_dtb(struct kimage *image, 
			return -EINVAL;

	}



	/* add kaslr-seed */

	ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_KASLR_SEED);

	if (ret && (ret != -FDT_ERR_NOTFOUND))

		return -EINVAL;



	if (rng_is_initialized()) {

		u64 r = get_random_u64();

		ret = fdt_setprop_u64(dtb, nodeoffset, FDT_PSTR_KASLR_SEED, r);

		if (ret)

			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);

	} else {

		pr_notice("RNG is not initialised: omitting \"%s\" property\n",

				FDT_PSTR_KASLR_SEED);

	}



	return 0;

}



/*

 * More space needed so that we can add initrd and bootargs.

 * More space needed so that we can add initrd, bootargs and kaslr-seed.

 */

#define DTB_EXTRA_SPACE 0x1000