From 884143f60c89acf8f2d06de4113d5e3057791701 Mon Sep 17 00:00:00 2001
From: AKASHI Takahiro <takahiro.akashi@linaro.org>
Date: Thu, 15 Nov 2018 14:52:55 +0900
Subject: [PATCH] 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: AKASHI 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: Will Deacon <will.deacon@arm.com>
---
arch/arm64/kernel/machine_kexec_file.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 7e9d5ed3e238f..0972c6d2c5bb0 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -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
--
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