[PATCH v12 16/16] arm64: kexec_file: add kaslr support

[AKASHI Takahiro]

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@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
 arch/arm64/kernel/machine_kexec_file.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 7356da5a53d5..47a4fbd0dc34 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/slab.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>
@@ -46,6 +47,7 @@ static int setup_dtb(struct kimage *image,
 	void *buf = NULL;
 	size_t buf_size, range_size;
 	int nodeoffset;
+	u64 value;
 	int ret;
 
 	/* check ranges against root's #address-cells and #size-cells */
@@ -158,6 +160,12 @@ static int setup_dtb(struct kimage *image,
 		}
 	}
 
+	/* add kaslr-seed */
+	get_random_bytes(&value, sizeof(value));
+	ret = fdt_setprop(buf, nodeoffset, "kaslr-seed", &value, sizeof(value));
+	if (ret)
+		goto out_err;
+
 	/* trim a buffer */
 	fdt_pack(buf);
 	*dtb_buf = buf;
-- 
2.18.0