linux-kernel - [PATCH v12 16/16] arm64: kexec

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Message-Id: <20180724065759.19186-17-takahiro.akashi@linaro.org>
Date:   Tue, 24 Jul 2018 15:57:59 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     catalin.marinas@....com, will.deacon@....com, dhowells@...hat.com,
        vgoyal@...hat.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, dyoung@...hat.com, bhe@...hat.com,
        arnd@...db.de, schwidefsky@...ibm.com, heiko.carstens@...ibm.com
Cc:     ard.biesheuvel@...aro.org, james.morse@....com,
        bhsharma@...hat.com, kexec@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        AKASHI Takahiro <takahiro.akashi@...aro.org>
Subject: [PATCH v12 16/16] 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@...aro.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
---
 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