This patch provides kexec_file_ops for "Image"-format kernel. In this
implementation, a binary is always loaded with a fixed offset identified
in text_offset field of its header.
Regarding signature verification for trusted boot, this patch doesn't
contains CONFIG_KEXEC_VERIFY_SIG support, which is to be added later
in this series, but file-attribute-based verification is still a viable
option by enabling IMA security subsystem.
You can sign(label) a to-be-kexec'ed kernel image on target file system
with:
$ evmctl ima_sign --key /path/to/private_key.pem Image
On live system, you must have IMA enforced with, at least, the following
security policy:
"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig"
See more details about IMA here:
https://sourceforge.net/p/linux-ima/wiki/Home/
Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm64/include/asm/kexec.h | 50 ++++++++++++++++
arch/arm64/kernel/Makefile | 2 +-
arch/arm64/kernel/kexec_image.c | 79 ++++++++++++++++++++++++++
arch/arm64/kernel/machine_kexec_file.c | 1 +
4 files changed, 131 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/kernel/kexec_image.c
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index e4de1223715f..3cba4161818a 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -102,6 +102,56 @@ struct kimage_arch {
void *dtb_buf;
};
+/**
+ * struct arm64_image_header - arm64 kernel image header
+ *
+ * @pe_sig: Optional PE format 'MZ' signature
+ * @branch_code: Instruction to branch to stext
+ * @text_offset: Image load offset, little endian
+ * @image_size: Effective image size, little endian
+ * @flags:
+ * Bit 0: Kernel endianness. 0=little endian, 1=big endian
+ * @reserved: Reserved
+ * @magic: Magic number, "ARM\x64"
+ * @pe_header: Optional offset to a PE format header
+ **/
+
+struct arm64_image_header {
+ u8 pe_sig[2];
+ u8 pad[2];
+ u32 branch_code;
+ u64 text_offset;
+ u64 image_size;
+ u64 flags;
+ u64 reserved[3];
+ u8 magic[4];
+ u32 pe_header;
+};
+
+static const u8 arm64_image_magic[4] = {'A', 'R', 'M', 0x64U};
+
+/**
+ * arm64_header_check_magic - Helper to check the arm64 image header.
+ *
+ * Returns non-zero if header is OK.
+ */
+
+static inline int arm64_header_check_magic(const struct arm64_image_header *h)
+{
+ if (!h)
+ return 0;
+
+ if (!h->text_offset)
+ return 0;
+
+ return (h->magic[0] == arm64_image_magic[0]
+ && h->magic[1] == arm64_image_magic[1]
+ && h->magic[2] == arm64_image_magic[2]
+ && h->magic[3] == arm64_image_magic[3]);
+}
+
+extern const struct kexec_file_ops kexec_image_ops;
+
struct kimage;
extern int load_other_segments(struct kimage *image,
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 2f2b2757ae7a..1e110aa571dd 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -50,7 +50,7 @@ arm64-obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
arm64-obj-$(CONFIG_HIBERNATION) += hibernate.o hibernate-asm.o
arm64-obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o \
cpu-reset.o
-arm64-obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o
+arm64-obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o kexec_image.o
arm64-obj-$(CONFIG_ARM64_RELOC_TEST) += arm64-reloc-test.o
arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o
arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
new file mode 100644
index 000000000000..4dd524ad6611
--- /dev/null
+++ b/arch/arm64/kernel/kexec_image.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kexec image loader
+
+ * Copyright (C) 2018 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
+ */
+
+#define pr_fmt(fmt) "kexec_file(Image): " fmt
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <asm/byteorder.h>
+#include <asm/memory.h>
+
+static int image_probe(const char *kernel_buf, unsigned long kernel_len)
+{
+ const struct arm64_image_header *h;
+
+ h = (const struct arm64_image_header *)(kernel_buf);
+
+ if ((kernel_len < sizeof(*h)) || !arm64_header_check_magic(h))
+ return -EINVAL;
+
+ return 0;
+}
+
+static void *image_load(struct kimage *image,
+ char *kernel, unsigned long kernel_len,
+ char *initrd, unsigned long initrd_len,
+ char *cmdline, unsigned long cmdline_len)
+{
+ struct kexec_buf kbuf;
+ struct arm64_image_header *h = (struct arm64_image_header *)kernel;
+ unsigned long text_offset;
+ int ret;
+
+ /* Load the kernel */
+ kbuf.image = image;
+ kbuf.buf_min = 0;
+ kbuf.buf_max = ULONG_MAX;
+ kbuf.top_down = false;
+
+ kbuf.buffer = kernel;
+ kbuf.bufsz = kernel_len;
+ kbuf.memsz = le64_to_cpu(h->image_size);
+ text_offset = le64_to_cpu(h->text_offset);
+ kbuf.buf_align = SZ_2M;
+
+ /* Adjust kernel segment with TEXT_OFFSET */
+ kbuf.memsz += text_offset;
+
+ ret = kexec_add_buffer(&kbuf);
+ if (ret)
+ goto out;
+
+ image->arch.kern_segment = image->nr_segments - 1;
+ image->segment[image->arch.kern_segment].mem += text_offset;
+ image->segment[image->arch.kern_segment].memsz -= text_offset;
+ image->start = image->segment[image->arch.kern_segment].mem;
+
+ pr_debug("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+ image->segment[image->arch.kern_segment].mem,
+ kbuf.bufsz, kbuf.memsz);
+
+ /* Load additional data */
+ ret = load_other_segments(image, initrd, initrd_len,
+ cmdline, cmdline_len);
+
+out:
+ return ERR_PTR(ret);
+}
+
+const struct kexec_file_ops kexec_image_ops = {
+ .probe = image_probe,
+ .load = image_load,
+};
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index b3b9b1725d8a..37c0a9dc2e47 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -23,6 +23,7 @@ static int __dt_root_addr_cells;
static int __dt_root_size_cells;
const struct kexec_file_ops * const kexec_file_loaders[] = {
+ &kexec_image_ops,
NULL
};
--
2.17.0
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