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Subject[PATCH v7 09/11] arm64: kexec_file: add Image format support
Date
The "Image" binary will be loaded at the offset of TEXT_OFFSET from
the start of system memory. TEXT_OFFSET is determined from the header
of the image.

This patch doesn't have CONFIG_KEXEC_VERIFY_SIG support. Nevertherless
kernel verification will be supported by enabling IMA security subsystem.
See more details about IMA here:
https://sourceforge.net/p/linux-ima/wiki/Home/

You can sign(label) a kernel image binary to be kexec-ed on target
filesystem 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"

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
arch/arm64/Kconfig | 7 +++
arch/arm64/include/asm/kexec.h | 50 +++++++++++++++++++
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/kexec_image.c | 90 ++++++++++++++++++++++++++++++++++
arch/arm64/kernel/machine_kexec_file.c | 3 ++
5 files changed, 151 insertions(+)
create mode 100644 arch/arm64/kernel/kexec_image.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 865d110809f9..c0b021736c10 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -807,6 +807,13 @@ config KEXEC_FILE
In addition to this option, you need to enable a specific type
of image support.

+config KEXEC_FILE_IMAGE_FMT
+ bool "Enable Image support"
+ default y
+ depends on KEXEC_FILE
+ ---help---
+ Select this option to enable 'Image' kernel loading.
+
config CRASH_DUMP
bool "Build kdump crash kernel"
help
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index edb702e64a8a..b6469bc64a89 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -104,6 +104,56 @@ struct kimage_arch {
unsigned long elf_load_addr;
};

+/**
+ * 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;

#define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 2cd982b779b9..17906a62d795 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -50,6 +50,7 @@ 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_IMAGE_FMT) += 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..1c106237901d
--- /dev/null
+++ b/arch/arm64/kernel/kexec_image.c
@@ -0,0 +1,90 @@
+/*
+ * Kexec image loader
+
+ * Copyright (C) 2017 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#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, kernel_load_addr;
+ int ret;
+
+ /* Create elf core header segment */
+ ret = load_crashdump_segments(image);
+ if (ret)
+ goto out;
+
+ /* Load the kernel */
+ kbuf.image = image;
+ if (image->type == KEXEC_TYPE_CRASH) {
+ kbuf.buf_min = crashk_res.start;
+ kbuf.buf_max = crashk_res.end + 1;
+ } else {
+ kbuf.buf_min = 0;
+ kbuf.buf_max = ULONG_MAX;
+ }
+ kbuf.top_down = 0;
+
+ 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->segment[image->nr_segments - 1].mem += text_offset;
+ image->segment[image->nr_segments - 1].memsz -= text_offset;
+ kernel_load_addr = kbuf.mem + text_offset;
+
+ pr_debug("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+ kernel_load_addr, kbuf.bufsz, kbuf.memsz);
+
+ /* Load additional data */
+ ret = load_other_segments(image, kernel_load_addr,
+ 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 012b2af4e27b..2b6d9164df8a 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -25,6 +25,9 @@ static int __dt_root_addr_cells;
static int __dt_root_size_cells;

const struct kexec_file_ops * const kexec_file_loaders[] = {
+#ifdef CONFIG_KEXEC_FILE_IMAGE_FMT
+ &kexec_image_ops,
+#endif
NULL
};

--
2.14.1
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