This patch provides kexec_file_ops for "Image"-format kernel. Please note
that a binary is always loaded at an offset based on its text_offset field.

While this patch doesn't contains CONFIG_KEXEC_VERIFY_SIG support,
that is to be added in a later patch in this series, file-attribute-based
kernel verification can now be materialised 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 on target filesystem to be kexec-ed
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.aka...@linaro.org>
Cc: Catalin Marinas <catalin.mari...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
---
 arch/arm64/include/asm/kexec.h         | 50 +++++++++++++++++++
 arch/arm64/kernel/Makefile             |  2 +-
 arch/arm64/kernel/kexec_image.c        | 90 ++++++++++++++++++++++++++++++++++
 arch/arm64/kernel/machine_kexec_file.c |  1 +
 4 files changed, 142 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 d7427d510e1b..592890085aae 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -105,6 +105,56 @@ 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 151dc890737c..454b2735603a 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -49,7 +49,7 @@ 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..de62def63dd6
--- /dev/null
+++ b/arch/arm64/kernel/kexec_image.c
@@ -0,0 +1,90 @@
+/*
+ * Kexec image loader
+
+ * Copyright (C) 2018 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.aka...@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;
+       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;
+       image->start = kbuf.mem + text_offset;
+
+       pr_debug("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+                image->start, kbuf.bufsz, kbuf.memsz);
+
+       /* Load additional data */
+       ret = load_other_segments(image, image->start,
+                           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 fc132047c8cd..384146583f8d 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -25,6 +25,7 @@ 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
 };
 
-- 
2.16.2

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