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    Subject[PATCH 13/14] 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 basically determined from
    the header of the image.

    Regarding kernel verification, it will be done through
    verify_pefile_signature() as arm64's "Image" binary can be seen as
    in PE format. This approach is consistent with x86 implementation.

    we can sign it with sbsign command.

    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 | 11 ++--
    arch/arm64/include/asm/kexec_file.h | 83 ++++++++++++++++++++++++
    arch/arm64/kernel/Makefile | 1 +
    arch/arm64/kernel/kexec_image.c | 112 +++++++++++++++++++++++++++++++++
    arch/arm64/kernel/machine_kexec_file.c | 6 +-
    5 files changed, 208 insertions(+), 5 deletions(-)
    create mode 100644 arch/arm64/include/asm/kexec_file.h
    create mode 100644 arch/arm64/kernel/kexec_image.c

    diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
    index cf10bc720d9e..c8f603700bdd 100644
    --- a/arch/arm64/Kconfig
    +++ b/arch/arm64/Kconfig
    @@ -766,18 +766,21 @@ config KEXEC_FILE
    for kernel and initramfs as opposed to list of segments as
    accepted by previous system call.

    +config KEXEC_FILE_IMAGE_FMT
    + bool "Enable Image support"
    + depends on KEXEC_FILE
    + ---help---
    + Select this option to enable 'Image' kernel loading.
    +
    config KEXEC_VERIFY_SIG
    bool "Verify kernel signature during kexec_file_load() syscall"
    depends on KEXEC_FILE
    select SYSTEM_DATA_VERIFICATION
    + select SIGNED_PE_FILE_VERIFICATION if KEXEC_FILE_IMAGE_FMT
    ---help---
    This option makes kernel signature verification mandatory for
    the kexec_file_load() syscall.

    - In addition to that option, you need to enable signature
    - verification for the corresponding kernel image type being
    - loaded in order for this to work.
    -
    config CRASH_DUMP
    bool "Build kdump crash kernel"
    help
    diff --git a/arch/arm64/include/asm/kexec_file.h b/arch/arm64/include/asm/kexec_file.h
    new file mode 100644
    index 000000000000..5df899aa0d2e
    --- /dev/null
    +++ b/arch/arm64/include/asm/kexec_file.h
    @@ -0,0 +1,83 @@
    +#ifndef _ASM_KEXEC_FILE_H
    +#define _ASM_KEXEC_FILE_H
    +
    +extern struct kexec_file_ops kexec_image_ops;
    +
    +/**
    + * struct arm64_image_header - arm64 kernel image header.
    + *
    + * @pe_sig: Optional PE format 'MZ' signature.
    + * @branch_code: Reserved for instructions to branch to stext.
    + * @text_offset: The image load offset in LSB byte order.
    + * @image_size: An estimated size of the memory image size in LSB byte order.
    + * @flags: Bit flags:
    + * Bit 7.0: Image byte order, 1=MSB.
    + * @reserved_1: Reserved.
    + * @magic: Magic number, "ARM\x64".
    + * @pe_header: Optional offset to a PE format header.
    + **/
    +
    +struct arm64_image_header {
    + u8 pe_sig[2];
    + u16 branch_code[3];
    + u64 text_offset;
    + u64 image_size;
    + u8 flags[8];
    + u64 reserved_1[3];
    + u8 magic[4];
    + u32 pe_header;
    +};
    +
    +static const u8 arm64_image_magic[4] = {'A', 'R', 'M', 0x64U};
    +static const u8 arm64_image_pe_sig[2] = {'M', 'Z'};
    +static const u64 arm64_image_flag_7_be = 0x01U;
    +
    +/**
    + * 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]);
    +}
    +
    +/**
    + * arm64_header_check_pe_sig - Helper to check the arm64 image header.
    + *
    + * Returns non-zero if 'MZ' signature is found.
    + */
    +
    +static inline int arm64_header_check_pe_sig(const struct arm64_image_header *h)
    +{
    + if (!h)
    + return 0;
    +
    + return (h->pe_sig[0] == arm64_image_pe_sig[0]
    + && h->pe_sig[1] == arm64_image_pe_sig[1]);
    +}
    +
    +/**
    + * arm64_header_check_msb - Helper to check the arm64 image header.
    + *
    + * Returns non-zero if the image was built as big endian.
    + */
    +
    +static inline int arm64_header_check_msb(const struct arm64_image_header *h)
    +{
    + if (!h)
    + return 0;
    +
    + return !!(h->flags[7] & arm64_image_flag_7_be);
    +}
    +#endif /* _ASM_KEXE_FILE_H */
    diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
    index 5df003d6157c..a1161bab6810 100644
    --- a/arch/arm64/kernel/Makefile
    +++ b/arch/arm64/kernel/Makefile
    @@ -51,6 +51,7 @@ 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..db4aa1379fec
    --- /dev/null
    +++ b/arch/arm64/kernel/kexec_image.c
    @@ -0,0 +1,112 @@
    +/*
    + * Kexec image loader
    +
    + * Copyright (C) 2017 Linaro Limited
    + * Authors: 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 <linux/verification.h>
    +#include <asm/byteorder.h>
    +#include <asm/kexec_file.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;
    +
    + pr_debug("%s: PE format: %s\n", __func__,
    + (arm64_header_check_pe_sig(h) ? "yes" : "no"));
    +
    + 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;
    + if (h->image_size) {
    + kbuf.memsz = le64_to_cpu(h->image_size);
    + text_offset = le64_to_cpu(h->text_offset);
    + } else {
    + /* v3.16 or older */
    + kbuf.memsz = kbuf.bufsz; /* NOTE: not including BSS */
    + text_offset = 0x80000;
    + }
    + 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);
    +}
    +
    +#ifdef CONFIG_KEXEC_VERIFY_SIG
    +static int image_verify_sig(const char *kernel, unsigned long kernel_len)
    +{
    + return verify_pefile_signature(kernel, kernel_len, NULL,
    + VERIFYING_KEXEC_PE_SIGNATURE);
    +}
    +#endif
    +
    +struct kexec_file_ops kexec_image_ops = {
    + .probe = image_probe,
    + .load = image_load,
    +#ifdef CONFIG_KEXEC_VERIFY_SIG
    + .verify_sig = image_verify_sig,
    +#endif
    +};
    diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
    index 012063307001..ab3b19d51727 100644
    --- a/arch/arm64/kernel/machine_kexec_file.c
    +++ b/arch/arm64/kernel/machine_kexec_file.c
    @@ -27,7 +27,11 @@
    static int __dt_root_addr_cells;
    static int __dt_root_size_cells;

    -static struct kexec_file_ops *kexec_file_loaders[0];
    +static struct kexec_file_ops *kexec_file_loaders[] = {
    +#ifdef CONFIG_KEXEC_FILE_IMAGE_FMT
    + &kexec_image_ops,
    +#endif
    +};

    int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
    unsigned long buf_len)
    --
    2.14.1
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