[PATCH v8 10/13] arm64: kexec_file: add Image format support
AKASHI Takahiro
takahiro.akashi at linaro.org
Thu Feb 22 03:17:29 PST 2018
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.akashi at linaro.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will.deacon at 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.akashi at 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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