Mark, On Tue, Oct 09, 2018 at 04:28:00PM +0100, Mark Rutland wrote: > On Fri, Sep 28, 2018 at 03:48:36PM +0900, AKASHI Takahiro wrote: > > 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> > > Reviewed-by: James Morse <james.morse@xxxxxxx> > > --- > > arch/arm64/include/asm/kexec.h | 28 +++++++ > > arch/arm64/kernel/Makefile | 2 +- > > arch/arm64/kernel/kexec_image.c | 108 +++++++++++++++++++++++++ > > arch/arm64/kernel/machine_kexec_file.c | 1 + > > 4 files changed, 138 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 157b2897d911..5e673481b3a3 100644 > > --- a/arch/arm64/include/asm/kexec.h > > +++ b/arch/arm64/include/asm/kexec.h > > @@ -101,6 +101,34 @@ struct kimage_arch { > > unsigned long dtb_mem; > > }; > > > > +/** > > + * struct arm64_image_header - arm64 kernel image header > > + * See Documentation/arm64/booting.txt for details > > + * > > + * @mz_magic: DOS header magic number ('MZ', optional) > > Please just call this code0. If CONFIG_EFI is disabled, it is not 'MZ'. How about this? (This definition will go into a new header, asm/image.h.) ---8<--- /* * struct arm64_image_header - arm64 kernel image header * See Documentation/arm64/booting.txt for details * * @code0: Executable code, or * @mz_header alternatively used for part of MZ header * @code1: Executable code * @text_offset: Image load offset * @image_size: Effective Image size * @flags: kernel flags * @reserved: reserved * @magic: Magic number * @reserved5: reserved, or * @pe_header: alternatively used for PE COFF offset */ struct arm64_image_header { union { __le32 code0; struct { __le16 magic; __le16 pad; } mz_header; }; __le32 code1; __le64 text_offset; __le64 image_size; __le64 flags; __le64 reserved[3]; __le32 magic; union { __le32 reserved5; __le32 pe_header; }; }; --->8--- > > + * @code1: Instruction (branch to stext) > > + * @text_offset: Image load offset > > + * @image_size: Effective image size > > + * @flags: Bit-field flags > > + * @reserved: Reserved > > + * @magic: Magic number > > + * @pe_header: Offset to PE COFF header (optional) > > + **/ > > + > > +struct arm64_image_header { > > + __le16 mz_magic; /* also code0 */ > > + __le16 pad; > > Likewise, just have __le32 code0 here, please. > > > + __le32 code1; > > + __le64 text_offset; > > + __le64 image_size; > > + __le64 flags; > > + __le64 reserved[3]; > > + __le32 magic; > > + __le32 pe_header; > > +}; > > + > > +extern const struct kexec_file_ops kexec_image_ops; > > + > > struct kimage; > > > > extern int arch_kimage_file_post_load_cleanup(struct kimage *image); > > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > > index 030a39bff117..48868255f09c 100644 > > --- a/arch/arm64/kernel/Makefile > > +++ b/arch/arm64/kernel/Makefile > > @@ -51,7 +51,7 @@ 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..d64f5e9f9d22 > > --- /dev/null > > +++ b/arch/arm64/kernel/kexec_image.c > > @@ -0,0 +1,108 @@ > > +// 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 <linux/string.h> > > +#include <asm/boot.h> > > +#include <asm/byteorder.h> > > +#include <asm/cpufeature.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 (!h || (kernel_len < sizeof(*h)) || > > + memcmp(&h->magic, ARM64_MAGIC, sizeof(h->magic))) > > + 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 arm64_image_header *h; > > + u64 flags, value; > > + struct kexec_buf kbuf; > > + unsigned long text_offset; > > + struct kexec_segment *kernel_segment; > > + int ret; > > + > > + /* Don't support old kernel */ > > + h = (struct arm64_image_header *)kernel; > > + if (!h->text_offset) > > + return ERR_PTR(-EINVAL); > > It's entirely valid for TEXT_OFFSET to be zero when > RANDOMIZE_TEXT_OFFSET is selected. > > I think you meant to check image_size here. Right, it's been a bug since the first appearance in v10. > We could do with a better comment, too, e.g. > > /* > * We require a kernel with an unambiguous Image header. Per > * Documentation/booting.txt, this is the case when image_size > * is non-zero (practically speaking, since v3.17). > */ > if (!h->image_size) > return ERR_PTR(-EINVAL); > > > + > > + /* Check cpu features */ > > + flags = le64_to_cpu(h->flags); > > + value = head_flag_field(flags, HEAD_FLAG_BE); > > + if (((value == HEAD_FLAG_BE) && !IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) || > > + ((value != HEAD_FLAG_BE) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))) > > + if (!system_supports_mixed_endian()) > > + return ERR_PTR(-EINVAL); > > I think this can be simplified: > > bool be_image = head_flag_field(flags, HEAD_FLAG_BE); > bool be_kernel = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN); > > if ((be_image != be_kernel) && !system_supports_mixed_endian) > return ERR_PTR(-EINVAL); Okay. > ... though do we need to police this at all? It's arguably policy given > the new image has to be signed anyway), and there are other fields that > could fall into that category in future. The aim here is to prevent any images from being loaded when there is no question that a new image will never be successfully kexec'ed since the core on a given SoC obviously doesn't support cpu features that are assumed and required by a image. I believe that this check is a good and easy practice to avoid possible failures before execution. > > + > > + value = head_flag_field(flags, HEAD_FLAG_PAGE_SIZE); > > + if (((value == HEAD_FLAG_PAGE_SIZE_4K) && > > + !system_supports_4kb_granule()) || > > + ((value == HEAD_FLAG_PAGE_SIZE_64K) && > > + !system_supports_64kb_granule()) || > > + ((value == HEAD_FLAG_PAGE_SIZE_16K) && > > + !system_supports_16kb_granule())) > > + return ERR_PTR(-EINVAL); > > ... likewise here? > > > + > > + /* 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.mem = 0; > > + kbuf.memsz = le64_to_cpu(h->image_size); > > + text_offset = le64_to_cpu(h->text_offset); > > + kbuf.buf_align = MIN_KIMG_ALIGN; > > + > > + /* Adjust kernel segment with TEXT_OFFSET */ > > + kbuf.memsz += text_offset; > > It's very surprising at first glance to add text_offset here, then undo > that below. This should have a better comment explaining what we're > doing. To respect TEXT_OFFSET particularly for older kernels. Will add some comments here. > > + > > + ret = kexec_add_buffer(&kbuf); > > + if (ret) > > + return ERR_PTR(ret); > > + > > + kernel_segment = &image->segment[image->nr_segments - 1]; > > I'm confused here. When/how can the image have muliple segments? kexec_add_buffer() allocates one contiguous region, and so nr_segments should be 1. But I think using nr_segments is resilient if some buffer may be added before this line. (Historically, in my old patches, a buffer for elfcoreheader was added before a kernel segument was added to image->segment[].) > > + kernel_segment->mem += text_offset; > > + kernel_segment->memsz -= text_offset; > > + image->start = kernel_segment->mem; > > As above, I don't like the fact that we're altering the result of > kexec_add_buffer here. It feels fragile, even if it works today. > > Can we teach the core kexec buffer code that we need an offset from an > aligned base? Adding another parameter to kexec_add_buffer() would be simple to do, but I doubt that there is any difference since how to fill an allocated segment with some data is totally up to the caller (arch-specific). (That said, let me think twice.) Thanks, -Takahiro Akashi > Thanks, > Mark. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
