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[PATCH v3 00/10] arm64: kexec: add kexec_file_load() support

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  [PATCH v3 00/10] arm64: kexec: add kexec_file_load() support AKASHI Takahiro <takahiro.akashi@linaro.org> - 2017-09-15 13:00 +0200
    [PATCH v3 06/10] arm64: kexec_file: create purgatory AKASHI Takahiro <takahiro.akashi@linaro.org> - 2017-09-15 13:00 +0200
    [PATCH v3 01/10] include: pe.h: remove message[] from mz header definition AKASHI Takahiro <takahiro.akashi@linaro.org> - 2017-09-15 13:00 +0200
    [PATCH v3 09/10] arm64: enable KEXEC_FILE config AKASHI Takahiro <takahiro.akashi@linaro.org> - 2017-09-15 13:00 +0200

#1732824 — [PATCH v3 00/10] arm64: kexec: add kexec_file_load() support

This is the third round of implementing kexec_file_load() support
on arm64.[1]
Most of the code is based on kexec-tools (along with some kernel code
from x86, which also came from kexec-tools).


This patch series enables us to
  * load the kernel, Image, with kexec_file_load system call, and
  * optionally verify its signature at load time for trusted boot.

To load the kernel via kexec_file_load system call, a small change
is also needed to kexec-tools. See [2]. This enables '-s' option.

As we discussed a long time ago, users may not be allowed to specify
device-tree file of the 2nd kernel explicitly with kexec-tools, hence
re-using the blob of the first kernel.

Regarding a signing method, we conform with x86 (or rather Microsoft?)
style of signing since the binary can also be seen as in PE format
(assuming that CONFIG_EFI is enabled).

    Powerpc is also going to support extended-file-attribute-based
    verification[3] with vmlinux, but arm64 doesn't for now partly
    because we don't have TPM-based IMA at this moment.

Accordingly, we can use the existing command, sbsign, to sign the kernel.

    $ sbsign --key ${KEY} --cert ${CERT} Image

Please note that it is totally up to the system what key/certificate is
used for signing, but one of easy ways to *try* this feature is to turn on
CONFIG_MODULE_SIG so that we can reuse certs/signing_key.pem as a signing
key, KEY and CERT above, for kernel.
(This also enables CONFIG_CRYPTO_SHA1 by default.)


Some concerns(or future works):
* Even if the kernel is configured with CONFIG_RANDOMIZE_BASE, the 2nd
  kernel won't be placed at a randomized address. We will have to
  add some boot code similar to efi-stub to implement the feature.
* While big-endian kernel can support kernel signing, I'm not sure that
  Image can be recognized as in PE format because x86 standard only
  defines little-endian-based format.
* IMA(and extended file attribute)-based kexec
* vmlinux support

  [1] http://git.linaro.org/people/takahiro.akashi/linux-aarch64.git
	branch:arm64/kexec_file
  [2] http://git.linaro.org/people/takahiro.akashi/kexec-tools.git
	branch:arm64/kexec_file
  [3] http://lkml.iu.edu//hypermail/linux/kernel/1707.0/03669.html


Changes in v3 (Sep 15, 2017)
* fix kbuild test error
* factor out arch_kexec_kernel_*() & arch_kimage_file_post_load_cleanup()
* remove CONFIG_CRASH_CORE guard from kexec_file.c
* add vmapped kernel region to vmcore for gdb backtracing
  (see prepare_elf64_headers())
* merge asm/kexec_file.h into asm/kexec.h
* and some cleanups

Changes in v2 (Sep 8, 2017)
* move core-header-related functions from crash_core.c to kexec_file.c
* drop hash-check code from purgatory
* modify purgatory asm to remove arch_kexec_apply_relocations_add()
* drop older kernel support
* drop vmlinux support (at least, for this series)

Patch #1 to #5 are all preparatory patches on generic side.
Patch #6 is purgatory code.
Patch #7 to #9 are common for enabling kexec_file_load.
Patch #10 is for 'Image' support.

AKASHI Takahiro (10):
  include: pe.h: remove message[] from mz header definition
  resource: add walk_system_ram_res_rev()
  kexec_file: factor out arch_kexec_kernel_*() from x86, powerpc
  kexec_file: factor out crashdump elf header function from x86
  asm-generic: add kexec_file_load system call to unistd.h
  arm64: kexec_file: create purgatory
  arm64: kexec_file: load initrd, device-tree and purgatory segments
  arm64: kexec_file: set up for crash dump adding elf core header
  arm64: enable KEXEC_FILE config
  arm64: kexec_file: add Image format support

 arch/arm64/Kconfig                          |  29 +++
 arch/arm64/Makefile                         |   1 +
 arch/arm64/include/asm/kexec.h              |  93 +++++++
 arch/arm64/kernel/Makefile                  |   4 +-
 arch/arm64/kernel/kexec_image.c             | 105 ++++++++
 arch/arm64/kernel/machine_kexec_file.c      | 365 ++++++++++++++++++++++++++++
 arch/arm64/purgatory/Makefile               |  24 ++
 arch/arm64/purgatory/entry.S                |  55 +++++
 arch/powerpc/include/asm/kexec.h            |   4 +
 arch/powerpc/kernel/machine_kexec_file_64.c |  36 +--
 arch/x86/kernel/crash.c                     | 324 ------------------------
 arch/x86/kernel/machine_kexec_64.c          |  59 +----
 include/linux/ioport.h                      |   3 +
 include/linux/kexec.h                       |  43 +++-
 include/linux/pe.h                          |   2 +-
 include/uapi/asm-generic/unistd.h           |   4 +-
 kernel/kexec_file.c                         | 360 ++++++++++++++++++++++++++-
 kernel/kexec_internal.h                     |  20 ++
 kernel/resource.c                           |  59 +++++
 19 files changed, 1156 insertions(+), 434 deletions(-)
 create mode 100644 arch/arm64/kernel/kexec_image.c
 create mode 100644 arch/arm64/kernel/machine_kexec_file.c
 create mode 100644 arch/arm64/purgatory/Makefile
 create mode 100644 arch/arm64/purgatory/entry.S

-- 
2.14.1

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#1732825 — [PATCH v3 06/10] arm64: kexec_file: create purgatory

This is a basic purgatory, or a kind of glue code between the two kernels,
for arm64.

Since purgatory is assumed to be relocatable (not executable) object by
kexec generic code, arch_kexec_apply_relocations_add() is required in
general. Arm64's purgatory, however, is a simple asm and all the references
can be resolved as local, no re-linking is needed here.

Please note that even if we don't support digest check at purgatory we
need purgatory_sha_regions and purgatory_sha256_digest as they are
referenced by generic kexec code.

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/Makefile           |  1 +
 arch/arm64/purgatory/Makefile | 24 +++++++++++++++++++
 arch/arm64/purgatory/entry.S  | 55 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+)
 create mode 100644 arch/arm64/purgatory/Makefile
 create mode 100644 arch/arm64/purgatory/entry.S

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 9b41f1e3b1a0..429f60728c0a 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -105,6 +105,7 @@ core-$(CONFIG_XEN) += arch/arm64/xen/
 core-$(CONFIG_CRYPTO) += arch/arm64/crypto/
 libs-y		:= arch/arm64/lib/ $(libs-y)
 core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
+core-$(CONFIG_KEXEC_FILE) += arch/arm64/purgatory/
 
 # Default target when executing plain make
 boot		:= arch/arm64/boot
diff --git a/arch/arm64/purgatory/Makefile b/arch/arm64/purgatory/Makefile
new file mode 100644
index 000000000000..c2127a2cbd51
--- /dev/null
+++ b/arch/arm64/purgatory/Makefile
@@ -0,0 +1,24 @@
+OBJECT_FILES_NON_STANDARD := y
+
+purgatory-y := entry.o
+
+targets += $(purgatory-y)
+PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
+
+LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined \
+					-nostdlib -z nodefaultlib
+targets += purgatory.ro
+
+$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
+		$(call if_changed,ld)
+
+targets += kexec_purgatory.c
+
+CMD_BIN2C = $(objtree)/scripts/basic/bin2c
+quiet_cmd_bin2c = BIN2C $@
+	cmd_bin2c = $(CMD_BIN2C) kexec_purgatory < $< > $@
+
+$(obj)/kexec_purgatory.c: $(obj)/purgatory.ro FORCE
+	$(call if_changed,bin2c)
+
+obj-${CONFIG_KEXEC_FILE}	+= kexec_purgatory.o
diff --git a/arch/arm64/purgatory/entry.S b/arch/arm64/purgatory/entry.S
new file mode 100644
index 000000000000..fe6e968076db
--- /dev/null
+++ b/arch/arm64/purgatory/entry.S
@@ -0,0 +1,55 @@
+/*
+ * kexec core purgatory
+ */
+#include <linux/linkage.h>
+#include <uapi/linux/kexec.h>
+
+#define SHA256_DIGEST_SIZE	32 /* defined in crypto/sha.h */
+
+.text
+
+ENTRY(purgatory_start)
+	/* Start new image. */
+	ldr	x17, __kernel_entry
+	ldr	x0, __dtb_addr
+	mov	x1, xzr
+	mov	x2, xzr
+	mov	x3, xzr
+	br	x17
+END(purgatory_start)
+
+/*
+ * data section:
+ * kernel_entry and dtb_addr are global but also labelled as local,
+ * "__xxx:", to avoid unwanted re-linking.
+ *
+ * purgatory_sha_regions and purgatory_sha256_digest are referenced
+ * by kexec generic code and so must exist, but not actually used
+ * here because hash check is not that useful in purgatory.
+ */
+.align 3
+
+.globl kernel_entry
+kernel_entry:
+__kernel_entry:
+	.quad	0
+END(kernel_entry)
+
+.globl dtb_addr
+dtb_addr:
+__dtb_addr:
+	.quad	0
+END(dtb_addr)
+
+.globl purgatory_sha_regions
+purgatory_sha_regions:
+	.rept	KEXEC_SEGMENT_MAX
+	.quad	0
+	.quad	0
+	.endr
+END(purgatory_sha_regions)
+
+.globl purgatory_sha256_digest
+purgatory_sha256_digest:
+        .skip   SHA256_DIGEST_SIZE
+END(purgatory_sha256_digest)
-- 
2.14.1

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#1732826 — [PATCH v3 01/10] include: pe.h: remove message[] from mz header definition

message[] field won't be part of the definition of mz header.

This change is crucial for enabling kexec_file_load on arm64 because
arm64's "Image" binary, as in PE format, doesn't have any data for it and
accordingly the following check in pefile_parse_binary() will fail:

	chkaddr(cursor, mz->peaddr, sizeof(*pe));

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
---
 include/linux/pe.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/pe.h b/include/linux/pe.h
index 143ce75be5f0..3482b18a48b5 100644
--- a/include/linux/pe.h
+++ b/include/linux/pe.h
@@ -166,7 +166,7 @@ struct mz_hdr {
 	uint16_t oem_info;	/* oem specific */
 	uint16_t reserved1[10];	/* reserved */
 	uint32_t peaddr;	/* address of pe header */
-	char     message[64];	/* message to print */
+	char     message[];	/* message to print */
 };
 
 struct mz_reloc {
-- 
2.14.1

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#1732827 — [PATCH v3 09/10] arm64: enable KEXEC_FILE config

Modify arm64/Kconfig and Makefile to enable kexec_file_load support.

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 | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index dfd908630631..fa7299f08cc6 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -756,6 +756,28 @@ config KEXEC
 	  but it is independent of the system firmware.   And like a reboot
 	  you can start any kernel with it, not just Linux.
 
+config KEXEC_FILE
+	bool "kexec file based system call"
+	select KEXEC_CORE
+	select BUILD_BIN2C
+	---help---
+	  This is new version of kexec system call. This system call is
+	  file based and takes file descriptors as system call argument
+	  for kernel and initramfs as opposed to list of segments as
+	  accepted by previous system call.
+
+	  In addition to this option, you need to enable a specific type
+	  of image support.
+
+config KEXEC_VERIFY_SIG
+	bool "Verify kernel signature during kexec_file_load() syscall"
+	depends on KEXEC_FILE
+	select SYSTEM_DATA_VERIFICATION
+	---help---
+	  Select this option to verify a signature with loaded kernel
+	  image. If configured, any attempt of loading a image without
+	  valid signature will fail.
+
 config CRASH_DUMP
 	bool "Build kdump crash kernel"
 	help
-- 
2.14.1

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