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SubjectRe: [PATCH 5/5] arm: kexec_file: load zImage or uImage, initrd and dtb
Date
It was <2020-06-01 pon 16:07>, when Russell King - ARM Linux admin wrote:
> On Mon, Jun 01, 2020 at 04:27:54PM +0200, Łukasz Stelmach wrote:
>> This is kexec_file_load implementation for ARM. It loads zImage and
>> initrd from file descripters and resuses DTB.
>>
>> Most code is derived from arm64 kexec_file_load implementation
>> and from kexec-tools.
>
> Please make the uImage loader able to be configured out of the
> kernel; it's a legacy image format now, and some of us just don't
> use it anymore. That way, those who wish to have it can, and
> those who wish not to can have a smaller kernel.

The difference in size of arch/arm/boot/Image is 160 bytes, but
OK. Done.

>> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
>> Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
>> ---
>> arch/arm/Kconfig | 15 ++
>> arch/arm/include/asm/image.h | 26 ++++
>> arch/arm/include/asm/kexec.h | 14 ++
>> arch/arm/kernel/Makefile | 5 +-
>> arch/arm/kernel/kexec_uimage.c | 80 ++++++++++
>> arch/arm/kernel/kexec_zimage.c | 199 +++++++++++++++++++++++++
>> arch/arm/kernel/machine_kexec.c | 11 +-
>> arch/arm/kernel/machine_kexec_file.c | 209 +++++++++++++++++++++++++++
>> 8 files changed, 554 insertions(+), 5 deletions(-)
>> create mode 100644 arch/arm/kernel/kexec_uimage.c
>> create mode 100644 arch/arm/kernel/kexec_zimage.c
>> create mode 100644 arch/arm/kernel/machine_kexec_file.c
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index c77c93c485a0..6adb849cb304 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -1917,6 +1917,21 @@ config KEXEC
>> is properly shutdown, so do not be surprised if this code does not
>> initially work for you.
>>
>> +config KEXEC_FILE
>> + bool "Kexec file based system call (EXPERIMENTAL)"
>> + depends on (!SMP || PM_SLEEP_SMP)
>> + depends on USE_OF
>> + select KEXEC_CORE
>> + select CRC32
>> + 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.
>> +
>> + The kernel to be loaded MUST support Flattened Device Tree
>> + (selected with CONFIG_USE_OF).
>> +
>> config ATAGS_PROC
>> bool "Export atags in procfs"
>> depends on ATAGS && KEXEC
>> diff --git a/arch/arm/include/asm/image.h b/arch/arm/include/asm/image.h
>> index 624438740f23..95f23837b04f 100644
>> --- a/arch/arm/include/asm/image.h
>> +++ b/arch/arm/include/asm/image.h
>> @@ -8,8 +8,13 @@
>> (((x) >> 8) & 0x0000ff00) | \
>> (((x) << 8) & 0x00ff0000) | \
>> (((x) << 24) & 0xff000000))
>> +#define UIMAGE_MAGIC(x) (x)
>> #else
>> #define ZIMAGE_MAGIC(x) (x)
>> +#define UIMAGE_MAGIC(x) ((((x) >> 24) & 0x000000ff) | \
>> + (((x) >> 8) & 0x0000ff00) | \
>> + (((x) << 8) & 0x00ff0000) | \
>> + (((x) << 24) & 0xff000000))
>> #endif
>>
>> #define ARM_ZIMAGE_MAGIC1 ZIMAGE_MAGIC(0x016f2818)
>> @@ -17,6 +22,12 @@
>> #define ARM_ZIMAGE_MAGIC3 ZIMAGE_MAGIC(0x5a534c4b)
>> #define ARM_ZIMAGE_MAGIC4 ZIMAGE_MAGIC(0x5a534344)
>>
>> +#define ARM_UIMAGE_MAGIC UIMAGE_MAGIC(0x27051956)
>> +#define ARM_UIMAGE_NAME_LEN 32
>> +#define ARM_UIMAGE_TYPE_KERNEL 2
>> +#define ARM_UIMAGE_TYPE_KERNEL_NOLOAD 14
>> +#define ARM_UIMAGE_ARCH_ARM 2
>> +
>> #ifndef __ASSEMBLY__
>>
>> #include <linux/types.h>
>> @@ -33,6 +44,21 @@ struct arm_zimage_header {
>> __le32 extension_tag_offset;
>> };
>>
>> +struct arm_uimage_header {
>> + __be32 magic;
>> + __be32 hdr_crc;
>> + __be32 time;
>> + __be32 size;
>> + __be32 load;
>> + __be32 entry;
>> + __be32 crc;
>> + __u8 os;
>> + __u8 arch;
>> + __u8 type;
>> + __u8 comp;
>> + __u8 name[ARM_UIMAGE_NAME_LEN];
>> +};
>> +
>> struct arm_zimage_tag {
>> struct tag_header hdr;
>> union {
>> diff --git a/arch/arm/include/asm/kexec.h b/arch/arm/include/asm/kexec.h
>> index 22751b5b5735..fda35afa7195 100644
>> --- a/arch/arm/include/asm/kexec.h
>> +++ b/arch/arm/include/asm/kexec.h
>> @@ -83,6 +83,20 @@ static inline struct page *boot_pfn_to_page(unsigned long boot_pfn)
>> }
>> #define boot_pfn_to_page boot_pfn_to_page
>>
>> +#ifdef CONFIG_KEXEC_FILE
>> +
>> +extern const struct kexec_file_ops kexec_zimage_ops;
>> +extern const struct kexec_file_ops kexec_uimage_ops;
>> +
>> +struct kimage;
>> +
>> +extern int load_other_segments(struct kimage *image,
>> + unsigned long kernel_load_addr, unsigned long kernel_size,
>> + char *initrd, unsigned long initrd_len,
>> + unsigned long initrd_offset, char *cmdline);
>> +
>> +#endif /* CONFIG_KEXEC_FILE */
>> +
>> #endif /* __ASSEMBLY__ */
>>
>> #endif /* CONFIG_KEXEC */
>> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
>> index 89e5d864e923..466c683bb551 100644
>> --- a/arch/arm/kernel/Makefile
>> +++ b/arch/arm/kernel/Makefile
>> @@ -3,6 +3,7 @@
>> # Makefile for the linux kernel.
>> #
>>
>> +CFLAGS_kexec_zimage.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
>> CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET)
>> AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
>>
>> @@ -56,7 +57,9 @@ obj-$(CONFIG_FUNCTION_TRACER) += entry-ftrace.o
>> obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o insn.o patch.o
>> obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o patch.o
>> obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o
>> -obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
>> +obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o
>> +obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o kexec_zimage.o \
>> + kexec_uimage.o
>> # Main staffs in KPROBES are in arch/arm/probes/ .
>> obj-$(CONFIG_KPROBES) += patch.o insn.o
>> obj-$(CONFIG_OABI_COMPAT) += sys_oabi-compat.o
>> diff --git a/arch/arm/kernel/kexec_uimage.c b/arch/arm/kernel/kexec_uimage.c
>> new file mode 100644
>> index 000000000000..47033574e24e
>> --- /dev/null
>> +++ b/arch/arm/kernel/kexec_uimage.c
>> @@ -0,0 +1,80 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Kexec uImage loader
>> + *
>> + * Copyright (C) 2020 Samsung Electronics
>> + * Author: Łukasz Stelmach <l.stelmach@samsung.com>
>> + */
>> +
>> +#define pr_fmt(fmt) "kexec_file(uImage): " fmt
>> +
>> +#include <asm/image.h>
>> +#include <linux/crc32.h>
>> +#include <linux/err.h>
>> +#include <linux/kexec.h>
>> +
>> +#define crc32_ones(crc, buf, len) \
>> + (crc32(crc ^ 0xffffffff, buf, len) ^ 0xffffffff)
>> +
>> +static int uimage_probe(const char *uimage_buf, unsigned long uimage_len)
>> +{
>> + const struct arm_uimage_header *h =
>> + (struct arm_uimage_header *) uimage_buf;
>> + struct arm_uimage_header uhdr;
>> + unsigned long zoff = sizeof(struct arm_uimage_header);
>> + uint32_t crc;
>> +
>> + if (h->magic != ARM_UIMAGE_MAGIC)
>> + return -EINVAL;
>> +
>> + if (h->type != ARM_UIMAGE_TYPE_KERNEL &&
>> + h->type != ARM_UIMAGE_TYPE_KERNEL_NOLOAD){
>> + pr_debug("Invalid image type: %d\n", h->type);
>> + return -EINVAL;
>> + }
>> +
>> + if (h->arch != ARM_UIMAGE_ARCH_ARM) {
>> + pr_debug("Invalidy image arch: %d\n", h->arch);
>> + return -EINVAL;
>> + }
>> +
>> + memcpy((char *)&uhdr, h, sizeof(uhdr));
>> + crc = be32_to_cpu(uhdr.hdr_crc);
>> + uhdr.hdr_crc = 0;
>> +
>> + if (crc32_ones(0, (char *)&uhdr, sizeof(uhdr)) != crc) {
>> + pr_debug("Corrupt header, CRC do not match\n");
>> + return -EINVAL;
>> + }
>> +
>> + crc = be32_to_cpu(uhdr.crc);
>> + if (crc32_ones(0, uimage_buf + zoff, uimage_len - zoff) != crc) {
>> + pr_debug("Corrupt zImage, CRC do not match\n");
>> + return -EINVAL;
>> + }
>> +
>> + return kexec_zimage_ops.probe(uimage_buf + zoff,
>> + uimage_len - zoff);
>> +}
>> +
>> +static void *uimage_load(struct kimage *image,
>> + char *uimage, unsigned long uimage_len,
>> + char *initrd, unsigned long initrd_len,
>> + char *cmdline, unsigned long cmdline_len)
>> +{
>> + const struct arm_uimage_header *h =
>> + (struct arm_uimage_header *) uimage;
>> + unsigned long zimage_offset = sizeof(struct arm_uimage_header);
>> +
>> + pr_debug("Loading uImage");
>> + return kexec_zimage_ops.load(image,
>> + uimage + zimage_offset,
>> + uimage_len - zimage_offset,
>> + initrd, initrd_len,
>> + cmdline, cmdline_len);
>> +}
>> +
>> +const struct kexec_file_ops kexec_uimage_ops = {
>> + .probe = uimage_probe,
>> + .load = uimage_load,
>> +};
>> diff --git a/arch/arm/kernel/kexec_zimage.c b/arch/arm/kernel/kexec_zimage.c
>> new file mode 100644
>> index 000000000000..d09795fc9072
>> --- /dev/null
>> +++ b/arch/arm/kernel/kexec_zimage.c
>> @@ -0,0 +1,199 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Kexec zImage loader
>> + *
>> + * Copyright (C) 2020 Samsung Electronics
>> + * Author: Łukasz Stelmach <l.stelmach@samsung.com>
>
> Please credit me as part author of this - you have taken some of my
> code from the userspace kexec tool (such as the contents of
> find_extension_tag()) and copied it in here, so this is not all your
> own work.

Done.

>> + */
>> +
>> +#define pr_fmt(fmt) "kexec_file(zImage): " fmt
>> +
>> +#include <asm/image.h>
>> +#include <asm/unaligned.h>
>> +#include <linux/err.h>
>> +#include <linux/kexec.h>
>> +#include <linux/memblock.h>
>> +
>> +#define byte_size(t) ((t)->hdr.size << 2)
>> +
>> +static const void *find_extension_tag(const char *buf,
>> + unsigned long len,
>> + uint32_t tag_id)
>> +{
>> + const struct arm_zimage_header *h = (const struct arm_zimage_header *)buf;
>> + const struct arm_zimage_tag *tag;
>> + uint32_t offset, size;
>> + uint32_t max = len - sizeof(struct tag_header);
>> +
>> + if (len < sizeof(*h) ||
>> + h->magic != ARM_ZIMAGE_MAGIC1 ||
>> + h->magic2 != ARM_ZIMAGE_MAGIC2)
>> + return NULL;
>> +
>> + for (offset = h->extension_tag_offset;
>> + (tag = (void *)(buf + offset)) != NULL &&
>> + offset < max &&
>> + (size = le32_to_cpu(byte_size(tag))) != 0 &&
>> + offset + size < len;
>> + offset += size) {
>> + pr_debug(" offset 0x%08x tag 0x%08x size %u\n",
>> + offset, le32_to_cpu(tag->hdr.tag), size);
>> + if (tag->hdr.tag == tag_id)
>> + return tag;
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +static int zimage_probe(const char *kernel_buf, unsigned long kernel_len)
>> +{
>> + const struct arm_zimage_header *h =
>> + (struct arm_zimage_header *)(kernel_buf);
>> +
>> + if (!h || (kernel_len < sizeof(*h)))
>> + return -EINVAL;
>> +
>> + if ((h->magic != ARM_ZIMAGE_MAGIC1) ||
>> + (h->magic2 != ARM_ZIMAGE_MAGIC2))
>> + return -EINVAL;
>> +
>> + return 0;
>> +}
>> +
>> +
>> +#if defined(DEBUG)
>> +#define debug_offsets() ({ \
>> + pr_debug("Image offsets:\n"); \
>> + pr_debug(" kernel 0x%08lx 0x%08lx\n", kernel_offset, kernel_len); \
>> + pr_debug(" zimage 0x%08lx 0x%08lx\n", zimage_offset, zimage_len); \
>> + pr_debug(" initrd 0x%08lx 0x%08lx\n", initrd_offset, initrd_len); \
>> +})
>> +#else
>> +#define debug_offsets()
>> +#endif
>> +
>> +static void *zimage_load(struct kimage *image,
>> + char *zimage, unsigned long zimage_len,
>> + char *initrd, unsigned long initrd_len,
>> + char *cmdline, unsigned long cmdline_len)
>> +{
>> + struct arm_zimage_header *h;
>> + struct kexec_buf kbuf;
>> + struct kexec_segment *zimage_segment;
>> + const struct arm_zimage_tag *klsz_tag;
>> + const struct arm_zimage_tag_dc *dcsz_tag;
>> + int ret = -EINVAL;
>> +
>> + unsigned long zimage_mem = 0x20000; /* malloc 64kB + stack 4 kB + some bss */
>> + unsigned long kernel_len = zimage_len * 4; /* 4:1 compression */
>
> This has been proven wrong.

5:1? The comment and the code in kexec-tools are inconsisten in this
regard. The comment says 4:1, but the code multiplies by 5. Your
recommendation? This value is used as a fallback anyway in a very
unlikely case, when tags are missing (see below).

>> + unsigned long kernel_offset = memblock_start_of_DRAM() +
>> + ALIGN(TEXT_OFFSET, PAGE_SIZE);
>
> TEXT_OFFSET is actually a property of the loaded kernel, not of the
> currently running kernel.

Indeed.

> I have a patch to add that into the zImage tag.

I am afraid, I haven't seen it before. Where can I find it?

>> + unsigned long zimage_offset = kernel_offset +
>> + ALIGN(kernel_len, PAGE_SIZE);
>> + unsigned long initrd_offset = zimage_offset +
>> + ALIGN(zimage_len + zimage_mem, PAGE_SIZE);
>
> Since kernel_len is wrong, these will be wrong... please only fall
> back to this if you don't find the extension tag - in other words,
> declare the variables here, but don't initialise them, set them
> lower down in the file if we fail to find the extension tag.

That is how it works now. This is the structure I have taken from
kexec-tools: initialize and change if additional information is
available. If the tags are not available use these values as a fallback.

>> +
>> + if (image->type == KEXEC_TYPE_CRASH) {
>> + kernel_offset += crashk_res.start;
>> + zimage_offset += crashk_res.start;
>> + initrd_offset += crashk_res.start;
>> + }
>> + debug_offsets();
>> +
>> + h = (struct arm_zimage_header *)zimage;
>> +
>> + klsz_tag = find_extension_tag(zimage, zimage_len, ZIMAGE_TAG_KRNL_SIZE);
>> + if (klsz_tag) {
>> + uint32_t *p = (void *)zimage +
>> + le32_to_cpu(klsz_tag->u.krnl_size.size_ptr);
>> + uint32_t edata_size = le32_to_cpu(get_unaligned(p));
>> + uint32_t bss_size = le32_to_cpu(klsz_tag->u.krnl_size.bss_size);
>> +
>> + kernel_len = edata_size + bss_size;
>> +
>> + pr_debug("Decompressed kernel sizes:\n");
>> + pr_debug(" text+data 0x%08lx bss 0x%08lx total 0x%08lx\n",
>> + (unsigned long)edata_size,
>> + (unsigned long)bss_size,
>> + (unsigned long)kernel_len);
>> +
>> + zimage_offset = kernel_offset + ALIGN(edata_size, PAGE_SIZE);
>> + initrd_offset = zimage_offset +
>> + max(ALIGN(zimage_len + 0x20000, PAGE_SIZE),
>> + ALIGN((unsigned long)bss_size, PAGE_SIZE));
>> + debug_offsets();
>
> This looks incorrect to me. Please see the kexec tool - what its doing
> in its corresponding section that you copied some of this code from is
> carefully thought out and can't be simplified. Ergo, I think this is
> wrong.

As I explained in <dleftjwo4qsqqf.fsf%l.stelmach@samsung.com> my
approach is slightly different. I am trying to avoid copying zImage by
putting it hight enough in the first place.


Kind regards,
--
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
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