Re: [PATCH v2 3/6] kexec_file: Allow skipping checksum calculation for some segments.

From: Dave Young
Date: Thu Aug 18 2016 - 05:04:04 EST

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On 08/13/16 at 12:18am, Thiago Jung Bauermann wrote:
> Adds checksum argument to kexec_add_buffer specifying whether the given
> segment should be part of the checksum calculation.
>

Since it is used with add buffer, could it be added to kbuf as a new
field?

Like kbuf.no_checksum, default value is 0 that means checksum is needed
if it is 1 then no need a checksum.

> The next patch will add a way to update segments after a kimage is loaded.
> Segments that will be updated in this way should not be checksummed,
> otherwise they will cause the purgatory checksum verification to fail
> when the machine is rebooted.
>
> As a bonus, we don't need to special-case the purgatory segment anymore
> to avoid checksumming it.
>
> Adjust call sites for the new argument.
>
> Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxxxxxxx>
> ---
> arch/powerpc/kernel/kexec_elf_64.c | 6 +++---
> arch/x86/kernel/crash.c | 4 ++--
> arch/x86/kernel/kexec-bzimage64.c | 6 +++---
> include/linux/kexec.h | 10 +++++++---
> kernel/kexec_file.c | 23 ++++++++++++-----------
> 5 files changed, 27 insertions(+), 22 deletions(-)
>
> diff --git a/arch/powerpc/kernel/kexec_elf_64.c b/arch/powerpc/kernel/kexec_elf_64.c
> index 22afc7b5ee73..4c528c81b076 100644
> --- a/arch/powerpc/kernel/kexec_elf_64.c
> +++ b/arch/powerpc/kernel/kexec_elf_64.c
> @@ -128,7 +128,7 @@ static int elf_exec_load(struct kimage *image, struct elfhdr *ehdr,
> kbuf.memsz = phdr->p_memsz;
> kbuf.buf_align = phdr->p_align;
> kbuf.buf_min = phdr->p_paddr + base;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> goto out;
> load_addr = kbuf.mem;
> @@ -188,7 +188,7 @@ void *elf64_load(struct kimage *image, char *kernel_buf,
> kbuf.bufsz = kbuf.memsz = initrd_len;
> kbuf.buf_align = PAGE_SIZE;
> kbuf.top_down = false;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> goto out;
> initrd_load_addr = kbuf.mem;
> @@ -245,7 +245,7 @@ void *elf64_load(struct kimage *image, char *kernel_buf,
> kbuf.bufsz = kbuf.memsz = fdt_size;
> kbuf.buf_align = PAGE_SIZE;
> kbuf.top_down = true;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> goto out;
> fdt_load_addr = kbuf.mem;
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 38a1cdf6aa05..634ab16377b1 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -642,7 +642,7 @@ int crash_load_segments(struct kimage *image)
> * copied in purgatory after crash. Just add a zero filled
> * segment for now to make sure checksum logic works fine.
> */
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> return ret;
> image->arch.backup_load_addr = kbuf.mem;
> @@ -661,7 +661,7 @@ int crash_load_segments(struct kimage *image)
>
> kbuf.memsz = kbuf.bufsz;
> kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret) {
> vfree((void *)image->arch.elf_headers);
> return ret;
> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> index 4b3a75329fb6..a46e3fbb0639 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -422,7 +422,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
> kbuf.memsz = kbuf.bufsz;
> kbuf.buf_align = 16;
> kbuf.buf_min = MIN_BOOTPARAM_ADDR;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> goto out_free_params;
> bootparam_load_addr = kbuf.mem;
> @@ -435,7 +435,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
> kbuf.memsz = PAGE_ALIGN(header->init_size);
> kbuf.buf_align = header->kernel_alignment;
> kbuf.buf_min = MIN_KERNEL_LOAD_ADDR;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> goto out_free_params;
> kernel_load_addr = kbuf.mem;
> @@ -449,7 +449,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
> kbuf.bufsz = kbuf.memsz = initrd_len;
> kbuf.buf_align = PAGE_SIZE;
> kbuf.buf_min = MIN_INITRD_LOAD_ADDR;
> - ret = kexec_add_buffer(&kbuf);
> + ret = kexec_add_buffer(&kbuf, true);
> if (ret)
> goto out_free_params;
> initrd_load_addr = kbuf.mem;
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 4559a1a01b0a..37eea32fdff1 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -100,6 +100,9 @@ struct kexec_segment {
> size_t bufsz;
> unsigned long mem;
> size_t memsz;
> +
> + /* Whether this segment is part of the checksum calculation. */
> + bool do_checksum;
> };
>
> #ifdef CONFIG_COMPAT
> @@ -175,7 +178,7 @@ struct kexec_buf {
>
> int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf,
> int (*func)(u64, u64, void *));
> -extern int kexec_add_buffer(struct kexec_buf *kbuf);
> +extern int kexec_add_buffer(struct kexec_buf *kbuf, bool checksum);
> int kexec_locate_mem_hole(struct kexec_buf *kbuf);
> int __weak arch_kexec_verify_buffer(enum kexec_file_type type, const void *buf,
> unsigned long size);
> @@ -393,7 +396,7 @@ bool __weak kexec_can_hand_over_buffer(void);
> int __weak arch_kexec_add_handover_buffer(struct kimage *image,
> unsigned long load_addr,
> unsigned long size);
> -int kexec_add_handover_buffer(struct kexec_buf *kbuf);
> +int kexec_add_handover_buffer(struct kexec_buf *kbuf, bool checksum);
> int __weak kexec_get_handover_buffer(void **addr, unsigned long *size);
> int __weak kexec_free_handover_buffer(void);
> #else
> @@ -402,7 +405,8 @@ static inline bool kexec_can_hand_over_buffer(void)
> return false;
> }
>
> -static inline int kexec_add_handover_buffer(struct kexec_buf *kbuf)
> +static inline int kexec_add_handover_buffer(struct kexec_buf *kbuf,
> + bool checksum)
> {
> return -ENOTSUPP;
> }
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index c8418d62e2fc..aed51175915f 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -161,6 +161,7 @@ int __weak arch_kexec_add_handover_buffer(struct kimage *image,
> /**
> * kexec_add_handover_buffer - add buffer to be used by the next kernel
> * @kbuf: Buffer contents and memory parameters.
> + * @checksum: Should the segment checksum be verified by the purgatory?
> *
> * This function assumes that kexec_mutex is held.
> * On successful return, @kbuf->mem will have the physical address of
> @@ -168,14 +169,14 @@ int __weak arch_kexec_add_handover_buffer(struct kimage *image,
> *
> * Return: 0 on success, negative errno on error.
> */
> -int kexec_add_handover_buffer(struct kexec_buf *kbuf)
> +int kexec_add_handover_buffer(struct kexec_buf *kbuf, bool checksum)
> {
> int ret;
>
> if (!kexec_can_hand_over_buffer())
> return -ENOTSUPP;
>
> - ret = kexec_add_buffer(kbuf);
> + ret = kexec_add_buffer(kbuf, checksum);
> if (ret)
> return ret;
>
> @@ -611,6 +612,7 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
> /**
> * kexec_add_buffer - place a buffer in a kexec segment
> * @kbuf: Buffer contents and memory parameters.
> + * @checksum: Should the segment checksum be verified by the purgatory?
> *
> * This function assumes that kexec_mutex is held.
> * On successful return, @kbuf->mem will have the physical address of
> @@ -618,7 +620,7 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
> *
> * Return: 0 on success, negative errno on error.
> */
> -int kexec_add_buffer(struct kexec_buf *kbuf)
> +int kexec_add_buffer(struct kexec_buf *kbuf, bool checksum)
> {
>
> struct kexec_segment *ksegment;
> @@ -658,6 +660,7 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
> ksegment->bufsz = kbuf->bufsz;
> ksegment->mem = kbuf->mem;
> ksegment->memsz = kbuf->memsz;
> + ksegment->do_checksum = checksum;
> kbuf->image->nr_segments++;
> return 0;
> }
> @@ -672,7 +675,6 @@ static int kexec_calculate_store_digests(struct kimage *image)
> char *digest;
> void *zero_buf;
> struct kexec_sha_region *sha_regions;
> - struct purgatory_info *pi = &image->purgatory_info;
>
> zero_buf = __va(page_to_pfn(ZERO_PAGE(0)) << PAGE_SHIFT);
> zero_buf_sz = PAGE_SIZE;
> @@ -712,11 +714,7 @@ static int kexec_calculate_store_digests(struct kimage *image)
> struct kexec_segment *ksegment;
>
> ksegment = &image->segment[i];
> - /*
> - * Skip purgatory as it will be modified once we put digest
> - * info in purgatory.
> - */
> - if (ksegment->kbuf == pi->purgatory_buf)
> + if (!ksegment->do_checksum)
> continue;
>
> ret = crypto_shash_update(desc, ksegment->kbuf,
> @@ -893,8 +891,11 @@ static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
> if (kbuf.buf_align < bss_align)
> kbuf.buf_align = bss_align;
>
> - /* Add buffer to segment list */
> - ret = kexec_add_buffer(&kbuf);
> + /*
> + * Add buffer to segment list. Don't checksum the segment as
> + * it will be modified once we put digest info in purgatory.
> + */
> + ret = kexec_add_buffer(&kbuf, false);
> if (ret)
> goto out;
> pi->purgatory_load_addr = kbuf.mem;
> --
> 1.9.1
>
>
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> kexec@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/kexec

Next message: Finlye Xiao: "[PATCH v2 1/4] nvmem: rockchip-efuse: Change initcall to subsys"
Previous message: Michal Hocko: "Re: [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS"
Next in thread: Thiago Jung Bauermann: "Re: [PATCH v2 3/6] kexec_file: Allow skipping checksum calculation for some segments."
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