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    Subject[PATCH v2 3/3] arm64: kexec_file: add crash dump support
    Date
    Enabling crash dump (kdump) includes
    * prepare contents of ELF header of a core dump file, /proc/vmcore,
    using crash_prepare_elf64_headers(), and
    * add two device tree properties, "linux,usable-memory-range" and
    "linux,elfcorehdr", which represent respectively a memory range
    to be used by crash dump kernel and the header's location

    Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Reviewed-by: James Morse <james.morse@arm.com>
    ---
    arch/arm64/include/asm/kexec.h | 4 +
    arch/arm64/kernel/kexec_image.c | 4 -
    arch/arm64/kernel/machine_kexec_file.c | 106 ++++++++++++++++++++++++-
    3 files changed, 106 insertions(+), 8 deletions(-)

    diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
    index 12a561a54128..d24b527e8c00 100644
    --- a/arch/arm64/include/asm/kexec.h
    +++ b/arch/arm64/include/asm/kexec.h
    @@ -96,6 +96,10 @@ static inline void crash_post_resume(void) {}
    struct kimage_arch {
    void *dtb;
    unsigned long dtb_mem;
    + /* Core ELF header buffer */
    + void *elf_headers;
    + unsigned long elf_headers_mem;
    + unsigned long elf_headers_sz;
    };

    extern const struct kexec_file_ops kexec_image_ops;
    diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
    index 29a9428486a5..af9987c154ca 100644
    --- a/arch/arm64/kernel/kexec_image.c
    +++ b/arch/arm64/kernel/kexec_image.c
    @@ -47,10 +47,6 @@ static void *image_load(struct kimage *image,
    struct kexec_segment *kernel_segment;
    int ret;

    - /* We don't support crash kernels yet. */
    - if (image->type == KEXEC_TYPE_CRASH)
    - return ERR_PTR(-EOPNOTSUPP);
    -
    /*
    * We require a kernel with an unambiguous Image header. Per
    * Documentation/arm64/booting.rst, this is the case when image_size
    diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
    index 7b08bf9499b6..f1d1bb895fd2 100644
    --- a/arch/arm64/kernel/machine_kexec_file.c
    +++ b/arch/arm64/kernel/machine_kexec_file.c
    @@ -17,12 +17,15 @@
    #include <linux/memblock.h>
    #include <linux/of_fdt.h>
    #include <linux/random.h>
    +#include <linux/slab.h>
    #include <linux/string.h>
    #include <linux/types.h>
    #include <linux/vmalloc.h>
    #include <asm/byteorder.h>

    /* relevant device tree properties */
    +#define FDT_PROP_KEXEC_ELFHDR "linux,elfcorehdr"
    +#define FDT_PROP_MEM_RANGE "linux,usable-memory-range"
    #define FDT_PROP_INITRD_START "linux,initrd-start"
    #define FDT_PROP_INITRD_END "linux,initrd-end"
    #define FDT_PROP_BOOTARGS "bootargs"
    @@ -40,6 +43,10 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
    vfree(image->arch.dtb);
    image->arch.dtb = NULL;

    + vfree(image->arch.elf_headers);
    + image->arch.elf_headers = NULL;
    + image->arch.elf_headers_sz = 0;
    +
    return kexec_image_post_load_cleanup_default(image);
    }

    @@ -55,6 +62,31 @@ static int setup_dtb(struct kimage *image,

    off = ret;

    + ret = fdt_delprop(dtb, off, FDT_PROP_KEXEC_ELFHDR);
    + if (ret && ret != -FDT_ERR_NOTFOUND)
    + goto out;
    + ret = fdt_delprop(dtb, off, FDT_PROP_MEM_RANGE);
    + if (ret && ret != -FDT_ERR_NOTFOUND)
    + goto out;
    +
    + if (image->type == KEXEC_TYPE_CRASH) {
    + /* add linux,elfcorehdr */
    + ret = fdt_appendprop_addrrange(dtb, 0, off,
    + FDT_PROP_KEXEC_ELFHDR,
    + image->arch.elf_headers_mem,
    + image->arch.elf_headers_sz);
    + if (ret)
    + return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
    +
    + /* add linux,usable-memory-range */
    + ret = fdt_appendprop_addrrange(dtb, 0, off,
    + FDT_PROP_MEM_RANGE,
    + crashk_res.start,
    + crashk_res.end - crashk_res.start + 1);
    + if (ret)
    + return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
    + }
    +
    /* add bootargs */
    if (cmdline) {
    ret = fdt_setprop_string(dtb, off, FDT_PROP_BOOTARGS, cmdline);
    @@ -125,8 +157,8 @@ static int setup_dtb(struct kimage *image,
    }

    /*
    - * More space needed so that we can add initrd, bootargs, kaslr-seed, and
    - * rng-seed.
    + * More space needed so that we can add initrd, bootargs, kaslr-seed,
    + * rng-seed, userable-memory-range and elfcorehdr.
    */
    #define DTB_EXTRA_SPACE 0x1000

    @@ -174,6 +206,43 @@ static int create_dtb(struct kimage *image,
    }
    }

    +static int prepare_elf_headers(void **addr, unsigned long *sz)
    +{
    + struct crash_mem *cmem;
    + unsigned int nr_ranges;
    + int ret;
    + u64 i;
    + phys_addr_t start, end;
    +
    + nr_ranges = 1; /* for exclusion of crashkernel region */
    + for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
    + MEMBLOCK_NONE, &start, &end, NULL)
    + nr_ranges++;
    +
    + cmem = kmalloc(sizeof(struct crash_mem) +
    + sizeof(struct crash_mem_range) * nr_ranges, GFP_KERNEL);
    + if (!cmem)
    + return -ENOMEM;
    +
    + cmem->max_nr_ranges = nr_ranges;
    + cmem->nr_ranges = 0;
    + for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
    + MEMBLOCK_NONE, &start, &end, NULL) {
    + cmem->ranges[cmem->nr_ranges].start = start;
    + cmem->ranges[cmem->nr_ranges].end = end - 1;
    + cmem->nr_ranges++;
    + }
    +
    + /* Exclude crashkernel region */
    + ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
    +
    + if (!ret)
    + ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
    +
    + kfree(cmem);
    + return ret;
    +}
    +
    int load_other_segments(struct kimage *image,
    unsigned long kernel_load_addr,
    unsigned long kernel_size,
    @@ -181,14 +250,43 @@ int load_other_segments(struct kimage *image,
    char *cmdline)
    {
    struct kexec_buf kbuf;
    - void *dtb = NULL;
    - unsigned long initrd_load_addr = 0, dtb_len;
    + void *headers, *dtb = NULL;
    + unsigned long headers_sz, initrd_load_addr = 0, dtb_len;
    int ret = 0;

    kbuf.image = image;
    /* not allocate anything below the kernel */
    kbuf.buf_min = kernel_load_addr + kernel_size;

    + /* load elf core header */
    + if (image->type == KEXEC_TYPE_CRASH) {
    + ret = prepare_elf_headers(&headers, &headers_sz);
    + if (ret) {
    + pr_err("Preparing elf core header failed\n");
    + goto out_err;
    + }
    +
    + kbuf.buffer = headers;
    + kbuf.bufsz = headers_sz;
    + kbuf.mem = 0;
    + kbuf.memsz = headers_sz;
    + kbuf.buf_align = SZ_64K; /* largest supported page size */
    + kbuf.buf_max = ULONG_MAX;
    + kbuf.top_down = true;
    +
    + ret = kexec_add_buffer(&kbuf);
    + if (ret) {
    + vfree(headers);
    + goto out_err;
    + }
    + image->arch.elf_headers = headers;
    + image->arch.elf_headers_mem = kbuf.mem;
    + image->arch.elf_headers_sz = headers_sz;
    +
    + pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
    + image->arch.elf_headers_mem, headers_sz, headers_sz);
    + }
    +
    /* load initrd */
    if (initrd) {
    kbuf.buffer = initrd;
    --
    2.21.0
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