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Date: Thu, 5 Dec 2019 02:14:14 +0530
From: Bhupesh Sharma <bhsharma@...hat.com>
To: AKASHI Takahiro <takahiro.akashi@...aro.org>,
catalin.marinas@....com, will.deacon@....com, robh+dt@...nel.org,
frowand.list@...il.com
Cc: kexec@...ts.infradead.org, james.morse@....com,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/3] arm64: kexec_file: add crash dump support
On 11/14/2019 10:45 AM, AKASHI Takahiro wrote:
> 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@...aro.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Reviewed-by: James Morse <james.morse@....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.
nitpick:
s/userable-memory-range/usable-memory-range
> */
> #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;
With commit c19d050f8088 ("arm64/kexec: Use consistent convention of
initializing 'kxec_buf.mem' with KEXEC_BUF_MEM_UNKNOWN"), we are trying
to standardize the way of setting up initial value of 'kbuf.mem'. So we
can use the following notion (in v3?) instead:
kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> + 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;
>
Thanks,
Bhupesh
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