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SubjectRe: [PATCH v2 3/3] arm64: kexec_file: add crash dump support
I have forgot to address Bhupesh's comment below in my v3.
I'm going to repost my patch.

Thank you, Bhupesh, for your review.

-Takahiro Akashi

On Thu, Dec 05, 2019 at 02:14:14AM +0530, Bhupesh Sharma wrote:
> 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@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.
>
> 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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