To enable crash dump (kdump), we need to
* prepare the contents of ELF header of /proc/vmcore through
  load_crashdump_segments(), and
* set up two device tree properties, "linux,usable-memory-range" and
  "linux,elfcorehdr", which repsectively represent a memory range to be
  used on crash dump kernel and a region of ELF core header
  (The logic of this cod is also from kexec-tools.)

Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
Cc: Catalin Marinas <catalin.mari...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
---
 arch/arm64/include/asm/kexec.h         |   5 +
 arch/arm64/kernel/machine_kexec_file.c | 211 +++++++++++++++++++++++++++++++++
 2 files changed, 216 insertions(+)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index fc562db22d46..d7427d510e1b 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -99,6 +99,10 @@ static inline void crash_post_resume(void) {}
 struct kimage_arch {
        phys_addr_t dtb_mem;
        void *dtb_buf;
+       /* Core ELF header buffer */
+       void *elf_headers;
+       unsigned long elf_headers_sz;
+       unsigned long elf_load_addr;
 };
 
 struct kimage;
@@ -110,6 +114,7 @@ extern int load_other_segments(struct kimage *image,
                unsigned long kernel_load_addr,
                char *initrd, unsigned long initrd_len,
                char *cmdline, unsigned long cmdline_len);
+extern int load_crashdump_segments(struct kimage *image);
 #endif
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/arm64/kernel/machine_kexec_file.c 
b/arch/arm64/kernel/machine_kexec_file.c
index 12012f247501..fc132047c8cd 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -19,6 +19,7 @@
 #include <linux/libfdt.h>
 #include <linux/memblock.h>
 #include <linux/of_fdt.h>
+#include <linux/vmalloc.h>
 
 static int __dt_root_addr_cells;
 static int __dt_root_size_cells;
@@ -32,6 +33,10 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
        vfree(image->arch.dtb_buf);
        image->arch.dtb_buf = NULL;
 
+       vfree(image->arch.elf_headers);
+       image->arch.elf_headers = NULL;
+       image->arch.elf_headers_sz = 0;
+
        return _kimage_file_post_load_cleanup(image);
 }
 
@@ -49,6 +54,78 @@ int arch_kexec_walk_mem(struct kexec_buf *kbuf,
                return walk_system_ram_res(0, ULONG_MAX, kbuf, func);
 }
 
+static int __init arch_kexec_file_init(void)
+{
+       /* Those values are used later on loading the kernel */
+       __dt_root_addr_cells = dt_root_addr_cells;
+       __dt_root_size_cells = dt_root_size_cells;
+
+       return 0;
+}
+late_initcall(arch_kexec_file_init);
+
+#define FDT_ALIGN(x, a)        (((x) + (a) - 1) & ~((a) - 1))
+#define FDT_TAGALIGN(x)        (FDT_ALIGN((x), FDT_TAGSIZE))
+
+static int fdt_prop_len(const char *prop_name, int len)
+{
+       return (strlen(prop_name) + 1) +
+               sizeof(struct fdt_property) +
+               FDT_TAGALIGN(len);
+}
+
+static bool cells_size_fitted(unsigned long base, unsigned long size)
+{
+       /* if *_cells >= 2, cells can hold 64-bit values anyway */
+       if ((__dt_root_addr_cells == 1) && (base >= (1ULL << 32)))
+               return false;
+
+       if ((__dt_root_size_cells == 1) && (size >= (1ULL << 32)))
+               return false;
+
+       return true;
+}
+
+static void fill_property(void *buf, u64 val64, int cells)
+{
+       u32 val32;
+
+       if (cells == 1) {
+               val32 = cpu_to_fdt32((u32)val64);
+               memcpy(buf, &val32, sizeof(val32));
+       } else {
+               memset(buf, 0, cells * sizeof(u32) - sizeof(u64));
+               buf += cells * sizeof(u32) - sizeof(u64);
+
+               val64 = cpu_to_fdt64(val64);
+               memcpy(buf, &val64, sizeof(val64));
+       }
+}
+
+static int fdt_setprop_range(void *fdt, int nodeoffset, const char *name,
+                               unsigned long addr, unsigned long size)
+{
+       void *buf, *prop;
+       size_t buf_size;
+       int result;
+
+       buf_size = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
+       prop = buf = vmalloc(buf_size);
+       if (!buf)
+               return -ENOMEM;
+
+       fill_property(prop, addr, __dt_root_addr_cells);
+       prop += __dt_root_addr_cells * sizeof(u32);
+
+       fill_property(prop, size, __dt_root_size_cells);
+
+       result = fdt_setprop(fdt, nodeoffset, name, buf, buf_size);
+
+       vfree(buf);
+
+       return result;
+}
+
 static int setup_dtb(struct kimage *image,
                unsigned long initrd_load_addr, unsigned long initrd_len,
                char *cmdline, unsigned long cmdline_len,
@@ -61,10 +138,26 @@ static int setup_dtb(struct kimage *image,
        int range_len;
        int ret;
 
+       /* check ranges against root's #address-cells and #size-cells */
+       if (image->type == KEXEC_TYPE_CRASH &&
+               (!cells_size_fitted(image->arch.elf_load_addr,
+                               image->arch.elf_headers_sz) ||
+                !cells_size_fitted(crashk_res.start,
+                               crashk_res.end - crashk_res.start + 1))) {
+               pr_err("Crash memory region doesn't fit into DT's root cell 
sizes.\n");
+               ret = -EINVAL;
+               goto out_err;
+       }
+
        /* duplicate dt blob */
        buf_size = fdt_totalsize(initial_boot_params);
        range_len = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
 
+       if (image->type == KEXEC_TYPE_CRASH)
+               buf_size += fdt_prop_len("linux,elfcorehdr", range_len)
+                               + fdt_prop_len("linux,usable-memory-range",
+                                                               range_len);
+
        if (initrd_load_addr)
                buf_size += fdt_prop_len("initrd-start", sizeof(u64))
                                + fdt_prop_len("initrd-end", sizeof(u64));
@@ -86,6 +179,23 @@ static int setup_dtb(struct kimage *image,
        if (nodeoffset < 0)
                goto out_err;
 
+       if (image->type == KEXEC_TYPE_CRASH) {
+               /* add linux,elfcorehdr */
+               ret = fdt_setprop_range(buf, nodeoffset, "linux,elfcorehdr",
+                               image->arch.elf_load_addr,
+                               image->arch.elf_headers_sz);
+               if (ret)
+                       goto out_err;
+
+               /* add linux,usable-memory-range */
+               ret = fdt_setprop_range(buf, nodeoffset,
+                               "linux,usable-memory-range",
+                               crashk_res.start,
+                               crashk_res.end - crashk_res.start + 1);
+               if (ret)
+                       goto out_err;
+       }
+
        /* add bootargs */
        if (cmdline) {
                ret = fdt_setprop(buf, nodeoffset, "bootargs",
@@ -187,3 +297,104 @@ int load_other_segments(struct kimage *image, unsigned 
long kernel_load_addr,
        image->arch.dtb_buf = NULL;
        return ret;
 }
+
+static int get_nr_ranges_callback(struct resource *res, void *arg)
+{
+       unsigned int *nr_ranges = arg;
+
+       (*nr_ranges)++;
+       return 0;
+}
+
+static int add_mem_range_callback(struct resource *res, void *arg)
+{
+       struct crash_mem *cmem = arg;
+
+       cmem->ranges[cmem->nr_ranges].start = res->start;
+       cmem->ranges[cmem->nr_ranges].end = res->end;
+       cmem->nr_ranges++;
+
+       return 0;
+}
+
+static struct crash_mem *get_crash_memory_ranges(void)
+{
+       unsigned int nr_ranges;
+       struct crash_mem *cmem;
+
+       nr_ranges = 1; /* for exclusion of crashkernel region */
+       walk_system_ram_res(0, -1, &nr_ranges, get_nr_ranges_callback);
+
+       cmem = vmalloc(sizeof(struct crash_mem) +
+                       sizeof(struct crash_mem_range) * nr_ranges);
+       if (!cmem)
+               return NULL;
+
+       cmem->max_nr_ranges = nr_ranges;
+       cmem->nr_ranges = 0;
+       walk_system_ram_res(0, -1, cmem, add_mem_range_callback);
+
+       /* Exclude crashkernel region */
+       if (crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end)) {
+               vfree(cmem);
+               return NULL;
+       }
+
+       return cmem;
+}
+
+static int prepare_elf_core_header(void **addr, unsigned long *sz)
+{
+       struct crash_mem *cmem;
+       int ret = 0;
+
+       cmem = get_crash_memory_ranges();
+       if (!cmem)
+               return -ENOMEM;
+
+       /* 1: add segment for kernel map */
+       ret =  crash_prepare_elf64_headers(cmem, 1, addr, sz);
+
+       vfree(cmem);
+       return ret;
+}
+
+int load_crashdump_segments(struct kimage *image)
+{
+       void *elf_addr;
+       unsigned long elf_sz;
+       struct kexec_buf kbuf;
+       int ret;
+
+       if (image->type != KEXEC_TYPE_CRASH)
+               return 0;
+
+       ret = prepare_elf_core_header(&elf_addr, &elf_sz);
+       if (ret) {
+               pr_err("Preparing elf core header failed\n");
+               return ret;
+       }
+
+       kbuf.image = image;
+       kbuf.buffer = elf_addr;
+       kbuf.bufsz = elf_sz;
+       kbuf.memsz = elf_sz;
+       kbuf.buf_align = PAGE_SIZE;
+       kbuf.buf_min = crashk_res.start;
+       kbuf.buf_max = crashk_res.end + 1;
+       kbuf.top_down = 1;
+
+       ret = kexec_add_buffer(&kbuf);
+       if (ret) {
+               vfree(elf_addr);
+               return ret;
+       }
+       image->arch.elf_headers = elf_addr;
+       image->arch.elf_headers_sz = elf_sz;
+       image->arch.elf_load_addr = kbuf.mem;
+
+       pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+                        image->arch.elf_load_addr, elf_sz, elf_sz);
+
+       return ret;
+}
-- 
2.16.2


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