[PATCH v8 02/11] kexec: Add helpers to load the elf core header, initrd and FDT

[Jinjie Ruan]

x86, arm64, LoongArch, RISC-V and powerpc all build an elf core header,
load the initrd by hand before loading the kdump kernel, while arm64 and
RISC-V also duplicate the code that builds the device tree for the kexec
kernel

Add the following 4 helpers for reuse:
- kexec_prepare_elf_core_header() builds the header once per image and
  returns the number of memory ranges, which x86 needs to reserve room
  for the crash hotplug updates.

- kexec_add_elf_core_header() places the prepared header as a segment.
  The caller provides the kexec_buf with its placement policy and the
  size to reserve.  On success it also records the segment index that
  the crash hotplug code uses to find the header.

- kexec_add_initrd() places the initrd from the image with the placement
  policy the caller put into the kexec_buf.

- kexec_add_fdt() builds the device tree for the kexec kernel, packs
  it and places it with the kexec_buf the caller passes in.

Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Baoquan He <baoquan.he at linux.dev>
Cc: Mike Rapoport <rppt at kernel.org>
Link: https://lore.kernel.org/all/179430504583.425130.15302016434972990362.b4-review@b4/
Suggested-by: Mike Rapoport <rppt at kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
---
 include/linux/kexec.h |  11 +++++
 kernel/kexec_file.c   | 104 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 115 insertions(+)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index bac11e940e74..89cb47521d6d 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -258,6 +258,17 @@ int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len);
 
 extern int kexec_add_buffer(struct kexec_buf *kbuf);
 int kexec_locate_mem_hole(struct kexec_buf *kbuf);
+int kexec_add_initrd(struct kimage *image, struct kexec_buf *kbuf);
+#ifdef CONFIG_CRASH_DUMP
+int kexec_prepare_elf_core_header(struct kimage *image, bool need_kernel_map,
+				  unsigned long *nr_ranges);
+int kexec_add_elf_core_header(struct kimage *image, struct kexec_buf *kbuf);
+#endif
+#if defined(CONFIG_OF) && defined(CONFIG_OF_FLATTREE)
+int kexec_add_fdt(struct kimage *image, struct kexec_buf *kbuf,
+		  unsigned long initrd_load_addr, const char *cmdline,
+		  void **fdt);
+#endif
 
 #ifndef arch_kexec_apply_relocations_add
 /*
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 1f128c6e6fa3..25c9bef639d2 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -14,7 +14,9 @@
 #include <linux/file.h>
 #include <linux/slab.h>
 #include <linux/kexec.h>
+#include <linux/libfdt.h>
 #include <linux/memblock.h>
+#include <linux/of.h>
 #include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/fs.h>
@@ -109,6 +111,108 @@ static void kexec_free_elf_headers(struct kimage *image)
 	image->elf_headers_sz = 0;
 }
 
+#ifdef CONFIG_CRASH_DUMP
+int kexec_prepare_elf_core_header(struct kimage *image, bool need_kernel_map,
+				  unsigned long *nr_ranges)
+{
+	int ret;
+
+	if (image->elf_headers)
+		return 0;
+
+	ret = crash_prepare_headers(need_kernel_map, &image->elf_headers,
+				    &image->elf_headers_sz, nr_ranges);
+	if (ret)
+		pr_err("Preparing elf core header failed\n");
+
+	return ret;
+}
+
+int kexec_add_elf_core_header(struct kimage *image, struct kexec_buf *kbuf)
+{
+	unsigned long memsz = kbuf->memsz;
+	int ret;
+
+	kbuf->buffer = image->elf_headers;
+	kbuf->bufsz = image->elf_headers_sz;
+	kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
+
+	ret = kexec_add_buffer(kbuf);
+	if (ret)
+		return ret;
+
+	image->elf_load_addr = kbuf->mem;
+
+	/* The crash hotplug reservation can exceed the header size. */
+	if (memsz > image->elf_headers_sz) {
+		image->elf_headers_sz = memsz;
+#ifdef CONFIG_CRASH_HOTPLUG
+		image->elfcorehdr_index = image->nr_segments - 1;
+#endif
+	}
+
+	kexec_dprintk("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		      image->elf_load_addr, kbuf->bufsz, kbuf->memsz);
+
+	return 0;
+}
+#endif /* CONFIG_CRASH_DUMP */
+
+int kexec_add_initrd(struct kimage *image, struct kexec_buf *kbuf)
+{
+	int ret;
+
+	kbuf->buffer = image->initrd_buf;
+	kbuf->bufsz = kbuf->memsz = image->initrd_buf_len;
+	kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
+
+	ret = kexec_add_buffer(kbuf);
+	if (ret)
+		return ret;
+
+	kexec_dprintk("Loaded initrd at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		      kbuf->mem, kbuf->bufsz, kbuf->memsz);
+
+	return 0;
+}
+
+#if defined(CONFIG_OF) && defined(CONFIG_OF_FLATTREE)
+int kexec_add_fdt(struct kimage *image, struct kexec_buf *kbuf,
+		  unsigned long initrd_load_addr, const char *cmdline,
+		  void **fdt)
+{
+	void *new_fdt;
+	int ret;
+
+	new_fdt = of_kexec_alloc_and_setup_fdt(image, initrd_load_addr,
+					       image->initrd_buf_len,
+					       cmdline, 0);
+	if (!new_fdt) {
+		pr_err("Preparing for new dtb failed\n");
+		return -EINVAL;
+	}
+
+	fdt_pack(new_fdt);
+
+	kbuf->buffer = new_fdt;
+	kbuf->bufsz = kbuf->memsz = fdt_totalsize(new_fdt);
+	kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
+
+	ret = kexec_add_buffer(kbuf);
+	if (ret) {
+		kvfree(new_fdt);
+		return ret;
+	}
+
+	*fdt = new_fdt;
+
+	kexec_dprintk("Loaded dtb at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		      kbuf->mem, kbuf->bufsz, kbuf->memsz);
+
+	return 0;
+}
+#endif /* CONFIG_OF && CONFIG_OF_FLATTREE */
+
 /*
  * Free up memory used by kernel, initrd, and command line. This is temporary
  * memory allocation which is not needed any more after these buffers have
-- 
2.34.1