Message-Id: <20230914020044.1397356-2-songshuaishuai@tinylab.org>
Date:   Thu, 14 Sep 2023 10:00:43 +0800
From:   Song Shuai <songshuaishuai@...ylab.org>
To:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, lihuafei1@...wei.com,
        conor.dooley@...rochip.com, liaochang1@...wei.com,
        guoren@...nel.org, ajones@...tanamicro.com, alexghiti@...osinc.com,
        evan@...osinc.com, sunilvl@...tanamicro.com,
        xianting.tian@...ux.alibaba.com, samitolvanen@...gle.com,
        masahiroy@...nel.org, apatel@...tanamicro.com, jszhang@...nel.org,
        duwe@...e.de, eric.devolder@...cle.com
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Song Shuai <songshuaishuai@...ylab.org>
Subject: [PATCH 1/2] riscv: kexec_file: Split the loading of kernel and others

This is the preparative patch for kexec_file_load Image support.

It separates the elf_kexec_load() as two parts:
- the first part loads the vmlinux (or Image)
- the second part loads other segments (e.g. initrd,fdt,purgatory)

And the second part is exported as the load_extra_segments() function
which would be used in both kexec-elf.c and kexec-image.c.

Signed-off-by: Song Shuai <songshuaishuai@...ylab.org>
---
 arch/riscv/include/asm/kexec.h         |   5 +
 arch/riscv/kernel/Makefile             |   2 +-
 arch/riscv/kernel/elf_kexec.c          | 469 -------------------------
 arch/riscv/kernel/kexec_elf.c          | 147 ++++++++
 arch/riscv/kernel/machine_kexec_file.c |   7 +
 5 files changed, 160 insertions(+), 470 deletions(-)
 delete mode 100644 arch/riscv/kernel/elf_kexec.c
 create mode 100644 arch/riscv/kernel/kexec_elf.c

diff --git a/arch/riscv/include/asm/kexec.h b/arch/riscv/include/asm/kexec.h
index 2b56769cb530..518825fe4160 100644
--- a/arch/riscv/include/asm/kexec.h
+++ b/arch/riscv/include/asm/kexec.h
@@ -67,6 +67,11 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 struct kimage;
 int arch_kimage_file_post_load_cleanup(struct kimage *image);
 #define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
+
+int load_extra_segments(struct kimage *image, unsigned long kernel_start,
+			unsigned long kernel_len, char *initrd,
+			unsigned long initrd_len, char *cmdline,
+			unsigned long cmdline_len);
 #endif
 
 #endif
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 95cf25d48405..1c62c639e875 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -86,7 +86,7 @@ endif
 obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_KEXEC_CORE)	+= kexec_relocate.o crash_save_regs.o machine_kexec.o
-obj-$(CONFIG_KEXEC_FILE)	+= elf_kexec.o machine_kexec_file.o
+obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o machine_kexec_file.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_CRASH_CORE)	+= crash_core.o
 
diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
deleted file mode 100644
index e60fbd8660c4..000000000000
--- a/arch/riscv/kernel/elf_kexec.c
+++ /dev/null
@@ -1,469 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Load ELF vmlinux file for the kexec_file_load syscall.
- *
- * Copyright (C) 2021 Huawei Technologies Co, Ltd.
- *
- * Author: Liao Chang (liaochang1@...wei.com)
- *
- * Based on kexec-tools' kexec-elf-riscv.c, heavily modified
- * for kernel.
- */
-
-#define pr_fmt(fmt)	"kexec_image: " fmt
-
-#include <linux/elf.h>
-#include <linux/kexec.h>
-#include <linux/slab.h>
-#include <linux/of.h>
-#include <linux/libfdt.h>
-#include <linux/types.h>
-#include <linux/memblock.h>
-#include <asm/setup.h>
-
-int arch_kimage_file_post_load_cleanup(struct kimage *image)
-{
-	kvfree(image->arch.fdt);
-	image->arch.fdt = NULL;
-
-	vfree(image->elf_headers);
-	image->elf_headers = NULL;
-	image->elf_headers_sz = 0;
-
-	return kexec_image_post_load_cleanup_default(image);
-}
-
-static int riscv_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
-				struct kexec_elf_info *elf_info, unsigned long old_pbase,
-				unsigned long new_pbase)
-{
-	int i;
-	int ret = 0;
-	size_t size;
-	struct kexec_buf kbuf;
-	const struct elf_phdr *phdr;
-
-	kbuf.image = image;
-
-	for (i = 0; i < ehdr->e_phnum; i++) {
-		phdr = &elf_info->proghdrs[i];
-		if (phdr->p_type != PT_LOAD)
-			continue;
-
-		size = phdr->p_filesz;
-		if (size > phdr->p_memsz)
-			size = phdr->p_memsz;
-
-		kbuf.buffer = (void *) elf_info->buffer + phdr->p_offset;
-		kbuf.bufsz = size;
-		kbuf.buf_align = phdr->p_align;
-		kbuf.mem = phdr->p_paddr - old_pbase + new_pbase;
-		kbuf.memsz = phdr->p_memsz;
-		kbuf.top_down = false;
-		ret = kexec_add_buffer(&kbuf);
-		if (ret)
-			break;
-	}
-
-	return ret;
-}
-
-/*
- * Go through the available phsyical memory regions and find one that hold
- * an image of the specified size.
- */
-static int elf_find_pbase(struct kimage *image, unsigned long kernel_len,
-			  struct elfhdr *ehdr, struct kexec_elf_info *elf_info,
-			  unsigned long *old_pbase, unsigned long *new_pbase)
-{
-	int i;
-	int ret;
-	struct kexec_buf kbuf;
-	const struct elf_phdr *phdr;
-	unsigned long lowest_paddr = ULONG_MAX;
-	unsigned long lowest_vaddr = ULONG_MAX;
-
-	for (i = 0; i < ehdr->e_phnum; i++) {
-		phdr = &elf_info->proghdrs[i];
-		if (phdr->p_type != PT_LOAD)
-			continue;
-
-		if (lowest_paddr > phdr->p_paddr)
-			lowest_paddr = phdr->p_paddr;
-
-		if (lowest_vaddr > phdr->p_vaddr)
-			lowest_vaddr = phdr->p_vaddr;
-	}
-
-	kbuf.image = image;
-	kbuf.buf_min = lowest_paddr;
-	kbuf.buf_max = ULONG_MAX;
-
-	/*
-	 * Current riscv boot protocol requires 2MB alignment for
-	 * RV64 and 4MB alignment for RV32
-	 *
-	 */
-	kbuf.buf_align = PMD_SIZE;
-	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-	kbuf.memsz = ALIGN(kernel_len, PAGE_SIZE);
-	kbuf.top_down = false;
-	ret = arch_kexec_locate_mem_hole(&kbuf);
-	if (!ret) {
-		*old_pbase = lowest_paddr;
-		*new_pbase = kbuf.mem;
-		image->start = ehdr->e_entry - lowest_vaddr + kbuf.mem;
-	}
-	return ret;
-}
-
-static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
-{
-	unsigned int *nr_ranges = arg;
-
-	(*nr_ranges)++;
-	return 0;
-}
-
-static int prepare_elf64_ram_headers_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 int prepare_elf_headers(void **addr, unsigned long *sz)
-{
-	struct crash_mem *cmem;
-	unsigned int nr_ranges;
-	int ret;
-
-	nr_ranges = 1; /* For exclusion of crashkernel region */
-	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
-
-	cmem = kmalloc(struct_size(cmem, ranges, nr_ranges), GFP_KERNEL);
-	if (!cmem)
-		return -ENOMEM;
-
-	cmem->max_nr_ranges = nr_ranges;
-	cmem->nr_ranges = 0;
-	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
-	if (ret)
-		goto out;
-
-	/* 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);
-
-out:
-	kfree(cmem);
-	return ret;
-}
-
-static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
-				 unsigned long cmdline_len)
-{
-	int elfcorehdr_strlen;
-	char *cmdline_ptr;
-
-	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
-	if (!cmdline_ptr)
-		return NULL;
-
-	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
-		image->elf_load_addr);
-
-	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
-		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
-		kfree(cmdline_ptr);
-		return NULL;
-	}
-
-	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
-	/* Ensure it's nul terminated */
-	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
-	return cmdline_ptr;
-}
-
-static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
-			    unsigned long kernel_len, char *initrd,
-			    unsigned long initrd_len, char *cmdline,
-			    unsigned long cmdline_len)
-{
-	int ret;
-	unsigned long old_kernel_pbase = ULONG_MAX;
-	unsigned long new_kernel_pbase = 0UL;
-	unsigned long initrd_pbase = 0UL;
-	unsigned long headers_sz;
-	unsigned long kernel_start;
-	void *fdt, *headers;
-	struct elfhdr ehdr;
-	struct kexec_buf kbuf;
-	struct kexec_elf_info elf_info;
-	char *modified_cmdline = NULL;
-
-	ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
-	if (ret)
-		return ERR_PTR(ret);
-
-	ret = elf_find_pbase(image, kernel_len, &ehdr, &elf_info,
-			     &old_kernel_pbase, &new_kernel_pbase);
-	if (ret)
-		goto out;
-	kernel_start = image->start;
-	pr_notice("The entry point of kernel at 0x%lx\n", image->start);
-
-	/* Add the kernel binary to the image */
-	ret = riscv_kexec_elf_load(image, &ehdr, &elf_info,
-				   old_kernel_pbase, new_kernel_pbase);
-	if (ret)
-		goto out;
-
-	kbuf.image = image;
-	kbuf.buf_min = new_kernel_pbase + kernel_len;
-	kbuf.buf_max = ULONG_MAX;
-
-	/* Add elfcorehdr */
-	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;
-		}
-
-		kbuf.buffer = headers;
-		kbuf.bufsz = headers_sz;
-		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-		kbuf.memsz = headers_sz;
-		kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
-		kbuf.top_down = true;
-
-		ret = kexec_add_buffer(&kbuf);
-		if (ret) {
-			vfree(headers);
-			goto out;
-		}
-		image->elf_headers = headers;
-		image->elf_load_addr = kbuf.mem;
-		image->elf_headers_sz = headers_sz;
-
-		pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
-			 image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
-
-		/* Setup cmdline for kdump kernel case */
-		modified_cmdline = setup_kdump_cmdline(image, cmdline,
-						       cmdline_len);
-		if (!modified_cmdline) {
-			pr_err("Setting up cmdline for kdump kernel failed\n");
-			ret = -EINVAL;
-			goto out;
-		}
-		cmdline = modified_cmdline;
-	}
-
-#ifdef CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY
-	/* Add purgatory to the image */
-	kbuf.top_down = true;
-	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-	ret = kexec_load_purgatory(image, &kbuf);
-	if (ret) {
-		pr_err("Error loading purgatory ret=%d\n", ret);
-		goto out;
-	}
-	ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",
-					     &kernel_start,
-					     sizeof(kernel_start), 0);
-	if (ret)
-		pr_err("Error update purgatory ret=%d\n", ret);
-#endif /* CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY */
-
-	/* Add the initrd to the image */
-	if (initrd != NULL) {
-		kbuf.buffer = initrd;
-		kbuf.bufsz = kbuf.memsz = initrd_len;
-		kbuf.buf_align = PAGE_SIZE;
-		kbuf.top_down = true;
-		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-		ret = kexec_add_buffer(&kbuf);
-		if (ret)
-			goto out;
-		initrd_pbase = kbuf.mem;
-		pr_notice("Loaded initrd at 0x%lx\n", initrd_pbase);
-	}
-
-	/* Add the DTB to the image */
-	fdt = of_kexec_alloc_and_setup_fdt(image, initrd_pbase,
-					   initrd_len, cmdline, 0);
-	if (!fdt) {
-		pr_err("Error setting up the new device tree.\n");
-		ret = -EINVAL;
-		goto out;
-	}
-
-	fdt_pack(fdt);
-	kbuf.buffer = fdt;
-	kbuf.bufsz = kbuf.memsz = fdt_totalsize(fdt);
-	kbuf.buf_align = PAGE_SIZE;
-	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-	kbuf.top_down = true;
-	ret = kexec_add_buffer(&kbuf);
-	if (ret) {
-		pr_err("Error add DTB kbuf ret=%d\n", ret);
-		goto out_free_fdt;
-	}
-	/* Cache the fdt buffer address for memory cleanup */
-	image->arch.fdt = fdt;
-	pr_notice("Loaded device tree at 0x%lx\n", kbuf.mem);
-	goto out;
-
-out_free_fdt:
-	kvfree(fdt);
-out:
-	kfree(modified_cmdline);
-	kexec_free_elf_info(&elf_info);
-	return ret ? ERR_PTR(ret) : NULL;
-}
-
-#define RV_X(x, s, n)  (((x) >> (s)) & ((1 << (n)) - 1))
-#define RISCV_IMM_BITS 12
-#define RISCV_IMM_REACH (1LL << RISCV_IMM_BITS)
-#define RISCV_CONST_HIGH_PART(x) \
-	(((x) + (RISCV_IMM_REACH >> 1)) & ~(RISCV_IMM_REACH - 1))
-#define RISCV_CONST_LOW_PART(x) ((x) - RISCV_CONST_HIGH_PART(x))
-
-#define ENCODE_ITYPE_IMM(x) \
-	(RV_X(x, 0, 12) << 20)
-#define ENCODE_BTYPE_IMM(x) \
-	((RV_X(x, 1, 4) << 8) | (RV_X(x, 5, 6) << 25) | \
-	(RV_X(x, 11, 1) << 7) | (RV_X(x, 12, 1) << 31))
-#define ENCODE_UTYPE_IMM(x) \
-	(RV_X(x, 12, 20) << 12)
-#define ENCODE_JTYPE_IMM(x) \
-	((RV_X(x, 1, 10) << 21) | (RV_X(x, 11, 1) << 20) | \
-	(RV_X(x, 12, 8) << 12) | (RV_X(x, 20, 1) << 31))
-#define ENCODE_CBTYPE_IMM(x) \
-	((RV_X(x, 1, 2) << 3) | (RV_X(x, 3, 2) << 10) | (RV_X(x, 5, 1) << 2) | \
-	(RV_X(x, 6, 2) << 5) | (RV_X(x, 8, 1) << 12))
-#define ENCODE_CJTYPE_IMM(x) \
-	((RV_X(x, 1, 3) << 3) | (RV_X(x, 4, 1) << 11) | (RV_X(x, 5, 1) << 2) | \
-	(RV_X(x, 6, 1) << 7) | (RV_X(x, 7, 1) << 6) | (RV_X(x, 8, 2) << 9) | \
-	(RV_X(x, 10, 1) << 8) | (RV_X(x, 11, 1) << 12))
-#define ENCODE_UJTYPE_IMM(x) \
-	(ENCODE_UTYPE_IMM(RISCV_CONST_HIGH_PART(x)) | \
-	(ENCODE_ITYPE_IMM(RISCV_CONST_LOW_PART(x)) << 32))
-#define ENCODE_UITYPE_IMM(x) \
-	(ENCODE_UTYPE_IMM(x) | (ENCODE_ITYPE_IMM(x) << 32))
-
-#define CLEAN_IMM(type, x) \
-	((~ENCODE_##type##_IMM((uint64_t)(-1))) & (x))
-
-int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
-				     Elf_Shdr *section,
-				     const Elf_Shdr *relsec,
-				     const Elf_Shdr *symtab)
-{
-	const char *strtab, *name, *shstrtab;
-	const Elf_Shdr *sechdrs;
-	Elf64_Rela *relas;
-	int i, r_type;
-
-	/* String & section header string table */
-	sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;
-	strtab = (char *)pi->ehdr + sechdrs[symtab->sh_link].sh_offset;
-	shstrtab = (char *)pi->ehdr + sechdrs[pi->ehdr->e_shstrndx].sh_offset;
-
-	relas = (void *)pi->ehdr + relsec->sh_offset;
-
-	for (i = 0; i < relsec->sh_size / sizeof(*relas); i++) {
-		const Elf_Sym *sym;	/* symbol to relocate */
-		unsigned long addr;	/* final location after relocation */
-		unsigned long val;	/* relocated symbol value */
-		unsigned long sec_base;	/* relocated symbol value */
-		void *loc;		/* tmp location to modify */
-
-		sym = (void *)pi->ehdr + symtab->sh_offset;
-		sym += ELF64_R_SYM(relas[i].r_info);
-
-		if (sym->st_name)
-			name = strtab + sym->st_name;
-		else
-			name = shstrtab + sechdrs[sym->st_shndx].sh_name;
-
-		loc = pi->purgatory_buf;
-		loc += section->sh_offset;
-		loc += relas[i].r_offset;
-
-		if (sym->st_shndx == SHN_ABS)
-			sec_base = 0;
-		else if (sym->st_shndx >= pi->ehdr->e_shnum) {
-			pr_err("Invalid section %d for symbol %s\n",
-			       sym->st_shndx, name);
-			return -ENOEXEC;
-		} else
-			sec_base = pi->sechdrs[sym->st_shndx].sh_addr;
-
-		val = sym->st_value;
-		val += sec_base;
-		val += relas[i].r_addend;
-
-		addr = section->sh_addr + relas[i].r_offset;
-
-		r_type = ELF64_R_TYPE(relas[i].r_info);
-
-		switch (r_type) {
-		case R_RISCV_BRANCH:
-			*(u32 *)loc = CLEAN_IMM(BTYPE, *(u32 *)loc) |
-				 ENCODE_BTYPE_IMM(val - addr);
-			break;
-		case R_RISCV_JAL:
-			*(u32 *)loc = CLEAN_IMM(JTYPE, *(u32 *)loc) |
-				 ENCODE_JTYPE_IMM(val - addr);
-			break;
-		/*
-		 * With no R_RISCV_PCREL_LO12_S, R_RISCV_PCREL_LO12_I
-		 * sym is expected to be next to R_RISCV_PCREL_HI20
-		 * in purgatory relsec. Handle it like R_RISCV_CALL
-		 * sym, instead of searching the whole relsec.
-		 */
-		case R_RISCV_PCREL_HI20:
-		case R_RISCV_CALL_PLT:
-		case R_RISCV_CALL:
-			*(u64 *)loc = CLEAN_IMM(UITYPE, *(u64 *)loc) |
-				 ENCODE_UJTYPE_IMM(val - addr);
-			break;
-		case R_RISCV_RVC_BRANCH:
-			*(u32 *)loc = CLEAN_IMM(CBTYPE, *(u32 *)loc) |
-				 ENCODE_CBTYPE_IMM(val - addr);
-			break;
-		case R_RISCV_RVC_JUMP:
-			*(u32 *)loc = CLEAN_IMM(CJTYPE, *(u32 *)loc) |
-				 ENCODE_CJTYPE_IMM(val - addr);
-			break;
-		case R_RISCV_ADD32:
-			*(u32 *)loc += val;
-			break;
-		case R_RISCV_SUB32:
-			*(u32 *)loc -= val;
-			break;
-		/* It has been applied by R_RISCV_PCREL_HI20 sym */
-		case R_RISCV_PCREL_LO12_I:
-		case R_RISCV_ALIGN:
-		case R_RISCV_RELAX:
-			break;
-		default:
-			pr_err("Unknown rela relocation: %d\n", r_type);
-			return -ENOEXEC;
-		}
-	}
-	return 0;
-}
-
-const struct kexec_file_ops elf_kexec_ops = {
-	.probe = kexec_elf_probe,
-	.load  = elf_kexec_load,
-};
diff --git a/arch/riscv/kernel/kexec_elf.c b/arch/riscv/kernel/kexec_elf.c
new file mode 100644
index 000000000000..f41272da6b2f
--- /dev/null
+++ b/arch/riscv/kernel/kexec_elf.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Load ELF vmlinux file for the kexec_file_load syscall.
+ *
+ * Copyright (C) 2021 Huawei Technologies Co, Ltd.
+ *
+ * Author: Liao Chang (liaochang1@...wei.com)
+ *
+ * Based on kexec-tools' kexec-elf-riscv.c, heavily modified
+ * for kernel.
+ */
+
+#define pr_fmt(fmt)	"kexec_image: " fmt
+
+#include <linux/elf.h>
+#include <linux/kexec.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/libfdt.h>
+#include <linux/types.h>
+#include <linux/memblock.h>
+#include <asm/setup.h>
+
+static int riscv_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
+				struct kexec_elf_info *elf_info, unsigned long old_pbase,
+				unsigned long new_pbase)
+{
+	int i;
+	int ret = 0;
+	size_t size;
+	struct kexec_buf kbuf;
+	const struct elf_phdr *phdr;
+
+	kbuf.image = image;
+
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		phdr = &elf_info->proghdrs[i];
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		size = phdr->p_filesz;
+		if (size > phdr->p_memsz)
+			size = phdr->p_memsz;
+
+		kbuf.buffer = (void *) elf_info->buffer + phdr->p_offset;
+		kbuf.bufsz = size;
+		kbuf.buf_align = phdr->p_align;
+		kbuf.mem = phdr->p_paddr - old_pbase + new_pbase;
+		kbuf.memsz = phdr->p_memsz;
+		kbuf.top_down = false;
+		ret = kexec_add_buffer(&kbuf);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/*
+ * Go through the available phsyical memory regions and find one that hold
+ * an image of the specified size.
+ */
+static int elf_find_pbase(struct kimage *image, unsigned long kernel_len,
+			  struct elfhdr *ehdr, struct kexec_elf_info *elf_info,
+			  unsigned long *old_pbase, unsigned long *new_pbase)
+{
+	int i;
+	int ret;
+	struct kexec_buf kbuf;
+	const struct elf_phdr *phdr;
+	unsigned long lowest_paddr = ULONG_MAX;
+	unsigned long lowest_vaddr = ULONG_MAX;
+
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		phdr = &elf_info->proghdrs[i];
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		if (lowest_paddr > phdr->p_paddr)
+			lowest_paddr = phdr->p_paddr;
+
+		if (lowest_vaddr > phdr->p_vaddr)
+			lowest_vaddr = phdr->p_vaddr;
+	}
+
+	kbuf.image = image;
+	kbuf.buf_min = lowest_paddr;
+	kbuf.buf_max = ULONG_MAX;
+
+	/*
+	 * Current riscv boot protocol requires 2MB alignment for
+	 * RV64 and 4MB alignment for RV32
+	 *
+	 */
+	kbuf.buf_align = PMD_SIZE;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	kbuf.memsz = ALIGN(kernel_len, PAGE_SIZE);
+	kbuf.top_down = false;
+	ret = arch_kexec_locate_mem_hole(&kbuf);
+	if (!ret) {
+		*old_pbase = lowest_paddr;
+		*new_pbase = kbuf.mem;
+		image->start = ehdr->e_entry - lowest_vaddr + kbuf.mem;
+	}
+	return ret;
+}
+
+static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
+			    unsigned long kernel_len, char *initrd,
+			    unsigned long initrd_len, char *cmdline,
+			    unsigned long cmdline_len)
+{
+	int ret;
+	unsigned long old_kernel_pbase = ULONG_MAX;
+	unsigned long new_kernel_pbase = 0UL;
+	struct elfhdr ehdr;
+	struct kexec_elf_info elf_info;
+
+	ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
+	if (ret)
+		return ERR_PTR(ret);
+
+	ret = elf_find_pbase(image, kernel_len, &ehdr, &elf_info,
+			     &old_kernel_pbase, &new_kernel_pbase);
+	if (ret)
+		goto out;
+
+	pr_notice("The entry point of kernel at 0x%lx\n", image->start);
+
+	/* Add the kernel binary to the image */
+	ret = riscv_kexec_elf_load(image, &ehdr, &elf_info,
+				   old_kernel_pbase, new_kernel_pbase);
+	if (ret)
+		goto out;
+
+	ret = load_extra_segments(image, image->start, kernel_len,
+				  initrd, initrd_len, cmdline, cmdline_len);
+out:
+	kexec_free_elf_info(&elf_info);
+	return ret ? ERR_PTR(ret) : NULL;
+}
+
+
+const struct kexec_file_ops elf_kexec_ops = {
+	.probe = kexec_elf_probe,
+	.load  = elf_kexec_load,
+};
diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index 6ebd3ab5a9eb..aedb8c16a283 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -7,6 +7,13 @@
  * Author: Liao Chang (liaochang1@...wei.com)
  */
 #include <linux/kexec.h>
+#include <linux/elf.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/libfdt.h>
+#include <linux/types.h>
+#include <linux/memblock.h>
+#include <asm/setup.h>
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
 	&elf_kexec_ops,
-- 
2.20.1

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