// SPDX-License-Identifier: GPL-2.0-only
  /*
   * Load ELF vmlinux file for the kexec_file_load syscall.
   *
   * Copyright (C) 2004  Adam Litke (agl@us.ibm.com)
   * Copyright (C) 2004  IBM Corp.
   * Copyright (C) 2005  R Sharada (sharada@in.ibm.com)
   * Copyright (C) 2006  Mohan Kumar M (mohan@in.ibm.com)
   * Copyright (C) 2016  IBM Corporation
   *
   * Based on kexec-tools' kexec-elf-exec.c and kexec-elf-ppc64.c.
   * Heavily modified for the kernel by
   * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>.
   */
  
  #define pr_fmt(fmt)	"kexec_elf: " fmt
  
  #include <linux/elf.h>
  #include <linux/kexec.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/types.h>

  static inline bool elf_is_elf_file(const struct elfhdr *ehdr)
  {
  	return memcmp(ehdr->e_ident, ELFMAG, SELFMAG) == 0;
  }
  
  static uint64_t elf64_to_cpu(const struct elfhdr *ehdr, uint64_t value)
  {
  	if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
  		value = le64_to_cpu(value);
  	else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
  		value = be64_to_cpu(value);
  
  	return value;
  }

  static uint32_t elf32_to_cpu(const struct elfhdr *ehdr, uint32_t value)

  {
  	if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB)

  		value = le32_to_cpu(value);

  	else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)

  		value = be32_to_cpu(value);

  
  	return value;
  }

  static uint16_t elf16_to_cpu(const struct elfhdr *ehdr, uint16_t value)

  {
  	if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB)

  		value = le16_to_cpu(value);

  	else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)

  		value = be16_to_cpu(value);

  
  	return value;
  }
  
  /**
   * elf_is_ehdr_sane - check that it is safe to use the ELF header
   * @buf_len:	size of the buffer in which the ELF file is loaded.
   */
  static bool elf_is_ehdr_sane(const struct elfhdr *ehdr, size_t buf_len)
  {
  	if (ehdr->e_phnum > 0 && ehdr->e_phentsize != sizeof(struct elf_phdr)) {
  		pr_debug("Bad program header size.
  ");
  		return false;
  	} else if (ehdr->e_shnum > 0 &&
  		   ehdr->e_shentsize != sizeof(struct elf_shdr)) {
  		pr_debug("Bad section header size.
  ");
  		return false;
  	} else if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
  		   ehdr->e_version != EV_CURRENT) {
  		pr_debug("Unknown ELF version.
  ");
  		return false;
  	}
  
  	if (ehdr->e_phoff > 0 && ehdr->e_phnum > 0) {
  		size_t phdr_size;
  
  		/*
  		 * e_phnum is at most 65535 so calculating the size of the
  		 * program header cannot overflow.
  		 */
  		phdr_size = sizeof(struct elf_phdr) * ehdr->e_phnum;
  
  		/* Sanity check the program header table location. */
  		if (ehdr->e_phoff + phdr_size < ehdr->e_phoff) {
  			pr_debug("Program headers at invalid location.
  ");
  			return false;
  		} else if (ehdr->e_phoff + phdr_size > buf_len) {
  			pr_debug("Program headers truncated.
  ");
  			return false;
  		}
  	}
  
  	if (ehdr->e_shoff > 0 && ehdr->e_shnum > 0) {
  		size_t shdr_size;
  
  		/*
  		 * e_shnum is at most 65536 so calculating
  		 * the size of the section header cannot overflow.
  		 */
  		shdr_size = sizeof(struct elf_shdr) * ehdr->e_shnum;
  
  		/* Sanity check the section header table location. */
  		if (ehdr->e_shoff + shdr_size < ehdr->e_shoff) {
  			pr_debug("Section headers at invalid location.
  ");
  			return false;
  		} else if (ehdr->e_shoff + shdr_size > buf_len) {
  			pr_debug("Section headers truncated.
  ");
  			return false;
  		}
  	}
  
  	return true;
  }
  
  static int elf_read_ehdr(const char *buf, size_t len, struct elfhdr *ehdr)
  {
  	struct elfhdr *buf_ehdr;
  
  	if (len < sizeof(*buf_ehdr)) {
  		pr_debug("Buffer is too small to hold ELF header.
  ");
  		return -ENOEXEC;
  	}
  
  	memset(ehdr, 0, sizeof(*ehdr));
  	memcpy(ehdr->e_ident, buf, sizeof(ehdr->e_ident));
  	if (!elf_is_elf_file(ehdr)) {
  		pr_debug("No ELF header magic.
  ");
  		return -ENOEXEC;
  	}
  
  	if (ehdr->e_ident[EI_CLASS] != ELF_CLASS) {
  		pr_debug("Not a supported ELF class.
  ");
  		return -ENOEXEC;
  	} else  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB &&
  		ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
  		pr_debug("Not a supported ELF data format.
  ");
  		return -ENOEXEC;
  	}
  
  	buf_ehdr = (struct elfhdr *) buf;
  	if (elf16_to_cpu(ehdr, buf_ehdr->e_ehsize) != sizeof(*buf_ehdr)) {
  		pr_debug("Bad ELF header size.
  ");
  		return -ENOEXEC;
  	}
  
  	ehdr->e_type      = elf16_to_cpu(ehdr, buf_ehdr->e_type);
  	ehdr->e_machine   = elf16_to_cpu(ehdr, buf_ehdr->e_machine);
  	ehdr->e_version   = elf32_to_cpu(ehdr, buf_ehdr->e_version);

  	ehdr->e_flags     = elf32_to_cpu(ehdr, buf_ehdr->e_flags);
  	ehdr->e_phentsize = elf16_to_cpu(ehdr, buf_ehdr->e_phentsize);
  	ehdr->e_phnum     = elf16_to_cpu(ehdr, buf_ehdr->e_phnum);
  	ehdr->e_shentsize = elf16_to_cpu(ehdr, buf_ehdr->e_shentsize);
  	ehdr->e_shnum     = elf16_to_cpu(ehdr, buf_ehdr->e_shnum);
  	ehdr->e_shstrndx  = elf16_to_cpu(ehdr, buf_ehdr->e_shstrndx);

  	switch (ehdr->e_ident[EI_CLASS]) {
  	case ELFCLASS64:
  		ehdr->e_entry = elf64_to_cpu(ehdr, buf_ehdr->e_entry);
  		ehdr->e_phoff = elf64_to_cpu(ehdr, buf_ehdr->e_phoff);
  		ehdr->e_shoff = elf64_to_cpu(ehdr, buf_ehdr->e_shoff);
  		break;
  
  	case ELFCLASS32:
  		ehdr->e_entry = elf32_to_cpu(ehdr, buf_ehdr->e_entry);
  		ehdr->e_phoff = elf32_to_cpu(ehdr, buf_ehdr->e_phoff);
  		ehdr->e_shoff = elf32_to_cpu(ehdr, buf_ehdr->e_shoff);
  		break;
  
  	default:
  		pr_debug("Unknown ELF class.
  ");
  		return -EINVAL;
  	}

  	return elf_is_ehdr_sane(ehdr, len) ? 0 : -ENOEXEC;
  }
  
  /**
   * elf_is_phdr_sane - check that it is safe to use the program header
   * @buf_len:	size of the buffer in which the ELF file is loaded.
   */
  static bool elf_is_phdr_sane(const struct elf_phdr *phdr, size_t buf_len)
  {
  
  	if (phdr->p_offset + phdr->p_filesz < phdr->p_offset) {
  		pr_debug("ELF segment location wraps around.
  ");
  		return false;
  	} else if (phdr->p_offset + phdr->p_filesz > buf_len) {
  		pr_debug("ELF segment not in file.
  ");
  		return false;
  	} else if (phdr->p_paddr + phdr->p_memsz < phdr->p_paddr) {
  		pr_debug("ELF segment address wraps around.
  ");
  		return false;
  	}
  
  	return true;
  }
  
  static int elf_read_phdr(const char *buf, size_t len,
  			 struct kexec_elf_info *elf_info,
  			 int idx)
  {
  	/* Override the const in proghdrs, we are the ones doing the loading. */
  	struct elf_phdr *phdr = (struct elf_phdr *) &elf_info->proghdrs[idx];

  	const struct elfhdr *ehdr = elf_info->ehdr;

  	const char *pbuf;
  	struct elf_phdr *buf_phdr;
  
  	pbuf = buf + elf_info->ehdr->e_phoff + (idx * sizeof(*buf_phdr));
  	buf_phdr = (struct elf_phdr *) pbuf;
  
  	phdr->p_type   = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_type);

  	phdr->p_flags  = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);

  	switch (ehdr->e_ident[EI_CLASS]) {
  	case ELFCLASS64:
  		phdr->p_offset = elf64_to_cpu(ehdr, buf_phdr->p_offset);
  		phdr->p_paddr  = elf64_to_cpu(ehdr, buf_phdr->p_paddr);
  		phdr->p_vaddr  = elf64_to_cpu(ehdr, buf_phdr->p_vaddr);
  		phdr->p_filesz = elf64_to_cpu(ehdr, buf_phdr->p_filesz);
  		phdr->p_memsz  = elf64_to_cpu(ehdr, buf_phdr->p_memsz);
  		phdr->p_align  = elf64_to_cpu(ehdr, buf_phdr->p_align);
  		break;
  
  	case ELFCLASS32:
  		phdr->p_offset = elf32_to_cpu(ehdr, buf_phdr->p_offset);
  		phdr->p_paddr  = elf32_to_cpu(ehdr, buf_phdr->p_paddr);
  		phdr->p_vaddr  = elf32_to_cpu(ehdr, buf_phdr->p_vaddr);
  		phdr->p_filesz = elf32_to_cpu(ehdr, buf_phdr->p_filesz);
  		phdr->p_memsz  = elf32_to_cpu(ehdr, buf_phdr->p_memsz);
  		phdr->p_align  = elf32_to_cpu(ehdr, buf_phdr->p_align);
  		break;
  
  	default:
  		pr_debug("Unknown ELF class.
  ");
  		return -EINVAL;
  	}

  
  	return elf_is_phdr_sane(phdr, len) ? 0 : -ENOEXEC;
  }
  
  /**
   * elf_read_phdrs - read the program headers from the buffer
   *
   * This function assumes that the program header table was checked for sanity.
   * Use elf_is_ehdr_sane() if it wasn't.
   */
  static int elf_read_phdrs(const char *buf, size_t len,
  			  struct kexec_elf_info *elf_info)
  {
  	size_t phdr_size, i;
  	const struct elfhdr *ehdr = elf_info->ehdr;
  
  	/*
  	 * e_phnum is at most 65535 so calculating the size of the
  	 * program header cannot overflow.
  	 */
  	phdr_size = sizeof(struct elf_phdr) * ehdr->e_phnum;
  
  	elf_info->proghdrs = kzalloc(phdr_size, GFP_KERNEL);
  	if (!elf_info->proghdrs)
  		return -ENOMEM;
  
  	for (i = 0; i < ehdr->e_phnum; i++) {
  		int ret;
  
  		ret = elf_read_phdr(buf, len, elf_info, i);
  		if (ret) {
  			kfree(elf_info->proghdrs);
  			elf_info->proghdrs = NULL;
  			return ret;
  		}
  	}
  
  	return 0;
  }
  
  /**

   * elf_read_from_buffer - read ELF file and sets up ELF header and ELF info
   * @buf:	Buffer to read ELF file from.
   * @len:	Size of @buf.
   * @ehdr:	Pointer to existing struct which will be populated.
   * @elf_info:	Pointer to existing struct which will be populated.
   *
   * This function allows reading ELF files with different byte order than
   * the kernel, byte-swapping the fields as needed.
   *
   * Return:
   * On success returns 0, and the caller should call
   * kexec_free_elf_info(elf_info) to free the memory allocated for the section
   * and program headers.
   */
  static int elf_read_from_buffer(const char *buf, size_t len,
  				struct elfhdr *ehdr,
  				struct kexec_elf_info *elf_info)
  {
  	int ret;
  
  	ret = elf_read_ehdr(buf, len, ehdr);
  	if (ret)
  		return ret;
  
  	elf_info->buffer = buf;
  	elf_info->ehdr = ehdr;
  	if (ehdr->e_phoff > 0 && ehdr->e_phnum > 0) {
  		ret = elf_read_phdrs(buf, len, elf_info);
  		if (ret)
  			return ret;
  	}

  	return 0;
  }
  
  /**
   * kexec_free_elf_info - free memory allocated by elf_read_from_buffer
   */
  void kexec_free_elf_info(struct kexec_elf_info *elf_info)
  {
  	kfree(elf_info->proghdrs);

  	memset(elf_info, 0, sizeof(*elf_info));
  }
  /**
   * kexec_build_elf_info - read ELF executable and check that we can use it
   */
  int kexec_build_elf_info(const char *buf, size_t len, struct elfhdr *ehdr,
  			       struct kexec_elf_info *elf_info)
  {
  	int i;
  	int ret;
  
  	ret = elf_read_from_buffer(buf, len, ehdr, elf_info);
  	if (ret)
  		return ret;
  
  	/* Big endian vmlinux has type ET_DYN. */
  	if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
  		pr_err("Not an ELF executable.
  ");
  		goto error;
  	} else if (!elf_info->proghdrs) {
  		pr_err("No ELF program header.
  ");
  		goto error;
  	}
  
  	for (i = 0; i < ehdr->e_phnum; i++) {
  		/*
  		 * Kexec does not support loading interpreters.
  		 * In addition this check keeps us from attempting
  		 * to kexec ordinay executables.
  		 */
  		if (elf_info->proghdrs[i].p_type == PT_INTERP) {
  			pr_err("Requires an ELF interpreter.
  ");
  			goto error;
  		}
  	}
  
  	return 0;
  error:
  	kexec_free_elf_info(elf_info);
  	return -ENOEXEC;
  }
  
  
  int kexec_elf_probe(const char *buf, unsigned long len)
  {
  	struct elfhdr ehdr;
  	struct kexec_elf_info elf_info;
  	int ret;
  
  	ret = kexec_build_elf_info(buf, len, &ehdr, &elf_info);
  	if (ret)
  		return ret;
  
  	kexec_free_elf_info(&elf_info);
  
  	return elf_check_arch(&ehdr) ? 0 : -ENOEXEC;
  }
  
  /**
   * kexec_elf_load - load ELF executable image
   * @lowest_load_addr:	On return, will be the address where the first PT_LOAD
   *			section will be loaded in memory.
   *
   * Return:
   * 0 on success, negative value on failure.
   */
  int kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
  			 struct kexec_elf_info *elf_info,
  			 struct kexec_buf *kbuf,
  			 unsigned long *lowest_load_addr)
  {

  	unsigned long lowest_addr = UINT_MAX;

  	int ret;
  	size_t i;
  
  	/* Read in the PT_LOAD segments. */
  	for (i = 0; i < ehdr->e_phnum; i++) {
  		unsigned long load_addr;
  		size_t size;
  		const struct elf_phdr *phdr;
  
  		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->memsz = phdr->p_memsz;
  		kbuf->buf_align = phdr->p_align;

  		kbuf->buf_min = phdr->p_paddr;

  		kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
  		ret = kexec_add_buffer(kbuf);
  		if (ret)
  			goto out;
  		load_addr = kbuf->mem;
  
  		if (load_addr < lowest_addr)
  			lowest_addr = load_addr;
  	}

  	*lowest_load_addr = lowest_addr;
  	ret = 0;
   out:
  	return ret;
  }