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Subject: Re: [PATCH v2 1/7] kexec: add KEXEC_ELF
To: Sven Schnelle <svens@stackframe.org>, kexec@lists.infradead.org
References: <20190709194328.16991-1-svens@stackframe.org>
 <20190709194328.16991-2-svens@stackframe.org>
From: Christophe Leroy <christophe.leroy@c-s.fr>
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Date: Wed, 10 Jul 2019 13:19:13 +0000
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

Hi Sven,

On 07/09/2019 07:43 PM, Sven Schnelle wrote:
> Right now powerpc provides an implementation to read elf files
> with the kexec_file() syscall. Make that available as a public
> kexec interface so it can be re-used on other architectures.
> 
> Signed-off-by: Sven Schnelle <svens@stackframe.org>
> ---
>   arch/Kconfig                       |   3 +
>   arch/powerpc/Kconfig               |   1 +
>   arch/powerpc/kernel/kexec_elf_64.c | 551 +----------------------------
>   include/linux/kexec.h              |  24 ++
>   kernel/Makefile                    |   1 +
>   kernel/kexec_elf.c                 | 537 ++++++++++++++++++++++++++++
>   6 files changed, 576 insertions(+), 541 deletions(-)
>   create mode 100644 kernel/kexec_elf.c

Why are you persisting at not using -C when creating your patch ? Do you 
want to hide the changes you did while copying 
arch/powerpc/kernel/kexec_elf_64.c to kernel/kexec_elf.c ?
Or you want to make life harder for the reviewers ?

git format-patch -C shows:

  arch/Kconfig                                       |   3 +
  arch/powerpc/Kconfig                               |   1 +
  arch/powerpc/kernel/kexec_elf_64.c                 | 551 
+--------------------
  include/linux/kexec.h                              |  24 +
  kernel/Makefile                                    |   1 +
  .../kernel/kexec_elf_64.c => kernel/kexec_elf.c    | 199 ++------
  6 files changed, 75 insertions(+), 704 deletions(-)
  copy arch/powerpc/kernel/kexec_elf_64.c => kernel/kexec_elf.c (71%)

I mentionned it a couple of times, I even resent your last patch 
formatted that way to show the advantage. I can ear if you find it 
worthless, but tell what your concern are with that, don't just ignore 
it please.

Cheers
Christophe

> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index c47b328eada0..30694aca4316 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -18,6 +18,9 @@ config KEXEC_CORE
>   	select CRASH_CORE
>   	bool
>   
> +config KEXEC_ELF
> +	bool
> +
>   config HAVE_IMA_KEXEC
>   	bool
>   
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 12cee37f15c4..addc2dad78e0 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -510,6 +510,7 @@ config KEXEC_FILE
>   	select KEXEC_CORE
>   	select HAVE_IMA_KEXEC
>   	select BUILD_BIN2C
> +	select KEXEC_ELF
>   	depends on PPC64
>   	depends on CRYPTO=y
>   	depends on CRYPTO_SHA256=y
> diff --git a/arch/powerpc/kernel/kexec_elf_64.c b/arch/powerpc/kernel/kexec_elf_64.c
> index ba4f18a43ee8..30bd57a93c17 100644
> --- a/arch/powerpc/kernel/kexec_elf_64.c
> +++ b/arch/powerpc/kernel/kexec_elf_64.c
> @@ -1,3 +1,4 @@
> +// SPDX-License-Identifier: GPL-2.0-only
>   /*
>    * Load ELF vmlinux file for the kexec_file_load syscall.
>    *
> @@ -10,15 +11,6 @@
>    * 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>.
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License as published by
> - * the Free Software Foundation (version 2 of the License).
> - *
> - * This program is distributed in the hope that it will be useful,
> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> - * GNU General Public License for more details.
>    */
>   
>   #define pr_fmt(fmt)	"kexec_elf: " fmt
> @@ -39,532 +31,6 @@
>   #define Elf_Rel		Elf64_Rel
>   #endif /* Elf_Rel */
>   
> -struct elf_info {
> -	/*
> -	 * Where the ELF binary contents are kept.
> -	 * Memory managed by the user of the struct.
> -	 */
> -	const char *buffer;
> -
> -	const struct elfhdr *ehdr;
> -	const struct elf_phdr *proghdrs;
> -	struct elf_shdr *sechdrs;
> -};
> -
> -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 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;
> -}
> -
> -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;
> -}
> -
> -/**
> - * 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.\n");
> -		return false;
> -	} else if (ehdr->e_shnum > 0 &&
> -		   ehdr->e_shentsize != sizeof(struct elf_shdr)) {
> -		pr_debug("Bad section header size.\n");
> -		return false;
> -	} else if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
> -		   ehdr->e_version != EV_CURRENT) {
> -		pr_debug("Unknown ELF version.\n");
> -		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.\n");
> -			return false;
> -		} else if (ehdr->e_phoff + phdr_size > buf_len) {
> -			pr_debug("Program headers truncated.\n");
> -			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.\n");
> -			return false;
> -		} else if (ehdr->e_shoff + shdr_size > buf_len) {
> -			pr_debug("Section headers truncated.\n");
> -			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.\n");
> -		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.\n");
> -		return -ENOEXEC;
> -	}
> -
> -	if (ehdr->e_ident[EI_CLASS] != ELF_CLASS) {
> -		pr_debug("Not a supported ELF class.\n");
> -		return -ENOEXEC;
> -	} else  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB &&
> -		ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
> -		pr_debug("Not a supported ELF data format.\n");
> -		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.\n");
> -		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_entry     = elf_addr_to_cpu(ehdr, buf_ehdr->e_entry);
> -	ehdr->e_phoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_phoff);
> -	ehdr->e_shoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_shoff);
> -	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);
> -
> -	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.\n");
> -		return false;
> -	} else if (phdr->p_offset + phdr->p_filesz > buf_len) {
> -		pr_debug("ELF segment not in file.\n");
> -		return false;
> -	} else if (phdr->p_paddr + phdr->p_memsz < phdr->p_paddr) {
> -		pr_debug("ELF segment address wraps around.\n");
> -		return false;
> -	}
> -
> -	return true;
> -}
> -
> -static int elf_read_phdr(const char *buf, size_t len, struct 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 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_offset = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_offset);
> -	phdr->p_paddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_paddr);
> -	phdr->p_vaddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_vaddr);
> -	phdr->p_flags  = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);
> -
> -	/*
> -	 * The following fields have a type equivalent to Elf_Addr
> -	 * both in 32 bit and 64 bit ELF.
> -	 */
> -	phdr->p_filesz = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_filesz);
> -	phdr->p_memsz  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_memsz);
> -	phdr->p_align  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_align);
> -
> -	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 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_is_shdr_sane - check that it is safe to use the section header
> - * @buf_len:	size of the buffer in which the ELF file is loaded.
> - */
> -static bool elf_is_shdr_sane(const struct elf_shdr *shdr, size_t buf_len)
> -{
> -	bool size_ok;
> -
> -	/* SHT_NULL headers have undefined values, so we can't check them. */
> -	if (shdr->sh_type == SHT_NULL)
> -		return true;
> -
> -	/* Now verify sh_entsize */
> -	switch (shdr->sh_type) {
> -	case SHT_SYMTAB:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Sym);
> -		break;
> -	case SHT_RELA:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Rela);
> -		break;
> -	case SHT_DYNAMIC:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Dyn);
> -		break;
> -	case SHT_REL:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Rel);
> -		break;
> -	case SHT_NOTE:
> -	case SHT_PROGBITS:
> -	case SHT_HASH:
> -	case SHT_NOBITS:
> -	default:
> -		/*
> -		 * This is a section whose entsize requirements
> -		 * I don't care about.  If I don't know about
> -		 * the section I can't care about it's entsize
> -		 * requirements.
> -		 */
> -		size_ok = true;
> -		break;
> -	}
> -
> -	if (!size_ok) {
> -		pr_debug("ELF section with wrong entry size.\n");
> -		return false;
> -	} else if (shdr->sh_addr + shdr->sh_size < shdr->sh_addr) {
> -		pr_debug("ELF section address wraps around.\n");
> -		return false;
> -	}
> -
> -	if (shdr->sh_type != SHT_NOBITS) {
> -		if (shdr->sh_offset + shdr->sh_size < shdr->sh_offset) {
> -			pr_debug("ELF section location wraps around.\n");
> -			return false;
> -		} else if (shdr->sh_offset + shdr->sh_size > buf_len) {
> -			pr_debug("ELF section not in file.\n");
> -			return false;
> -		}
> -	}
> -
> -	return true;
> -}
> -
> -static int elf_read_shdr(const char *buf, size_t len, struct elf_info *elf_info,
> -			 int idx)
> -{
> -	struct elf_shdr *shdr = &elf_info->sechdrs[idx];
> -	const struct elfhdr *ehdr = elf_info->ehdr;
> -	const char *sbuf;
> -	struct elf_shdr *buf_shdr;
> -
> -	sbuf = buf + ehdr->e_shoff + idx * sizeof(*buf_shdr);
> -	buf_shdr = (struct elf_shdr *) sbuf;
> -
> -	shdr->sh_name      = elf32_to_cpu(ehdr, buf_shdr->sh_name);
> -	shdr->sh_type      = elf32_to_cpu(ehdr, buf_shdr->sh_type);
> -	shdr->sh_addr      = elf_addr_to_cpu(ehdr, buf_shdr->sh_addr);
> -	shdr->sh_offset    = elf_addr_to_cpu(ehdr, buf_shdr->sh_offset);
> -	shdr->sh_link      = elf32_to_cpu(ehdr, buf_shdr->sh_link);
> -	shdr->sh_info      = elf32_to_cpu(ehdr, buf_shdr->sh_info);
> -
> -	/*
> -	 * The following fields have a type equivalent to Elf_Addr
> -	 * both in 32 bit and 64 bit ELF.
> -	 */
> -	shdr->sh_flags     = elf_addr_to_cpu(ehdr, buf_shdr->sh_flags);
> -	shdr->sh_size      = elf_addr_to_cpu(ehdr, buf_shdr->sh_size);
> -	shdr->sh_addralign = elf_addr_to_cpu(ehdr, buf_shdr->sh_addralign);
> -	shdr->sh_entsize   = elf_addr_to_cpu(ehdr, buf_shdr->sh_entsize);
> -
> -	return elf_is_shdr_sane(shdr, len) ? 0 : -ENOEXEC;
> -}
> -
> -/**
> - * elf_read_shdrs - read the section headers from the buffer
> - *
> - * This function assumes that the section header table was checked for sanity.
> - * Use elf_is_ehdr_sane() if it wasn't.
> - */
> -static int elf_read_shdrs(const char *buf, size_t len,
> -			  struct elf_info *elf_info)
> -{
> -	size_t shdr_size, i;
> -
> -	/*
> -	 * e_shnum is at most 65536 so calculating
> -	 * the size of the section header cannot overflow.
> -	 */
> -	shdr_size = sizeof(struct elf_shdr) * elf_info->ehdr->e_shnum;
> -
> -	elf_info->sechdrs = kzalloc(shdr_size, GFP_KERNEL);
> -	if (!elf_info->sechdrs)
> -		return -ENOMEM;
> -
> -	for (i = 0; i < elf_info->ehdr->e_shnum; i++) {
> -		int ret;
> -
> -		ret = elf_read_shdr(buf, len, elf_info, i);
> -		if (ret) {
> -			kfree(elf_info->sechdrs);
> -			elf_info->sechdrs = 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 elf_free_info(elf_info) to
> - * free the memory allocated for the section and program headers.
> - */
> -int elf_read_from_buffer(const char *buf, size_t len, struct elfhdr *ehdr,
> -			 struct 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;
> -	}
> -	if (ehdr->e_shoff > 0 && ehdr->e_shnum > 0) {
> -		ret = elf_read_shdrs(buf, len, elf_info);
> -		if (ret) {
> -			kfree(elf_info->proghdrs);
> -			return ret;
> -		}
> -	}
> -
> -	return 0;
> -}
> -
> -/**
> - * elf_free_info - free memory allocated by elf_read_from_buffer
> - */
> -void elf_free_info(struct elf_info *elf_info)
> -{
> -	kfree(elf_info->proghdrs);
> -	kfree(elf_info->sechdrs);
> -	memset(elf_info, 0, sizeof(*elf_info));
> -}
> -/**
> - * build_elf_exec_info - read ELF executable and check that we can use it
> - */
> -static int build_elf_exec_info(const char *buf, size_t len, struct elfhdr *ehdr,
> -			       struct 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.\n");
> -		goto error;
> -	} else if (!elf_info->proghdrs) {
> -		pr_err("No ELF program header.\n");
> -		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.\n");
> -			goto error;
> -		}
> -	}
> -
> -	return 0;
> -error:
> -	elf_free_info(elf_info);
> -	return -ENOEXEC;
> -}
> -
> -static int elf64_probe(const char *buf, unsigned long len)
> -{
> -	struct elfhdr ehdr;
> -	struct elf_info elf_info;
> -	int ret;
> -
> -	ret = build_elf_exec_info(buf, len, &ehdr, &elf_info);
> -	if (ret)
> -		return ret;
> -
> -	elf_free_info(&elf_info);
> -
> -	return elf_check_arch(&ehdr) ? 0 : -ENOEXEC;
> -}
> -
> -/**
> - * elf_exec_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.
> - */
> -static int elf_exec_load(struct kimage *image, struct elfhdr *ehdr,
> -			 struct elf_info *elf_info,
> -			 unsigned long *lowest_load_addr)
> -{
> -	unsigned long base = 0, lowest_addr = UINT_MAX;
> -	int ret;
> -	size_t i;
> -	struct kexec_buf kbuf = { .image = image, .buf_max = ppc64_rma_size,
> -				  .top_down = false };
> -
> -	/* 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 + base;
> -		ret = kexec_add_buffer(&kbuf);
> -		if (ret)
> -			goto out;
> -		load_addr = kbuf.mem;
> -
> -		if (load_addr < lowest_addr)
> -			lowest_addr = load_addr;
> -	}
> -
> -	/* Update entry point to reflect new load address. */
> -	ehdr->e_entry += base;
> -
> -	*lowest_load_addr = lowest_addr;
> -	ret = 0;
> - out:
> -	return ret;
> -}
> -
>   static void *elf64_load(struct kimage *image, char *kernel_buf,
>   			unsigned long kernel_len, char *initrd,
>   			unsigned long initrd_len, char *cmdline,
> @@ -577,17 +43,18 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   	void *fdt;
>   	const void *slave_code;
>   	struct elfhdr ehdr;
> -	struct elf_info elf_info;
> +	struct kexec_elf_info elf_info;
>   	struct kexec_buf kbuf = { .image = image, .buf_min = 0,
>   				  .buf_max = ppc64_rma_size };
>   	struct kexec_buf pbuf = { .image = image, .buf_min = 0,
> -				  .buf_max = ppc64_rma_size, .top_down = true };
> +				  .buf_max = ppc64_rma_size, .top_down = true,
> +				  .mem = KEXEC_BUF_MEM_UNKNOWN };
>   
> -	ret = build_elf_exec_info(kernel_buf, kernel_len, &ehdr, &elf_info);
> +	ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
>   	if (ret)
>   		goto out;
>   
> -	ret = elf_exec_load(image, &ehdr, &elf_info, &kernel_load_addr);
> +	ret = kexec_elf_load(image, &ehdr, &elf_info, &kbuf, &kernel_load_addr);
>   	if (ret)
>   		goto out;
>   
> @@ -606,6 +73,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   		kbuf.bufsz = kbuf.memsz = initrd_len;
>   		kbuf.buf_align = PAGE_SIZE;
>   		kbuf.top_down = false;
> +		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>   		ret = kexec_add_buffer(&kbuf);
>   		if (ret)
>   			goto out;
> @@ -638,6 +106,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   	kbuf.bufsz = kbuf.memsz = fdt_size;
>   	kbuf.buf_align = PAGE_SIZE;
>   	kbuf.top_down = true;
> +	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>   	ret = kexec_add_buffer(&kbuf);
>   	if (ret)
>   		goto out;
> @@ -652,13 +121,13 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   		pr_err("Error setting up the purgatory.\n");
>   
>   out:
> -	elf_free_info(&elf_info);
> +	kexec_free_elf_info(&elf_info);
>   
>   	/* Make kimage_file_post_load_cleanup free the fdt buffer for us. */
>   	return ret ? ERR_PTR(ret) : fdt;
>   }
>   
>   const struct kexec_file_ops kexec_elf64_ops = {
> -	.probe = elf64_probe,
> +	.probe = kexec_elf_probe,
>   	.load = elf64_load,
>   };
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index b9b1bc5f9669..da2a6b1d69e7 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -216,6 +216,30 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
>   				       void **addr, unsigned long *sz);
>   #endif /* CONFIG_KEXEC_FILE */
>   
> +#ifdef CONFIG_KEXEC_ELF
> +struct kexec_elf_info {
> +	/*
> +	 * Where the ELF binary contents are kept.
> +	 * Memory managed by the user of the struct.
> +	 */
> +	const char *buffer;
> +
> +	const struct elfhdr *ehdr;
> +	const struct elf_phdr *proghdrs;
> +	struct elf_shdr *sechdrs;
> +};
> +
> +int kexec_build_elf_info(const char *buf, size_t len, struct elfhdr *ehdr,
> +			       struct kexec_elf_info *elf_info);
> +
> +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);
> +
> +void kexec_free_elf_info(struct kexec_elf_info *elf_info);
> +int kexec_elf_probe(const char *buf, unsigned long len);
> +#endif
>   struct kimage {
>   	kimage_entry_t head;
>   	kimage_entry_t *entry;
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 33824f0385b3..7062306de9b7 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -64,6 +64,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
>   obj-$(CONFIG_KEXEC_CORE) += kexec_core.o
>   obj-$(CONFIG_KEXEC) += kexec.o
>   obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
> +obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
>   obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
>   obj-$(CONFIG_COMPAT) += compat.o
>   obj-$(CONFIG_CGROUPS) += cgroup/
> diff --git a/kernel/kexec_elf.c b/kernel/kexec_elf.c
> new file mode 100644
> index 000000000000..6e9f52171ede
> --- /dev/null
> +++ b/kernel/kexec_elf.c
> @@ -0,0 +1,537 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#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>
> +
> +#define PURGATORY_STACK_SIZE	(16 * 1024)
> +
> +#define elf_addr_to_cpu	elf64_to_cpu
> +
> +#ifndef Elf_Rel
> +#define Elf_Rel		Elf64_Rel
> +#endif /* Elf_Rel */
> +
> +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 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;
> +}
> +
> +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;
> +}
> +
> +/**
> + * 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.\n");
> +		return false;
> +	} else if (ehdr->e_shnum > 0 &&
> +		   ehdr->e_shentsize != sizeof(struct elf_shdr)) {
> +		pr_debug("Bad section header size.\n");
> +		return false;
> +	} else if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
> +		   ehdr->e_version != EV_CURRENT) {
> +		pr_debug("Unknown ELF version.\n");
> +		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.\n");
> +			return false;
> +		} else if (ehdr->e_phoff + phdr_size > buf_len) {
> +			pr_debug("Program headers truncated.\n");
> +			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.\n");
> +			return false;
> +		} else if (ehdr->e_shoff + shdr_size > buf_len) {
> +			pr_debug("Section headers truncated.\n");
> +			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.\n");
> +		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.\n");
> +		return -ENOEXEC;
> +	}
> +
> +	if (ehdr->e_ident[EI_CLASS] != ELF_CLASS) {
> +		pr_debug("Not a supported ELF class.\n");
> +		return -ENOEXEC;
> +	} else  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB &&
> +		ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
> +		pr_debug("Not a supported ELF data format.\n");
> +		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.\n");
> +		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_entry     = elf_addr_to_cpu(ehdr, buf_ehdr->e_entry);
> +	ehdr->e_phoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_phoff);
> +	ehdr->e_shoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_shoff);
> +	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);
> +
> +	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.\n");
> +		return false;
> +	} else if (phdr->p_offset + phdr->p_filesz > buf_len) {
> +		pr_debug("ELF segment not in file.\n");
> +		return false;
> +	} else if (phdr->p_paddr + phdr->p_memsz < phdr->p_paddr) {
> +		pr_debug("ELF segment address wraps around.\n");
> +		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 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_offset = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_offset);
> +	phdr->p_paddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_paddr);
> +	phdr->p_vaddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_vaddr);
> +	phdr->p_flags  = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);
> +
> +	/*
> +	 * The following fields have a type equivalent to Elf_Addr
> +	 * both in 32 bit and 64 bit ELF.
> +	 */
> +	phdr->p_filesz = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_filesz);
> +	phdr->p_memsz  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_memsz);
> +	phdr->p_align  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_align);
> +
> +	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_is_shdr_sane - check that it is safe to use the section header
> + * @buf_len:	size of the buffer in which the ELF file is loaded.
> + */
> +static bool elf_is_shdr_sane(const struct elf_shdr *shdr, size_t buf_len)
> +{
> +	bool size_ok;
> +
> +	/* SHT_NULL headers have undefined values, so we can't check them. */
> +	if (shdr->sh_type == SHT_NULL)
> +		return true;
> +
> +	/* Now verify sh_entsize */
> +	switch (shdr->sh_type) {
> +	case SHT_SYMTAB:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Sym);
> +		break;
> +	case SHT_RELA:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Rela);
> +		break;
> +	case SHT_DYNAMIC:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Dyn);
> +		break;
> +	case SHT_REL:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Rel);
> +		break;
> +	case SHT_NOTE:
> +	case SHT_PROGBITS:
> +	case SHT_HASH:
> +	case SHT_NOBITS:
> +	default:
> +		/*
> +		 * This is a section whose entsize requirements
> +		 * I don't care about.  If I don't know about
> +		 * the section I can't care about it's entsize
> +		 * requirements.
> +		 */
> +		size_ok = true;
> +		break;
> +	}
> +
> +	if (!size_ok) {
> +		pr_debug("ELF section with wrong entry size.\n");
> +		return false;
> +	} else if (shdr->sh_addr + shdr->sh_size < shdr->sh_addr) {
> +		pr_debug("ELF section address wraps around.\n");
> +		return false;
> +	}
> +
> +	if (shdr->sh_type != SHT_NOBITS) {
> +		if (shdr->sh_offset + shdr->sh_size < shdr->sh_offset) {
> +			pr_debug("ELF section location wraps around.\n");
> +			return false;
> +		} else if (shdr->sh_offset + shdr->sh_size > buf_len) {
> +			pr_debug("ELF section not in file.\n");
> +			return false;
> +		}
> +	}
> +
> +	return true;
> +}
> +
> +static int elf_read_shdr(const char *buf, size_t len,
> +			 struct kexec_elf_info *elf_info,
> +			 int idx)
> +{
> +	struct elf_shdr *shdr = &elf_info->sechdrs[idx];
> +	const struct elfhdr *ehdr = elf_info->ehdr;
> +	const char *sbuf;
> +	struct elf_shdr *buf_shdr;
> +
> +	sbuf = buf + ehdr->e_shoff + idx * sizeof(*buf_shdr);
> +	buf_shdr = (struct elf_shdr *) sbuf;
> +
> +	shdr->sh_name      = elf32_to_cpu(ehdr, buf_shdr->sh_name);
> +	shdr->sh_type      = elf32_to_cpu(ehdr, buf_shdr->sh_type);
> +	shdr->sh_addr      = elf_addr_to_cpu(ehdr, buf_shdr->sh_addr);
> +	shdr->sh_offset    = elf_addr_to_cpu(ehdr, buf_shdr->sh_offset);
> +	shdr->sh_link      = elf32_to_cpu(ehdr, buf_shdr->sh_link);
> +	shdr->sh_info      = elf32_to_cpu(ehdr, buf_shdr->sh_info);
> +
> +	/*
> +	 * The following fields have a type equivalent to Elf_Addr
> +	 * both in 32 bit and 64 bit ELF.
> +	 */
> +	shdr->sh_flags     = elf_addr_to_cpu(ehdr, buf_shdr->sh_flags);
> +	shdr->sh_size      = elf_addr_to_cpu(ehdr, buf_shdr->sh_size);
> +	shdr->sh_addralign = elf_addr_to_cpu(ehdr, buf_shdr->sh_addralign);
> +	shdr->sh_entsize   = elf_addr_to_cpu(ehdr, buf_shdr->sh_entsize);
> +
> +	return elf_is_shdr_sane(shdr, len) ? 0 : -ENOEXEC;
> +}
> +
> +/**
> + * elf_read_shdrs - read the section headers from the buffer
> + *
> + * This function assumes that the section header table was checked for sanity.
> + * Use elf_is_ehdr_sane() if it wasn't.
> + */
> +static int elf_read_shdrs(const char *buf, size_t len,
> +			  struct kexec_elf_info *elf_info)
> +{
> +	size_t shdr_size, i;
> +
> +	/*
> +	 * e_shnum is at most 65536 so calculating
> +	 * the size of the section header cannot overflow.
> +	 */
> +	shdr_size = sizeof(struct elf_shdr) * elf_info->ehdr->e_shnum;
> +
> +	elf_info->sechdrs = kzalloc(shdr_size, GFP_KERNEL);
> +	if (!elf_info->sechdrs)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < elf_info->ehdr->e_shnum; i++) {
> +		int ret;
> +
> +		ret = elf_read_shdr(buf, len, elf_info, i);
> +		if (ret) {
> +			kfree(elf_info->sechdrs);
> +			elf_info->sechdrs = 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;
> +	}
> +	if (ehdr->e_shoff > 0 && ehdr->e_shnum > 0) {
> +		ret = elf_read_shdrs(buf, len, elf_info);
> +		if (ret) {
> +			kfree(elf_info->proghdrs);
> +			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);
> +	kfree(elf_info->sechdrs);
> +	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.\n");
> +		goto error;
> +	} else if (!elf_info->proghdrs) {
> +		pr_err("No ELF program header.\n");
> +		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.\n");
> +			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 base = 0, 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 + base;
> +		ret = kexec_add_buffer(kbuf);
> +		if (ret)
> +			goto out;
> +		load_addr = kbuf->mem;
> +
> +		if (load_addr < lowest_addr)
> +			lowest_addr = load_addr;
> +	}
> +
> +	/* Update entry point to reflect new load address. */
> +	ehdr->e_entry += base;
> +
> +	*lowest_load_addr = lowest_addr;
> +	ret = 0;
> + out:
> +	return ret;
> +}
> +
> +
> 



From mboxrd@z Thu Jan  1 00:00:00 1970
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 for kexec@lists.infradead.org; Wed, 10 Jul 2019 13:22:51 +0000
Subject: Re: [PATCH v2 1/7] kexec: add KEXEC_ELF
References: <20190709194328.16991-1-svens@stackframe.org>
 <20190709194328.16991-2-svens@stackframe.org>
From: Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <64306f6c-0a0d-a6ea-537c-5e72deaba1c0@c-s.fr>
Date: Wed, 10 Jul 2019 13:19:13 +0000
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To: Sven Schnelle <svens@stackframe.org>, kexec@lists.infradead.org
Cc: deller@gmx.de, linuxppc-dev@lists.ozlabs.org

Hi Sven,

On 07/09/2019 07:43 PM, Sven Schnelle wrote:
> Right now powerpc provides an implementation to read elf files
> with the kexec_file() syscall. Make that available as a public
> kexec interface so it can be re-used on other architectures.
> 
> Signed-off-by: Sven Schnelle <svens@stackframe.org>
> ---
>   arch/Kconfig                       |   3 +
>   arch/powerpc/Kconfig               |   1 +
>   arch/powerpc/kernel/kexec_elf_64.c | 551 +----------------------------
>   include/linux/kexec.h              |  24 ++
>   kernel/Makefile                    |   1 +
>   kernel/kexec_elf.c                 | 537 ++++++++++++++++++++++++++++
>   6 files changed, 576 insertions(+), 541 deletions(-)
>   create mode 100644 kernel/kexec_elf.c

Why are you persisting at not using -C when creating your patch ? Do you 
want to hide the changes you did while copying 
arch/powerpc/kernel/kexec_elf_64.c to kernel/kexec_elf.c ?
Or you want to make life harder for the reviewers ?

git format-patch -C shows:

  arch/Kconfig                                       |   3 +
  arch/powerpc/Kconfig                               |   1 +
  arch/powerpc/kernel/kexec_elf_64.c                 | 551 
+--------------------
  include/linux/kexec.h                              |  24 +
  kernel/Makefile                                    |   1 +
  .../kernel/kexec_elf_64.c => kernel/kexec_elf.c    | 199 ++------
  6 files changed, 75 insertions(+), 704 deletions(-)
  copy arch/powerpc/kernel/kexec_elf_64.c => kernel/kexec_elf.c (71%)

I mentionned it a couple of times, I even resent your last patch 
formatted that way to show the advantage. I can ear if you find it 
worthless, but tell what your concern are with that, don't just ignore 
it please.

Cheers
Christophe

> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index c47b328eada0..30694aca4316 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -18,6 +18,9 @@ config KEXEC_CORE
>   	select CRASH_CORE
>   	bool
>   
> +config KEXEC_ELF
> +	bool
> +
>   config HAVE_IMA_KEXEC
>   	bool
>   
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 12cee37f15c4..addc2dad78e0 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -510,6 +510,7 @@ config KEXEC_FILE
>   	select KEXEC_CORE
>   	select HAVE_IMA_KEXEC
>   	select BUILD_BIN2C
> +	select KEXEC_ELF
>   	depends on PPC64
>   	depends on CRYPTO=y
>   	depends on CRYPTO_SHA256=y
> diff --git a/arch/powerpc/kernel/kexec_elf_64.c b/arch/powerpc/kernel/kexec_elf_64.c
> index ba4f18a43ee8..30bd57a93c17 100644
> --- a/arch/powerpc/kernel/kexec_elf_64.c
> +++ b/arch/powerpc/kernel/kexec_elf_64.c
> @@ -1,3 +1,4 @@
> +// SPDX-License-Identifier: GPL-2.0-only
>   /*
>    * Load ELF vmlinux file for the kexec_file_load syscall.
>    *
> @@ -10,15 +11,6 @@
>    * 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>.
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License as published by
> - * the Free Software Foundation (version 2 of the License).
> - *
> - * This program is distributed in the hope that it will be useful,
> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> - * GNU General Public License for more details.
>    */
>   
>   #define pr_fmt(fmt)	"kexec_elf: " fmt
> @@ -39,532 +31,6 @@
>   #define Elf_Rel		Elf64_Rel
>   #endif /* Elf_Rel */
>   
> -struct elf_info {
> -	/*
> -	 * Where the ELF binary contents are kept.
> -	 * Memory managed by the user of the struct.
> -	 */
> -	const char *buffer;
> -
> -	const struct elfhdr *ehdr;
> -	const struct elf_phdr *proghdrs;
> -	struct elf_shdr *sechdrs;
> -};
> -
> -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 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;
> -}
> -
> -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;
> -}
> -
> -/**
> - * 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.\n");
> -		return false;
> -	} else if (ehdr->e_shnum > 0 &&
> -		   ehdr->e_shentsize != sizeof(struct elf_shdr)) {
> -		pr_debug("Bad section header size.\n");
> -		return false;
> -	} else if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
> -		   ehdr->e_version != EV_CURRENT) {
> -		pr_debug("Unknown ELF version.\n");
> -		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.\n");
> -			return false;
> -		} else if (ehdr->e_phoff + phdr_size > buf_len) {
> -			pr_debug("Program headers truncated.\n");
> -			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.\n");
> -			return false;
> -		} else if (ehdr->e_shoff + shdr_size > buf_len) {
> -			pr_debug("Section headers truncated.\n");
> -			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.\n");
> -		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.\n");
> -		return -ENOEXEC;
> -	}
> -
> -	if (ehdr->e_ident[EI_CLASS] != ELF_CLASS) {
> -		pr_debug("Not a supported ELF class.\n");
> -		return -ENOEXEC;
> -	} else  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB &&
> -		ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
> -		pr_debug("Not a supported ELF data format.\n");
> -		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.\n");
> -		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_entry     = elf_addr_to_cpu(ehdr, buf_ehdr->e_entry);
> -	ehdr->e_phoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_phoff);
> -	ehdr->e_shoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_shoff);
> -	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);
> -
> -	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.\n");
> -		return false;
> -	} else if (phdr->p_offset + phdr->p_filesz > buf_len) {
> -		pr_debug("ELF segment not in file.\n");
> -		return false;
> -	} else if (phdr->p_paddr + phdr->p_memsz < phdr->p_paddr) {
> -		pr_debug("ELF segment address wraps around.\n");
> -		return false;
> -	}
> -
> -	return true;
> -}
> -
> -static int elf_read_phdr(const char *buf, size_t len, struct 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 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_offset = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_offset);
> -	phdr->p_paddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_paddr);
> -	phdr->p_vaddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_vaddr);
> -	phdr->p_flags  = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);
> -
> -	/*
> -	 * The following fields have a type equivalent to Elf_Addr
> -	 * both in 32 bit and 64 bit ELF.
> -	 */
> -	phdr->p_filesz = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_filesz);
> -	phdr->p_memsz  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_memsz);
> -	phdr->p_align  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_align);
> -
> -	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 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_is_shdr_sane - check that it is safe to use the section header
> - * @buf_len:	size of the buffer in which the ELF file is loaded.
> - */
> -static bool elf_is_shdr_sane(const struct elf_shdr *shdr, size_t buf_len)
> -{
> -	bool size_ok;
> -
> -	/* SHT_NULL headers have undefined values, so we can't check them. */
> -	if (shdr->sh_type == SHT_NULL)
> -		return true;
> -
> -	/* Now verify sh_entsize */
> -	switch (shdr->sh_type) {
> -	case SHT_SYMTAB:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Sym);
> -		break;
> -	case SHT_RELA:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Rela);
> -		break;
> -	case SHT_DYNAMIC:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Dyn);
> -		break;
> -	case SHT_REL:
> -		size_ok = shdr->sh_entsize == sizeof(Elf_Rel);
> -		break;
> -	case SHT_NOTE:
> -	case SHT_PROGBITS:
> -	case SHT_HASH:
> -	case SHT_NOBITS:
> -	default:
> -		/*
> -		 * This is a section whose entsize requirements
> -		 * I don't care about.  If I don't know about
> -		 * the section I can't care about it's entsize
> -		 * requirements.
> -		 */
> -		size_ok = true;
> -		break;
> -	}
> -
> -	if (!size_ok) {
> -		pr_debug("ELF section with wrong entry size.\n");
> -		return false;
> -	} else if (shdr->sh_addr + shdr->sh_size < shdr->sh_addr) {
> -		pr_debug("ELF section address wraps around.\n");
> -		return false;
> -	}
> -
> -	if (shdr->sh_type != SHT_NOBITS) {
> -		if (shdr->sh_offset + shdr->sh_size < shdr->sh_offset) {
> -			pr_debug("ELF section location wraps around.\n");
> -			return false;
> -		} else if (shdr->sh_offset + shdr->sh_size > buf_len) {
> -			pr_debug("ELF section not in file.\n");
> -			return false;
> -		}
> -	}
> -
> -	return true;
> -}
> -
> -static int elf_read_shdr(const char *buf, size_t len, struct elf_info *elf_info,
> -			 int idx)
> -{
> -	struct elf_shdr *shdr = &elf_info->sechdrs[idx];
> -	const struct elfhdr *ehdr = elf_info->ehdr;
> -	const char *sbuf;
> -	struct elf_shdr *buf_shdr;
> -
> -	sbuf = buf + ehdr->e_shoff + idx * sizeof(*buf_shdr);
> -	buf_shdr = (struct elf_shdr *) sbuf;
> -
> -	shdr->sh_name      = elf32_to_cpu(ehdr, buf_shdr->sh_name);
> -	shdr->sh_type      = elf32_to_cpu(ehdr, buf_shdr->sh_type);
> -	shdr->sh_addr      = elf_addr_to_cpu(ehdr, buf_shdr->sh_addr);
> -	shdr->sh_offset    = elf_addr_to_cpu(ehdr, buf_shdr->sh_offset);
> -	shdr->sh_link      = elf32_to_cpu(ehdr, buf_shdr->sh_link);
> -	shdr->sh_info      = elf32_to_cpu(ehdr, buf_shdr->sh_info);
> -
> -	/*
> -	 * The following fields have a type equivalent to Elf_Addr
> -	 * both in 32 bit and 64 bit ELF.
> -	 */
> -	shdr->sh_flags     = elf_addr_to_cpu(ehdr, buf_shdr->sh_flags);
> -	shdr->sh_size      = elf_addr_to_cpu(ehdr, buf_shdr->sh_size);
> -	shdr->sh_addralign = elf_addr_to_cpu(ehdr, buf_shdr->sh_addralign);
> -	shdr->sh_entsize   = elf_addr_to_cpu(ehdr, buf_shdr->sh_entsize);
> -
> -	return elf_is_shdr_sane(shdr, len) ? 0 : -ENOEXEC;
> -}
> -
> -/**
> - * elf_read_shdrs - read the section headers from the buffer
> - *
> - * This function assumes that the section header table was checked for sanity.
> - * Use elf_is_ehdr_sane() if it wasn't.
> - */
> -static int elf_read_shdrs(const char *buf, size_t len,
> -			  struct elf_info *elf_info)
> -{
> -	size_t shdr_size, i;
> -
> -	/*
> -	 * e_shnum is at most 65536 so calculating
> -	 * the size of the section header cannot overflow.
> -	 */
> -	shdr_size = sizeof(struct elf_shdr) * elf_info->ehdr->e_shnum;
> -
> -	elf_info->sechdrs = kzalloc(shdr_size, GFP_KERNEL);
> -	if (!elf_info->sechdrs)
> -		return -ENOMEM;
> -
> -	for (i = 0; i < elf_info->ehdr->e_shnum; i++) {
> -		int ret;
> -
> -		ret = elf_read_shdr(buf, len, elf_info, i);
> -		if (ret) {
> -			kfree(elf_info->sechdrs);
> -			elf_info->sechdrs = 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 elf_free_info(elf_info) to
> - * free the memory allocated for the section and program headers.
> - */
> -int elf_read_from_buffer(const char *buf, size_t len, struct elfhdr *ehdr,
> -			 struct 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;
> -	}
> -	if (ehdr->e_shoff > 0 && ehdr->e_shnum > 0) {
> -		ret = elf_read_shdrs(buf, len, elf_info);
> -		if (ret) {
> -			kfree(elf_info->proghdrs);
> -			return ret;
> -		}
> -	}
> -
> -	return 0;
> -}
> -
> -/**
> - * elf_free_info - free memory allocated by elf_read_from_buffer
> - */
> -void elf_free_info(struct elf_info *elf_info)
> -{
> -	kfree(elf_info->proghdrs);
> -	kfree(elf_info->sechdrs);
> -	memset(elf_info, 0, sizeof(*elf_info));
> -}
> -/**
> - * build_elf_exec_info - read ELF executable and check that we can use it
> - */
> -static int build_elf_exec_info(const char *buf, size_t len, struct elfhdr *ehdr,
> -			       struct 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.\n");
> -		goto error;
> -	} else if (!elf_info->proghdrs) {
> -		pr_err("No ELF program header.\n");
> -		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.\n");
> -			goto error;
> -		}
> -	}
> -
> -	return 0;
> -error:
> -	elf_free_info(elf_info);
> -	return -ENOEXEC;
> -}
> -
> -static int elf64_probe(const char *buf, unsigned long len)
> -{
> -	struct elfhdr ehdr;
> -	struct elf_info elf_info;
> -	int ret;
> -
> -	ret = build_elf_exec_info(buf, len, &ehdr, &elf_info);
> -	if (ret)
> -		return ret;
> -
> -	elf_free_info(&elf_info);
> -
> -	return elf_check_arch(&ehdr) ? 0 : -ENOEXEC;
> -}
> -
> -/**
> - * elf_exec_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.
> - */
> -static int elf_exec_load(struct kimage *image, struct elfhdr *ehdr,
> -			 struct elf_info *elf_info,
> -			 unsigned long *lowest_load_addr)
> -{
> -	unsigned long base = 0, lowest_addr = UINT_MAX;
> -	int ret;
> -	size_t i;
> -	struct kexec_buf kbuf = { .image = image, .buf_max = ppc64_rma_size,
> -				  .top_down = false };
> -
> -	/* 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 + base;
> -		ret = kexec_add_buffer(&kbuf);
> -		if (ret)
> -			goto out;
> -		load_addr = kbuf.mem;
> -
> -		if (load_addr < lowest_addr)
> -			lowest_addr = load_addr;
> -	}
> -
> -	/* Update entry point to reflect new load address. */
> -	ehdr->e_entry += base;
> -
> -	*lowest_load_addr = lowest_addr;
> -	ret = 0;
> - out:
> -	return ret;
> -}
> -
>   static void *elf64_load(struct kimage *image, char *kernel_buf,
>   			unsigned long kernel_len, char *initrd,
>   			unsigned long initrd_len, char *cmdline,
> @@ -577,17 +43,18 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   	void *fdt;
>   	const void *slave_code;
>   	struct elfhdr ehdr;
> -	struct elf_info elf_info;
> +	struct kexec_elf_info elf_info;
>   	struct kexec_buf kbuf = { .image = image, .buf_min = 0,
>   				  .buf_max = ppc64_rma_size };
>   	struct kexec_buf pbuf = { .image = image, .buf_min = 0,
> -				  .buf_max = ppc64_rma_size, .top_down = true };
> +				  .buf_max = ppc64_rma_size, .top_down = true,
> +				  .mem = KEXEC_BUF_MEM_UNKNOWN };
>   
> -	ret = build_elf_exec_info(kernel_buf, kernel_len, &ehdr, &elf_info);
> +	ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
>   	if (ret)
>   		goto out;
>   
> -	ret = elf_exec_load(image, &ehdr, &elf_info, &kernel_load_addr);
> +	ret = kexec_elf_load(image, &ehdr, &elf_info, &kbuf, &kernel_load_addr);
>   	if (ret)
>   		goto out;
>   
> @@ -606,6 +73,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   		kbuf.bufsz = kbuf.memsz = initrd_len;
>   		kbuf.buf_align = PAGE_SIZE;
>   		kbuf.top_down = false;
> +		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>   		ret = kexec_add_buffer(&kbuf);
>   		if (ret)
>   			goto out;
> @@ -638,6 +106,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   	kbuf.bufsz = kbuf.memsz = fdt_size;
>   	kbuf.buf_align = PAGE_SIZE;
>   	kbuf.top_down = true;
> +	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>   	ret = kexec_add_buffer(&kbuf);
>   	if (ret)
>   		goto out;
> @@ -652,13 +121,13 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   		pr_err("Error setting up the purgatory.\n");
>   
>   out:
> -	elf_free_info(&elf_info);
> +	kexec_free_elf_info(&elf_info);
>   
>   	/* Make kimage_file_post_load_cleanup free the fdt buffer for us. */
>   	return ret ? ERR_PTR(ret) : fdt;
>   }
>   
>   const struct kexec_file_ops kexec_elf64_ops = {
> -	.probe = elf64_probe,
> +	.probe = kexec_elf_probe,
>   	.load = elf64_load,
>   };
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index b9b1bc5f9669..da2a6b1d69e7 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -216,6 +216,30 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
>   				       void **addr, unsigned long *sz);
>   #endif /* CONFIG_KEXEC_FILE */
>   
> +#ifdef CONFIG_KEXEC_ELF
> +struct kexec_elf_info {
> +	/*
> +	 * Where the ELF binary contents are kept.
> +	 * Memory managed by the user of the struct.
> +	 */
> +	const char *buffer;
> +
> +	const struct elfhdr *ehdr;
> +	const struct elf_phdr *proghdrs;
> +	struct elf_shdr *sechdrs;
> +};
> +
> +int kexec_build_elf_info(const char *buf, size_t len, struct elfhdr *ehdr,
> +			       struct kexec_elf_info *elf_info);
> +
> +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);
> +
> +void kexec_free_elf_info(struct kexec_elf_info *elf_info);
> +int kexec_elf_probe(const char *buf, unsigned long len);
> +#endif
>   struct kimage {
>   	kimage_entry_t head;
>   	kimage_entry_t *entry;
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 33824f0385b3..7062306de9b7 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -64,6 +64,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
>   obj-$(CONFIG_KEXEC_CORE) += kexec_core.o
>   obj-$(CONFIG_KEXEC) += kexec.o
>   obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
> +obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
>   obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
>   obj-$(CONFIG_COMPAT) += compat.o
>   obj-$(CONFIG_CGROUPS) += cgroup/
> diff --git a/kernel/kexec_elf.c b/kernel/kexec_elf.c
> new file mode 100644
> index 000000000000..6e9f52171ede
> --- /dev/null
> +++ b/kernel/kexec_elf.c
> @@ -0,0 +1,537 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#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>
> +
> +#define PURGATORY_STACK_SIZE	(16 * 1024)
> +
> +#define elf_addr_to_cpu	elf64_to_cpu
> +
> +#ifndef Elf_Rel
> +#define Elf_Rel		Elf64_Rel
> +#endif /* Elf_Rel */
> +
> +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 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;
> +}
> +
> +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;
> +}
> +
> +/**
> + * 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.\n");
> +		return false;
> +	} else if (ehdr->e_shnum > 0 &&
> +		   ehdr->e_shentsize != sizeof(struct elf_shdr)) {
> +		pr_debug("Bad section header size.\n");
> +		return false;
> +	} else if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
> +		   ehdr->e_version != EV_CURRENT) {
> +		pr_debug("Unknown ELF version.\n");
> +		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.\n");
> +			return false;
> +		} else if (ehdr->e_phoff + phdr_size > buf_len) {
> +			pr_debug("Program headers truncated.\n");
> +			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.\n");
> +			return false;
> +		} else if (ehdr->e_shoff + shdr_size > buf_len) {
> +			pr_debug("Section headers truncated.\n");
> +			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.\n");
> +		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.\n");
> +		return -ENOEXEC;
> +	}
> +
> +	if (ehdr->e_ident[EI_CLASS] != ELF_CLASS) {
> +		pr_debug("Not a supported ELF class.\n");
> +		return -ENOEXEC;
> +	} else  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB &&
> +		ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
> +		pr_debug("Not a supported ELF data format.\n");
> +		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.\n");
> +		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_entry     = elf_addr_to_cpu(ehdr, buf_ehdr->e_entry);
> +	ehdr->e_phoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_phoff);
> +	ehdr->e_shoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_shoff);
> +	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);
> +
> +	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.\n");
> +		return false;
> +	} else if (phdr->p_offset + phdr->p_filesz > buf_len) {
> +		pr_debug("ELF segment not in file.\n");
> +		return false;
> +	} else if (phdr->p_paddr + phdr->p_memsz < phdr->p_paddr) {
> +		pr_debug("ELF segment address wraps around.\n");
> +		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 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_offset = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_offset);
> +	phdr->p_paddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_paddr);
> +	phdr->p_vaddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_vaddr);
> +	phdr->p_flags  = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);
> +
> +	/*
> +	 * The following fields have a type equivalent to Elf_Addr
> +	 * both in 32 bit and 64 bit ELF.
> +	 */
> +	phdr->p_filesz = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_filesz);
> +	phdr->p_memsz  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_memsz);
> +	phdr->p_align  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_align);
> +
> +	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_is_shdr_sane - check that it is safe to use the section header
> + * @buf_len:	size of the buffer in which the ELF file is loaded.
> + */
> +static bool elf_is_shdr_sane(const struct elf_shdr *shdr, size_t buf_len)
> +{
> +	bool size_ok;
> +
> +	/* SHT_NULL headers have undefined values, so we can't check them. */
> +	if (shdr->sh_type == SHT_NULL)
> +		return true;
> +
> +	/* Now verify sh_entsize */
> +	switch (shdr->sh_type) {
> +	case SHT_SYMTAB:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Sym);
> +		break;
> +	case SHT_RELA:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Rela);
> +		break;
> +	case SHT_DYNAMIC:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Dyn);
> +		break;
> +	case SHT_REL:
> +		size_ok = shdr->sh_entsize == sizeof(Elf_Rel);
> +		break;
> +	case SHT_NOTE:
> +	case SHT_PROGBITS:
> +	case SHT_HASH:
> +	case SHT_NOBITS:
> +	default:
> +		/*
> +		 * This is a section whose entsize requirements
> +		 * I don't care about.  If I don't know about
> +		 * the section I can't care about it's entsize
> +		 * requirements.
> +		 */
> +		size_ok = true;
> +		break;
> +	}
> +
> +	if (!size_ok) {
> +		pr_debug("ELF section with wrong entry size.\n");
> +		return false;
> +	} else if (shdr->sh_addr + shdr->sh_size < shdr->sh_addr) {
> +		pr_debug("ELF section address wraps around.\n");
> +		return false;
> +	}
> +
> +	if (shdr->sh_type != SHT_NOBITS) {
> +		if (shdr->sh_offset + shdr->sh_size < shdr->sh_offset) {
> +			pr_debug("ELF section location wraps around.\n");
> +			return false;
> +		} else if (shdr->sh_offset + shdr->sh_size > buf_len) {
> +			pr_debug("ELF section not in file.\n");
> +			return false;
> +		}
> +	}
> +
> +	return true;
> +}
> +
> +static int elf_read_shdr(const char *buf, size_t len,
> +			 struct kexec_elf_info *elf_info,
> +			 int idx)
> +{
> +	struct elf_shdr *shdr = &elf_info->sechdrs[idx];
> +	const struct elfhdr *ehdr = elf_info->ehdr;
> +	const char *sbuf;
> +	struct elf_shdr *buf_shdr;
> +
> +	sbuf = buf + ehdr->e_shoff + idx * sizeof(*buf_shdr);
> +	buf_shdr = (struct elf_shdr *) sbuf;
> +
> +	shdr->sh_name      = elf32_to_cpu(ehdr, buf_shdr->sh_name);
> +	shdr->sh_type      = elf32_to_cpu(ehdr, buf_shdr->sh_type);
> +	shdr->sh_addr      = elf_addr_to_cpu(ehdr, buf_shdr->sh_addr);
> +	shdr->sh_offset    = elf_addr_to_cpu(ehdr, buf_shdr->sh_offset);
> +	shdr->sh_link      = elf32_to_cpu(ehdr, buf_shdr->sh_link);
> +	shdr->sh_info      = elf32_to_cpu(ehdr, buf_shdr->sh_info);
> +
> +	/*
> +	 * The following fields have a type equivalent to Elf_Addr
> +	 * both in 32 bit and 64 bit ELF.
> +	 */
> +	shdr->sh_flags     = elf_addr_to_cpu(ehdr, buf_shdr->sh_flags);
> +	shdr->sh_size      = elf_addr_to_cpu(ehdr, buf_shdr->sh_size);
> +	shdr->sh_addralign = elf_addr_to_cpu(ehdr, buf_shdr->sh_addralign);
> +	shdr->sh_entsize   = elf_addr_to_cpu(ehdr, buf_shdr->sh_entsize);
> +
> +	return elf_is_shdr_sane(shdr, len) ? 0 : -ENOEXEC;
> +}
> +
> +/**
> + * elf_read_shdrs - read the section headers from the buffer
> + *
> + * This function assumes that the section header table was checked for sanity.
> + * Use elf_is_ehdr_sane() if it wasn't.
> + */
> +static int elf_read_shdrs(const char *buf, size_t len,
> +			  struct kexec_elf_info *elf_info)
> +{
> +	size_t shdr_size, i;
> +
> +	/*
> +	 * e_shnum is at most 65536 so calculating
> +	 * the size of the section header cannot overflow.
> +	 */
> +	shdr_size = sizeof(struct elf_shdr) * elf_info->ehdr->e_shnum;
> +
> +	elf_info->sechdrs = kzalloc(shdr_size, GFP_KERNEL);
> +	if (!elf_info->sechdrs)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < elf_info->ehdr->e_shnum; i++) {
> +		int ret;
> +
> +		ret = elf_read_shdr(buf, len, elf_info, i);
> +		if (ret) {
> +			kfree(elf_info->sechdrs);
> +			elf_info->sechdrs = 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;
> +	}
> +	if (ehdr->e_shoff > 0 && ehdr->e_shnum > 0) {
> +		ret = elf_read_shdrs(buf, len, elf_info);
> +		if (ret) {
> +			kfree(elf_info->proghdrs);
> +			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);
> +	kfree(elf_info->sechdrs);
> +	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.\n");
> +		goto error;
> +	} else if (!elf_info->proghdrs) {
> +		pr_err("No ELF program header.\n");
> +		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.\n");
> +			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 base = 0, 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 + base;
> +		ret = kexec_add_buffer(kbuf);
> +		if (ret)
> +			goto out;
> +		load_addr = kbuf->mem;
> +
> +		if (load_addr < lowest_addr)
> +			lowest_addr = load_addr;
> +	}
> +
> +	/* Update entry point to reflect new load address. */
> +	ehdr->e_entry += base;
> +
> +	*lowest_load_addr = lowest_addr;
> +	ret = 0;
> + out:
> +	return ret;
> +}
> +
> +
> 



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