kexec: add KEXEC_ELF

Right now powerpc provides an implementation to read elf files
with the kexec_file_load() 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>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Helge Deller <deller@gmx.de>

6 files changed, 583 insertions, 540 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index a7b57dd42c26..01244412f393 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 77f6ebf97113..3c85ef270338 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -512,6 +512,7 @@ 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 83cf7b852876..3072fd6dbe94 100644
--- a/arch/powerpc/kernel/kexec_elf_64.c
+++ b/arch/powerpc/kernel/kexec_elf_64.c
@@ -23,541 +23,6 @@
 #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 */
-
-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;
-		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;
-	}
-
-	/* 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,
@@ -570,18 +35,18 @@ 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,
 				  .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;
 
@@ -648,13 +113,13 @@ 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 a8d923b5481b..002220b7ca7c 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..26c6310167a0
--- /dev/null
+++ b/kernel/kexec_elf.c
@@ -0,0 +1,549 @@
+// 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>
+
+#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;
+		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;
+	}
+
+	/* Update entry point to reflect new load address. */
+	ehdr->e_entry += base;
+
+	*lowest_load_addr = lowest_addr;
+	ret = 0;
+ out:
+	return ret;
+}