Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 175fca3b authored by Sven Schnelle's avatar Sven Schnelle Committed by Helge Deller
Browse files

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: default avatarSven Schnelle <svens@stackframe.org>
Reviewed-by: default avatarThiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent 544f4485

arch/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -18,6 +18,9 @@ config KEXEC_CORE 
	select CRASH_CORE

	bool



config KEXEC_ELF

	bool



config HAVE_IMA_KEXEC

	bool

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/kexec_elf_64.c

+5 −540
Original line number Diff line number Diff line
@@ -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,

};

include/linux/kexec.h

+24 −0
Original line number Diff line number Diff line
@@ -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;

kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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/