#include <limits.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include "elf.h"
#include <boot/elf_boot.h>
#include "kexec.h"
#include "kexec-elf.h"
#include "crashdump.h"

static const int probe_debug = 0;

uint16_t elf16_to_cpu(const struct mem_ehdr *ehdr, uint16_t value)
{
	if (ehdr->ei_data == ELFDATA2LSB) {
		value = le16_to_cpu(value);
	}
	else if (ehdr->ei_data == ELFDATA2MSB) {
		value = be16_to_cpu(value);
	}
	return value;
}

uint32_t elf32_to_cpu(const struct mem_ehdr *ehdr, uint32_t value)
{
	if (ehdr->ei_data == ELFDATA2LSB) {
		value = le32_to_cpu(value);
	}
	else if (ehdr->ei_data == ELFDATA2MSB) {
		value = be32_to_cpu(value);
	}
	return value;
}

uint64_t elf64_to_cpu(const struct mem_ehdr *ehdr, uint64_t value)
{
	if (ehdr->ei_data == ELFDATA2LSB) {
		value = le64_to_cpu(value);
	}
	else if (ehdr->ei_data == ELFDATA2MSB) {
		value = be64_to_cpu(value);
	}
	return value;
}

uint16_t cpu_to_elf16(const struct mem_ehdr *ehdr, uint16_t value)
{
	if (ehdr->ei_data == ELFDATA2LSB) {
		value = cpu_to_le16(value);
	}
	else if (ehdr->ei_data == ELFDATA2MSB) {
		value = cpu_to_be16(value);
	}
	return value;
}

uint32_t cpu_to_elf32(const struct mem_ehdr *ehdr, uint32_t value)
{
	if (ehdr->ei_data == ELFDATA2LSB) {
		value = cpu_to_le32(value);
	}
	else if (ehdr->ei_data == ELFDATA2MSB) {
		value = cpu_to_be32(value);
	}
	return value;
}

uint64_t cpu_to_elf64(const struct mem_ehdr *ehdr, uint64_t value)
{
	if (ehdr->ei_data == ELFDATA2LSB) {
		value = cpu_to_le64(value);
	}
	else if (ehdr->ei_data == ELFDATA2MSB) {
		value = cpu_to_be64(value);
	}
	return value;
}

#define ELF32_MAX 0xffffffff
#define ELF64_MAX 0xffffffffffffffff
#if ELF64_MAX > ULONG_MAX
#undef ELF64_MAX
#define ELF64_MAX ULONG_MAX
#endif

unsigned long elf_max_addr(const struct mem_ehdr *ehdr)
{
	unsigned long max_addr = 0;
	if (ehdr->ei_class == ELFCLASS32) {
		max_addr = ELF32_MAX;
	}
	else if (ehdr->ei_class == ELFCLASS64) {
		max_addr = ELF64_MAX;
	}
	return max_addr;
}
static int build_mem_elf32_ehdr(const char *buf, off_t len, struct mem_ehdr *ehdr)
{
	Elf32_Ehdr lehdr;
	if ((uintmax_t)len < (uintmax_t)sizeof(lehdr)) {
		/* Buffer is to small to be an elf executable */
		if (probe_debug) {
			fprintf(stderr, "Buffer is to small to hold ELF header\n");
		}
		return -1;
	}
	memcpy(&lehdr, buf, sizeof(lehdr));
	if (elf16_to_cpu(ehdr, lehdr.e_ehsize) != sizeof(Elf32_Ehdr)) {
		/* Invalid Elf header size */
		if (probe_debug) {
			fprintf(stderr, "Bad ELF header size\n");
		}
		return -1;
	}
	if (elf32_to_cpu(ehdr, lehdr.e_entry) > UINT32_MAX) {
		/* entry is to large */
		if (probe_debug) {
			fprintf(stderr, "ELF e_entry to large\n");
		}
		return -1;
	}
	if (elf32_to_cpu(ehdr, lehdr.e_phoff) > UINT32_MAX) {
		/* phoff is to large */
		if (probe_debug) {
			fprintf(stderr, "ELF e_phoff to large\n");
		}
		return -1;
	}
	if (elf32_to_cpu(ehdr, lehdr.e_shoff) > UINT32_MAX) {
		/* shoff is to large */
		if (probe_debug) {
			fprintf(stderr, "ELF e_shoff to large\n");
		}
		return -1;
	}
	ehdr->e_type      = elf16_to_cpu(ehdr, lehdr.e_type);
	ehdr->e_machine   = elf16_to_cpu(ehdr, lehdr.e_machine);
	ehdr->e_version   = elf32_to_cpu(ehdr, lehdr.e_version);
	ehdr->e_entry     = elf32_to_cpu(ehdr, lehdr.e_entry);
	ehdr->e_phoff     = elf32_to_cpu(ehdr, lehdr.e_phoff);
	ehdr->e_shoff     = elf32_to_cpu(ehdr, lehdr.e_shoff);
	ehdr->e_flags     = elf32_to_cpu(ehdr, lehdr.e_flags);
	ehdr->e_phnum     = elf16_to_cpu(ehdr, lehdr.e_phnum);
	ehdr->e_shnum     = elf16_to_cpu(ehdr, lehdr.e_shnum);
	ehdr->e_shstrndx  = elf16_to_cpu(ehdr, lehdr.e_shstrndx);

	if ((ehdr->e_phnum > 0) &&
		(elf16_to_cpu(ehdr, lehdr.e_phentsize) != sizeof(Elf32_Phdr)))
	{
		/* Invalid program header size */
		if (probe_debug) {
			fprintf(stderr, "ELF bad program header size\n");
		}
		return -1;
	}
	if ((ehdr->e_shnum > 0) &&
		(elf16_to_cpu(ehdr, lehdr.e_shentsize) != sizeof(Elf32_Shdr)))
	{
		/* Invalid section header size */
		if (probe_debug) {
			fprintf(stderr, "ELF bad section header size\n");
		}
		return -1;
	}

	return 0;
}

static int build_mem_elf64_ehdr(const char *buf, off_t len, struct mem_ehdr *ehdr)
{
	Elf64_Ehdr lehdr;
	if ((uintmax_t)len < (uintmax_t)sizeof(lehdr)) {
		/* Buffer is to small to be an elf executable */
		if (probe_debug) {
			fprintf(stderr, "Buffer is to small to hold ELF header\n");
		}
		return -1;
	}
	memcpy(&lehdr, buf, sizeof(lehdr));
	if (elf16_to_cpu(ehdr, lehdr.e_ehsize) != sizeof(Elf64_Ehdr)) {
		/* Invalid Elf header size */
		if (probe_debug) {
			fprintf(stderr, "Bad ELF header size\n");
		}
		return -1;
	}
	if (elf32_to_cpu(ehdr, lehdr.e_entry) > UINT32_MAX) {
		/* entry is to large */
		if (probe_debug) {
			fprintf(stderr, "ELF e_entry to large\n");
		}
		return -1;
	}
	if (elf32_to_cpu(ehdr, lehdr.e_phoff) > UINT32_MAX) {
		/* phoff is to large */
		if (probe_debug) {
			fprintf(stderr, "ELF e_phoff to large\n");
		}
		return -1;
	}
	if (elf32_to_cpu(ehdr, lehdr.e_shoff) > UINT32_MAX) {
		/* shoff is to large */
		if (probe_debug) {
			fprintf(stderr, "ELF e_shoff to large\n");
		}
		return -1;
	}
	ehdr->e_type      = elf16_to_cpu(ehdr, lehdr.e_type);
	ehdr->e_machine   = elf16_to_cpu(ehdr, lehdr.e_machine);
	ehdr->e_version   = elf32_to_cpu(ehdr, lehdr.e_version);
	ehdr->e_entry     = elf64_to_cpu(ehdr, lehdr.e_entry);
	ehdr->e_phoff     = elf64_to_cpu(ehdr, lehdr.e_phoff);
	ehdr->e_shoff     = elf64_to_cpu(ehdr, lehdr.e_shoff);
	ehdr->e_flags     = elf32_to_cpu(ehdr, lehdr.e_flags);
	ehdr->e_phnum     = elf16_to_cpu(ehdr, lehdr.e_phnum);
	ehdr->e_shnum     = elf16_to_cpu(ehdr, lehdr.e_shnum);
	ehdr->e_shstrndx  = elf16_to_cpu(ehdr, lehdr.e_shstrndx);

	if ((ehdr->e_phnum > 0) &&
		(elf16_to_cpu(ehdr, lehdr.e_phentsize) != sizeof(Elf64_Phdr)))
	{
		/* Invalid program header size */
		if (probe_debug) {
			fprintf(stderr, "ELF bad program header size\n");
		}
		return -1;
	}
	if ((ehdr->e_shnum > 0) &&
		(elf16_to_cpu(ehdr, lehdr.e_shentsize) != sizeof(Elf64_Shdr)))
	{
		/* Invalid section header size */
		if (probe_debug) {
			fprintf(stderr, "ELF bad section header size\n");
		}
		return -1;
	}

	return 0;
}

static int build_mem_ehdr(const char *buf, off_t len, struct mem_ehdr *ehdr)
{
	unsigned char e_ident[EI_NIDENT];
	int result;
	memset(ehdr, 0, sizeof(*ehdr));
	if ((uintmax_t)len < (uintmax_t)sizeof(e_ident)) {
		/* Buffer is to small to be an elf executable */
		if (probe_debug) {
			fprintf(stderr, "Buffer is to small to hold ELF e_ident\n");
		}
		return -1;
	}
	memcpy(e_ident, buf, sizeof(e_ident));
	if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
		/* No ELF header magic */
		if (probe_debug) {
			fprintf(stderr, "NO ELF header magic\n");
		}
		return -1;
	}
	ehdr->ei_class   = e_ident[EI_CLASS];
	ehdr->ei_data    = e_ident[EI_DATA];
	if (	(ehdr->ei_class != ELFCLASS32) &&
		(ehdr->ei_class != ELFCLASS64))
	{
		/* Not a supported elf class */
		if (probe_debug) {
			fprintf(stderr, "Not a supported ELF class\n");
		}
		return -1;
	}
	if (	(ehdr->ei_data != ELFDATA2LSB) &&
		(ehdr->ei_data != ELFDATA2MSB))
	{
		/* Not a supported elf data type */
		if (probe_debug) {
			fprintf(stderr, "Not a supported ELF data format\n");
		}
		return -1;
	}

	result = -1;
	if (ehdr->ei_class == ELFCLASS32) {
		result = build_mem_elf32_ehdr(buf, len, ehdr);
	}
	else if (ehdr->ei_class == ELFCLASS64) {
		result = build_mem_elf64_ehdr(buf, len, ehdr);
	}
	if (result < 0) {
		return result;
	}
	if ((e_ident[EI_VERSION] != EV_CURRENT) ||
		(ehdr->e_version != EV_CURRENT))
	{
		if (probe_debug) {
			fprintf(stderr, "Unknown ELF version\n");
		}
		/* Unknwon elf version */
		return -1;
	}
	return 0;
}

static int build_mem_elf32_phdr(const char *buf, struct mem_ehdr *ehdr, int idx)
{
	struct mem_phdr *phdr;
	const char *pbuf;
	Elf32_Phdr lphdr;
	pbuf = buf + ehdr->e_phoff + (idx * sizeof(lphdr));
	phdr = &ehdr->e_phdr[idx];
	memcpy(&lphdr, pbuf, sizeof(lphdr));

	if (	(elf32_to_cpu(ehdr, lphdr.p_filesz) > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lphdr.p_memsz)  > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lphdr.p_offset) > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lphdr.p_paddr)  > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lphdr.p_vaddr)  > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lphdr.p_align)  > UINT32_MAX))
	{
		fprintf(stderr, "Program segment size out of range\n");
		return -1;
	}

	phdr->p_type   = elf32_to_cpu(ehdr, lphdr.p_type);
	phdr->p_paddr  = elf32_to_cpu(ehdr, lphdr.p_paddr);
	phdr->p_vaddr  = elf32_to_cpu(ehdr, lphdr.p_vaddr);
	phdr->p_filesz = elf32_to_cpu(ehdr, lphdr.p_filesz);
	phdr->p_memsz  = elf32_to_cpu(ehdr, lphdr.p_memsz);
	phdr->p_offset = elf32_to_cpu(ehdr, lphdr.p_offset);
	phdr->p_flags  = elf32_to_cpu(ehdr, lphdr.p_flags);
	phdr->p_align  = elf32_to_cpu(ehdr, lphdr.p_align);

	return 0;
}

static int build_mem_elf64_phdr(const char *buf, struct mem_ehdr *ehdr, int idx)
{
	struct mem_phdr *phdr;
	const char *pbuf;
	Elf64_Phdr lphdr;
	pbuf = buf + ehdr->e_phoff + (idx * sizeof(lphdr));
	phdr = &ehdr->e_phdr[idx];
	memcpy(&lphdr, pbuf, sizeof(lphdr));

	if (	(elf64_to_cpu(ehdr, lphdr.p_filesz) > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lphdr.p_memsz)  > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lphdr.p_offset) > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lphdr.p_paddr)  > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lphdr.p_vaddr)  > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lphdr.p_align)  > UINT64_MAX))
	{
		fprintf(stderr, "Program segment size out of range\n");
		return -1;
	}

	phdr->p_type   = elf32_to_cpu(ehdr, lphdr.p_type);
	phdr->p_paddr  = elf64_to_cpu(ehdr, lphdr.p_paddr);
	phdr->p_vaddr  = elf64_to_cpu(ehdr, lphdr.p_vaddr);
	phdr->p_filesz = elf64_to_cpu(ehdr, lphdr.p_filesz);
	phdr->p_memsz  = elf64_to_cpu(ehdr, lphdr.p_memsz);
	phdr->p_offset = elf64_to_cpu(ehdr, lphdr.p_offset);
	phdr->p_flags  = elf32_to_cpu(ehdr, lphdr.p_flags);
	phdr->p_align  = elf64_to_cpu(ehdr, lphdr.p_align);

	return 0;
}

static int build_mem_phdrs(const char *buf, off_t len, struct mem_ehdr *ehdr,
				uint32_t flags)
{
	size_t phdr_size, mem_phdr_size, i;

	/* e_phnum is at most 65535 so calculating
	 * the size of the program header cannot overflow.
	 */
	/* Is the program header in the file buffer? */
	phdr_size = 0;
	if (ehdr->ei_class == ELFCLASS32) {
		phdr_size = sizeof(Elf32_Phdr);
	}
	else if (ehdr->ei_class == ELFCLASS64) {
		phdr_size = sizeof(Elf64_Phdr);
	}
	else {
		fprintf(stderr, "Invalid ei_class?\n");
		return -1;
	}
	phdr_size *= ehdr->e_phnum;
	if ((uintmax_t)(ehdr->e_phoff + phdr_size) > (uintmax_t)len) {
		/* The program header did not fit in the file buffer */
		if (probe_debug || (flags & ELF_SKIP_FILESZ_CHECK)) {
			fprintf(stderr, "ELF program headers truncated"
				" have %ju bytes need %ju bytes\n",
				(uintmax_t)len,
				(uintmax_t)(ehdr->e_phoff + phdr_size));
		}
		return -1;
	}

	/* Allocate the e_phdr array */
	mem_phdr_size = sizeof(ehdr->e_phdr[0]) * ehdr->e_phnum;
	ehdr->e_phdr = xmalloc(mem_phdr_size);

	for(i = 0; i < ehdr->e_phnum; i++) {
		struct mem_phdr *phdr;
		int result;
		result = -1;
		if (ehdr->ei_class == ELFCLASS32) {
			result = build_mem_elf32_phdr(buf, ehdr, i);

		}
		else if (ehdr->ei_class == ELFCLASS64) {
			result = build_mem_elf64_phdr(buf, ehdr, i);
		}
		if (result < 0) {
			return result;
		}

		/* Check the program headers to be certain
		 * they are safe to use.
		 * Skip the check if ELF_SKIP_FILESZ_CHECK is set.
		 */
		phdr = &ehdr->e_phdr[i];
		if (!(flags & ELF_SKIP_FILESZ_CHECK)
			&& (uintmax_t)(phdr->p_offset + phdr->p_filesz) >
			   (uintmax_t)len) {
			/* The segment does not fit in the buffer */
			if (probe_debug) {
				fprintf(stderr, "ELF segment not in file\n");
			}
			return -1;
		}
		if ((phdr->p_paddr + phdr->p_memsz) < phdr->p_paddr) {
			/* The memory address wraps */
			if (probe_debug) {
				fprintf(stderr, "ELF address wrap around\n");
			}
			return -1;
		}
		/* Remember where the segment lives in the buffer */
		phdr->p_data = buf + phdr->p_offset;
	}
	return 0;
}

static int build_mem_elf32_shdr(const char *buf, struct mem_ehdr *ehdr, int idx)
{
	struct mem_shdr *shdr;
	const char *sbuf;
	int size_ok;
	Elf32_Shdr lshdr;
	sbuf = buf + ehdr->e_shoff + (idx * sizeof(lshdr));
	shdr = &ehdr->e_shdr[idx];
	memcpy(&lshdr, sbuf, sizeof(lshdr));

	if (	(elf32_to_cpu(ehdr, lshdr.sh_flags)     > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lshdr.sh_addr)      > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lshdr.sh_offset)    > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lshdr.sh_size)      > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lshdr.sh_addralign) > UINT32_MAX) ||
		(elf32_to_cpu(ehdr, lshdr.sh_entsize)   > UINT32_MAX))
	{
		fprintf(stderr, "Program section size out of range\n");
		return -1;
	}

	shdr->sh_name      = elf32_to_cpu(ehdr, lshdr.sh_name);
	shdr->sh_type      = elf32_to_cpu(ehdr, lshdr.sh_type);
	shdr->sh_flags     = elf32_to_cpu(ehdr, lshdr.sh_flags);
	shdr->sh_addr      = elf32_to_cpu(ehdr, lshdr.sh_addr);
	shdr->sh_offset    = elf32_to_cpu(ehdr, lshdr.sh_offset);
	shdr->sh_size      = elf32_to_cpu(ehdr, lshdr.sh_size);
	shdr->sh_link      = elf32_to_cpu(ehdr, lshdr.sh_link);
	shdr->sh_info      = elf32_to_cpu(ehdr, lshdr.sh_info);
	shdr->sh_addralign = elf32_to_cpu(ehdr, lshdr.sh_addralign);
	shdr->sh_entsize   = elf32_to_cpu(ehdr, lshdr.sh_entsize);

	/* Now verify sh_entsize */
	size_ok = 0;
	switch(shdr->sh_type) {
	case SHT_SYMTAB:
		size_ok = shdr->sh_entsize == sizeof(Elf32_Sym);
		break;
	case SHT_RELA:
		size_ok = shdr->sh_entsize == sizeof(Elf32_Rela);
		break;
	case SHT_DYNAMIC:
		size_ok = shdr->sh_entsize == sizeof(Elf32_Dyn);
		break;
	case SHT_REL:
		size_ok = shdr->sh_entsize == sizeof(Elf32_Rel);
		break;
	case SHT_NOTE:
	case SHT_NULL:
	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 = 1;
		break;
	}
	if (!size_ok) {
		fprintf(stderr, "Bad section header(%x) entsize: %lld\n",
			shdr->sh_type, shdr->sh_entsize);
		return -1;
	}
	return 0;
}

static int build_mem_elf64_shdr(const char *buf, struct mem_ehdr *ehdr, int idx)
{
	struct mem_shdr *shdr;
	const char *sbuf;
	int size_ok;
	Elf64_Shdr lshdr;
	sbuf = buf + ehdr->e_shoff + (idx * sizeof(lshdr));
	shdr = &ehdr->e_shdr[idx];
	memcpy(&lshdr, sbuf, sizeof(lshdr));

	if (	(elf64_to_cpu(ehdr, lshdr.sh_flags)     > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lshdr.sh_addr)      > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lshdr.sh_offset)    > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lshdr.sh_size)      > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lshdr.sh_addralign) > UINT64_MAX) ||
		(elf64_to_cpu(ehdr, lshdr.sh_entsize)   > UINT64_MAX))
	{
		fprintf(stderr, "Program section size out of range\n");
		return -1;
	}

	shdr->sh_name      = elf32_to_cpu(ehdr, lshdr.sh_name);
	shdr->sh_type      = elf32_to_cpu(ehdr, lshdr.sh_type);
	shdr->sh_flags     = elf64_to_cpu(ehdr, lshdr.sh_flags);
	shdr->sh_addr      = elf64_to_cpu(ehdr, lshdr.sh_addr);
	shdr->sh_offset    = elf64_to_cpu(ehdr, lshdr.sh_offset);
	shdr->sh_size      = elf64_to_cpu(ehdr, lshdr.sh_size);
	shdr->sh_link      = elf32_to_cpu(ehdr, lshdr.sh_link);
	shdr->sh_info      = elf32_to_cpu(ehdr, lshdr.sh_info);
	shdr->sh_addralign = elf64_to_cpu(ehdr, lshdr.sh_addralign);
	shdr->sh_entsize   = elf64_to_cpu(ehdr, lshdr.sh_entsize);

	/* Now verify sh_entsize */
	size_ok = 0;
	switch(shdr->sh_type) {
	case SHT_SYMTAB:
		size_ok = shdr->sh_entsize == sizeof(Elf64_Sym);
		break;
	case SHT_RELA:
		size_ok = shdr->sh_entsize == sizeof(Elf64_Rela);
		break;
	case SHT_DYNAMIC:
		size_ok = shdr->sh_entsize == sizeof(Elf64_Dyn);
		break;
	case SHT_REL:
		size_ok = shdr->sh_entsize == sizeof(Elf64_Rel);
		break;
	case SHT_NOTE:
	case SHT_NULL:
	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 = 1;
		break;
	}
	if (!size_ok) {
		fprintf(stderr, "Bad section header(%x) entsize: %lld\n",
			shdr->sh_type, shdr->sh_entsize);
		return -1;
	}
	return 0;
}

static int build_mem_shdrs(const char *buf, off_t len, struct mem_ehdr *ehdr,
				uint32_t flags)
{
	size_t shdr_size, mem_shdr_size, i;

	/* e_shnum is at most 65536 so calculating
	 * the size of the section header cannot overflow.
	 */
	/* Is the program header in the file buffer? */
	shdr_size = 0;
	if (ehdr->ei_class == ELFCLASS32) {
		shdr_size = sizeof(Elf32_Shdr);
	}
	else if (ehdr->ei_class == ELFCLASS64) {
		shdr_size = sizeof(Elf64_Shdr);
	}
	else {
		fprintf(stderr, "Invalid ei_class?\n");
		return -1;
	}
	shdr_size *= ehdr->e_shnum;
	if ((uintmax_t)(ehdr->e_shoff + shdr_size) > (uintmax_t)len) {
		/* The section header did not fit in the file buffer */
		if (probe_debug) {
			fprintf(stderr, "ELF section header does not fit in file\n");
		}
		return -1;
	}

	/* Allocate the e_shdr array */
	mem_shdr_size = sizeof(ehdr->e_shdr[0]) * ehdr->e_shnum;
	ehdr->e_shdr = xmalloc(mem_shdr_size);

	for(i = 0; i < ehdr->e_shnum; i++) {
		struct mem_shdr *shdr;
		int result;
		result = -1;
		if (ehdr->ei_class == ELFCLASS32) {
			result = build_mem_elf32_shdr(buf, ehdr, i);
		}
		else if (ehdr->ei_class == ELFCLASS64) {
			result = build_mem_elf64_shdr(buf, ehdr, i);
		}
		if (result < 0) {
			return result;
		}
		/* Check the section headers to be certain
		 * they are safe to use.
		 * Skip the check if ELF_SKIP_FILESZ_CHECK is set.
		 */
		shdr = &ehdr->e_shdr[i];
		if (!(flags & ELF_SKIP_FILESZ_CHECK)
			&& (shdr->sh_type != SHT_NOBITS)
			&& (uintmax_t)(shdr->sh_offset + shdr->sh_size) >
			   (uintmax_t)len) {
			/* The section does not fit in the buffer */
			if (probe_debug) {
				fprintf(stderr, "ELF section %zd not in file\n",
					i);
			}
			return -1;
		}
		if ((shdr->sh_addr + shdr->sh_size) < shdr->sh_addr) {
			/* The memory address wraps */
			if (probe_debug) {
				fprintf(stderr, "ELF address wrap around\n");
			}
			return -1;
		}
		/* Remember where the section lives in the buffer */
		shdr->sh_data = (unsigned char *)(buf + shdr->sh_offset);
	}
	return 0;
}

static void read_nhdr(const struct mem_ehdr *ehdr,
	ElfNN_Nhdr *hdr, const unsigned char *note)
{
	memcpy(hdr, note, sizeof(*hdr));
	hdr->n_namesz = elf32_to_cpu(ehdr, hdr->n_namesz);
	hdr->n_descsz = elf32_to_cpu(ehdr, hdr->n_descsz);
	hdr->n_type   = elf32_to_cpu(ehdr, hdr->n_type);

}
static int build_mem_notes(struct mem_ehdr *ehdr)
{
	const unsigned char *note_start, *note_end, *note;
	size_t note_size, i;
	/* First find the note segment or section */
	note_start = note_end = NULL;
	for(i = 0; !note_start && (i < ehdr->e_phnum); i++) {
		struct mem_phdr *phdr = &ehdr->e_phdr[i];
		/*
		 * binutils <= 2.17 has a bug where it can create the
		 * PT_NOTE segment with an offset of 0. Therefore
		 * check p_offset > 0.
		 *
		 * See: http://sourceware.org/bugzilla/show_bug.cgi?id=594
		 */
		if (phdr->p_type == PT_NOTE && phdr->p_offset) {
			note_start = (unsigned char *)phdr->p_data;
			note_end = note_start + phdr->p_filesz;
		}
	}
	for(i = 0; !note_start && (i < ehdr->e_shnum); i++) {
		struct mem_shdr *shdr = &ehdr->e_shdr[i];
		if (shdr->sh_type == SHT_NOTE) {
			note_start = shdr->sh_data;
			note_end = note_start + shdr->sh_size;
		}
	}
	if (!note_start) {
		return 0;
	}

	/* Walk through and count the notes */
	ehdr->e_notenum = 0;
	for(note = note_start; note < note_end; note+= note_size) {
		ElfNN_Nhdr hdr;
		read_nhdr(ehdr, &hdr, note);
		note_size  = sizeof(hdr);
		note_size += (hdr.n_namesz + 3) & ~3;
		note_size += (hdr.n_descsz + 3) & ~3;
		ehdr->e_notenum += 1;
	}
	/* Now walk and normalize the notes */
	ehdr->e_note = xmalloc(sizeof(*ehdr->e_note) * ehdr->e_notenum);
	for(i = 0, note = note_start; note < note_end; note+= note_size, i++) {
		const unsigned char *name, *desc;
		ElfNN_Nhdr hdr;
		read_nhdr(ehdr, &hdr, note);
		note_size  = sizeof(hdr);
		name       = note + note_size;
		note_size += (hdr.n_namesz + 3) & ~3;
		desc       = note + note_size;
		note_size += (hdr.n_descsz + 3) & ~3;

		if ((hdr.n_namesz != 0) && (name[hdr.n_namesz -1] != '\0')) {
			/* If note name string is not null terminated, just
			 * warn user about it and continue processing. This
			 * allows us to parse /proc/kcore on older kernels
			 * where /proc/kcore elf notes were not null
			 * terminated. It has been fixed in 2.6.19.
			 */
			fprintf(stderr, "Warning: Elf Note name is not null "
					"terminated\n");
		}
		ehdr->e_note[i].n_type = hdr.n_type;
		ehdr->e_note[i].n_name = (char *)name;
		ehdr->e_note[i].n_desc = desc;
		ehdr->e_note[i].n_descsz = hdr.n_descsz;

	}
	return 0;
}

void free_elf_info(struct mem_ehdr *ehdr)
{
	free(ehdr->e_phdr);
	free(ehdr->e_shdr);
	memset(ehdr, 0, sizeof(*ehdr));
}

int build_elf_info(const char *buf, off_t len, struct mem_ehdr *ehdr,
			uint32_t flags)
{
	int result;
	result = build_mem_ehdr(buf, len, ehdr);
	if (result < 0) {
		return result;
	}
	if ((ehdr->e_phoff > 0) && (ehdr->e_phnum > 0)) {
		result = build_mem_phdrs(buf, len, ehdr, flags);
		if (result < 0) {
			free_elf_info(ehdr);
			return result;
		}
	}
	if ((ehdr->e_shoff > 0) && (ehdr->e_shnum > 0)) {
		result = build_mem_shdrs(buf, len, ehdr, flags);
		if (result < 0) {
			free_elf_info(ehdr);
			return result;
		}
	}
	result = build_mem_notes(ehdr);
	if (result < 0) {
		free_elf_info(ehdr);
		return result;
	}
	return 0;
}

