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kexec: add KEXEC_ELF

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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>
This commit is contained in:
Sven Schnelle 2019-08-23 21:49:13 +02:00 committed by Helge Deller
parent 544f448599
commit 175fca3bf9
6 changed files with 583 additions and 540 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/Kconfig
View File

@ -18,6 +18,9 @@ config KEXEC_CORE
select CRASH_CORE
bool
config KEXEC_ELF
bool
config HAVE_IMA_KEXEC
bool

1
arch/powerpc/Kconfig
View File

@ -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

545
arch/powerpc/kernel/kexec_elf_64.c
View File

@ -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,
};

24
include/linux/kexec.h
View File

@ -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;

1
kernel/Makefile
View File

@ -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/

549
kernel/kexec_elf.c Normal file
View File

@ -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;
}