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![Sven Schnelle](/assets/img/avatar_default.png)
The powerpc version only supported 64 bit. Add some code to switch decoding of fields during runtime so we can kexec a 32 bit kernel from a 64 bit kernel and vice versa. 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>
430 lines
11 KiB
C
430 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Load ELF vmlinux file for the kexec_file_load syscall.
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*
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* Copyright (C) 2004 Adam Litke (agl@us.ibm.com)
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* Copyright (C) 2004 IBM Corp.
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* Copyright (C) 2005 R Sharada (sharada@in.ibm.com)
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* Copyright (C) 2006 Mohan Kumar M (mohan@in.ibm.com)
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* Copyright (C) 2016 IBM Corporation
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*
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* Based on kexec-tools' kexec-elf-exec.c and kexec-elf-ppc64.c.
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* Heavily modified for the kernel by
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* Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>.
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*/
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#define pr_fmt(fmt) "kexec_elf: " fmt
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#include <linux/elf.h>
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#include <linux/kexec.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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static inline bool elf_is_elf_file(const struct elfhdr *ehdr)
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{
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return memcmp(ehdr->e_ident, ELFMAG, SELFMAG) == 0;
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}
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static uint64_t elf64_to_cpu(const struct elfhdr *ehdr, uint64_t value)
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{
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if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
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value = le64_to_cpu(value);
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else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
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value = be64_to_cpu(value);
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return value;
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}
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static uint32_t elf32_to_cpu(const struct elfhdr *ehdr, uint32_t value)
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{
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if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
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value = le32_to_cpu(value);
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else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
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value = be32_to_cpu(value);
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return value;
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}
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static uint16_t elf16_to_cpu(const struct elfhdr *ehdr, uint16_t value)
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{
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if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
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value = le16_to_cpu(value);
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else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
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value = be16_to_cpu(value);
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return value;
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}
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/**
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* elf_is_ehdr_sane - check that it is safe to use the ELF header
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* @buf_len: size of the buffer in which the ELF file is loaded.
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*/
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static bool elf_is_ehdr_sane(const struct elfhdr *ehdr, size_t buf_len)
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{
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if (ehdr->e_phnum > 0 && ehdr->e_phentsize != sizeof(struct elf_phdr)) {
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pr_debug("Bad program header size.\n");
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return false;
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} else if (ehdr->e_shnum > 0 &&
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ehdr->e_shentsize != sizeof(struct elf_shdr)) {
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pr_debug("Bad section header size.\n");
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return false;
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} else if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
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ehdr->e_version != EV_CURRENT) {
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pr_debug("Unknown ELF version.\n");
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return false;
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}
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if (ehdr->e_phoff > 0 && ehdr->e_phnum > 0) {
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size_t phdr_size;
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/*
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* e_phnum is at most 65535 so calculating the size of the
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* program header cannot overflow.
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*/
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phdr_size = sizeof(struct elf_phdr) * ehdr->e_phnum;
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/* Sanity check the program header table location. */
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if (ehdr->e_phoff + phdr_size < ehdr->e_phoff) {
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pr_debug("Program headers at invalid location.\n");
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return false;
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} else if (ehdr->e_phoff + phdr_size > buf_len) {
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pr_debug("Program headers truncated.\n");
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return false;
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}
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}
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if (ehdr->e_shoff > 0 && ehdr->e_shnum > 0) {
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size_t shdr_size;
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/*
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* e_shnum is at most 65536 so calculating
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* the size of the section header cannot overflow.
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*/
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shdr_size = sizeof(struct elf_shdr) * ehdr->e_shnum;
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/* Sanity check the section header table location. */
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if (ehdr->e_shoff + shdr_size < ehdr->e_shoff) {
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pr_debug("Section headers at invalid location.\n");
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return false;
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} else if (ehdr->e_shoff + shdr_size > buf_len) {
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pr_debug("Section headers truncated.\n");
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return false;
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}
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}
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return true;
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}
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static int elf_read_ehdr(const char *buf, size_t len, struct elfhdr *ehdr)
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{
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struct elfhdr *buf_ehdr;
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if (len < sizeof(*buf_ehdr)) {
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pr_debug("Buffer is too small to hold ELF header.\n");
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return -ENOEXEC;
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}
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memset(ehdr, 0, sizeof(*ehdr));
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memcpy(ehdr->e_ident, buf, sizeof(ehdr->e_ident));
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if (!elf_is_elf_file(ehdr)) {
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pr_debug("No ELF header magic.\n");
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return -ENOEXEC;
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}
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if (ehdr->e_ident[EI_CLASS] != ELF_CLASS) {
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pr_debug("Not a supported ELF class.\n");
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return -ENOEXEC;
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} else if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB &&
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ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
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pr_debug("Not a supported ELF data format.\n");
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return -ENOEXEC;
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}
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buf_ehdr = (struct elfhdr *) buf;
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if (elf16_to_cpu(ehdr, buf_ehdr->e_ehsize) != sizeof(*buf_ehdr)) {
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pr_debug("Bad ELF header size.\n");
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return -ENOEXEC;
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}
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ehdr->e_type = elf16_to_cpu(ehdr, buf_ehdr->e_type);
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ehdr->e_machine = elf16_to_cpu(ehdr, buf_ehdr->e_machine);
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ehdr->e_version = elf32_to_cpu(ehdr, buf_ehdr->e_version);
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ehdr->e_flags = elf32_to_cpu(ehdr, buf_ehdr->e_flags);
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ehdr->e_phentsize = elf16_to_cpu(ehdr, buf_ehdr->e_phentsize);
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ehdr->e_phnum = elf16_to_cpu(ehdr, buf_ehdr->e_phnum);
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ehdr->e_shentsize = elf16_to_cpu(ehdr, buf_ehdr->e_shentsize);
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ehdr->e_shnum = elf16_to_cpu(ehdr, buf_ehdr->e_shnum);
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ehdr->e_shstrndx = elf16_to_cpu(ehdr, buf_ehdr->e_shstrndx);
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switch (ehdr->e_ident[EI_CLASS]) {
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case ELFCLASS64:
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ehdr->e_entry = elf64_to_cpu(ehdr, buf_ehdr->e_entry);
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ehdr->e_phoff = elf64_to_cpu(ehdr, buf_ehdr->e_phoff);
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ehdr->e_shoff = elf64_to_cpu(ehdr, buf_ehdr->e_shoff);
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break;
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case ELFCLASS32:
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ehdr->e_entry = elf32_to_cpu(ehdr, buf_ehdr->e_entry);
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ehdr->e_phoff = elf32_to_cpu(ehdr, buf_ehdr->e_phoff);
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ehdr->e_shoff = elf32_to_cpu(ehdr, buf_ehdr->e_shoff);
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break;
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default:
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pr_debug("Unknown ELF class.\n");
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return -EINVAL;
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}
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return elf_is_ehdr_sane(ehdr, len) ? 0 : -ENOEXEC;
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}
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/**
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* elf_is_phdr_sane - check that it is safe to use the program header
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* @buf_len: size of the buffer in which the ELF file is loaded.
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*/
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static bool elf_is_phdr_sane(const struct elf_phdr *phdr, size_t buf_len)
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{
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if (phdr->p_offset + phdr->p_filesz < phdr->p_offset) {
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pr_debug("ELF segment location wraps around.\n");
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return false;
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} else if (phdr->p_offset + phdr->p_filesz > buf_len) {
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pr_debug("ELF segment not in file.\n");
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return false;
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} else if (phdr->p_paddr + phdr->p_memsz < phdr->p_paddr) {
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pr_debug("ELF segment address wraps around.\n");
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return false;
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}
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return true;
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}
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static int elf_read_phdr(const char *buf, size_t len,
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struct kexec_elf_info *elf_info,
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int idx)
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{
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/* Override the const in proghdrs, we are the ones doing the loading. */
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struct elf_phdr *phdr = (struct elf_phdr *) &elf_info->proghdrs[idx];
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const struct elfhdr *ehdr = elf_info->ehdr;
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const char *pbuf;
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struct elf_phdr *buf_phdr;
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pbuf = buf + elf_info->ehdr->e_phoff + (idx * sizeof(*buf_phdr));
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buf_phdr = (struct elf_phdr *) pbuf;
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phdr->p_type = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_type);
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phdr->p_flags = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);
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switch (ehdr->e_ident[EI_CLASS]) {
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case ELFCLASS64:
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phdr->p_offset = elf64_to_cpu(ehdr, buf_phdr->p_offset);
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phdr->p_paddr = elf64_to_cpu(ehdr, buf_phdr->p_paddr);
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phdr->p_vaddr = elf64_to_cpu(ehdr, buf_phdr->p_vaddr);
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phdr->p_filesz = elf64_to_cpu(ehdr, buf_phdr->p_filesz);
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phdr->p_memsz = elf64_to_cpu(ehdr, buf_phdr->p_memsz);
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phdr->p_align = elf64_to_cpu(ehdr, buf_phdr->p_align);
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break;
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case ELFCLASS32:
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phdr->p_offset = elf32_to_cpu(ehdr, buf_phdr->p_offset);
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phdr->p_paddr = elf32_to_cpu(ehdr, buf_phdr->p_paddr);
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phdr->p_vaddr = elf32_to_cpu(ehdr, buf_phdr->p_vaddr);
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phdr->p_filesz = elf32_to_cpu(ehdr, buf_phdr->p_filesz);
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phdr->p_memsz = elf32_to_cpu(ehdr, buf_phdr->p_memsz);
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phdr->p_align = elf32_to_cpu(ehdr, buf_phdr->p_align);
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break;
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default:
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pr_debug("Unknown ELF class.\n");
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return -EINVAL;
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}
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return elf_is_phdr_sane(phdr, len) ? 0 : -ENOEXEC;
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}
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/**
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* elf_read_phdrs - read the program headers from the buffer
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*
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* This function assumes that the program header table was checked for sanity.
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* Use elf_is_ehdr_sane() if it wasn't.
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*/
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static int elf_read_phdrs(const char *buf, size_t len,
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struct kexec_elf_info *elf_info)
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{
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size_t phdr_size, i;
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const struct elfhdr *ehdr = elf_info->ehdr;
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/*
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* e_phnum is at most 65535 so calculating the size of the
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* program header cannot overflow.
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*/
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phdr_size = sizeof(struct elf_phdr) * ehdr->e_phnum;
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elf_info->proghdrs = kzalloc(phdr_size, GFP_KERNEL);
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if (!elf_info->proghdrs)
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return -ENOMEM;
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for (i = 0; i < ehdr->e_phnum; i++) {
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int ret;
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ret = elf_read_phdr(buf, len, elf_info, i);
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if (ret) {
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kfree(elf_info->proghdrs);
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elf_info->proghdrs = NULL;
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return ret;
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}
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}
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return 0;
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}
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/**
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* elf_read_from_buffer - read ELF file and sets up ELF header and ELF info
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* @buf: Buffer to read ELF file from.
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* @len: Size of @buf.
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* @ehdr: Pointer to existing struct which will be populated.
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* @elf_info: Pointer to existing struct which will be populated.
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*
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* This function allows reading ELF files with different byte order than
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* the kernel, byte-swapping the fields as needed.
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*
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* Return:
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* On success returns 0, and the caller should call
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* kexec_free_elf_info(elf_info) to free the memory allocated for the section
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* and program headers.
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*/
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static int elf_read_from_buffer(const char *buf, size_t len,
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struct elfhdr *ehdr,
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struct kexec_elf_info *elf_info)
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{
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int ret;
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ret = elf_read_ehdr(buf, len, ehdr);
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if (ret)
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return ret;
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elf_info->buffer = buf;
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elf_info->ehdr = ehdr;
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if (ehdr->e_phoff > 0 && ehdr->e_phnum > 0) {
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ret = elf_read_phdrs(buf, len, elf_info);
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if (ret)
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return ret;
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}
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return 0;
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}
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/**
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* kexec_free_elf_info - free memory allocated by elf_read_from_buffer
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*/
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void kexec_free_elf_info(struct kexec_elf_info *elf_info)
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{
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kfree(elf_info->proghdrs);
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memset(elf_info, 0, sizeof(*elf_info));
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}
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/**
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* kexec_build_elf_info - read ELF executable and check that we can use it
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*/
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int kexec_build_elf_info(const char *buf, size_t len, struct elfhdr *ehdr,
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struct kexec_elf_info *elf_info)
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{
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int i;
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int ret;
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ret = elf_read_from_buffer(buf, len, ehdr, elf_info);
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if (ret)
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return ret;
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/* Big endian vmlinux has type ET_DYN. */
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if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
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pr_err("Not an ELF executable.\n");
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goto error;
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} else if (!elf_info->proghdrs) {
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pr_err("No ELF program header.\n");
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goto error;
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}
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for (i = 0; i < ehdr->e_phnum; i++) {
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/*
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* Kexec does not support loading interpreters.
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* In addition this check keeps us from attempting
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* to kexec ordinay executables.
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*/
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if (elf_info->proghdrs[i].p_type == PT_INTERP) {
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pr_err("Requires an ELF interpreter.\n");
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goto error;
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}
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}
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return 0;
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error:
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kexec_free_elf_info(elf_info);
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return -ENOEXEC;
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}
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int kexec_elf_probe(const char *buf, unsigned long len)
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{
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struct elfhdr ehdr;
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struct kexec_elf_info elf_info;
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int ret;
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ret = kexec_build_elf_info(buf, len, &ehdr, &elf_info);
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if (ret)
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return ret;
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kexec_free_elf_info(&elf_info);
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return elf_check_arch(&ehdr) ? 0 : -ENOEXEC;
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}
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/**
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* kexec_elf_load - load ELF executable image
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* @lowest_load_addr: On return, will be the address where the first PT_LOAD
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* section will be loaded in memory.
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*
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* Return:
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* 0 on success, negative value on failure.
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*/
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int kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
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struct kexec_elf_info *elf_info,
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struct kexec_buf *kbuf,
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unsigned long *lowest_load_addr)
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{
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unsigned long lowest_addr = UINT_MAX;
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int ret;
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size_t i;
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/* Read in the PT_LOAD segments. */
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for (i = 0; i < ehdr->e_phnum; i++) {
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unsigned long load_addr;
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size_t size;
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const struct elf_phdr *phdr;
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phdr = &elf_info->proghdrs[i];
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if (phdr->p_type != PT_LOAD)
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continue;
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size = phdr->p_filesz;
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if (size > phdr->p_memsz)
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size = phdr->p_memsz;
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kbuf->buffer = (void *) elf_info->buffer + phdr->p_offset;
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kbuf->bufsz = size;
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kbuf->memsz = phdr->p_memsz;
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kbuf->buf_align = phdr->p_align;
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kbuf->buf_min = phdr->p_paddr;
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kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
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ret = kexec_add_buffer(kbuf);
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if (ret)
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goto out;
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load_addr = kbuf->mem;
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if (load_addr < lowest_addr)
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lowest_addr = load_addr;
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}
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*lowest_load_addr = lowest_addr;
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ret = 0;
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out:
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return ret;
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}
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