/*
 * 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>.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation (version 2 of the License).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#define pr_fmt(fmt)     "kexec_elf: " fmt

#include <linux/elf.h>
#include <linux/kexec.h>
#include <linux/libfdt.h>
#include <linux/module.h>
#include <linux/of_fdt.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 */

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;
                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,
                        unsigned long cmdline_len)
{
        int ret;
        unsigned int fdt_size;
        unsigned long kernel_load_addr;
        unsigned long initrd_load_addr = 0, fdt_load_addr;
        void *fdt;
        const void *slave_code;
        struct elfhdr ehdr;
        struct 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 };

        ret = build_elf_exec_info(kernel_buf, kernel_len, &ehdr, &elf_info);
        if (ret)
                goto out;

        ret = elf_exec_load(image, &ehdr, &elf_info, &kernel_load_addr);
        if (ret)
                goto out;

        pr_debug("Loaded the kernel at 0x%lx\n", kernel_load_addr);

        ret = kexec_load_purgatory(image, &pbuf);
        if (ret) {
                pr_err("Loading purgatory failed.\n");
                goto out;
        }

        pr_debug("Loaded purgatory at 0x%lx\n", pbuf.mem);

        if (initrd != NULL) {
                kbuf.buffer = initrd;
                kbuf.bufsz = kbuf.memsz = initrd_len;
                kbuf.buf_align = PAGE_SIZE;
                kbuf.top_down = false;
                ret = kexec_add_buffer(&kbuf);
                if (ret)
                        goto out;
                initrd_load_addr = kbuf.mem;

                pr_debug("Loaded initrd at 0x%lx\n", initrd_load_addr);
        }

        fdt_size = fdt_totalsize(initial_boot_params) * 2;
        fdt = kmalloc(fdt_size, GFP_KERNEL);
        if (!fdt) {
                pr_err("Not enough memory for the device tree.\n");
                ret = -ENOMEM;
                goto out;
        }
        ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
        if (ret < 0) {
                pr_err("Error setting up the new device tree.\n");
                ret = -EINVAL;
                goto out;
        }

        ret = setup_new_fdt(image, fdt, initrd_load_addr, initrd_len, cmdline);
        if (ret)
                goto out;

        fdt_pack(fdt);

        kbuf.buffer = fdt;
        kbuf.bufsz = kbuf.memsz = fdt_size;
        kbuf.buf_align = PAGE_SIZE;
        kbuf.top_down = true;
        ret = kexec_add_buffer(&kbuf);
        if (ret)
                goto out;
        fdt_load_addr = kbuf.mem;

        pr_debug("Loaded device tree at 0x%lx\n", fdt_load_addr);

        slave_code = elf_info.buffer + elf_info.proghdrs[0].p_offset;
        ret = setup_purgatory(image, slave_code, fdt, kernel_load_addr,
                              fdt_load_addr);
        if (ret)
                pr_err("Error setting up the purgatory.\n");

out:
        elf_free_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,
        .load = elf64_load,
};