/*-
 * Copyright (c) 2021 Roger Pau Monné <royger@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * This multiboot2 implementation only implements a subset of the full
 * multiboot2 specification in order to be able to boot Xen and a
 * FreeBSD Dom0. Trying to use it to boot other multiboot2 compliant
 * kernels will most surely fail.
 *
 * The full multiboot specification can be found here:
 * https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html
 */

#include <sys/param.h>
#include <sys/exec.h>
#include <sys/linker.h>
#include <sys/module.h>
#include <sys/stdint.h>
#define _MACHINE_ELF_WANT_32BIT
#include <machine/elf.h>
#include <machine/metadata.h>
#include <string.h>
#include <stand.h>

#include <efi.h>
#include <efilib.h>

#include "bootstrap.h"
#include "multiboot2.h"
#include "loader_efi.h"
#include "modinfo.h"

extern int elf32_loadfile_raw(char *filename, uint64_t dest,
    struct preloaded_file **result, int multiboot);
extern int elf64_load_modmetadata(struct preloaded_file *fp, uint64_t dest);
extern int elf64_obj_loadfile(char *filename, uint64_t dest,
    struct preloaded_file **result);

extern void multiboot2_exec(void *entry, uint64_t multiboot_info,
    uint64_t stack);

/*
 * Multiboot2 header information to pass between the loading and the exec
 * functions.
 */
struct mb2hdr {
        uint32_t efi64_entry;
};

static int
loadfile(char *filename, uint64_t dest, struct preloaded_file **result)
{
        unsigned int             i;
        int                      error, fd;
        void                    *header_search = NULL;
        void                    *multiboot = NULL;
        ssize_t                  search_size;
        struct multiboot_header *header;
        struct mb2hdr            hdr;
        bool                     keep_bs = false;

        /*
         * Read MULTIBOOT_SEARCH size in order to search for the
         * multiboot magic header.
         */
        if (filename == NULL)
                return (EFTYPE);
        if ((fd = open(filename, O_RDONLY)) == -1)
                return (errno);
        header_search = malloc(MULTIBOOT_SEARCH);
        if (header_search == NULL) {
                error = ENOMEM;
                goto out;
        }
        search_size = read(fd, header_search, MULTIBOOT_SEARCH);

        for (i = 0; i < search_size; i += MULTIBOOT_HEADER_ALIGN) {
                header = header_search + i;
                if (header->magic == MULTIBOOT2_HEADER_MAGIC)
                        break;
        }

        if (i >= search_size) {
                error = EFTYPE;
                goto out;
        }

        /* Valid multiboot header has been found, validate checksum */
        if (header->magic + header->architecture + header->header_length +
            header->checksum != 0) {
                printf("Multiboot checksum failed, magic: %#x "
                    "architecture: %#x header_length %#x checksum: %#x\n",
                    header->magic, header->architecture, header->header_length,
                    header->checksum);
                error = EFTYPE;
                goto out;
        }

        if (header->architecture != MULTIBOOT2_ARCHITECTURE_I386) {
                printf("Unsupported architecture: %#x\n",
                    header->architecture);
                error = EFTYPE;
                goto out;
        }

        multiboot = malloc(header->header_length - sizeof(*header));
        error = lseek(fd, i + sizeof(*header), SEEK_SET);
        if (error != i + sizeof(*header)) {
                printf("Unable to set file pointer to header location: %d\n",
                    error);
                goto out;
        }
        search_size = read(fd, multiboot,
            header->header_length - sizeof(*header));

        bzero(&hdr, sizeof(hdr));
        for (i = 0; i < search_size; ) {
                struct multiboot_header_tag *tag;
                struct multiboot_header_tag_entry_address *entry;
                struct multiboot_header_tag_information_request *req;
                unsigned int j;

                tag = multiboot + i;

                switch(tag->type) {
                case MULTIBOOT_HEADER_TAG_INFORMATION_REQUEST:
                        req = (void *)tag;
                        for (j = 0;
                            j < (tag->size - sizeof(*tag)) / sizeof(uint32_t);
                            j++) {
                                switch (req->requests[j]) {
                                case MULTIBOOT_TAG_TYPE_MMAP:
                                case MULTIBOOT_TAG_TYPE_BASIC_MEMINFO:
                                        /* Only applicable to BIOS. */
                                        break;

                                case MULTIBOOT_TAG_TYPE_EFI_BS:
                                case MULTIBOOT_TAG_TYPE_EFI64:
                                case MULTIBOOT_TAG_TYPE_EFI64_IH:
                                        /* Tags unconditionally added. */
                                        break;

                                default:
                                        if (req->flags &
                                            MULTIBOOT_HEADER_TAG_OPTIONAL)
                                                break;

                                        printf(
                                "Unknown non-optional information request %u\n",
                                            req->requests[j]);
                                        error = EINVAL;
                                        goto out;
                                }
                        }
                        break;

                case MULTIBOOT_HEADER_TAG_EFI_BS:
                        /* Never shut down BS. */
                        keep_bs = true;
                        break;

                case MULTIBOOT_HEADER_TAG_MODULE_ALIGN:
                        /* We will align modules by default already. */
                case MULTIBOOT_HEADER_TAG_END:
                        break;

                case MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS_EFI64:
                        entry = (void *)tag;
                        hdr.efi64_entry = entry->entry_addr;
                        break;

                default:
                        if (tag->flags & MULTIBOOT_HEADER_TAG_OPTIONAL)
                                break;
                        printf("Unknown header tag %#x not optional\n",
                            tag->type);
                        error = EINVAL;
                        goto out;
                }

                i += roundup2(tag->size, MULTIBOOT_TAG_ALIGN);
                if (tag->type == MULTIBOOT_HEADER_TAG_END)
                        break;
        }

        if (hdr.efi64_entry == 0) {
                printf("No EFI64 entry address provided\n");
                error = EINVAL;
                goto out;
        }
        if (!keep_bs) {
                printf("Unable to boot MB2 with BS exited\n");
                error = EINVAL;
                goto out;
        }

        error = elf32_loadfile_raw(filename, dest, result, 1);
        if (error != 0) {
                printf(
        "elf32_loadfile_raw failed: %d unable to load multiboot kernel\n",
                    error);
                goto out;
        }

        file_addmetadata(*result, MODINFOMD_NOCOPY | MODINFOMD_MB2HDR,
            sizeof(hdr), &hdr);

        /*
         * f_addr is already aligned to PAGE_SIZE, make sure
         * f_size it's also aligned so when the modules are loaded
         * they are aligned to PAGE_SIZE.
         */
        (*result)->f_size = roundup((*result)->f_size, PAGE_SIZE);

out:
        if (header_search != NULL)
                free(header_search);
        if (multiboot != NULL)
                free(multiboot);
        close(fd);
        return (error);
}

static unsigned int add_string(void *buf, unsigned int type, const char *str)
{
        struct multiboot_tag *tag;

        tag = buf;
        tag->type = type;
        tag->size = sizeof(*tag) + strlen(str) + 1;
        strcpy(buf + sizeof(*tag), str);
        return (roundup2(tag->size, MULTIBOOT_TAG_ALIGN));
}

static unsigned int add_efi(void *buf)
{
        struct multiboot_tag *bs;
        struct multiboot_tag_efi64 *efi64;
        struct multiboot_tag_efi64_ih *ih;
        unsigned int len;

        len = 0;
        bs = buf;
        bs->type = MULTIBOOT_TAG_TYPE_EFI_BS;
        bs->size = sizeof(*bs);
        len += roundup2(bs->size, MULTIBOOT_TAG_ALIGN);

        efi64 = buf + len;
        efi64->type = MULTIBOOT_TAG_TYPE_EFI64;
        efi64->size = sizeof(*efi64);
        efi64->pointer = (uintptr_t)ST;
        len += roundup2(efi64->size, MULTIBOOT_TAG_ALIGN);

        ih = buf + len;
        ih->type = MULTIBOOT_TAG_TYPE_EFI64_IH;
        ih->size = sizeof(*ih);
        ih->pointer = (uintptr_t)IH;

        return (len + roundup2(ih->size, MULTIBOOT_TAG_ALIGN));
}

static unsigned int add_module(void *buf, vm_offset_t start, vm_offset_t end,
    const char *cmdline)
{
        struct multiboot_tag_module *mod;

        mod = buf;
        mod->type = MULTIBOOT_TAG_TYPE_MODULE;
        mod->size = sizeof(*mod);
        mod->mod_start = start;
        mod->mod_end = end;
        if (cmdline != NULL)
        {
                strcpy(buf + sizeof(*mod), cmdline);
                mod->size += strlen(cmdline) + 1;
        }

        return (roundup2(mod->size, MULTIBOOT_TAG_ALIGN));
}

static unsigned int add_end(void *buf)
{
        struct multiboot_tag *tag;

        tag = buf;
        tag->type = MULTIBOOT_TAG_TYPE_END;
        tag->size = sizeof(*tag);

        return (roundup2(tag->size, MULTIBOOT_TAG_ALIGN));
}

static int
exec(struct preloaded_file *fp)
{
        EFI_PHYSICAL_ADDRESS             addr = 0;
        EFI_PHYSICAL_ADDRESS             stack = 0;
        EFI_STATUS                       status;
        void                            *multiboot_space;
        vm_offset_t                      modulep, kernend, kern_base,
                                         payload_base;
        char                            *cmdline = NULL;
        size_t                           len;
        int                              error;
        uint32_t                        *total_size;
        struct file_metadata            *md;
        struct xen_header                header;
        struct mb2hdr                   *hdr;


        _Static_assert(sizeof(header) <= PAGE_SIZE, "header too big");

        if ((md = file_findmetadata(fp,
            MODINFOMD_NOCOPY | MODINFOMD_MB2HDR)) == NULL) {
                printf("Missing Multiboot2 EFI64 entry point\n");
                return(EFTYPE);
        }
        hdr = (void *)&md->md_data;

        status = BS->AllocatePages(AllocateAnyPages, EfiLoaderData,
            EFI_SIZE_TO_PAGES(PAGE_SIZE), &addr);
        if (EFI_ERROR(status)) {
                printf("Failed to allocate pages for multiboot2 header: %lu\n",
                    DECODE_ERROR(status));
                error = ENOMEM;
                goto error;
        }
        status = BS->AllocatePages(AllocateAnyPages, EfiLoaderData,
            EFI_SIZE_TO_PAGES(128 * 1024), &stack);
        if (EFI_ERROR(status)) {
                printf("Failed to allocate pages for Xen stack: %lu\n",
                    DECODE_ERROR(status));
                error = ENOMEM;
                goto error;
        }

        /*
         * Scratch space to build the multiboot2 header. Reserve the start of
         * the space to place the header with the size, which we don't know
         * yet.
         */
        multiboot_space = (void *)(uintptr_t)(addr + sizeof(uint32_t) * 2);

        /*
         * Don't pass the memory size found by the bootloader, the memory
         * available to Dom0 will be lower than that.
         */
        unsetenv("smbios.memory.enabled");

        /* Set the Xen command line. */
        if (fp->f_args == NULL) {
                /* Add the Xen command line if it is set. */
                cmdline = getenv("xen_cmdline");
                if (cmdline != NULL) {
                        fp->f_args = strdup(cmdline);
                        if (fp->f_args == NULL) {
                                error = ENOMEM;
                                goto error;
                        }
                }
        }
        if (fp->f_args != NULL) {
                len = strlen(fp->f_name) + 1 + strlen(fp->f_args) + 1;
                cmdline = malloc(len);
                if (cmdline == NULL) {
                        error = ENOMEM;
                        goto error;
                }
                snprintf(cmdline, len, "%s %s", fp->f_name, fp->f_args);
                multiboot_space += add_string(multiboot_space,
                    MULTIBOOT_TAG_TYPE_CMDLINE, cmdline);
                free(cmdline);
        }

        multiboot_space += add_string(multiboot_space,
            MULTIBOOT_TAG_TYPE_BOOT_LOADER_NAME, "FreeBSD Loader");
        multiboot_space += add_efi(multiboot_space);

        /*
         * Prepare the multiboot module list, Xen assumes the first
         * module is the Dom0 kernel, and the second one is the initramfs.
         * This is not optimal for FreeBSD, that doesn't have a initramfs
         * but instead loads modules dynamically and creates the metadata
         * info on-the-fly.
         *
         * As expected, the first multiboot module is going to be the
         * FreeBSD kernel loaded as a raw file. The second module is going
         * to contain the metadata info and the loaded modules.
         *
         * There's a small header prefixed in the second module that contains
         * some information required to calculate the relocated address of
         * modulep based on the original offset of modulep from the start of
         * the module address. Note other fields might be added to this header
         * if required.
         *
         * Native layout:
         *           fp->f_addr + fp->f_size
         * +---------+----------------+------------+
         * |         |                |            |
         * | Kernel  |    Modules     |  Metadata  |
         * |         |                |            |
         * +---------+----------------+------------+
         * fp->f_addr                 modulep      kernend
         *
         * Xen dom0 layout:
         * fp->f_addr             fp->f_addr + fp->f_size
         * +---------+------------+----------------+------------+
         * |         |            |                |            |
         * | Kernel  | xen_header |    Modules     |  Metadata  |
         * |         |            |                |            |
         * +---------+------------+----------------+------------+
         *                                         modulep      kernend
         * \________/\__________________________________________/
         *  module 0                 module 1
         */

        fp = file_findfile(NULL, md_kerntype);
        if (fp == NULL) {
                printf("No FreeBSD kernel provided, aborting\n");
                error = EINVAL;
                goto error;
        }

        error = bi_load(fp->f_args, &modulep, &kernend, false);
        if (error != 0)
                goto error;

        /*
         * Note that the Xen kernel requires to be started with BootServices
         * enabled, and hence we cannot use efi_copy_finish to relocate the
         * loaded data from the staging area to the expected loaded addresses.
         * This is fine because the Xen kernel is relocatable, so it can boot
         * fine straight from the staging area. We use efi_translate to get the
         * staging addresses where the kernels and metadata are currently
         * loaded.
         */
        kern_base = (uintptr_t)efi_translate(fp->f_addr);
        payload_base = kern_base + fp->f_size - PAGE_SIZE;
        multiboot_space += add_module(multiboot_space, kern_base, payload_base,
            NULL);
        multiboot_space += add_module(multiboot_space, payload_base,
            (uintptr_t)efi_translate(kernend), "header");

        header.flags = XENHEADER_HAS_MODULEP_OFFSET;
        header.modulep_offset = modulep - (fp->f_addr + fp->f_size - PAGE_SIZE);
        archsw.arch_copyin(&header, fp->f_addr + fp->f_size - PAGE_SIZE,
            sizeof(header));

        multiboot_space += add_end(multiboot_space);
        total_size = (uint32_t *)(uintptr_t)(addr);
        *total_size = (uintptr_t)multiboot_space - addr;

        if (*total_size > PAGE_SIZE)
                panic("Multiboot header exceeds fixed size");

        efi_time_fini();
        dev_cleanup();
        multiboot2_exec(efi_translate(hdr->efi64_entry), addr,
            stack + 128 * 1024);

        panic("exec returned");

error:
        if (addr)
                BS->FreePages(addr, EFI_SIZE_TO_PAGES(PAGE_SIZE));
        if (stack)
                BS->FreePages(stack, EFI_SIZE_TO_PAGES(128 * 1024));
        return (error);
}

static int
obj_loadfile(char *filename, uint64_t dest, struct preloaded_file **result)
{
        struct preloaded_file   *mfp, *kfp, *rfp;
        int                      error;

        /* See if there's a multiboot kernel loaded */
        mfp = file_findfile(NULL, md_kerntype_mb);
        if (mfp == NULL)
                return (EFTYPE);

        /*
         * We have a multiboot kernel loaded, see if there's a FreeBSD
         * kernel loaded also.
         */
        kfp = file_findfile(NULL, md_kerntype);
        if (kfp == NULL) {
                /*
                 * No kernel loaded, this must be it. The kernel has to
                 * be loaded as a raw file, it will be processed by
                 * Xen and correctly loaded as an ELF file.
                 */
                rfp = file_loadraw(filename, md_kerntype, 0);
                if (rfp == NULL) {
                        printf(
                        "Unable to load %s as a multiboot payload kernel\n",
                        filename);
                        return (EINVAL);
                }

                /* Load kernel metadata... */
                setenv("kernelname", filename, 1);
                error = elf64_load_modmetadata(rfp, rfp->f_addr + rfp->f_size);
                if (error) {
                        printf("Unable to load kernel %s metadata error: %d\n",
                            rfp->f_name, error);
                        return (EINVAL);
                }


                /*
                 * Reserve one page at the end of the kernel to place some
                 * metadata in order to cope for Xen relocating the modules and
                 * the metadata information.
                 */
                rfp->f_size = roundup(rfp->f_size, PAGE_SIZE);
                rfp->f_size += PAGE_SIZE;
                *result = rfp;
        } else {
                /* The rest should be loaded as regular modules */
                error = elf64_obj_loadfile(filename, dest, result);
                if (error != 0) {
                        printf("Unable to load %s as an object file, error: %d",
                            filename, error);
                        return (error);
                }
        }

        return (0);
}

static int
obj_exec(struct preloaded_file *fp)
{

        return (EFTYPE);
}

struct file_format multiboot2 = {
        .l_load = loadfile,
        .l_exec = exec
};
struct file_format multiboot2_obj = {
        .l_load = obj_loadfile,
        .l_exec = obj_exec
};