system/ulib/libzbi/zbi.c

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <libzbi/zbi.h>
#include <stdbool.h>
#include <string.h>

struct check_state {
    zbi_header_t** err;
    bool seen_bootfs;
};

static zbi_result_t for_each_check_entry(zbi_header_t* hdr, void* payload,
                                         void* cookie) {
    struct check_state* const state = cookie;

    zbi_result_t result = ZBI_RESULT_OK;

    if (hdr->magic != ZBI_ITEM_MAGIC) {
        result = ZBI_RESULT_BAD_MAGIC;
    } else if ((hdr->flags & ZBI_FLAG_VERSION) == 0) {
        result = ZBI_RESULT_BAD_VERSION;
    } else if ((hdr->flags & ZBI_FLAG_CRC32) == 0 &&
               hdr->crc32 != ZBI_ITEM_NO_CRC32) {
        result = ZBI_RESULT_BAD_CRC;
    }

    // If we found a problem, try to report it back up to the caller.
    if (state->err != NULL && result != ZBI_RESULT_OK) {
        *state->err = hdr;
    }

    if (hdr->type == ZBI_TYPE_STORAGE_BOOTFS) {
        state->seen_bootfs = true;
    }

    return result;
}


static zbi_result_t zbi_check_internal(const void* base,
                                       uint32_t check_complete,
                                       zbi_header_t** err) {
    zbi_result_t res = ZBI_RESULT_OK;
    const zbi_header_t* header = base;

    if (header->type != ZBI_TYPE_CONTAINER) {
        res = ZBI_RESULT_BAD_TYPE;
    } else if (header->extra != ZBI_CONTAINER_MAGIC) {
        res = ZBI_RESULT_BAD_MAGIC;
    } else if ((header->flags & ZBI_FLAG_VERSION) == 0) {
        res = ZBI_RESULT_BAD_VERSION;
    } else if ((header->flags & ZBI_FLAG_CRC32) == 0 &&
               header->crc32 != ZBI_ITEM_NO_CRC32) {
        res = ZBI_RESULT_BAD_CRC;
    }

    // Something was wrong with the container.  Don't even attempt to process
    // the rest of the image.  Return diagnostic information back to the caller
    // if they requested it.
    if (res != ZBI_RESULT_OK) {
        if (err) { *err = (zbi_header_t*)header; }
        return res;
    }

    struct check_state state = { .err = err };
    res = zbi_for_each(base, for_each_check_entry, &state);

    if (res == ZBI_RESULT_OK && check_complete != 0) {
        if (header->length == 0) {
            res = ZBI_RESULT_ERR_TRUNCATED;
        } else if (header[1].type != check_complete) {
            res = ZBI_RESULT_INCOMPLETE_KERNEL;
            if (err) {
                *err = (zbi_header_t*)(header + 1);
            }
        } else if (!state.seen_bootfs) {
            res = ZBI_RESULT_INCOMPLETE_BOOTFS;
            if (err) {
                *err = (zbi_header_t*)header;
            }
        }
    }

    if (err && res == ZBI_RESULT_ERR_TRUNCATED) {
        // A truncated image perhaps indicates a problem with the container?
        *err = (zbi_header_t*)header;
    }

    return res;
}

zbi_result_t zbi_check(const void* base, zbi_header_t** err) {
    return zbi_check_internal(base, 0, err);
}

zbi_result_t zbi_check_complete(const void* base, zbi_header_t** err) {
    return zbi_check_internal(base,
#ifdef __aarch64__
                              ZBI_TYPE_KERNEL_ARM64,
#elif defined(__x86_64__) || defined(__i386__)
                              ZBI_TYPE_KERNEL_X64,
#else
#error "what architecture?"
#endif
                              err);
}

zbi_result_t zbi_for_each(const void* base, const zbi_foreach_cb_t cb,
                          void* cookie) {
    zbi_header_t* header = (zbi_header_t*)(base);

    // Skip container header.
    const uint32_t totalSize = (uint32_t)sizeof(zbi_header_t) + header->length;
    uint32_t offset = sizeof(zbi_header_t);
    while (offset < totalSize) {
        zbi_header_t* entryHeader =
            (zbi_header_t*)(base + offset);

        zbi_result_t result = cb(entryHeader, entryHeader + 1, cookie);

        if (result != ZBI_RESULT_OK) return result;

        if ((offset + entryHeader->length + sizeof(zbi_header_t)) > totalSize)
            return ZBI_RESULT_ERR_TRUNCATED;

        offset = ZBI_ALIGN(offset + entryHeader->length + sizeof(zbi_header_t));
    }

    return ZBI_RESULT_OK;
}

zbi_result_t zbi_append_section(void* base, const size_t capacity,
                                uint32_t section_length, uint32_t type,
                                uint32_t extra, uint32_t flags,
                                const void* payload) {

    uint8_t* new_section;
    zbi_result_t result = zbi_create_section(base, capacity, section_length,
                                             type, extra, flags,
                                             (void**)&new_section);

    if (result != ZBI_RESULT_OK) return result;

    // Copy in the payload.
    memcpy(new_section, payload, section_length);
    return ZBI_RESULT_OK;
}

zbi_result_t zbi_create_section(void* base, size_t capacity,
                                uint32_t section_length, uint32_t type,
                                uint32_t extra, uint32_t flags,
                                void** payload) {
    // We don't support CRC computation (yet?)
    if (flags & ZBI_FLAG_CRC32) return ZBI_RESULT_ERROR;

    zbi_header_t* hdr = (zbi_header_t*)base;

    // Make sure we were actually passed a bootdata container.
    if ((hdr->type != ZBI_TYPE_CONTAINER) ||
        (hdr->magic != ZBI_ITEM_MAGIC)    ||
        (hdr->extra != ZBI_CONTAINER_MAGIC)) {
        return ZBI_RESULT_BAD_TYPE;
    }

    // Make sure we have enough space in the buffer to append the new section.
    if (capacity - sizeof(*hdr) < hdr->length) {
        return ZBI_RESULT_TOO_BIG;
    }
    const size_t available = capacity - sizeof(*hdr) - hdr->length;
    if (available < sizeof(*hdr) ||
        available - sizeof(*hdr) < ZBI_ALIGN(section_length)) {
        return ZBI_RESULT_TOO_BIG;
    }

    // Fill in the new section header.
    zbi_header_t* new_header = (void*)((uint8_t*)(hdr + 1) + hdr->length);
    *new_header = (zbi_header_t) {
        .type = type,
        .length = section_length,
        .extra = extra,
        .flags = flags | ZBI_FLAG_VERSION,
        .magic = ZBI_ITEM_MAGIC,
        .crc32 = ZBI_ITEM_NO_CRC32,
    };

    // Tell the caller where to fill in the payload.
    *payload = new_header + 1;

    // Update the container header, always keeping the length aligned.
    hdr->length += sizeof(*new_header) + new_header->length;
    if (hdr->length % ZBI_ALIGNMENT != 0) {
        uint32_t aligned_length = ZBI_ALIGN(hdr->length);
        if (capacity - sizeof(*hdr) < aligned_length) {
            return ZBI_RESULT_TOO_BIG;
        }
        memset((uint8_t*)(hdr + 1) + hdr->length, 0,
               aligned_length - hdr->length);
        hdr->length = aligned_length;
    }

    return ZBI_RESULT_OK;
}