Function load_kernel

src/kernel.js:40–177

(mem8, bzimage, initrd, cmdline)

function load_kernel(mem8, bzimage, initrd, cmdline)
{
    dbg_log("Trying to load kernel of size " + bzimage.byteLength);

    const KERNEL_HIGH_ADDRESS = 0x100000;

    // Put the initrd at the 64 MB boundary. This means the minimum memory size
    // is 64 MB plus the size of the initrd.
    // Note: If set too low, kernel may fail to load the initrd with "invalid magic at start of compressed archive"
    const INITRD_ADDRESS = 64 << 20;

    const quiet = false;

    const bzimage8 = new Uint8Array(bzimage);
    const bzimage16 = new Uint16Array(bzimage);
    const bzimage32 = new Uint32Array(bzimage);

    const setup_sects = bzimage8[LINUX_BOOT_HDR_SETUP_SECTS] || 4;
    const syssize = bzimage32[LINUX_BOOT_HDR_SYSSIZE >> 2] << 4;

    const vidmode = bzimage16[LINUX_BOOT_HDR_VIDMODE >> 1];

    const checksum1 = bzimage16[LINUX_BOOT_HDR_BOOT_FLAG >> 1];
    if(checksum1 !== LINUX_BOOT_HDR_CHECKSUM1)
    {
        dbg_log("Bad checksum1: " + h(checksum1));
        return;
    }

    // Not aligned, so split into two 16-bit reads
    const checksum2 =
        bzimage16[LINUX_BOOT_HDR_HEADER >> 1] |
        bzimage16[LINUX_BOOT_HDR_HEADER + 2 >> 1] << 16;
    if(checksum2 !== LINUX_BOOT_HDR_CHECKSUM2)
    {
        dbg_log("Bad checksum2: " + h(checksum2));
        return;
    }

    const protocol = bzimage16[LINUX_BOOT_HDR_VERSION >> 1];
    dbg_assert(protocol >= 0x202); // older not supported by us

    const flags = bzimage8[LINUX_BOOT_HDR_LOADFLAGS];
    dbg_assert(flags & LINUX_BOOT_HDR_LOADFLAGS_LOADED_HIGH); // low kernels not supported by us

    // we don't relocate the kernel, so we don't care much about most of these

    const flags2 = bzimage16[LINUX_BOOT_HDR_XLOADFLAGS >> 1];
    const initrd_addr_max = bzimage32[LINUX_BOOT_HDR_INITRD_ADDR_MAX >> 2];
    const kernel_alignment = bzimage32[LINUX_BOOT_HDR_KERNEL_ALIGNMENT >> 2];
    const relocatable_kernel = bzimage8[LINUX_BOOT_HDR_RELOCATABLE_KERNEL];
    const min_alignment = bzimage8[LINUX_BOOT_HDR_MIN_ALIGNMENT];
    const cmdline_size = protocol >= 0x206 ? bzimage32[LINUX_BOOT_HDR_CMDLINE_SIZE >> 2] : 255;
    const payload_offset = bzimage32[LINUX_BOOT_HDR_PAYLOAD_OFFSET >> 2];
    const payload_length = bzimage32[LINUX_BOOT_HDR_PAYLOAD_LENGTH >> 2];
    const pref_address = bzimage32[LINUX_BOOT_HDR_PREF_ADDRESS >> 2];
    const pref_address_high = bzimage32[LINUX_BOOT_HDR_PREF_ADDRESS + 4 >> 2];
    const init_size = bzimage32[LINUX_BOOT_HDR_INIT_SIZE >> 2];