Function init_syscall_array

g2all/900/module/memtools.js:181–242

(
    syscall_array,
    libkernel_web_base,
    max_search_size,
)

}

export function init_syscall_array(
    syscall_array,
    libkernel_web_base,
    max_search_size,
) {
    if (!Number.isInteger(max_search_size)) {
        throw TypeError(
            `max_search_size is not a integer: ${max_search_size}`);
    }
    if (max_search_size < 0) {
        throw Error(`max_search_size is less than 0: ${max_search_size}`);
    }

    const libkernel_web_buffer = make_buffer(
        libkernel_web_base,
        max_search_size,
    );
    const kbuf = new BufferView(libkernel_web_buffer);

    // Search 'rdlo' string from libkernel_web's .rodata section to gain an
    // upper bound on the size of the .text section.
    let text_size = 0;
    let found = false;
    for (let i = 0; i < max_search_size; i++) {
        if (kbuf[i] === 0x72
            && kbuf[i + 1] === 0x64
            && kbuf[i + 2] === 0x6c
            && kbuf[i + 3] === 0x6f
        ) {
            text_size = i;
            found = true;
            break;
        }
    }
    if (!found) {
        throw Error(
            '"rdlo" string not found in libkernel_web, base address:'
            + ` ${libkernel_web_base}`);
    }

    // search for the instruction sequence:
    // syscall_X:
    //     mov rax, X
    //     mov r10, rcx
    //     syscall
    for (let i = 0; i < text_size; i++) {
        if (kbuf[i] === 0x48
            && kbuf[i + 1] === 0xc7
            && kbuf[i + 2] === 0xc0
            && kbuf[i + 7] === 0x49
            && kbuf[i + 8] === 0x89
            && kbuf[i + 9] === 0xca
            && kbuf[i + 10] === 0x0f
            && kbuf[i + 11] === 0x05
        ) {
            const syscall_num = kbuf.read32(i + 3);
            syscall_array[syscall_num] = libkernel_web_base.add(i);
            // skip the sequence