Function e9init

src/e9patch/e9loader_elf.cpp:337–451

* Loader initialization code. */

 * Loader initialization code.
 */
void *e9init(int argc, char **argv, char **envp, const e9_config_s *config)
{
    // Step (0): Sanity checks & initialization:
    if (config->magic[0] != 'E' || config->magic[1] != '9' ||
            config->magic[2] != 'P' || config->magic[3] != 'A' ||
            config->magic[4] != 'T' || config->magic[5] != 'C' ||
            config->magic[6] != 'H' || config->magic[7] != '\0')
        e9panic("missing \"E9PATCH\" magic number");
    const uint8_t *loader_base = (const uint8_t *)config;
    const uint8_t *loader_end  = loader_base + config->size;
    const uint8_t *elf_base    = loader_base - config->base;
    const void *dynamic = NULL;
    const struct e9_config_elf_s *config_elf =
        (const struct e9_config_elf_s *)(config + 1);
    if (config_elf->dynamic != 0x0)
        dynamic = (const void *)(elf_base + config_elf->dynamic);

    // Step (1): Call the pre-initialization routine:
    const uint32_t *preinits =
        (const uint32_t *)(loader_base + config->preinits);
    for (uint32_t i = 0; i < config->num_preinits; i++)
    {
        init_t preinit = (init_t)(loader_base + preinits[i]);
        preinit(argc, argv, envp, dynamic, config);
    }

    // Step (2): Find & open the binary:
    char buf[BUFSIZ];
    const char *path = "/proc/self/exe";
    if ((config->flags & E9_FLAG_EXE) == 0)
    {
        // This is a shared object, so use the /proc/self/map_files/
        // method to find the binary.
        char *str = buf;
        str = e9write_format(str, "/proc/self/map_files/%X-%X", loader_base,
            loader_end);
        str = e9write_char(str, '\0');
        path = buf;
    }
    ssize_t len = (ssize_t)e9syscall(SYS_readlink, path, buf, sizeof(buf));
    if (len < 0)
        e9panic("readlink(path=\"%s\") failed (errno=%u)", buf, -len);
    buf[len] = '\0';
    int fd = (int)e9syscall(SYS_open, buf, O_RDONLY, 0);
    if (fd < 0)
        e9panic("open(path=\"%s\") failed (errno=%u)", buf, -fd);

    // Step (3): Setup dummy TLS (if necessary):
    struct e9scratch_s *scratch = NULL;
    uintptr_t tls = 0x0;
    intptr_t r = e9syscall(SYS_arch_prctl, ARCH_GET_FS, &tls);
    if (r < 0)
        e9panic("arch_prctl() failed (errno=%u)", -r);
    if (tls == 0x0)
    {
        // No libc == no tls:
        scratch = e9scratch(config, /*alloc=*/true);
        tls = (uintptr_t)&scratch->tls;