photon/libc/sys/horizon/dlfcn.c

#include <magenta/types.h>
#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <mio/fs.h>

__attribute__((weak)) void *dyld_load_object(const char *path, mx_handle_t handle, int mode) { return NULL; }
__attribute__((weak)) void *dyld_get_symbol(void *handle, const char *name) { return NULL; }
__attribute__((weak)) int dyld_close_object(void *handle) { return 0; }
__attribute__((weak)) char *dyld_get_error(void) { return NULL; }

static char dl_error[512] = {};

void *dlopen(const char *path, int mode)
{
    /* TODO include error message from errno */

    int fd = open(path, O_RDONLY);
    if (fd == -1) {
        snprintf(dl_error, sizeof dl_error, "cannot open '%s'", path);
        return NULL;
    }

    mx_handle_t image_vmo = MX_NULL_HANDLE;
    int err = mio_map_file(fd, &image_vmo);
    close(fd);

    if (err != 0) {
        snprintf(dl_error, sizeof dl_error, "cannot load '%s'", path);
        return NULL;
    }

    dl_error[0] = '\0';
    return dyld_load_object(path, image_vmo, mode);
}

void *dlsym(void *handle, const char *name)
{
    return dyld_get_symbol(handle, name);
}

int dlclose(void *handle)
{
    return dyld_close_object(handle);
}

char *dlerror(void)
{
    if (dl_error[0] != '\0') {
        return dl_error;
    }

    return dyld_get_error();
}