Add a "fork" of musl as //fusl.

fusl/src/mman/shm_open.c

+#include <sys/mman.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <limits.h>
+#include <pthread.h>
+
+char *__strchrnul(const char *, int);
+
+char *__shm_mapname(const char *name, char *buf)
+{
+        char *p;
+        while (*name == '/') name++;
+        if (*(p = __strchrnul(name, '/')) || p==name ||
+            (p-name <= 2 && name[0]=='.' && p[-1]=='.')) {
+                errno = EINVAL;
+                return 0;
+        }
+        if (p-name > NAME_MAX) {
+                errno = ENAMETOOLONG;
+                return 0;
+        }
+        memcpy(buf, "/dev/shm/", 9);
+        memcpy(buf+9, name, p-name+1);
+        return buf;
+}
+
+int shm_open(const char *name, int flag, mode_t mode)
+{
+        int cs;
+        char buf[NAME_MAX+10];
+        if (!(name = __shm_mapname(name, buf))) return -1;
+        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+        int fd = open(name, flag|O_NOFOLLOW|O_CLOEXEC|O_NONBLOCK, mode);
+        pthread_setcancelstate(cs, 0);
+        return fd;
+}
+
+int shm_unlink(const char *name)
+{
+        char buf[NAME_MAX+10];
+        if (!(name = __shm_mapname(name, buf))) return -1;
+        return unlink(name);
+}