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

fusl/src/mman/shm_open.c

Index: fusl/src/mman/shm_open.c
diff --git a/fusl/src/mman/shm_open.c b/fusl/src/mman/shm_open.c
new file mode 100644
index 0000000000000000000000000000000000000000..d042a5a882bd347dd937bceb8f851bb98cb418b8
--- /dev/null
+++ b/fusl/src/mman/shm_open.c
@@ -0,0 +1,45 @@
+#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);
+}