libc: real mmap()/munmap() implementation

libc/mman.cc

 #include <sys/mman.h>
+#include <memory>
+#include "mmu.hh"
 #include "debug.hh"
 
 int mprotect(void *addr, size_t len, int prot)
@@ -6,3 +8,26 @@ int mprotect(void *addr, size_t len, int prot)
     debug("stub mprotect()");
     return 0;
 }
+
+void *mmap(void *addr, size_t length, int prot, int flags,
+           int fd, off_t offset)
+{
+    if (fd != -1) {
+        abort();
+    }
+
+    std::unique_ptr<mmu::vma> v;
+    if (!(flags & MAP_FIXED)) {
+        v.reset(mmu::reserve(addr, length));
+        addr = v->addr();
+    }
+    mmu::map_anon(addr, length, 0);
+    v.release();
+    return addr;
+}
+
+int munmap(void *addr, size_t length)
+{
+    mmu::unmap(addr, length);
+    return 0;
+}

runtime.cc

@@ -258,22 +258,6 @@ namespace __cxxabiv1 {
 
 }
 
-
-void *mmap(void *addr, size_t length, int prot, int flags,
-	   int fd, off_t offset)
-{
-    if (fd != -1) {
-	abort();
-    }
-
-    return malloc(length);
-}
-
-int munmap(void *addr, size_t length)
-{
-    return 0;
-}
-
 int getpagesize()
 {
     return 4096;