From 08706fcc6d7bac3dfe27e2f99542db41e71829f2 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Sun, 5 Oct 2014 18:04:18 +0300
Subject: [PATCH] posix: wrap mmap() for anonymous maps

Automatically munmap() when the result is destroyed.
---
 core/posix.cc | 11 +++++++++++
 core/posix.hh |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/core/posix.cc b/core/posix.cc
index cfed8120b2..a5f1d574e7 100644
--- a/core/posix.cc
+++ b/core/posix.cc
@@ -3,6 +3,17 @@
  */
 
 #include "posix.hh"
+#include <sys/mman.h>
+
+void mmap_deleter::operator()(void* ptr) const {
+    ::munmap(ptr, _size);
+}
+
+mmap_area mmap_anonymous(void* addr, size_t length, int prot, int flags) {
+    auto ret = ::mmap(addr, length, prot, flags | MAP_ANONYMOUS, -1, 0);
+    throw_system_error_on(ret == MAP_FAILED);
+    return mmap_area(reinterpret_cast<char*>(ret), mmap_deleter{length});
+}
 
 void* posix_thread::start_routine(void* arg) {
     auto pfunc = reinterpret_cast<std::function<void ()>*>(arg);
diff --git a/core/posix.hh b/core/posix.hh
index 1e4f372a6d..60e7fbb85a 100644
--- a/core/posix.hh
+++ b/core/posix.hh
@@ -185,6 +185,15 @@ private:
     file_desc(int fd) : _fd(fd) {}
  };
 
+struct mmap_deleter {
+    size_t _size;
+    void operator()(void* ptr) const;
+};
+
+using mmap_area = std::unique_ptr<char[], mmap_deleter>;
+
+mmap_area mmap_anonymous(void* addr, size_t length, int prot, int flags);
+
 class posix_thread {
     // must allocate, since this class is moveable
     std::unique_ptr<std::function<void ()>> _func;