src/os/posix/vm/os_posix.cpp

*** 91,100 ****
--- 91,135 ----
  void os::wait_for_keypress_at_exit(void) {
    // don't do anything on posix platforms
    return;
  }
  
+ char* os::reserve_memory_aligned(size_t size, size_t alignment) {
+   assert(alignment & (os::vm_allocation_granularity() - 1) == 0,
+       "Alignment must be a multiple of allocation granularity (page size)");
+   assert(size & (alignment -1) == 0, "size must be 'alignment' aligned");
+   size_t extra_size = size + alignment;
+   char* extra_base = os::reserve_memory(extra_size, NULL, alignment);
+ 
+   if (extra_base == NULL) {
+     return NULL;
+   }
+ 
+   // Do manual alignment
+   char* aligned_base = (char*) align_size_up((uintptr_t) extra_base, alignment);
+ 
+   // [  |                                       |  ]
+   // ^ extra_base
+   //    ^ extra_base + begin_offset == aligned_base
+   //     extra_base + begin_offset + size       ^
+   //                       extra_base + extra_size ^
+   // |<>| == begin_offset
+   //                              end_offset == |<>|
+   size_t begin_offset = aligned_base - extra_base;
+   size_t end_offset = (extra_base + extra_size) - (aligned_base + size);
+ 
+   if (begin_offset > 0) {
+       os::release_memory(extra_base, begin_offset);
+   }
+ 
+   if (end_offset > 0) {
+       os::release_memory(extra_base + begin_offset + size, end_offset);
+   }
+ 
+   return aligned_base;
+ }
+ 
  void os::Posix::print_load_average(outputStream* st) {
    st->print("load average:");
    double loadavg[3];
    os::loadavg(loadavg, 3);
    st->print("%0.02f %0.02f %0.02f", loadavg[0], loadavg[1], loadavg[2]);