Modify the NaCl_page_alloc_hint function to use VirtualQuery to check

src/trusted/service_runtime/win/sel_memory.c

Index: src/trusted/service_runtime/win/sel_memory.c
===================================================================
--- src/trusted/service_runtime/win/sel_memory.c	(revision 6397)
+++ src/trusted/service_runtime/win/sel_memory.c	(working copy)
@@ -61,6 +61,10 @@
   void        *chunk;
   void        *unroll;
 
+  MEMORY_BASIC_INFORMATION mem;
+  const SIZE_T kOneGb = 0x40000000;
+  char* start;
+
   /*
    * We have to allocate every 64KB -- the windows allocation
    * granularity -- because VirtualFree will only accept an address
@@ -101,11 +105,32 @@
    */
   num_bytes = NaClRoundAllocPage(num_bytes);
 
+  /*
+   * If the request is for 1Gb (the sandbox), look for a memory region that
+   * was reserved by our parent process.
+   */
+  addr = 0;
+  if (num_bytes == kOneGb) {

[Mark Seaborn, 2011/08/12 21:57:54]

Having a special case for 1GB in NaCl_page_alloc() seems hacky, because this
function is used for purposes other than allocating address space.  I'd add a
case to NaClAllocateSpace() in sel_addrspace_x86_32.c instead, which already has
an #if for the related zero-based-sandbox case.

+    start = sys_info.lpMinimumApplicationAddress;
+    while (VirtualQuery((LPCVOID)start, &mem, sizeof(mem)))
+    {

[Mark Seaborn, 2011/08/12 21:57:54]

Style: '{' should be on previous line

+      if (mem.State == MEM_RESERVE && mem.RegionSize == kOneGb)
+      {

[Mark Seaborn, 2011/08/12 21:57:54]

Ditto

+        addr = start;
+        break;
+      }
+      start += mem.RegionSize;
+      if ((LPVOID)start > sys_info.lpMaximumApplicationAddress)
+        break;
+    }
+  }
+
   for (attempt_count = 0;
        attempt_count < NACL_MEMORY_ALLOC_RETRY_MAX;
        ++attempt_count) {
 
-    addr = VirtualAlloc(hint, num_bytes, MEM_RESERVE, PAGE_NOACCESS);
+    if (addr == NULL)
+      addr = VirtualAlloc(hint, num_bytes, MEM_RESERVE, PAGE_NOACCESS);
     if (addr == NULL) {
       NaClLog(0,
               "NaCl_page_alloc: VirtualAlloc(*,0x%"NACL_PRIxS") failed\n",
@@ -153,6 +178,10 @@
  retry:
     NaClLog(2, "NaCl_page_alloc_hint: retrying w/o hint\n");
     hint = NULL;
+    /*
+     * If the parent process had reserved memory, it's gone now.
+     */
+    addr = NULL;
   }
 
   return -ENOMEM;