Modify the NaCl_page_alloc_hint function to use VirtualQuery to check

src/trusted/service_runtime/win/sel_memory.c

 /*
  * Copyright (c) 2011 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
  * NaCl Service Runtime memory allocation code
  */
 #include "native_client/src/include/portability.h"
@@ skipping 43 matching lines @@
   SYSTEM_INFO sys_info;
 
   int         attempt_count;
 
   void        *hint = *p;
   void        *addr;
   void        *end_addr;
   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
    * that was returned by a call to VirtualAlloc.  NB: memory pages
    * put into the address space via MapViewOfFile{,Ex} must be
    * released by UnmapViewOfFile.  Thus, in order for us to open up a
    * hole in the NaCl application's address space to map in a file, we
    * must allocate the entire address space in 64KB chunks, so we can
    * later pick an arbitrary range of addresses (in 64KB chunks) to
    * free up and map in a file later.
@@ skipping 20 matching lines @@
             sys_info.dwAllocationGranularity,
             NACL_MAP_PAGESIZE);
   }
 
   /*
    * Round allocation request up to next NACL_MAP_PAGESIZE.  This is
    * assumed to have taken place in NaCl_page_free.
    */
   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",
               num_bytes);
       return -ENOMEM;
     }
     NaClLog(3,
             ("NaCl_page_alloc:"
              "  VirtualAlloc(*,0x%"NACL_PRIxS")"
              " succeeded, 0x%016"NACL_PRIxPTR","
@@ skipping 27 matching lines @@
     }
     NaClLog(2,
             ("NaCl_page_alloc: *p = 0x%016"NACL_PRIxPTR","
              " returning success.\n"),
             (uintptr_t) addr);
     *p = addr;
     return 0;
  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;
 }
 
 int   NaCl_page_alloc(void    **p,
                       size_t  num_bytes) {
   *p = NULL;
   return NaCl_page_alloc_hint(p, num_bytes);
 }
@@ skipping 233 matching lines @@
       break;
     case MADV_NORMAL:
       memset(start, 0, length);
       break;
     default:
       return -EINVAL;
   }
   NaClLog(2, "NaCl_madvise: done\n");
   return 0;
 }