+2011-07-21 Corinna Vinschen <corinna@vinschen.de>
+
+ * heap.cc (eval_start_address): New static function to evaluate the
+ best start address for the application heap.
+ (heap_init): Call eval_start_address to fetch the start value for
+ start_address. Move preceeding comment to eval_start_address.
+
2011-07-21 Yaakov Selkowitz <yselkowitz@users.sourceforge.net>
* cygwin.din (pthread_condattr_getclock): Export.
#define MINHEAP_SIZE (4 * 1024 * 1024)
+static uintptr_t
+eval_start_address ()
+{
+ /* Starting with Vista, Windows performs heap ASLR. This spoils the entire
+ region below 0x20000000 for us, because that region is used by Windows
+ to randomize heap and stack addresses. Therefore we put our heap into a
+ safe region starting at 0x20000000. This should work right from the start
+ in 99% of the cases. */
+ uintptr_t start_address = 0x20000000L;
+ if (wincap.is_wow64 ())
+ {
+ /* However, if we're running on a 64 bit system, we test here if the
+ executable is large address aware. If so, the application gets a
+ 4 Gigs virtual address space, with almost all of the upper 2 Gigs
+ being unused by Windows (only PEB and TEBs are allocated here,
+ apparently). So what we do here is to test if the large address
+ awareness flag is set in the file header and, if so, allocate our
+ heap in that region. What we get are 1.999 Gigs free for heap,
+ thread stacks, and shared memory regions. */
+ PIMAGE_DOS_HEADER idh = (PIMAGE_DOS_HEADER) GetModuleHandle (NULL);
+ PIMAGE_NT_HEADERS32 inh = (PIMAGE_NT_HEADERS32)
+ ((PBYTE) idh + idh->e_lfanew);
+ if (inh->FileHeader.Characteristics & IMAGE_FILE_LARGE_ADDRESS_AWARE)
+ start_address = 0x80000000L;
+ }
+ return start_address;
+}
+
/* Initialize the heap at process start up. */
void
heap_init ()
page_const = wincap.page_size ();
if (!cygheap->user_heap.base)
{
- /* Starting with Vista, Windows performs heap ASLR. This spoils
- the entire region below 0x20000000 for us, because that region
- is used by Windows to randomize heap and stack addresses.
- Therefore we put our heap into a safe region starting at 0x20000000.
- This should work right from the start in 99% of the cases. But,
- there's always a but. Read on... */
- uintptr_t start_address = 0x20000000L;
+ uintptr_t start_address = eval_start_address ();
PVOID largest_found = NULL;
size_t largest_found_size = 0;
SIZE_T ret;