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* 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.
This commit is contained in:
Corinna Vinschen 2011-07-21 15:23:24 +00:00
parent 8a7b0a00df
commit 86719a10d0
2 changed files with 36 additions and 7 deletions
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7
winsup/cygwin/ChangeLog
View File

@ -1,3 +1,10 @@
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.

36
winsup/cygwin/heap.cc
View File

@ -25,6 +25,34 @@ static unsigned page_const;
#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 ()
@ -36,13 +64,7 @@ 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;