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newlib/winsup/cygwin/heap.cc

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/* heap.cc: Cygwin heap manager.
Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
2007, 2008, 2009, 2010, 2011, 2012, 2013 Red Hat, Inc.
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#include "winsup.h"
#include "cygerrno.h"
#include "shared_info.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "child_info.h"
#include "ntdll.h"
#include <sys/param.h>
#define assert(x)
static ptrdiff_t page_const;
#define MINHEAP_SIZE (4 * 1024 * 1024)
static uintptr_t
eval_start_address ()
{
#ifdef __x86_64__
/* On 64 bit, we choose a fixed address outside the 32 bit area. The
executable starts at 0x1:00400000L, the Cygwin DLL starts at
0x1:80040000L, other rebased DLLs are located in the region from
0x2:00000000L up to 0x4:00000000L, -auto-image-based DLLs are located
in the region from 0x4:00000000L up to 0x6:00000000L.
So we let the heap start at 0x6:00000000L. */
uintptr_t start_address = 0x600000000L;
#else
/* 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 ((uintptr_t) NtCurrentTeb () >= 0xbf000000L)
{
/* However, if we're running on a /3GB enabled 32 bit system or on
a 64 bit system, and the executable is large address aware, then
we know that we have spare 1 Gig (32 bit) or even 2 Gigs (64 bit)
virtual address space. This memory region is practically unused
by Windows, only PEB and TEBs are allocated top-down here. We use
the current TEB address as very simple test that this is a large
address aware executable.
The above test for an address beyond 0xbf000000 is supposed to
make sure that we really have 3GB on a 32 bit system. XP and
later support smaller large address regions, but then it's not
that interesting for us to use it for the heap.
If the region is big enough, the heap gets allocated at its
start. What we get are 0.999 or 1.999 Gigs of free contiguous
memory for heap, thread stacks, and shared memory regions. */
start_address = 0x80000000L;
}
#endif
return start_address;
}
static SIZE_T
eval_initial_heap_size ()
{
PIMAGE_DOS_HEADER dosheader;
PIMAGE_NT_HEADERS ntheader;
SIZE_T size;
dosheader = (PIMAGE_DOS_HEADER) GetModuleHandle (NULL);
ntheader = (PIMAGE_NT_HEADERS) ((PBYTE) dosheader + dosheader->e_lfanew);
/* LoaderFlags is an obsolete DWORD member of the PE/COFF file header.
It's value is ignored by the loader, so we're free to use it for
Cygwin. If it's 0, we default to the usual 384 Megs on 32 bit and
512 on 64 bit. Otherwise, we use it as the default initial heap size
in megabyte. Valid values are between 4 and 2048/8388608 Megs. */
size = ntheader->OptionalHeader.LoaderFlags;
#ifdef __x86_64__
if (size == 0)
size = 512;
else if (size < 4)
size = 4;
else if (size > 8388608)
size = 8388608;
#else
if (size == 0)
size = 384;
else if (size < 4)
size = 4;
else if (size > 2048)
size = 2048;
#endif
return size << 20;
}
/* Initialize the heap at process start up. */
void
heap_init ()
{
const DWORD alloctype = MEM_RESERVE;
/* If we're the forkee, we must allocate the heap at exactly the same place
as our parent. If not, we (almost) don't care where it ends up. */
page_const = wincap.page_size ();
if (!cygheap->user_heap.base)
{
uintptr_t start_address = eval_start_address ();
PVOID largest_found = NULL;
SIZE_T largest_found_size = 0;
SIZE_T ret;
MEMORY_BASIC_INFORMATION mbi;
cygheap->user_heap.chunk = eval_initial_heap_size ();
do
{
cygheap->user_heap.base = VirtualAlloc ((LPVOID) start_address,
cygheap->user_heap.chunk,
alloctype, PAGE_NOACCESS);
if (cygheap->user_heap.base)
break;
/* Ok, so we are at the 1% which didn't work with 0x20000000 out
of the box. What we do now is to search for the next free
region which matches our desired heap size. While doing that,
we keep track of the largest region we found, including the
region starting at 0x20000000. */
while ((ret = VirtualQuery ((LPCVOID) start_address, &mbi,
sizeof mbi)) != 0)
{
if (mbi.State == MEM_FREE)
{
if (mbi.RegionSize >= cygheap->user_heap.chunk)
break;
if (mbi.RegionSize > largest_found_size)
{
largest_found = mbi.BaseAddress;
largest_found_size = mbi.RegionSize;
}
}
/* Since VirtualAlloc only reserves at allocation granularity
boundaries, we round up here, too. Otherwise we might end
up at a bogus page-aligned address. */
start_address = roundup2 (start_address + mbi.RegionSize,
wincap.allocation_granularity ());
}
if (!ret)
{
/* In theory this should not happen. But if it happens, we have
collected the information about the largest available region
in the above loop. So, next we squeeze the heap into that
region, unless it's smaller than the minimum size. */
if (largest_found_size >= MINHEAP_SIZE)
{
cygheap->user_heap.chunk = largest_found_size;
cygheap->user_heap.base =
VirtualAlloc (largest_found, cygheap->user_heap.chunk,
alloctype, PAGE_NOACCESS);
}
/* Last resort (but actually we are probably broken anyway):
Use the minimal heap size and let the system decide. */
if (!cygheap->user_heap.base)
{
cygheap->user_heap.chunk = MINHEAP_SIZE;
cygheap->user_heap.base =
VirtualAlloc (NULL, cygheap->user_heap.chunk,
alloctype, PAGE_NOACCESS);
}
}
}
while (!cygheap->user_heap.base && ret);
if (cygheap->user_heap.base == NULL)
api_fatal ("unable to allocate heap, heap_chunk_size %ly, %E",
cygheap->user_heap.chunk);
cygheap->user_heap.ptr = cygheap->user_heap.top = cygheap->user_heap.base;
cygheap->user_heap.max = (char *) cygheap->user_heap.base
+ cygheap->user_heap.chunk;
}
else
{
SIZE_T chunk = cygheap->user_heap.chunk; /* allocation chunk */
/* total size commited in parent */
SIZE_T allocsize = (char *) cygheap->user_heap.top -
(char *) cygheap->user_heap.base;
/* Loop until we've managed to reserve an adequate amount of memory. */
char *p;
SIZE_T reserve_size = chunk * ((allocsize + (chunk - 1)) / chunk);
/* With ptmalloc3 there's a good chance that there has been no memory
allocated on the heap. If we don't check that, reserve_size will
be 0 and from there, the below loop will end up overallocating due
to integer overflow. */
if (!reserve_size)
reserve_size = chunk;
while (1)
{
p = (char *) VirtualAlloc (cygheap->user_heap.base, reserve_size,
alloctype, PAGE_READWRITE);
if (p)
break;
if ((reserve_size -= page_const) < allocsize)
break;
}
if (!p && in_forkee && !fork_info->abort (NULL))
api_fatal ("couldn't allocate heap, %E, base %p, top %p, "
"reserve_size %ld, allocsize %ld, page_const %d",
cygheap->user_heap.base, cygheap->user_heap.top,
reserve_size, allocsize, page_const);
if (p != cygheap->user_heap.base)
api_fatal ("heap allocated at wrong address %p (mapped) "
"!= %p (expected)", p, cygheap->user_heap.base);
if (allocsize && !VirtualAlloc (cygheap->user_heap.base, allocsize,
MEM_COMMIT, PAGE_READWRITE))
api_fatal ("MEM_COMMIT failed, %E");
}
/* CV 2012-05-21: Moved printing heap size here from strace::activate.
The value printed in strace.activate was always wrong, because at the
time it's called, cygheap points to cygheap_dummy. Above all, the heap
size has not been evaluated yet, except in a forked child. Since
heap_init is called early, the heap size is printed pretty much at the
start of the strace output, so there isn't anything lost. */
debug_printf ("heap base %p, heap top %p, heap size %ly (%lu)",
cygheap->user_heap.base, cygheap->user_heap.top,
cygheap->user_heap.chunk, cygheap->user_heap.chunk);
page_const--;
// malloc_init ();
}
#define pround(n) (((size_t)(n) + page_const) & ~page_const)
/* FIXME: This function no longer handles "split heaps". */
/* Linux defines n to be intptr_t, newlib defines it to be ptrdiff_t.
It shouldn't matter much, though, since the function is not standarized
and sizeof(ptrdiff_t) == sizeof(intptr_t) anyway. */
extern "C" void *
sbrk (ptrdiff_t n)
{
char *newtop, *newbrk;
SIZE_T commitbytes, newbrksize;
if (n == 0)
return cygheap->user_heap.ptr; /* Just wanted to find current cygheap->user_heap.ptr address */
newbrk = (char *) cygheap->user_heap.ptr + n; /* Where new cygheap->user_heap.ptr will be */
newtop = (char *) pround (newbrk); /* Actual top of allocated memory -
on page boundary */
if (newtop == cygheap->user_heap.top)
goto good;
if (n < 0)
{ /* Freeing memory */
assert (newtop < cygheap->user_heap.top);
n = (char *) cygheap->user_heap.top - newtop;
if (VirtualFree (newtop, n, MEM_DECOMMIT)) /* Give it back to OS */
goto good;
goto err; /* Didn't take */
}
assert (newtop > cygheap->user_heap.top);
/* Find the number of bytes to commit, rounded up to the nearest page. */
commitbytes = pround (newtop - (char *) cygheap->user_heap.top);
/* Need to grab more pages from the OS. If this fails it may be because
we have used up previously reserved memory. Or, we're just plumb out
of memory. Only attempt to commit memory that we know we've previously
reserved. */
if (newtop <= cygheap->user_heap.max)
{
if (VirtualAlloc (cygheap->user_heap.top, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL)
goto good;
}
/* Couldn't allocate memory. Maybe we can reserve some more.
Reserve either the maximum of the standard cygwin_shared->heap_chunk_size ()
or the requested amount. Then attempt to actually allocate it. */
if ((newbrksize = cygheap->user_heap.chunk) < commitbytes)
newbrksize = commitbytes;
if ((VirtualAlloc (cygheap->user_heap.top, newbrksize,
MEM_RESERVE, PAGE_NOACCESS)
|| VirtualAlloc (cygheap->user_heap.top, newbrksize = commitbytes,
MEM_RESERVE, PAGE_NOACCESS))
&& VirtualAlloc (cygheap->user_heap.top, commitbytes,
MEM_COMMIT, PAGE_READWRITE) != NULL)
{
cygheap->user_heap.max = (char *) cygheap->user_heap.max
+ pround (newbrksize);
goto good;
}
err:
set_errno (ENOMEM);
return (void *) -1;
good:
void *oldbrk = cygheap->user_heap.ptr;
cygheap->user_heap.ptr = newbrk;
cygheap->user_heap.top = newtop;
return oldbrk;
}
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