277 lines
9.7 KiB
C++
277 lines
9.7 KiB
C++
/* heap.cc: Cygwin heap manager.
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Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
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2006, 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
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This file is part of Cygwin.
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for
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details. */
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#include "winsup.h"
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#include "cygerrno.h"
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#include "shared_info.h"
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#include "path.h"
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#include "fhandler.h"
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#include "dtable.h"
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#include "cygheap.h"
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#include "child_info.h"
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#include "ntdll.h"
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#include <sys/param.h>
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#define assert(x)
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static unsigned page_const;
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#define MINHEAP_SIZE (4 * 1024 * 1024)
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static uintptr_t
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eval_start_address ()
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{
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/* Starting with Vista, Windows performs heap ASLR. This spoils the entire
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region below 0x20000000 for us, because that region is used by Windows
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to randomize heap and stack addresses. Therefore we put our heap into a
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safe region starting at 0x20000000. This should work right from the start
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in 99% of the cases. */
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uintptr_t start_address = 0x20000000L;
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if ((uintptr_t) NtCurrentTeb () >= 0xbf000000L)
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{
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/* However, if we're running on a /3GB enabled 32 bit system or on
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a 64 bit system, and the executable is large address aware, then
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we know that we have spare 1 Gig (32 bit) or even 2 Gigs (64 bit)
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virtual address space. This memory region is practically unused
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by Windows, only PEB and TEBs are allocated top-down here. We use
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the current TEB address as very simple test that this is a large
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address aware executable.
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The above test for an address beyond 0xbf000000 is supposed to
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make sure that we really have 3GB on a 32 bit system. XP and
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later support smaller large address regions, but then it's not
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that interesting for us to use it for the heap.
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If the region is big enough, the heap gets allocated at its
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start. What we get are 0.999 or 1.999 Gigs of free contiguous
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memory for heap, thread stacks, and shared memory regions. */
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start_address = 0x80000000L;
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}
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return start_address;
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}
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static unsigned
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eval_initial_heap_size ()
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{
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PIMAGE_DOS_HEADER dosheader;
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PIMAGE_NT_HEADERS32 ntheader;
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unsigned size;
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dosheader = (PIMAGE_DOS_HEADER) GetModuleHandle (NULL);
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ntheader = (PIMAGE_NT_HEADERS32) ((PBYTE) dosheader + dosheader->e_lfanew);
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/* LoaderFlags is an obsolete DWORD member of the PE/COFF file header.
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It's value is ignored by the loader, so we're free to use it for
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Cygwin. If it's 0, we default to the usual 384 Megs. Otherwise,
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we use it as the default initial heap size in megabyte. Valid values
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are between 4 and 2048 Megs. */
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size = ntheader->OptionalHeader.LoaderFlags;
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if (size == 0)
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size = 384;
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else if (size < 4)
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size = 4;
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else if (size > 2048)
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size = 2048;
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return size << 20;
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}
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/* Initialize the heap at process start up. */
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void
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heap_init ()
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{
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const DWORD alloctype = MEM_RESERVE;
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/* If we're the forkee, we must allocate the heap at exactly the same place
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as our parent. If not, we (almost) don't care where it ends up. */
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page_const = wincap.page_size ();
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if (!cygheap->user_heap.base)
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{
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uintptr_t start_address = eval_start_address ();
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PVOID largest_found = NULL;
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size_t largest_found_size = 0;
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SIZE_T ret;
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MEMORY_BASIC_INFORMATION mbi;
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cygheap->user_heap.chunk = eval_initial_heap_size ();
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do
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{
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cygheap->user_heap.base = VirtualAlloc ((LPVOID) start_address,
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cygheap->user_heap.chunk,
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alloctype, PAGE_NOACCESS);
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if (cygheap->user_heap.base)
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break;
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/* Ok, so we are at the 1% which didn't work with 0x20000000 out
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of the box. What we do now is to search for the next free
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region which matches our desired heap size. While doing that,
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we keep track of the largest region we found, including the
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region starting at 0x20000000. */
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while ((ret = VirtualQuery ((LPCVOID) start_address, &mbi,
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sizeof mbi)) != 0)
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{
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if (mbi.State == MEM_FREE)
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{
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if (mbi.RegionSize >= cygheap->user_heap.chunk)
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break;
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if (mbi.RegionSize > largest_found_size)
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{
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largest_found = mbi.BaseAddress;
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largest_found_size = mbi.RegionSize;
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}
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}
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/* Since VirtualAlloc only reserves at allocation granularity
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boundaries, we round up here, too. Otherwise we might end
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up at a bogus page-aligned address. */
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start_address = roundup2 (start_address + mbi.RegionSize,
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wincap.allocation_granularity ());
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}
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if (!ret)
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{
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/* In theory this should not happen. But if it happens, we have
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collected the information about the largest available region
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in the above loop. So, next we squeeze the heap into that
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region, unless it's smaller than the minimum size. */
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if (largest_found_size >= MINHEAP_SIZE)
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{
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cygheap->user_heap.chunk = largest_found_size;
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cygheap->user_heap.base =
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VirtualAlloc (largest_found, cygheap->user_heap.chunk,
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alloctype, PAGE_NOACCESS);
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}
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/* Last resort (but actually we are probably broken anyway):
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Use the minimal heap size and let the system decide. */
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if (!cygheap->user_heap.base)
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{
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cygheap->user_heap.chunk = MINHEAP_SIZE;
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cygheap->user_heap.base =
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VirtualAlloc (NULL, cygheap->user_heap.chunk,
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alloctype, PAGE_NOACCESS);
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}
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}
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}
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while (!cygheap->user_heap.base && ret);
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if (cygheap->user_heap.base == NULL)
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api_fatal ("unable to allocate heap, heap_chunk_size %p, %E",
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cygheap->user_heap.chunk);
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cygheap->user_heap.ptr = cygheap->user_heap.top = cygheap->user_heap.base;
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cygheap->user_heap.max = (char *) cygheap->user_heap.base
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+ cygheap->user_heap.chunk;
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}
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else
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{
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DWORD chunk = cygheap->user_heap.chunk; /* allocation chunk */
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/* total size commited in parent */
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DWORD allocsize = (char *) cygheap->user_heap.top -
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(char *) cygheap->user_heap.base;
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/* Loop until we've managed to reserve an adequate amount of memory. */
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char *p;
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DWORD reserve_size = chunk * ((allocsize + (chunk - 1)) / chunk);
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while (1)
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{
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p = (char *) VirtualAlloc (cygheap->user_heap.base, reserve_size,
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alloctype, PAGE_READWRITE);
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if (p)
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break;
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if ((reserve_size -= page_const) < allocsize)
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break;
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}
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if (!p && in_forkee && !fork_info->abort (NULL))
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api_fatal ("couldn't allocate heap, %E, base %p, top %p, "
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"reserve_size %d, allocsize %d, page_const %d",
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cygheap->user_heap.base, cygheap->user_heap.top,
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reserve_size, allocsize, page_const);
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if (p != cygheap->user_heap.base)
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api_fatal ("heap allocated at wrong address %p (mapped) != %p (expected)", p, cygheap->user_heap.base);
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if (allocsize && !VirtualAlloc (cygheap->user_heap.base, allocsize, MEM_COMMIT, PAGE_READWRITE))
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api_fatal ("MEM_COMMIT failed, %E");
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}
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/* CV 2012-05-21: Moved printing heap size here from strace::activate.
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The value printed in strace.activate was always wrong, because at the
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time it's called, cygheap points to cygheap_dummy. Above all, the heap
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size has not been evaluated yet, except in a forked child. Since
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heap_init is called early, the heap size is printed pretty much at the
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start of the strace output, so there isn't anything lost. */
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debug_printf ("heap base %p, heap top %p, heap size %p (%u)",
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cygheap->user_heap.base, cygheap->user_heap.top,
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cygheap->user_heap.chunk, cygheap->user_heap.chunk);
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page_const--;
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// malloc_init ();
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}
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#define pround(n) (((size_t)(n) + page_const) & ~page_const)
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/* FIXME: This function no longer handles "split heaps". */
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extern "C" void *
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sbrk (int n)
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{
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char *newtop, *newbrk;
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unsigned commitbytes, newbrksize;
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if (n == 0)
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return cygheap->user_heap.ptr; /* Just wanted to find current cygheap->user_heap.ptr address */
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newbrk = (char *) cygheap->user_heap.ptr + n; /* Where new cygheap->user_heap.ptr will be */
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newtop = (char *) pround (newbrk); /* Actual top of allocated memory -
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on page boundary */
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if (newtop == cygheap->user_heap.top)
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goto good;
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if (n < 0)
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{ /* Freeing memory */
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assert (newtop < cygheap->user_heap.top);
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n = (char *) cygheap->user_heap.top - newtop;
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if (VirtualFree (newtop, n, MEM_DECOMMIT)) /* Give it back to OS */
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goto good; /* Didn't take */
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else
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goto err;
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}
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assert (newtop > cygheap->user_heap.top);
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/* Find the number of bytes to commit, rounded up to the nearest page. */
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commitbytes = pround (newtop - (char *) cygheap->user_heap.top);
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/* Need to grab more pages from the OS. If this fails it may be because
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we have used up previously reserved memory. Or, we're just plumb out
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of memory. Only attempt to commit memory that we know we've previously
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reserved. */
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if (newtop <= cygheap->user_heap.max)
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{
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if (VirtualAlloc (cygheap->user_heap.top, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL)
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goto good;
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}
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/* Couldn't allocate memory. Maybe we can reserve some more.
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Reserve either the maximum of the standard cygwin_shared->heap_chunk_size ()
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or the requested amount. Then attempt to actually allocate it. */
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if ((newbrksize = cygheap->user_heap.chunk) < commitbytes)
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newbrksize = commitbytes;
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if ((VirtualAlloc (cygheap->user_heap.top, newbrksize, MEM_RESERVE, PAGE_NOACCESS)
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|| VirtualAlloc (cygheap->user_heap.top, newbrksize = commitbytes, MEM_RESERVE, PAGE_NOACCESS))
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&& VirtualAlloc (cygheap->user_heap.top, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL)
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{
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cygheap->user_heap.max = (char *) cygheap->user_heap.max + pround (newbrksize);
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goto good;
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}
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err:
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set_errno (ENOMEM);
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return (void *) -1;
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good:
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void *oldbrk = cygheap->user_heap.ptr;
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cygheap->user_heap.ptr = newbrk;
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cygheap->user_heap.top = newtop;
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return oldbrk;
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}
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