338 lines
11 KiB
C++
338 lines
11 KiB
C++
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/* heap.cc: Cygwin heap manager.
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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 ptrdiff_t page_const;
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/* Minimum size of the base heap. */
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#define MINHEAP_SIZE (4 * 1024 * 1024)
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/* Chunksize of subsequent heap reservations. */
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#define RAISEHEAP_SIZE (1 * 1024 * 1024)
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static uintptr_t
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eval_start_address ()
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{
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#ifdef __x86_64__
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/* On 64 bit, we choose a fixed address outside the 32 bit area. The
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executable starts at 0x1:00400000L, the Cygwin DLL starts at
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0x1:80040000L, other rebased DLLs are located in the region from
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0x2:00000000L up to 0x4:00000000L, -auto-image-based DLLs are located
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in the region from 0x4:00000000L up to 0x6:00000000L. Leave another
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8 Gigs slack space, so lets start the heap at 0x8:00000000L. */
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uintptr_t start_address = 0x800000000L;
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#else
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/* Windows performs heap ASLR. This spoils the entire region below
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0x20000000 for us, because that region is used by Windows to randomize
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heap and stack addresses. Therefore we put our heap into a safe region
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starting at 0x20000000. This should work right from the start in 99%
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of the cases. */
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uintptr_t start_address = 0x20000000L;
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MEMORY_BASIC_INFORMATION mbi;
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if (VirtualQuery ((void *) 0xbf000000L, &mbi, sizeof mbi))
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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.
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We used to use the current TEB address as very simple test that
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this is a large address aware executable, but that fails on W10
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WOW64 because the main TEB is apparently commited in the lower
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2 Gigs these days.
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The above test for address 0xbf000000 is supposed to make sure
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that we really have 3GB on a 32 bit system. Windows supports
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smaller large address regions, but then it's not that interesting
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for us to use it for the heap. If the region is big enough, the
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heap gets allocated at its start. What we get are 0.999 or 1.999
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Gigs of free contiguous memory for heap, thread stacks, and shared
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memory regions. */
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start_address = 0x80000000L;
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}
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#endif
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return start_address;
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}
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static SIZE_T
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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_HEADERS ntheader;
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SIZE_T size;
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dosheader = (PIMAGE_DOS_HEADER) GetModuleHandle (NULL);
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ntheader = (PIMAGE_NT_HEADERS) ((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 on 32 bit and
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512 on 64 bit. Otherwise, we use it as the default initial heap size
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in megabyte. Valid values are between 4 and 2048/8388608 Megs. */
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size = ntheader->OptionalHeader.LoaderFlags;
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#ifdef __x86_64__
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if (size == 0)
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size = 512;
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else if (size < 4)
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size = 4;
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else if (size > 8388608)
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size = 8388608;
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#else
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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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#endif
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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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user_heap_info::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 (!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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chunk = eval_initial_heap_size ();
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do
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{
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base = VirtualAlloc ((LPVOID) start_address, chunk, alloctype,
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PAGE_NOACCESS);
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if (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 >= 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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chunk = largest_found_size;
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base = VirtualAlloc (largest_found, chunk, alloctype,
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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 (!base)
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{
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chunk = MINHEAP_SIZE;
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base = VirtualAlloc (NULL, chunk, alloctype, PAGE_NOACCESS);
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}
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}
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}
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while (!base && ret);
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if (base == NULL)
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api_fatal ("unable to allocate heap, heap_chunk_size %ly, %E",
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chunk);
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ptr = top = base;
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max = (char *) base + chunk;
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}
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else
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{
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/* total size commited in parent */
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SIZE_T allocsize = (char *) top - (char *) base;
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/* Loop until we've managed to reserve an adequate amount of memory. */
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SIZE_T reserve_size = chunk * ((allocsize + (chunk - 1)) / chunk);
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/* With ptmalloc3 there's a good chance that there has been no memory
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allocated on the heap. If we don't check that, reserve_size will
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be 0 and from there, the below loop will end up overallocating due
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to integer overflow. */
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if (!reserve_size)
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reserve_size = chunk;
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char *p;
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while (1)
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{
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p = (char *) VirtualAlloc (base, reserve_size, alloctype,
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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 %ld, allocsize %ld, page_const %d",
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base, top,
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reserve_size, allocsize, page_const);
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if (p != base)
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api_fatal ("heap allocated at wrong address %p (mapped) "
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"!= %p (expected)", p, base);
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if (allocsize && !VirtualAlloc (base, allocsize,
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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 %ly (%lu)",
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base, top, chunk, 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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/* Linux defines n to be intptr_t, newlib defines it to be ptrdiff_t.
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It shouldn't matter much, though, since the function is not standarized
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and sizeof(ptrdiff_t) == sizeof(intptr_t) anyway. */
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extern "C" void *
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sbrk (ptrdiff_t n)
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{
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return cygheap->user_heap.sbrk (n);
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}
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void __reg2 *
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user_heap_info::sbrk (ptrdiff_t n)
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{
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/* FIXME: This function no longer handles "split heaps". */
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char *newtop, *newbrk;
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SIZE_T commitbytes, newbrksize, reservebytes;
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if (n == 0)
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return ptr; /* Just wanted to find current ptr
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address */
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newbrk = (char *) ptr + n; /* Where new cptr 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 == 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 < top);
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n = (char *) top - newtop;
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/* FIXME: This doesn't work if we cross a virtual memory reservation
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border. If that happens, we have to free the space in multiple
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VirtualFree calls, aligned to the former reservation borders. */
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if (VirtualFree (newtop, n, MEM_DECOMMIT)) /* Give it back to OS */
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goto good;
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goto err; /* Didn't take */
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}
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assert (newtop > 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 *) 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 <= max)
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{
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if (VirtualAlloc (top, commitbytes, MEM_COMMIT, PAGE_READWRITE))
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goto good;
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goto err;
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}
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/* The remainder of the existing heap is too small to fulfill the memory
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request. We have to extend the heap, so we reserve some more memory
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and then commit the remainder of the old heap, if any, and the rest of
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the required space from the extended heap. */
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/* For subsequent chunks following the base heap, reserve either 1 Megs
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per chunk, or the requested amount if it's bigger than 1 Megs. */
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reservebytes = commitbytes - ((char *) max - (char *) top);
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commitbytes -= reservebytes;
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if ((newbrksize = RAISEHEAP_SIZE) < reservebytes)
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newbrksize = reservebytes;
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if (VirtualAlloc (max, newbrksize, MEM_RESERVE, PAGE_NOACCESS)
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|| VirtualAlloc (max, newbrksize = reservebytes, MEM_RESERVE,
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PAGE_NOACCESS))
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{
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/* Now commit the requested memory. Windows keeps all virtual
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reservations separate, so we can't commit the two regions in a single,
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combined call or we suffer an ERROR_INVALID_ADDRESS. The same error
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is returned when trying to VirtualAlloc 0 bytes, which would occur if
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the existing heap was already full. */
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if ((!commitbytes || VirtualAlloc (top, commitbytes, MEM_COMMIT,
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PAGE_READWRITE))
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&& VirtualAlloc (max, reservebytes, MEM_COMMIT, PAGE_READWRITE))
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{
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max = (char *) max + pround (newbrksize);
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goto good;
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}
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/* If committing the memory failed, we must free the extendend reserved
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region, otherwise any other try to fetch memory (for instance by using
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mmap) may fail just because we still reserve memory we don't even know
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about. */
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VirtualFree (max, newbrksize, MEM_RELEASE);
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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 = ptr;
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ptr = newbrk;
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top = newtop;
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return oldbrk;
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}
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