Cygwin: mmap: Remove AT_ROUND_TO_PAGE workaround
It's working on 32 bit OSes only anyway. It even fails on WOW64. Drop unsupported NtMapViewOfSection flags. Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen
Ken Brown
parent
16baeb7fb7
commit
7218c5466f
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@ -172,8 +172,7 @@ CreateMapping (HANDLE fhdl, size_t len, off_t off, DWORD openflags,
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}
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else
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{
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/* Zero len creates mapping for whole file and allows
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AT_EXTENDABLE_FILE mapping, if we ever use it... */
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/* Zero len creates mapping for whole file */
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sectionsize.QuadPart = 0;
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status = NtCreateSection (&h, SECTION_ALL_ACCESS, &oa, §ionsize,
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protect, attributes, fhdl);
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@ -195,12 +194,7 @@ MapView (HANDLE h, void *addr, size_t len, DWORD openflags,
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DWORD protect = gen_create_protect (openflags, flags);
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void *base = addr;
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SIZE_T viewsize = len;
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#ifdef __x86_64__ /* AT_ROUND_TO_PAGE isn't supported on 64 bit systems. */
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ULONG alloc_type = MEM_TOP_DOWN;
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#else
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ULONG alloc_type = (base && !wincap.is_wow64 () ? AT_ROUND_TO_PAGE : 0)
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| MEM_TOP_DOWN;
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#endif
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#ifdef __x86_64__
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/* Don't call NtMapViewOfSectionEx during fork. It requires autoloading
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@ -878,6 +872,10 @@ mmap64 (void *addr, size_t len, int prot, int flags, int fd, off_t off)
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if (!anonymous (flags) && fd != -1)
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{
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UNICODE_STRING fname;
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IO_STATUS_BLOCK io;
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FILE_STANDARD_INFORMATION fsi;
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/* Ensure that fd is open */
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cygheap_fdget cfd (fd);
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if (cfd < 0)
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@ -896,19 +894,16 @@ mmap64 (void *addr, size_t len, int prot, int flags, int fd, off_t off)
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/* The autoconf mmap test maps a file of size 1 byte. It then tests
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every byte of the entire mapped page of 64K for 0-bytes since that's
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what POSIX requires. The problem is, we can't create that mapping on
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64 bit systems. The file mapping will be only a single page, 4K, and
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since 64 bit systems don't support the AT_ROUND_TO_PAGE flag, the
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remainder of the 64K slot will result in a SEGV when accessed.
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what POSIX requires. The problem is, we can't create that mapping.
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The file mapping will be only a single page, 4K, and the remainder
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of the 64K slot will result in a SEGV when accessed.
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So, what we do here is cheating for the sake of the autoconf test
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on 64 bit systems. The justification is that there's very likely
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no application actually utilizing the map beyond EOF, and we know that
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all bytes beyond EOF are set to 0 anyway. If this test doesn't work
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on 64 bit systems, it will result in not using mmap at all in a
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package. But we want that mmap is treated as usable by autoconf,
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regardless whether the autoconf test runs on a 32 bit or a 64 bit
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system.
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So, what we do here is cheating for the sake of the autoconf test.
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The justification is that there's very likely no application actually
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utilizing the map beyond EOF, and we know that all bytes beyond EOF
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are set to 0 anyway. If this test doesn't work, it will result in
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not using mmap at all in a package. But we want mmap being treated
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as usable by autoconf.
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Ok, so we know exactly what autoconf is doing. The file is called
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"conftest.txt", it has a size of 1 byte, the mapping size is the
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@ -916,31 +911,19 @@ mmap64 (void *addr, size_t len, int prot, int flags, int fd, off_t off)
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mapping is MAP_SHARED, the offset is 0.
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If all these requirements are given, we just return an anonymous map.
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This will help to get over the autoconf test even on 64 bit systems.
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The tests are ordered for speed. */
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#ifdef __x86_64__
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if (1)
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#else
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if (wincap.is_wow64 ())
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#endif
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{
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UNICODE_STRING fname;
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IO_STATUS_BLOCK io;
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FILE_STANDARD_INFORMATION fsi;
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if (len == pagesize
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&& prot == (PROT_READ | PROT_WRITE)
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&& flags == MAP_SHARED
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&& off == 0
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&& (RtlSplitUnicodePath (fh->pc.get_nt_native_path (), NULL,
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&fname),
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wcscmp (fname.Buffer, L"conftest.txt") == 0)
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&& NT_SUCCESS (NtQueryInformationFile (fh->get_handle (), &io,
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&fsi, sizeof fsi,
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FileStandardInformation))
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&& fsi.EndOfFile.QuadPart == 1LL)
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flags |= MAP_ANONYMOUS;
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}
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if (len == pagesize
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&& prot == (PROT_READ | PROT_WRITE)
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&& flags == MAP_SHARED
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&& off == 0
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&& (RtlSplitUnicodePath (fh->pc.get_nt_native_path (), NULL,
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&fname),
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wcscmp (fname.Buffer, L"conftest.txt") == 0)
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&& NT_SUCCESS (NtQueryInformationFile (fh->get_handle (), &io,
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&fsi, sizeof fsi,
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FileStandardInformation))
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&& fsi.EndOfFile.QuadPart == 1LL)
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flags |= MAP_ANONYMOUS;
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}
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if (anonymous (flags) || fd == -1)
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@ -1025,20 +1008,8 @@ mmap64 (void *addr, size_t len, int prot, int flags, int fd, off_t off)
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goto go_ahead;
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}
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fsiz -= off;
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/* We're creating the pages beyond EOF as reserved, anonymous pages.
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Note that 64 bit environments don't support the AT_ROUND_TO_PAGE
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flag, which is required to get this right for the remainder of
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the first 64K block the file ends in. We perform the workaround
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nevertheless to support expectations that the range mapped beyond
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EOF can be safely munmap'ed instead of being taken by another,
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totally unrelated mapping. */
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if ((off_t) len > fsiz && !autogrow (flags))
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orig_len = len;
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#ifdef __i386__
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else if (!wincap.is_wow64 () && roundup2 (len, wincap.page_size ())
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< roundup2 (len, pagesize))
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orig_len = len;
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#endif
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/* We're creating the pages beyond EOF as reserved, anonymous
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pages if MAP_AUTOGROW is not set. */
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if ((off_t) len > fsiz)
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{
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if (autogrow (flags))
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@ -1053,9 +1024,12 @@ mmap64 (void *addr, size_t len, int prot, int flags, int fd, off_t off)
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}
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}
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else
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/* Otherwise, don't map beyond EOF, since Windows would change
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the file to the new length, in contrast to POSIX. */
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len = fsiz;
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{
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/* Otherwise, don't map beyond EOF, since Windows would change
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the file to the new length, in contrast to POSIX. */
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orig_len = len;
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len = fsiz;
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}
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}
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/* If the requested offset + len is <= file size, drop MAP_AUTOGROW.
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@ -1088,6 +1062,7 @@ go_ahead:
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}
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}
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orig_len = roundup2 (orig_len, pagesize);
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#ifdef __x86_64__
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if (!wincap.has_extended_mem_api ())
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addr = mmap_alloc.alloc (addr, orig_len ?: len, fixed (flags));
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@ -1099,7 +1074,6 @@ go_ahead:
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deallocated and the address we got is used as base address for the
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subsequent real mappings. This ensures that we have enough space
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for the whole thing. */
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orig_len = roundup2 (orig_len, pagesize);
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PVOID newaddr = VirtualAlloc (addr, orig_len, MEM_TOP_DOWN | MEM_RESERVE,
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PAGE_READWRITE);
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if (!newaddr)
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@ -1132,51 +1106,18 @@ go_ahead:
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if (orig_len)
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{
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/* If the requested length is bigger than the file size, the
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remainder is created as anonymous mapping. Actually two
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mappings are created, first the remainder from the file end to
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the next 64K boundary as accessible pages with the same
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protection as the file's pages, then as much pages as necessary
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to accomodate the requested length, but as reserved pages which
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raise a SIGBUS when trying to access them. AT_ROUND_TO_PAGE
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and page protection on shared pages is only supported by the
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32 bit environment, so don't even try on 64 bit or even WOW64.
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This results in an allocation gap in the first 64K block the file
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ends in, but there's nothing at all we can do about that. */
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#ifdef __x86_64__
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len = roundup2 (len, wincap.allocation_granularity ());
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orig_len = roundup2 (orig_len, wincap.allocation_granularity ());
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#else
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len = roundup2 (len, wincap.is_wow64 () ? wincap.allocation_granularity ()
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: wincap.page_size ());
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#endif
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remainder is created as anonymous mapping, as reserved pages which
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raise a SIGBUS when trying to access them. This results in an
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allocation gap in the first 64K block the file ends in, but there's
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nothing at all we can do about that. */
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len = roundup2 (len, pagesize);
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if (orig_len - len)
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{
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orig_len -= len;
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size_t valid_page_len = 0;
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#ifndef __x86_64__
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if (!wincap.is_wow64 ())
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valid_page_len = orig_len % pagesize;
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#endif
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size_t sigbus_page_len = orig_len - valid_page_len;
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size_t sigbus_page_len = orig_len - len;
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caddr_t at_base = base + len;
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if (valid_page_len)
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{
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prot |= __PROT_FILLER;
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flags &= MAP_SHARED | MAP_PRIVATE;
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flags |= MAP_ANONYMOUS | MAP_FIXED;
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at_base = mmap_worker (NULL, &fh_anonymous, at_base,
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valid_page_len, prot, flags, -1, 0, NULL);
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if (!at_base)
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{
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fh->munmap (fh->get_handle (), base, len);
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set_errno (ENOMEM);
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goto out_with_unlock;
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}
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at_base += valid_page_len;
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}
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if (sigbus_page_len)
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{
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caddr_t at_base = base + len;
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prot = PROT_READ | PROT_WRITE | __PROT_ATTACH;
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flags = MAP_ANONYMOUS | MAP_NORESERVE | MAP_FIXED;
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at_base = mmap_worker (NULL, &fh_anonymous, at_base,
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@ -51,10 +51,6 @@ extern GUID __cygwin_socket_guid;
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#define FILE_AUTOGENERATED_DEVICE_NAME 0x00000080
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#define FILE_DEVICE_SECURE_OPEN 0x00000100
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/* Allocation type values in NtMapViewOfSection call. */
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#define AT_EXTENDABLE_FILE 0x00002000
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#define AT_ROUND_TO_PAGE 0x40000000
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/* Lock type in NtLockVirtualMemory/NtUnlockVirtualMemory call. */
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#define MAP_PROCESS 1
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#define MAP_SYSTEM 2
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