214 lines
8.7 KiB
C++
214 lines
8.7 KiB
C++
/* wow64.cc
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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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#ifndef __x86_64__
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/* WOW64 only plays a role in the 32 bit version. Don't use any of this
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in the 64 bit version. */
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#include "winsup.h"
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#include "cygtls.h"
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#include "ntdll.h"
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#include <sys/param.h>
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#define PTR_ADD(p,o) ((PVOID)((PBYTE)(p)+(o)))
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bool NO_COPY wow64_needs_stack_adjustment = false;
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static void
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wow64_eval_expected_main_stack (PVOID &allocbase, PVOID &stackbase)
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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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/* The main thread stack is expected to be located at 0x30000, which is the
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case for all observed NT systems up to Server 2003 R2, unless the
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stacksize requested by the StackReserve field in the PE/COFF header is
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so big that the stack doesn't fit in the area between 0x30000 and the
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start of the image. In case of a conflict, the OS allocates the stack
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right after the image.
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Sidenote: While post-2K3 32 bit systems continue to have the default
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main thread stack address located at 0x30000, the default main thread
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stack address on Vista/2008 64 bit is 0x80000 and on W7/2K8R2 64 bit
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it is 0x90000. However, this is no problem because the system sticks
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to that address for all WOW64 processes, not only for the first one
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started from a 64 bit parent. */
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allocbase = (PVOID) 0x30000;
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/* Stack size. The OS always rounds the size up to allocation granularity
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and it never allocates less than 256K. */
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size = roundup2 (ntheader->OptionalHeader.SizeOfStackReserve,
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wincap.allocation_granularity ());
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if (size < 256 * 1024)
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size = 256 * 1024;
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/* If the stack doesn't fit in the area before the image, it's allocated
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right after the image, rounded up to allocation granularity boundary. */
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if (PTR_ADD (allocbase, size) > (PVOID) ntheader->OptionalHeader.ImageBase)
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allocbase = PTR_ADD (ntheader->OptionalHeader.ImageBase,
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ntheader->OptionalHeader.SizeOfImage);
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allocbase = (PVOID) roundup2 ((uintptr_t) allocbase,
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wincap.allocation_granularity ());
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stackbase = PTR_ADD (allocbase, size);
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debug_printf ("expected allocbase: %p, stackbase: %p", allocbase, stackbase);
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}
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bool
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wow64_test_for_64bit_parent ()
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{
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/* On Windows XP 64 and 2003 64 there's a problem with processes running
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under WOW64. The first process started from a 64 bit process has its
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main thread stack not where it should be. Rather, it uses another
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stack while the original stack is used for other purposes.
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The problem is, the child has its stack in the usual spot again, thus
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we have to "alloc_stack_hard_way". However, this fails in almost all
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cases because the stack slot of the parent process is taken by something
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else in the child process.
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What we do here is to check if the current stack is the expected main
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thread stack and if not, if we really have been started from a 64 bit
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process here. If so, we note this fact in wow64_needs_stack_adjustment
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so we can workaround the stack problem in _dll_crt0. See there for how
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we go along. */
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NTSTATUS ret;
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PROCESS_BASIC_INFORMATION pbi;
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HANDLE parent;
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PVOID allocbase, stackbase;
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ULONG_PTR wow64 = TRUE; /* Opt on the safe side. */
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/* First check if the current stack is where it belongs. If so, we don't
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have to do anything special. This is the case on Vista and later. */
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wow64_eval_expected_main_stack (allocbase, stackbase);
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if (&wow64 >= (PULONG_PTR) allocbase && &wow64 < (PULONG_PTR) stackbase)
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return false;
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/* Check if the parent is a native 64 bit process. Unfortunately there's
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no simpler way to retrieve the parent process in NT, as far as I know.
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Hints welcome. */
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ret = NtQueryInformationProcess (NtCurrentProcess (),
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ProcessBasicInformation,
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&pbi, sizeof pbi, NULL);
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if (NT_SUCCESS (ret)
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&& (parent = OpenProcess (PROCESS_QUERY_INFORMATION,
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FALSE,
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(DWORD) pbi.InheritedFromUniqueProcessId)))
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{
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NtQueryInformationProcess (parent, ProcessWow64Information,
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&wow64, sizeof wow64, NULL);
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CloseHandle (parent);
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}
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return !wow64;
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}
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PVOID
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wow64_revert_to_original_stack (PVOID &allocationbase)
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{
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/* Test if the original stack exists and has been set up as usual. Even
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though the stack of the WOW64 process is at an unusual address, it appears
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that the "normal" stack has been created as usual. It's partially in use
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by the 32->64 bit transition layer of the OS to help along the WOW64
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process, but it's otherwise mostly unused. */
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MEMORY_BASIC_INFORMATION mbi;
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PVOID stackbase;
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wow64_eval_expected_main_stack (allocationbase, stackbase);
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/* The stack is allocated in a single call, so the entire stack has the
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same AllocationBase. At the start we expect a reserved region big
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enough still to host as the main stack. The OS apparently reserves
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always at least 256K for the main thread stack. We err on the side
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of caution so we test here for a reserved region of at least 256K.
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That should be enough (knock on wood). */
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VirtualQuery (allocationbase, &mbi, sizeof mbi);
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if (mbi.State != MEM_RESERVE || mbi.RegionSize < 256 * 1024)
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return NULL;
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/* Next we expect a guard page. We fetch the size of the guard area to
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see how big it is. Apparently the guard area on 64 bit systems spans
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2 pages, only for the main thread for some reason. We better keep it
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that way. */
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PVOID addr = PTR_ADD (mbi.BaseAddress, mbi.RegionSize);
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VirtualQuery (addr, &mbi, sizeof mbi);
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if (mbi.AllocationBase != allocationbase
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|| mbi.State != MEM_COMMIT
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|| !(mbi.Protect & PAGE_GUARD))
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return NULL;
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PVOID guardaddr = mbi.BaseAddress;
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SIZE_T guardsize = mbi.RegionSize;
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/* Next we expect a committed R/W region, the in-use area of that stack.
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This is just a sanity check. */
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addr = PTR_ADD (mbi.BaseAddress, mbi.RegionSize);
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VirtualQuery (addr, &mbi, sizeof mbi);
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if (mbi.AllocationBase != allocationbase
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|| PTR_ADD (mbi.BaseAddress, mbi.RegionSize) != stackbase
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|| mbi.State != MEM_COMMIT
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|| mbi.Protect != PAGE_READWRITE)
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return NULL;
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/* The original stack is used by the OS. Leave enough space for the OS
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to be happy (another 64K) and constitute a second stack within the so
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far reserved stack area. */
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PVOID newbase = PTR_ADD (guardaddr, -wincap.allocation_granularity ());
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PVOID newtop = PTR_ADD (newbase, -wincap.allocation_granularity ());
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guardaddr = PTR_ADD (newtop, -guardsize);
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if (!VirtualAlloc (newtop, wincap.allocation_granularity (),
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MEM_COMMIT, PAGE_READWRITE))
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return NULL;
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if (!VirtualAlloc (guardaddr, guardsize, MEM_COMMIT,
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PAGE_READWRITE | PAGE_GUARD))
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return NULL;
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/* We're going to reuse the original stack. Yay, no more respawn!
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Set the StackBase and StackLimit values in the TEB, set _main_tls
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accordingly, and return the new, 16 byte aligned address for the
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stack pointer. The second half of the stack move is done by the
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caller _dll_crt0. */
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NtCurrentTeb ()->Tib.StackBase = (char *) newbase;
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NtCurrentTeb ()->Tib.StackLimit = (char *) newtop;
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_main_tls = &_my_tls;
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return PTR_ADD (NtCurrentTeb ()->Tib.StackBase, -16);
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}
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/* Respawn WOW64 process. This is only called if we can't reuse the original
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stack. See comment in wow64_revert_to_original_stack for details. See
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_dll_crt0 for the call of this function.
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Historical note:
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Originally we just always respawned, right from dll_entry. This stopped
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working with Cygwin 1.7.10 on Windows 2003 R2 64. Starting with Cygwin
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1.7.10 we don't link against advapi32.dll anymore. However, any process
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linked against advapi32, directly or indirectly, failed to respawn when
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trying respawning during DLL_PROCESS_ATTACH initialization. In that
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case CreateProcessW returns with ERROR_ACCESS_DENIED for some reason. */
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void
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wow64_respawn_process ()
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{
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PROCESS_INFORMATION pi;
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STARTUPINFOW si;
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DWORD ret = 0;
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GetStartupInfoW (&si);
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if (!CreateProcessW (global_progname, GetCommandLineW (), NULL, NULL, TRUE,
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CREATE_DEFAULT_ERROR_MODE
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| GetPriorityClass (GetCurrentProcess ()),
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NULL, NULL, &si, &pi))
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api_fatal ("Failed to create process <%W> <%W>, %E",
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global_progname, GetCommandLineW ());
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CloseHandle (pi.hThread);
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if (WaitForSingleObject (pi.hProcess, INFINITE) == WAIT_FAILED)
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api_fatal ("Waiting for process %u failed, %E", pi.dwProcessId);
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GetExitCodeProcess (pi.hProcess, &ret);
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CloseHandle (pi.hProcess);
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TerminateProcess (GetCurrentProcess (), ret);
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ExitProcess (ret);
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}
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#endif /* !__x86_64__ */
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