Remember me?-)

Christopher Faylor cgf@redhat.com
Wed Feb 7 17:15:00 GMT 2001


Hi Sergey,

Long time, no communicate!

Do you think that this would be a general replacement for cygwin's fork?

cgf

On Wed, Feb 07, 2001 at 08:08:42PM -0500, Sergey Okhapkin wrote:
>Hi!
>
>Here is an example of NT-specific fork() implementation. It seems to me
>interesting, isn't it?
>
>#include "ntdll.h"
>#include <stdio.h>
>
>namespace NT {
>    extern "C" {
>
>NTSTATUS
>NTAPI
>CsrClientCallServer(
>    IN PVOID Message,
>    IN PVOID,
>    IN ULONG Opcode,
>    IN ULONG Size
>    );
>
>    }
>}
>
>VOID InheritAll()
>{
>    ULONG n = 0x1000;
>    PULONG p = new ULONG[n];
>
>    while (NT::ZwQuerySystemInformation(NT::SystemHandleInformation,
>                                        p, n * sizeof *p, 0)
>           == STATUS_INFO_LENGTH_MISMATCH)
>        delete [] p, p = new ULONG[n *= 2];
>
>    NT::PSYSTEM_HANDLE_INFORMATION h = NT::PSYSTEM_HANDLE_INFORMATION(p +
>1);
>
>    ULONG pid = GetCurrentProcessId();
>
>    for (ULONG i = 0; i < *p; i++)
>        if (h[i].ProcessId == pid)
>            SetHandleInformation(HANDLE(h[i].Handle),
>                                 HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT);
>    delete [] p;
>}
>
>VOID InformCsrss(HANDLE hProcess, HANDLE hThread, ULONG pid, ULONG tid)
>{
>    struct CSRSS_MESSAGE {
>        ULONG Unknown1;
>        ULONG Opcode;
>        ULONG Status;
>        ULONG Unknown2;
>    };
>
>    struct {
>        NT::PORT_MESSAGE PortMessage;
>        CSRSS_MESSAGE CsrssMessage;
>        PROCESS_INFORMATION ProcessInformation;
>        NT::CLIENT_ID Debugger;
>        ULONG CreationFlags;
>        ULONG VdmInfo[2];
>    } csrmsg = {{0}, {0}, {hProcess, hThread, pid, tid}, {0}, 0, {0}};
>
>    NT::CsrClientCallServer(&csrmsg, 0, 0x10000, 0x24);
>}
>
>   __declspec(naked) int child()
>{
>    typedef BOOL (WINAPI *CsrpConnectToServer)(PWSTR);
>
>    CsrpConnectToServer(0x77F8F65D)(L"\\Windows");
>    __asm mov   eax, 0
>    __asm mov   esp, ebp
>    __asm pop   ebp
>    __asm ret
>}
>
>
>#pragma optimize("y", off)  // disable frame pointer omission
>
>int fork()
>{
>    HANDLE hProcess, hThread;
>
>    InheritAll();
>
>    NT::OBJECT_ATTRIBUTES oa = {sizeof oa};
>
>    NT::ZwCreateProcess(&hProcess, PROCESS_ALL_ACCESS, &oa,
>                        NtCurrentProcess(), TRUE, 0, 0, 0);
>
>    NT::CONTEXT context = {CONTEXT_FULL
>                          | CONTEXT_DEBUG_REGISTERS
>                          | CONTEXT_FLOATING_POINT};
>
>    NT::ZwGetContextThread(NtCurrentThread(), &context);
>
>    context.Eip = ULONG(child);
>
>    MEMORY_BASIC_INFORMATION mbi;
>
>    NT::ZwQueryVirtualMemory(NtCurrentProcess(), PVOID(context.Esp),
>                             NT::MemoryBasicInformation, &mbi, sizeof mbi,
>0);
>
>    NT::USER_STACK stack = {0, 0, PCHAR(mbi.BaseAddress) + mbi.RegionSize,
>                            mbi.BaseAddress, mbi.AllocationBase};
>
>    NT::CLIENT_ID cid;
>
>    NT::ZwCreateThread(&hThread, THREAD_ALL_ACCESS, &oa,
>                       hProcess, &cid, &context, &stack, TRUE);
>
>    NT::THREAD_BASIC_INFORMATION tbi;
>
>    NT::ZwQueryInformationThread(NtCurrentThread(),
>                                 NT::ThreadBasicInformation,
>                                 &tbi, sizeof tbi, 0);
>
>    NT::PNT_TIB tib = tbi.TebBaseAddress;
>
>    NT::ZwQueryInformationThread(hThread, NT::ThreadBasicInformation,
>                                 &tbi, sizeof tbi, 0);
>
>    NT::ZwWriteVirtualMemory(hProcess, tbi.TebBaseAddress,
>                             &tib->ExceptionList, sizeof tib->ExceptionList,
>                             0);
>
>    InformCsrss(hProcess, hThread,
>                ULONG(cid.UniqueProcess), ULONG(cid.UniqueThread));
>
>    NT::ZwResumeThread(hThread, 0);
>
>    NT::ZwClose(hThread);
>    NT::ZwClose(hProcess);
>
>    return int(cid.UniqueProcess);
>}
>
>#pragma optimize("", on)
>
>
>int main()
>{
>    int n = fork();
>    Sleep(n * 10);
>    Beep(100, 100);
>    printf("%d\n", n);
>    return 0;
>}
>
>
>Sergey Okhapkin, http://www.lexa.ru/sos
>Somerset, NJ
>

-- 
cgf@cygnus.com                        Red Hat, Inc.
http://sources.redhat.com/            http://www.redhat.com/


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