diff options
Diffstat (limited to 'winsup/cygwin/fork.cc')
| -rw-r--r-- | winsup/cygwin/fork.cc | 624 |
1 files changed, 624 insertions, 0 deletions
diff --git a/winsup/cygwin/fork.cc b/winsup/cygwin/fork.cc new file mode 100644 index 000000000..a82d2dc76 --- /dev/null +++ b/winsup/cygwin/fork.cc @@ -0,0 +1,624 @@ +/* fork.cc + + Copyright 1996, 1997, 1998, 1999 Cygnus Solutions. + +This file is part of Cygwin. + +This software is a copyrighted work licensed under the terms of the +Cygwin license. Please consult the file "CYGWIN_LICENSE" for +details. */ + +#include <stdio.h> +#include <unistd.h> +#include <stdlib.h> +#include <fcntl.h> +#include <stdarg.h> +#include <errno.h> +#include "winsup.h" +#include "dll_init.h" + +DWORD chunksize = 0; +/* Timeout to wait for child to start, parent to init child, etc. */ +/* FIXME: Once things stabilize, bump up to a few minutes. */ +#define FORK_WAIT_TIMEOUT (300 * 1000) /* 300 seconds */ + +#define dll_data_start &_data_start__ +#define dll_data_end &_data_end__ +#define dll_bss_start &_bss_start__ +#define dll_bss_end &_bss_end__ + +void +per_thread::set (void *s) + { + if (s == PER_THREAD_FORK_CLEAR) + { + tls = TlsAlloc (); + s = NULL; + } + TlsSetValue (get_tls (), s); + } + +static void +stack_base (child_info_fork &ch) +{ + MEMORY_BASIC_INFORMATION m; + memset (&m, 0, sizeof m); + if (!VirtualQuery ((LPCVOID) &m, &m, sizeof m)) + system_printf ("couldn't get memory info, %E"); + + ch.stacktop = m.AllocationBase; + ch.stackbottom = (LPBYTE) m.BaseAddress + m.RegionSize; + ch.stacksize = (DWORD) ch.stackbottom - (DWORD) &m; + debug_printf ("bottom %p, top %p, stack %p, size %d, reserve %d", + ch.stackbottom, ch.stacktop, &m, ch.stacksize, + (DWORD) ch.stackbottom - (DWORD) ch.stacktop); +} + +/* Copy memory from parent to child. + The result is a boolean indicating success. */ + +static int +fork_copy (PROCESS_INFORMATION &pi, const char *what, ...) +{ + va_list args; + char *low; + int pass = 0; + + va_start (args, what); + + while ((low = va_arg (args, char *))) + { + char *high = va_arg (args, char *); + DWORD todo = chunksize ?: high - low; + char *here; + + for (here = low; here < high; here += todo) + { + DWORD done = 0; + if (here + todo > high) + todo = high - here; + int res = WriteProcessMemory (pi.hProcess, here, here, todo, &done); + debug_printf ("child handle %p, low %p, high %p, res %d", pi.hProcess, + low, high, res); + if (!res || todo != done) + { + if (!res) + __seterrno (); + /* If this happens then there is a bug in our fork + implementation somewhere. */ + system_printf ("%s pass %d failed, %p..%p, done %d, %E", + what, pass, low, high, done); + goto err; + } + } + + pass++; + } + + debug_printf ("done"); + return 1; + +err: + TerminateProcess (pi.hProcess, 1); + set_errno (EAGAIN); + return 0; +} + +/* Wait for child to finish what it's doing and signal us. + We don't want to wait forever here.If there's a problem somewhere + it'll hang the entire system (since all forks are mutex'd). If we + time out, set errno = EAGAIN and hope the app tries again. */ +static int +sync_with_child (PROCESS_INFORMATION &pi, HANDLE subproc_ready, + BOOL hang_child, const char *s) +{ + /* We also add the child process handle to the wait. If the child fails + to initialize (eg. because of a missing dll). Then this + handle will become signalled. This stops a *looong* timeout wait. + */ + HANDLE w4[2]; + + debug_printf ("waiting for child. reason: %s", s); + w4[1] = pi.hProcess; + w4[0] = subproc_ready; + DWORD rc = WaitForMultipleObjects (2, w4, FALSE, FORK_WAIT_TIMEOUT); + + if (rc == WAIT_OBJECT_0 || + WaitForSingleObject (subproc_ready, 0) == WAIT_OBJECT_0) + /* That's ok */; + else if (rc == WAIT_FAILED || rc == WAIT_TIMEOUT) + { + if (rc != WAIT_FAILED) + system_printf ("WaitForMultipleObjects timed out"); + else + system_printf ("WaitForMultipleObjects failed, %E"); + set_errno (EAGAIN); + syscall_printf ("-1 = fork(), WaitForMultipleObjects failed"); + TerminateProcess (pi.hProcess, 1); + return 0; + } + else + { + /* Child died. Clean up and exit. */ + DWORD errcode; + GetExitCodeProcess (pi.hProcess, &errcode); + /* Fix me. This is not enough. The fork should not be considered + * to have failed if the process was essentially killed by a signal. + */ + if (errcode != STATUS_CONTROL_C_EXIT) + { + system_printf ("child %d(%p) died before initialization with status code %p", + pi.dwProcessId, pi.hProcess, errcode); + system_printf ("*** child state %s", s); +#ifdef DEBUGGING + abort (); +#endif + } + set_errno (EAGAIN); + syscall_printf ("Child died before subproc_ready signalled"); + return 0; + } + + debug_printf ("child signalled me"); + if (hang_child) + { + int n = SuspendThread (pi.hThread); + debug_printf ("suspend count %d", n); \ + } + return 1; +} + +static int +resume_child (PROCESS_INFORMATION &pi, HANDLE forker_finished) +{ + int rc; + + debug_printf ("here"); + SetEvent (forker_finished); + + rc = ResumeThread (pi.hThread); + + debug_printf ("rc %d", rc); + if (rc == 1) + return 1; // Successful resumption + + /* Can't resume the thread. Not sure why this would happen unless + there's a bug in the system. Things seem to be working OK now + though, so flag this with EAGAIN, but print a message on the + console. */ + small_printf ("fork: ResumeThread failed, rc = %d, %E\n", rc); + set_errno (EAGAIN); + syscall_printf ("-1 = fork(), ResumeThread failed"); + TerminateProcess (pi.hProcess, 1); + return 0; +} + +/* Notify parent that it is time for the next step. + Note that this has to be a macro since the parent may be messing with + our stack. */ +#define sync_with_parent(s, hang_self) \ +((void) ({ \ + debug_printf ("signalling parent: %s", s); \ + /* Tell our parent we're waiting. */ \ + if (!SetEvent (child_proc_info->subproc_ready)) \ + api_fatal ("fork child - SetEvent failed, %E"); \ + if (hang_self) \ + { \ + /* Wait for the parent to fill in our stack and heap. \ + Don't wait forever here. If our parent dies we don't want to clog \ + the system. If the wait fails, we really can't continue so exit. */ \ + DWORD psync_rc = WaitForSingleObject (child_proc_info->forker_finished, FORK_WAIT_TIMEOUT); \ + switch (psync_rc) \ + { \ + case WAIT_TIMEOUT: \ + api_fatal ("sync_with_parent - WFSO timed out"); \ + break; \ + case WAIT_FAILED: \ + if (GetLastError () == ERROR_INVALID_HANDLE && \ + WaitForSingleObject (child_proc_info->forker_finished, 1) != WAIT_FAILED) \ + break; \ + api_fatal ("sync_with_parent - WFSO failed, fork_finished %p, %E", child_proc_info->forker_finished); \ + break; \ + default: \ + break; \ + } \ + debug_printf ("awake"); \ + } \ + 0; \ +})) + +static volatile void grow_stack_slack(); + +static void * +stack_dummy (int here) +{ + return &here; +} + +extern "C" int +fork () +{ + int res; + DWORD rc; + HANDLE hParent; + pinfo *child; + HANDLE subproc_ready, forker_finished; + void *stack_here; + int x; + PROCESS_INFORMATION pi = {0}; + + MALLOC_CHECK; + + /* FIXME: something is broken when copying the stack from the parent + to the child; we try various tricks here to make sure that the + stack is good enough to prevent page faults, but the true cause + is still unknown. DJ */ + volatile char dummy[4096]; + dummy[0] = dummy[4095] = 0; // Just to leave some slack in the stack + + grow_stack_slack (); + + debug_printf ("entering"); + /* Calculate how much of stack to copy to child */ + stack_here = stack_dummy (0); + + if (ISSTATE(myself, PID_SPLIT_HEAP)) + { + system_printf ("The heap has been split, CYGWIN can't fork this process."); + system_printf ("Increase the heap_chunk_size in the registry and try again."); + set_errno (ENOMEM); + syscall_printf ("-1 = fork (), split heap"); + return -1; + } + + /* Don't start the fork until we have the lock. */ + child = cygwin_shared->p.allocate_pid (); + if (!child) + { + set_errno (EAGAIN); + syscall_printf ("-1 = fork (), process table full"); + return -1; + } + + static child_info_fork ch; + x = setjmp (ch.jmp); + + if (x == 0) + { + + /* This will help some of the confusion. */ + fflush (stdout); + + debug_printf ("parent pid %d, child pid %d", myself->pid, child->pid); + + subproc_ready = CreateEvent (&sec_all, FALSE, FALSE, NULL); + forker_finished = CreateEvent (&sec_all, FALSE, FALSE, NULL); + ProtectHandle (subproc_ready); + ProtectHandle (forker_finished); + + /* If we didn't obtain all the resources we need to fork, allow the program + to continue, but record the fact that fork won't work. */ + if (forker_finished == NULL || subproc_ready == NULL) + { + system_printf ("unable to allocate fork() resources."); + system_printf ("fork() disabled."); + return -1; + } + + subproc_init (); + + debug_printf ("about to call setjmp"); + /* Parent. */ +#ifdef DEBUGGING + /* The ProtectHandle call allocates memory so we need to make sure + that enough is set aside here so that the sbrk pointer does not + move when ProtectHandle is called after the child is started. + Otherwise the sbrk pointers in the parent will not agree with + the child and when user_data is (regrettably) copied over, + the user_data->ptr field will not be accurate. */ + free (malloc (4096)); +#endif + + init_child_info (PROC_FORK1, &ch, child->pid, subproc_ready); + + ch.forker_finished = forker_finished; + ch.heaptop = user_data->heaptop; + ch.heapbase = user_data->heapbase; + ch.heapptr = user_data->heapptr; + + stack_base (ch); + + /* Initialize things that are done later in dll_crt0_1 that aren't done + for the forkee. */ + strcpy(child->progname, myself->progname); + + STARTUPINFO si = {0}; + + si.cb = sizeof (STARTUPINFO); + si.lpReserved2 = (LPBYTE)&ch; + si.cbReserved2 = sizeof(ch); + + int c_flags = GetPriorityClass (hMainProc) /*| + CREATE_NEW_PROCESS_GROUP*/; + + /* If we don't have a console, then don't create a console for the + child either. */ + HANDLE console_handle = CreateFileA ("CONOUT$", GENERIC_WRITE, + FILE_SHARE_WRITE, &sec_none_nih, + OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, + NULL); + + syscall_printf ("CreateProcessA (%s, %s,0,0,1,%x, 0,0,%p,%p)", + myself->progname, myself->progname, c_flags, &si, &pi); + if (console_handle != INVALID_HANDLE_VALUE && console_handle != 0) + CloseHandle (console_handle); + else + c_flags |= DETACHED_PROCESS; + + hParent = NULL; + if (!DuplicateHandle (hMainProc, hMainProc, hMainProc, &hParent, 0, 1, + DUPLICATE_SAME_ACCESS)) + { + system_printf ("couldn't create handle to myself for child, %E"); + goto cleanup; + } + + rc = CreateProcessA (myself->progname, /* image to run */ + myself->progname, /* what we send in arg0 */ + &sec_none_nih, /* process security attrs */ + &sec_none_nih, /* thread security attrs */ + TRUE, /* inherit handles from parent */ + c_flags, + NULL, /* environment filled in later */ + 0, /* use current drive/directory */ + &si, + &pi); + + CloseHandle (hParent); + + if (!rc) + { + __seterrno (); + syscall_printf ("-1 = fork(), CreateProcessA failed"); + child->process_state = PID_NOT_IN_USE; + ForceCloseHandle(subproc_ready); + ForceCloseHandle(forker_finished); + subproc_ready = forker_finished = NULL; + return -1; + } + + ProtectHandle (pi.hThread); + /* Protect the handle but name it similarly to the way it will + be called in subproc handling. */ + ProtectHandle1 (pi.hProcess, childhProc); + + /* Fill in fields in the child's process table entry. */ + child->ppid = myself->pid; + child->hProcess = pi.hProcess; + child->dwProcessId = pi.dwProcessId; + child->uid = myself->uid; + child->gid = myself->gid; + child->pgid = myself->pgid; + child->sid = myself->sid; + child->ctty = myself->ctty; + child->umask = myself->umask; + child->copysigs(myself); + child->process_state |= PID_INITIALIZING | + (myself->process_state & PID_USETTY); + memcpy (child->username, myself->username, MAX_USER_NAME); + child->psid = myself->psid; + memcpy (child->sidbuf, myself->sidbuf, 40); + memcpy (child->logsrv, myself->logsrv, 256); + memcpy (child->domain, myself->domain, MAX_COMPUTERNAME_LENGTH+1); + set_child_mmap_ptr (child); + + /* Wait for subproc to initialize itself. */ + if (!sync_with_child(pi, subproc_ready, TRUE, "waiting for longjmp")) + goto cleanup; + + /* CHILD IS STOPPED */ + debug_printf ("child is alive (but stopped)"); + + /* Initialize, in order: data, bss, heap, stack, dll data, dll bss + Note: variables marked as NO_COPY will not be copied + since they are placed in a protected segment. */ + + + MALLOC_CHECK; + rc = fork_copy (pi, "user/cygwin data", + user_data->data_start, user_data->data_end, + user_data->bss_start, user_data->bss_end, + ch.heapbase, ch.heapptr, + stack_here, ch.stackbottom, + dll_data_start, dll_data_end, + dll_bss_start, dll_bss_end, NULL); + + MALLOC_CHECK; + if (!rc) + goto cleanup; + + /* Now fill data/bss of linked dll */ + DO_LINKED_DLL (p) + { + debug_printf ("copying data/bss of a linked dll"); + if (!fork_copy (pi, "linked dll data/bss", p->data_start, p->data_end, + p->bss_start, p->bss_end, + NULL)) + goto cleanup; + } + DLL_DONE; + + proc_register (child); + int load_dll = DllList::the().forkeeMustReloadDlls() && + DllList::the().numberOfOpenedDlls(); + + /* Start thread, and wait for it to reload dlls. */ + if (!resume_child (pi, forker_finished) || + !sync_with_child (pi, subproc_ready, load_dll, "child loading dlls")) + goto cleanup; + + /* child reload dlls & then write their data and bss */ + if (load_dll) + { + /* CHILD IS STOPPED */ + /* write memory of reloaded dlls */ + DO_LOADED_DLL (p) + { + debug_printf ("copying data/bss for a loaded dll"); + if (!fork_copy (pi, "loaded dll data/bss", p->data_start, p->data_end, + p->bss_start, p->bss_end, + NULL)) + goto cleanup; + } + DLL_DONE; + /* Start the child up again. */ + (void) resume_child (pi, forker_finished); + } + + ForceCloseHandle (subproc_ready); + ForceCloseHandle (pi.hThread); + ForceCloseHandle (forker_finished); + forker_finished = NULL; + pi.hThread = NULL; + + res = child->pid; + } + else + { + /**** Child *****/ + + /* We arrive here via a longjmp from "crt0". */ + (void) stack_dummy (0); // Just to make sure + debug_printf ("child is running %d", x); + + debug_printf ("self %p, pid %d, ppid %d", + myself, x, myself ? myself->ppid : -1); + + sync_with_parent ("after longjmp.", TRUE); + ProtectHandle (hParent); + +#ifdef DEBUGGING + char c; + if (GetEnvironmentVariable ("FORKDEBUG", &c, 1)) + try_to_debug (); +#endif + + /* If we've played with the stack, stacksize != 0. That means that + fork() was invoked from other than the main thread. Make sure that + when the "main" thread exits it calls do_exit, like a normal process. + Exit with a status code of 0. */ + if (child_proc_info->stacksize) + { + ((DWORD *)child_proc_info->stackbottom)[-17] = (DWORD)do_exit; + ((DWORD *)child_proc_info->stackbottom)[-15] = (DWORD)0; + } + + MALLOC_CHECK; + + dtable.fixup_after_fork (hParent); + ForceCloseHandle (hParent); + + MALLOC_CHECK; + + /* reload dlls if necessary */ + if (!DllList::the().forkeeMustReloadDlls() || + !DllList::the().numberOfOpenedDlls()) + sync_with_parent ("performed fork fixup.", FALSE); + else + { + DllList::the().forkeeLoadDlls(); + sync_with_parent ("loaded dlls", TRUE); + } + + (void) ForceCloseHandle (child_proc_info->subproc_ready); + (void) ForceCloseHandle (child_proc_info->forker_finished); + + if (recreate_mmaps_after_fork (myself->mmap_ptr)) + api_fatal ("recreate_mmaps_after_fork_failed"); + + res = 0; + /* Set thread local stuff to zero. Under Windows 95/98 this is sometimes + non-zero, for some reason. + FIXME: There is a memory leak here after a fork. */ + for (per_thread **t = threadstuff; *t; t++) + if ((*t)->clear_on_fork ()) + (*t)->set (); + + /* Initialize signal/process handling */ + sigproc_init (); + } + + + MALLOC_CHECK; + syscall_printf ("%d = fork()", res); + return res; + +/* Common cleanup code for failure cases */ +cleanup: + /* Remember to de-allocate the fd table. */ + child->process_state = PID_NOT_IN_USE; + if (pi.hProcess) + ForceCloseHandle1 (pi.hProcess, childhProc); + if (pi.hThread) + ForceCloseHandle (pi.hThread); + if (subproc_ready) + ForceCloseHandle (subproc_ready); + if (forker_finished) + ForceCloseHandle (forker_finished); + forker_finished = subproc_ready = child->hProcess = NULL; + return -1; +} + +static volatile void +grow_stack_slack () +{ + volatile char dummy[16384]; + dummy[0] = dummy[16383] = 0; // Just to make some slack in the stack +} + +#ifdef NEWVFORK +/* Dummy function to force second assignment below to actually be + carried out */ +static vfork_save * +get_vfork_val () +{ + return vfork_storage.val (); +} +#endif + +extern "C" +int +vfork () +{ +#ifndef NEWVFORK + return fork (); +#else + vfork_save *vf = get_vfork_val (); + + if (vf == NULL) + vf = vfork_storage.create (); + + if (!setjmp (vf->j)) + { + vf->pid = -1; + __asm__ volatile ("movl %%ebp,%0": "=r" (vf->vfork_ebp):); + __asm__ volatile ("movl (%%ebp),%0": "=r" (vf->caller_ebp):); + __asm__ volatile ("movl 4(%%ebp),%0": "=r" (vf->retaddr):); + return dtable.vfork_child_dup () ? 0 : -1; + } + + dtable.vfork_parent_restore (); + + vf = get_vfork_val (); + if (vf->pid < 0) + { + int exitval = -vf->pid; + if ((vf->pid = fork ()) == 0) + exit (exitval); + } + + vf->vfork_ebp[0] = vf->caller_ebp; + vf->vfork_ebp[1] = vf->retaddr; + return vf->pid; +#endif +} |