/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "ape/sections.internal.h"
#include "libc/assert.h"
#include "libc/atomic.h"
#include "libc/calls/internal.h"
#include "libc/calls/sig.internal.h"
#include "libc/calls/state.internal.h"
#include "libc/calls/syscall_support-nt.internal.h"
#include "libc/errno.h"
#include "libc/fmt/itoa.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/directmap.h"
#include "libc/intrin/kprintf.h"
#include "libc/intrin/maps.h"
#include "libc/intrin/strace.h"
#include "libc/intrin/tree.h"
#include "libc/intrin/weaken.h"
#include "libc/macros.h"
#include "libc/nt/createfile.h"
#include "libc/nt/enum/accessmask.h"
#include "libc/nt/enum/creationdisposition.h"
#include "libc/nt/enum/filemapflags.h"
#include "libc/nt/enum/pageflags.h"
#include "libc/nt/enum/startf.h"
#include "libc/nt/errors.h"
#include "libc/nt/ipc.h"
#include "libc/nt/memory.h"
#include "libc/nt/process.h"
#include "libc/nt/runtime.h"
#include "libc/nt/signals.h"
#include "libc/nt/struct/ntexceptionpointers.h"
#include "libc/nt/thread.h"
#include "libc/nt/thunk/msabi.h"
#include "libc/proc/ntspawn.h"
#include "libc/proc/proc.internal.h"
#include "libc/runtime/internal.h"
#include "libc/runtime/memtrack.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/stack.h"
#include "libc/runtime/symbols.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/at.h"
#include "libc/sysv/consts/limits.h"
#include "libc/sysv/consts/map.h"
#include "libc/sysv/consts/prot.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/itimer.internal.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/tls.h"
#include "libc/thread/tls2.internal.h"
#ifdef __x86_64__

extern long __klog_handle;
void WipeKeystrokes(void);
__msabi extern typeof(GetCurrentProcessId) *const __imp_GetCurrentProcessId;

static textwindows wontreturn void AbortFork(const char *func, void *addr) {
#if SYSDEBUG
  kprintf("fork() %!s(%lx) failed with win32 error %u\n", func, addr,
          GetLastError());
#endif
  TerminateThisProcess(SIGSTKFLT);
}

static textwindows char16_t *ParseInt(char16_t *p, int64_t *x) {
  *x = 0;
  while (*p == ' ')
    p++;
  while ('0' <= *p && *p <= '9') {
    *x *= 10;
    *x += *p++ - '0';
  }
  return p;
}

static inline textwindows ssize_t ForkIo(int64_t h, char *p, size_t n,
                                         bool32 (*f)(int64_t, void *, uint32_t,
                                                     uint32_t *,
                                                     struct NtOverlapped *)) {
  size_t i;
  uint32_t x;
  for (i = 0; i < n; i += x) {
    if (!f(h, p + i, n - i, &x, 0))
      return __winerr();
    if (!x)
      break;
  }
  return i;
}

static dontinline textwindows ssize_t ForkIo2(
    int64_t h, void *buf, size_t n,
    bool32 (*fn)(int64_t, void *, uint32_t, uint32_t *, struct NtOverlapped *),
    const char *sf, bool ischild) {
  ssize_t rc = ForkIo(h, buf, n, fn);
  if (ischild) {
    // prevent crashes
    __tls_enabled = false;
    __pid = __imp_GetCurrentProcessId();
    __klog_handle = 0;
    __maps.maps = 0;
  }
  NTTRACE("%s(%ld, %p, %'zu) → %'zd% m", sf, h, buf, n, rc);
  return rc;
}

static dontinline textwindows bool WriteAll(int64_t h, void *buf, size_t n) {
  bool ok;
  ok = ForkIo2(h, buf, n, (void *)WriteFile, "WriteFile", false) != -1;
  if (!ok) {
    STRACE("fork() failed in parent due to WriteAll(%ld, %p, %'zu) → %u", h,
           buf, n, GetLastError());
    __print_maps(0);
  }
  return ok;
}

static textwindows dontinline void ReadOrDie(int64_t h, void *buf, size_t n) {
  ssize_t got;
  if ((got = ForkIo2(h, buf, n, ReadFile, "ReadFile", true)) == -1)
    AbortFork("ReadFile1", buf);
  if (got != n)
    AbortFork("ReadFile2", buf);
}

static textwindows int64_t MapOrDie(uint32_t prot, uint64_t size) {
  int64_t h;
  for (;;) {
    if ((h = CreateFileMapping(-1, 0, prot, size >> 32, size, 0)))
      return h;
    if (GetLastError() == kNtErrorAccessDenied) {
      switch (prot) {
        case kNtPageExecuteWritecopy:
          prot = kNtPageWritecopy;
          continue;
        case kNtPageExecuteReadwrite:
          prot = kNtPageReadwrite;
          continue;
        case kNtPageExecuteRead:
          prot = kNtPageReadonly;
          continue;
        default:
          break;
      }
    }
    AbortFork("MapOrDie", (void *)size);
  }
}

static textwindows void ViewOrDie(int64_t h, uint32_t access, size_t pos,
                                  size_t size, void *base) {
TryAgain:
  if (!MapViewOfFileEx(h, access, pos >> 32, pos, size, base)) {
    if ((access & kNtFileMapExecute) &&
        GetLastError() == kNtErrorAccessDenied) {
      access &= ~kNtFileMapExecute;
      goto TryAgain;
    }
    AbortFork("ViewOrDie", base);
  }
}

static __msabi textwindows int OnForkCrash(struct NtExceptionPointers *ep) {
  kprintf("error: fork() child crashed!%n"
          "\tExceptionCode = %#x%n"
          "\tRip = %x%n",
          ep->ExceptionRecord->ExceptionCode,
          ep->ContextRecord ? ep->ContextRecord->Rip : -1);
  TerminateThisProcess(SIGSTKFLT);
}

static textwindows void *Malloc(size_t size) {
  return HeapAlloc(GetProcessHeap(), 0, size);
}

textwindows void WinMainForked(void) {
  jmp_buf jb;
  int64_t reader;
  int64_t savetsc;
  uint32_t varlen;
  atomic_ulong *sigproc;
  char16_t fvar[21 + 1 + 21 + 1];
  struct Fds *fds = __veil("r", &g_fds);

  // save signal pointer
  sigproc = __sig.process;

  // check to see if the process was actually forked
  // this variable should have the pipe handle numba
  varlen = GetEnvironmentVariable(u"_FORK", fvar, ARRAYLEN(fvar));
  if (!varlen || varlen >= ARRAYLEN(fvar))
    return;
  /* STRACE("WinMainForked()"); */
  SetEnvironmentVariable(u"_FORK", NULL);
#if SYSDEBUG
  int64_t oncrash = AddVectoredExceptionHandler(1, (void *)OnForkCrash);
#endif
  ParseInt(fvar, &reader);

  // read the cpu state from the parent process & plus
  ReadOrDie(reader, jb, sizeof(jb));

  // read memory mappings from parent process
  struct Tree *maps = 0;
  for (;;) {
    struct Map *map = Malloc(sizeof(struct Map));
    ReadOrDie(reader, map, sizeof(struct Map));
    if (map->addr == MAP_FAILED)
      break;
    tree_insert(&maps, &map->tree, __maps_compare);
  }

  // map memory into process
  int granularity = __gransize;
  for (struct Tree *e = tree_first(maps); e; e = tree_next(e)) {
    struct Map *map = MAP_TREE_CONTAINER(e);
    if ((uintptr_t)map->addr & (granularity - 1))
      continue;
    // get true length in case mprotect() chopped up actual win32 map
    size_t size = map->size;
    for (struct Tree *e2 = tree_next(e); e2; e2 = tree_next(e2)) {
      struct Map *map2 = MAP_TREE_CONTAINER(e2);
      if (map2->hand == -1 && map->addr + size == map2->addr) {
        size += map2->size;
      } else {
        break;
      }
    }
    // obtain the most permissive access possible
    unsigned prot, access;
    if (map->readonlyfile) {
      prot = kNtPageExecuteRead;
      access = kNtFileMapRead | kNtFileMapExecute;
    } else {
      prot = kNtPageExecuteReadwrite;
      access = kNtFileMapWrite | kNtFileMapExecute;
    }
    if ((map->flags & MAP_TYPE) != MAP_SHARED) {
      // we don't need to close the map handle because sys_mmap_nt
      // doesn't mark it inheritable across fork() for MAP_PRIVATE
      map->hand = MapOrDie(prot, size);
      ViewOrDie(map->hand, access, 0, size, map->addr);
      ReadOrDie(reader, map->addr, size);
    } else {
      // we can however safely inherit MAP_SHARED with zero copy
      ViewOrDie(map->hand, access, map->off, size, map->addr);
    }
  }

  // read the .data and .bss program image sections
  savetsc = kStartTsc;
  ReadOrDie(reader, __data_start, __data_end - __data_start);
  ReadOrDie(reader, __bss_start, __bss_end - __bss_start);
  kStartTsc = savetsc;
  __tls_enabled = false;

  // fixup memory manager
  __maps.maps = 0;
  __maps.freed = 0;
  __maps.count = 0;
  __maps.pages = 0;
  for (struct Tree *e = tree_first(maps); e; e = tree_next(e)) {
    struct Map *map = MAP_TREE_CONTAINER(e);
    __maps.count += 1;
    __maps.pages += (map->size + __pagesize - 1) / __pagesize;
    unsigned old_protect;
    if (!VirtualProtect(map->addr, map->size, __prot2nt(map->prot, map->iscow),
                        &old_protect))
      AbortFork("VirtualProtect", map->addr);
  }
  __maps.maps = maps;
  __maps_init();

  // mitosis complete
  if (!CloseHandle(reader))
    AbortFork("CloseHandle", (void *)reader);

  // rewrap the stdin named pipe hack
  // since the handles closed on fork
  fds->p[0].handle = GetStdHandle(kNtStdInputHandle);
  fds->p[1].handle = GetStdHandle(kNtStdOutputHandle);
  fds->p[2].handle = GetStdHandle(kNtStdErrorHandle);

  // restore signal pointer
  __sig.process = sigproc;

  // restore the crash reporting stuff
#if SYSDEBUG
  RemoveVectoredExceptionHandler(oncrash);
#endif

  // jump back into function below
  longjmp(jb, 1);
}

textwindows int sys_fork_nt(uint32_t dwCreationFlags) {
  char ok;
  jmp_buf jb;
  char **args;
  int rc = -1;
  struct Proc *proc;
  struct CosmoTib *tib;
  char16_t pipename[64];
  int64_t reader, writer;
  struct NtStartupInfo startinfo;
  struct NtProcessInformation procinfo;
  char *p, forkvar[6 + 21 + 1 + 21 + 1];
  tib = __get_tls();
  if (!(proc = __proc_new()))
    return -1;
  ftrace_enabled(-1);
  strace_enabled(-1);
  if (!setjmp(jb)) {
    reader = CreateNamedPipe(__create_pipe_name(pipename), kNtPipeAccessInbound,
                             kNtPipeTypeByte | kNtPipeReadmodeByte, 1, PIPE_BUF,
                             PIPE_BUF, 0, &kNtIsInheritable);
    writer = CreateFile(pipename, kNtGenericWrite, 0, 0, kNtOpenExisting, 0, 0);
    if (reader != -1 && writer != -1) {
      p = stpcpy(forkvar, "_FORK=");
      p = FormatUint64(p, reader);
      bzero(&startinfo, sizeof(startinfo));
      startinfo.cb = sizeof(struct NtStartupInfo);
      startinfo.dwFlags = kNtStartfUsestdhandles;
      startinfo.hStdInput = g_fds.p[0].handle;
      startinfo.hStdOutput = g_fds.p[1].handle;
      startinfo.hStdError = g_fds.p[2].handle;
      args = __argv;
#if SYSDEBUG
      int i;
      // If --strace was passed to this program, then propagate it the
      // forked process since the flag was removed by __intercept_flag
      if (strace_enabled(0) > 0) {
        int n;
        for (n = 0; args[n];)
          ++n;
#pragma GCC push_options
#pragma GCC diagnostic ignored "-Walloca-larger-than="
        int nbytes = (n + 2) * sizeof(char *);
        char **args2 = alloca(nbytes);
        CheckLargeStackAllocation(args2, nbytes);
#pragma GCC pop_options
        for (i = 0; i < n; ++i)
          args2[i] = args[i];
        args2[i++] = "--strace";
        args2[i] = 0;
        args = args2;
      }
#endif
      NTTRACE("STARTING SPAWN");
      int spawnrc = ntspawn(&(struct NtSpawnArgs){
          AT_FDCWD, GetProgramExecutableName(), args, environ,
          (char *[]){forkvar, 0}, dwCreationFlags, 0, 0, 0, 0, &startinfo,
          &procinfo});
      if (spawnrc != -1) {
        CloseHandle(procinfo.hThread);
        ok = WriteAll(writer, jb, sizeof(jb));
        // this list will be populated with the maps we're transferring
        for (struct Map *map = __maps_first(); ok && map;
             map = __maps_next(map)) {
          if (map->flags & MAP_NOFORK)
            continue;
          if (MAX((char *)__executable_start, map->addr) <
              MIN((char *)_end, map->addr + map->size))
            continue;  // executable image is loaded by windows
          ok = WriteAll(writer, map, sizeof(*map));
        }
        // send a terminating Map struct to child
        if (ok) {
          struct Map map;
          map.addr = MAP_FAILED;
          ok = WriteAll(writer, &map, sizeof(map));
        }
        // now write content of each map to child
        int granularity = __gransize;
        for (struct Map *map = __maps_first(); ok && map;
             map = __maps_next(map)) {
          if (map->flags & MAP_NOFORK)
            continue;
          // we only need to worry about the base mapping
          if ((uintptr_t)map->addr & (granularity - 1))
            continue;
          if (MAX((char *)__executable_start, map->addr) <
              MIN((char *)_end, map->addr + map->size))
            continue;  // executable image is loaded by windows
          // shared mappings don't need to be copied
          if ((map->flags & MAP_TYPE) == MAP_SHARED)
            continue;
          // get true length in case mprotect() chopped up actual win32 map
          size_t size = map->size;
          for (struct Map *map2 = __maps_next(map); map2;
               map2 = __maps_next(map2)) {
            if (map2->hand == -1 && map->addr + size == map2->addr) {
              size += map2->size;
            } else {
              break;
            }
          }
          for (struct Map *map2 = map; ok && map2; map2 = __maps_next(map2)) {
            if (!(map2->prot & PROT_READ))
              if (map->addr >= map2->addr && map->addr < map->addr + size)
                ok = VirtualProtect(
                    map2->addr, map2->size,
                    __prot2nt(map2->prot | PROT_READ, map2->iscow),
                    &map2->visited);
          }
          if (ok)
            ok = WriteAll(writer, map->addr, size);
          for (struct Map *map2 = map; ok && map2; map2 = __maps_next(map2)) {
            if (!(map2->prot & PROT_READ))
              if (map->addr >= map2->addr && map->addr < map->addr + size)
                ok = VirtualProtect(map2->addr, map2->size, map2->visited,
                                    &map2->visited);
          }
        }
        if (ok)
          ok = WriteAll(writer, __data_start, __data_end - __data_start);
        if (ok)
          ok = WriteAll(writer, __bss_start, __bss_end - __bss_start);
        if (ok) {
          if (!CloseHandle(writer))
            ok = false;
          writer = -1;
        }
        if (ok) {
          proc->wasforked = true;
          proc->handle = procinfo.hProcess;
          rc = proc->pid = procinfo.dwProcessId;
          __proc_add(proc);
        } else {
          TerminateProcess(procinfo.hProcess, SIGKILL);
          CloseHandle(procinfo.hProcess);
          rc = -1;
        }
      }
    }
    if (reader != -1)
      CloseHandle(reader);
    if (writer != -1)
      CloseHandle(writer);
    if (rc == -1 && errno != ENOMEM)
      eagain();  // posix fork() only specifies two errors
  } else {
    rc = 0;
    // re-apply code morphing for thread-local storage
    __tls_index = TlsAlloc();
    __set_tls_win32(tib);
    __morph_tls();
    __tls_enabled = true;
    // the child's pending signals is initially empty
    atomic_store_explicit(__sig.process, 0, memory_order_relaxed);
    atomic_store_explicit(&tib->tib_sigpending, 0, memory_order_relaxed);
    // re-apply code morphing for function tracing
    if (ftrace_stackdigs)
      _weaken(__hook)(_weaken(ftrace_hook), _weaken(GetSymbolTable)());
    // reset core runtime services
    __proc_wipe();
    WipeKeystrokes();
    if (_weaken(__sig_init))
      _weaken(__sig_init)();
    if (_weaken(__itimer_wipe))
      _weaken(__itimer_wipe)();
    // notify pthread join
    atomic_store_explicit(&_pthread_static.ptid, GetCurrentThreadId(),
                          memory_order_release);
  }
  if (rc == -1)
    dll_make_first(&__proc.free, &proc->elem);
  ftrace_enabled(+1);
  strace_enabled(+1);
  return rc;
}

#endif /* __x86_64__ */