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cosmopolitan/libc/proc/fork-nt.c
Justine Tunney 624573207e
Make threads faster and more reliable 
This change doubles the performance of thread spawning. That's thanks to
our new stack manager, which allows us to avoid zeroing stacks. It gives
us 15µs spawns rather than 30µs spawns on Linux. Also, pthread_exit() is
faster now, since it doesn't need to acquire the pthread GIL. On NetBSD,
that helps us avoid allocating too many semaphores. Even if that happens
we're now able to survive semaphores running out and even memory running
out, when allocating *NSYNC waiter objects. I found a lot more rare bugs
in the POSIX threads runtime that could cause things to crash, if you've
got dozens of threads all spawning and joining dozens of threads. I want
cosmo to be world class production worthy for 2025 so happy holidays all
2024-12-21 22:13:00 -08:00

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/*-*- 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.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/tls.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());
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) {
intptr_t jb[5];
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
__builtin_longjmp(jb, 1);
}
textwindows int sys_fork_nt(uint32_t dwCreationFlags) {
char ok;
char **args;
int rc = -1;
intptr_t jb[5];
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 (!__builtin_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(&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
WipeKeystrokes();
// 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__ */
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