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cosmopolitan/libc/calls/sig.c
Justine Tunney ec480f5aa0
Make improvements 
- Every unit test now passes on Apple Silicon. The final piece of this
  puzzle was porting our POSIX threads cancelation support, since that
  works differently on ARM64 XNU vs. AMD64. Our semaphore support on
  Apple Silicon is also superior now compared to AMD64, thanks to the
  grand central dispatch library which lets *NSYNC locks go faster.

- The Cosmopolitan runtime is now more stable, particularly on Windows.
  To do this, thread local storage is mandatory at all runtime levels,
  and the innermost packages of the C library is no longer being built
  using ASAN. TLS is being bootstrapped with a 128-byte TIB during the
  process startup phase, and then later on the runtime re-allocates it
  either statically or dynamically to support code using _Thread_local.
  fork() and execve() now do a better job cooperating with threads. We
  can now check how much stack memory is left in the process or thread
  when functions like kprintf() / execve() etc. call alloca(), so that
  ENOMEM can be raised, reduce a buffer size, or just print a warning.

- POSIX signal emulation is now implemented the same way kernels do it
  with pthread_kill() and raise(). Any thread can interrupt any other
  thread, regardless of what it's doing. If it's blocked on read/write
  then the killer thread will cancel its i/o operation so that EINTR can
  be returned in the mark thread immediately. If it's doing a tight CPU
  bound operation, then that's also interrupted by the signal delivery.
  Signal delivery works now by suspending a thread and pushing context
  data structures onto its stack, and redirecting its execution to a
  trampoline function, which calls SetThreadContext(GetCurrentThread())
  when it's done.

- We're now doing a better job managing locks and handles. On NetBSD we
  now close semaphore file descriptors in forked children. Semaphores on
  Windows can now be canceled immediately, which means mutexes/condition
  variables will now go faster. Apple Silicon semaphores can be canceled
  too. We're now using Apple's pthread_yield() funciton. Apple _nocancel
  syscalls are now used on XNU when appropriate to ensure pthread_cancel
  requests aren't lost. The MbedTLS library has been updated to support
  POSIX thread cancelations. See tool/build/runitd.c for an example of
  how it can be used for production multi-threaded tls servers. Handles
  on Windows now leak less often across processes. All i/o operations on
  Windows are now overlapped, which means file pointers can no longer be
  inherited across dup() and fork() for the time being.

- We now spawn a thread on Windows to deliver SIGCHLD and wakeup wait4()
  which means, for example, that posix_spawn() now goes 3x faster. POSIX
  spawn is also now more correct. Like Musl, it's now able to report the
  failure code of execve() via a pipe although our approach favors using
  shared memory to do that on systems that have a true vfork() function.

- We now spawn a thread to deliver SIGALRM to threads when setitimer()
  is used. This enables the most precise wakeups the OS makes possible.

- The Cosmopolitan runtime now uses less memory. On NetBSD for example,
  it turned out the kernel would actually commit the PT_GNU_STACK size
  which caused RSS to be 6mb for every process. Now it's down to ~4kb.
  On Apple Silicon, we reduce the mandatory upstream thread size to the
  smallest possible size to reduce the memory overhead of Cosmo threads.
  The examples directory has a program called greenbean which can spawn
  a web server on Linux with 10,000 worker threads and have the memory
  usage of the process be ~77mb. The 1024 byte overhead of POSIX-style
  thread-local storage is now optional; it won't be allocated until the
  pthread_setspecific/getspecific functions are called. On Windows, the
  threads that get spawned which are internal to the libc implementation
  use reserve rather than commit memory, which shaves a few hundred kb.

- sigaltstack() is now supported on Windows, however it's currently not
  able to be used to handle stack overflows, since crash signals are
  still generated by WIN32. However the crash handler will still switch
  to the alt stack, which is helpful in environments with tiny threads.

- Test binaries are now smaller. Many of the mandatory dependencies of
  the test runner have been removed. This ensures many programs can do a
  better job only linking the the thing they're testing. This caused the
  test binaries for LIBC_FMT for example, to decrease from 200kb to 50kb

- long double is no longer used in the implementation details of libc,
  except in the APIs that define it. The old code that used long double
  for time (instead of struct timespec) has now been thoroughly removed.

- ShowCrashReports() is now much tinier in MODE=tiny. Instead of doing
  backtraces itself, it'll just print a command you can run on the shell
  using our new `cosmoaddr2line` program to view the backtrace.

- Crash report signal handling now works in a much better way. Instead
  of terminating the process, it now relies on SA_RESETHAND so that the
  default SIG_IGN behavior can terminate the process if necessary.

- Our pledge() functionality has now been fully ported to AARCH64 Linux.
2023-09-18 21:04:47 -07:00

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 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 "libc/sysv/consts/sig.h"
#include "ape/sections.internal.h"
#include "libc/atomic.h"
#include "libc/calls/blockcancel.internal.h"
#include "libc/calls/blocksigs.internal.h"
#include "libc/calls/calls.h"
#include "libc/calls/sig.internal.h"
#include "libc/calls/state.internal.h"
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/siginfo.h"
#include "libc/calls/struct/ucontext.internal.h"
#include "libc/calls/ucontext.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/fmt/itoa.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/describebacktrace.internal.h"
#include "libc/intrin/kprintf.h"
#include "libc/intrin/popcnt.h"
#include "libc/intrin/strace.internal.h"
#include "libc/intrin/weaken.h"
#include "libc/nt/console.h"
#include "libc/nt/enum/context.h"
#include "libc/nt/enum/exceptionhandleractions.h"
#include "libc/nt/enum/signal.h"
#include "libc/nt/enum/status.h"
#include "libc/nt/errors.h"
#include "libc/nt/runtime.h"
#include "libc/nt/signals.h"
#include "libc/nt/struct/context.h"
#include "libc/nt/struct/ntexceptionpointers.h"
#include "libc/nt/synchronization.h"
#include "libc/nt/thread.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/sa.h"
#include "libc/sysv/consts/sicode.h"
#include "libc/sysv/consts/ss.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/tls.h"
#ifdef __x86_64__
struct SignalFrame {
struct PosixThread *pt;
struct NtContext *nc;
unsigned rva;
unsigned flags;
siginfo_t si;
};
struct ContextFrame {
struct SignalFrame sf;
struct NtContext nc;
};
void __stack_call(int, siginfo_t *, void *, long,
void (*)(int, siginfo_t *, void *), void *);
static textwindows bool __sig_ignored_by_default(int sig) {
return sig == SIGURG || //
sig == SIGCONT || //
sig == SIGCHLD || //
sig == SIGWINCH;
}
textwindows bool __sig_ignored(int sig) {
return __sighandrvas[sig] == (intptr_t)SIG_IGN ||
(__sighandrvas[sig] == (intptr_t)SIG_DFL &&
__sig_ignored_by_default(sig));
}
static textwindows bool __sig_should_use_altstack(unsigned flags,
struct CosmoTib *tib) {
return (flags & SA_ONSTACK) && //
tib->tib_sigstack_size && //
!(tib->tib_sigstack_flags & (SS_DISABLE | SS_ONSTACK));
}
static textwindows wontreturn void __sig_terminate(int sig) {
TerminateThisProcess(sig);
}
static textwindows bool __sig_start(struct PosixThread *pt, int sig,
unsigned *rva, unsigned *flags) {
*rva = __sighandrvas[sig];
*flags = __sighandflags[sig];
if (*rva == (intptr_t)SIG_IGN ||
(*rva == (intptr_t)SIG_DFL && __sig_ignored_by_default(sig))) {
STRACE("ignoring %G", sig);
return false;
}
if (pt->tib->tib_sigmask & (1ull << (sig - 1))) {
STRACE("tid %d masked %G delivering to tib_sigpending", _pthread_tid(pt),
sig);
pt->tib->tib_sigpending |= 1ull << (sig - 1);
return false;
}
if (*rva == (intptr_t)SIG_DFL) {
STRACE("terminating on %G due to no handler", sig);
__sig_terminate(sig);
}
if (*flags & SA_RESETHAND) {
STRACE("resetting %G handler", sig);
__sighandrvas[sig] = (int32_t)(intptr_t)SIG_DFL;
}
return true;
}
static textwindows void __sig_call(int sig, siginfo_t *si, ucontext_t *ctx,
unsigned rva, unsigned flags,
struct CosmoTib *tib) {
sigaction_f handler;
handler = (sigaction_f)(__executable_start + rva);
++__sig.count;
if (__sig_should_use_altstack(flags, tib)) {
tib->tib_sigstack_flags |= SS_ONSTACK;
__stack_call(sig, si, ctx, 0, handler,
tib->tib_sigstack_addr + tib->tib_sigstack_size);
tib->tib_sigstack_flags &= ~SS_ONSTACK;
} else {
handler(sig, si, ctx);
}
}
textwindows int __sig_raise(int sig, int sic) {
unsigned rva, flags;
struct CosmoTib *tib = __get_tls();
struct PosixThread *pt = (struct PosixThread *)tib->tib_pthread;
ucontext_t ctx = {.uc_sigmask.__bits[0] = tib->tib_sigmask};
if (!__sig_start(pt, sig, &rva, &flags)) return 0;
siginfo_t si = {.si_signo = sig, .si_code = sic};
struct NtContext nc;
nc.ContextFlags = kNtContextAll;
GetThreadContext(GetCurrentThread(), &nc);
_ntcontext2linux(&ctx, &nc);
STRACE("raising %G", sig);
if (!(flags & SA_NODEFER)) {
tib->tib_sigmask |= 1ull << (sig - 1);
}
__sig_call(sig, &si, &ctx, rva, flags, tib);
tib->tib_sigmask = ctx.uc_sigmask.__bits[0];
return (flags & SA_RESTART) ? 2 : 1;
}
textwindows void __sig_cancel(struct PosixThread *pt, unsigned flags) {
atomic_int *futex;
if (_weaken(WakeByAddressSingle) &&
(futex = atomic_load_explicit(&pt->pt_futex, memory_order_acquire))) {
_weaken(WakeByAddressSingle)(futex);
} else if (!(flags & SA_RESTART) && pt->iohandle > 0) {
pt->abort_errno = EINTR;
if (!CancelIoEx(pt->iohandle, pt->ioverlap)) {
int err = GetLastError();
if (err != kNtErrorNotFound) {
STRACE("CancelIoEx() failed w/ %d", err);
}
}
} else if (pt->pt_flags & PT_INSEMAPHORE) {
pt->abort_errno = EINTR;
if (!ReleaseSemaphore(pt->semaphore, 1, 0)) {
STRACE("ReleaseSemaphore() failed w/ %d", GetLastError());
}
}
}
static textwindows wontreturn void __sig_panic(const char *msg) {
#ifndef TINY
char s[128], *p = s;
p = stpcpy(p, "sig panic: ");
p = stpcpy(p, msg);
p = stpcpy(p, " failed w/ ");
p = FormatInt32(p, GetLastError());
*p++ = '\n';
WriteFile(GetStdHandle(kNtStdErrorHandle), s, p - s, 0, 0);
#endif
TerminateThisProcess(SIGVTALRM);
}
static textwindows wontreturn void __sig_tramp(struct SignalFrame *sf) {
ucontext_t ctx = {0};
sigaction_f handler = (sigaction_f)(__executable_start + sf->rva);
STRACE("__sig_tramp(%G, %t)", sf->si.si_signo, handler);
_ntcontext2linux(&ctx, sf->nc);
ctx.uc_sigmask.__bits[0] = sf->pt->tib->tib_sigmask;
if (!(sf->flags & SA_NODEFER)) {
sf->pt->tib->tib_sigmask |= 1ull << (sf->si.si_signo - 1);
}
++__sig.count;
handler(sf->si.si_signo, &sf->si, &ctx);
sf->pt->tib->tib_sigmask = ctx.uc_sigmask.__bits[0];
_ntlinux2context(sf->nc, &ctx);
SetThreadContext(GetCurrentThread(), sf->nc);
__sig_panic("SetThreadContext(GetCurrentThread)");
}
static textwindows int __sig_killer(struct PosixThread *pt, int sig, int sic) {
uintptr_t th;
unsigned rva, flags;
if (!__sig_start(pt, sig, &rva, &flags)) return 0;
th = _pthread_syshand(pt);
uint32_t old_suspend_count;
old_suspend_count = SuspendThread(th);
if (old_suspend_count == -1u) {
STRACE("SuspendThread failed w/ %d", GetLastError());
return ESRCH;
}
if (old_suspend_count) {
STRACE("kill contention of %u on tid %d", old_suspend_count,
_pthread_tid(pt));
pt->tib->tib_sigpending |= 1ull << (sig - 1);
return 0;
}
struct NtContext nc;
nc.ContextFlags = kNtContextAll;
if (!GetThreadContext(th, &nc)) {
STRACE("GetThreadContext failed w/ %d", GetLastError());
return ESRCH;
}
uintptr_t sp;
if (__sig_should_use_altstack(flags, pt->tib)) {
pt->tib->tib_sigstack_flags |= SS_ONSTACK;
sp = (uintptr_t)pt->tib->tib_sigstack_addr + pt->tib->tib_sigstack_size;
pt->tib->tib_sigstack_flags &= ~SS_ONSTACK;
} else {
sp = (nc.Rsp - 128 - sizeof(struct ContextFrame)) & -16;
}
struct ContextFrame *cf = (struct ContextFrame *)sp;
bzero(&cf->sf.si, sizeof(cf->sf.si));
memcpy(&cf->nc, &nc, sizeof(nc));
cf->sf.pt = pt;
cf->sf.rva = rva;
cf->sf.nc = &cf->nc;
cf->sf.flags = flags;
cf->sf.si.si_code = sic;
cf->sf.si.si_signo = sig;
*(uintptr_t *)(sp -= sizeof(uintptr_t)) = nc.Rip;
nc.Rip = (intptr_t)__sig_tramp;
nc.Rdi = (intptr_t)&cf->sf;
nc.Rsp = sp;
if (!SetThreadContext(th, &nc)) {
STRACE("SetThreadContext failed w/ %d", GetLastError());
return ESRCH;
}
ResumeThread(th); // doesn't actually resume if doing blocking i/o
__sig_cancel(pt, flags); // we can wake it up immediately by canceling it
return 0;
}
textwindows int __sig_kill(struct PosixThread *pt, int sig, int sic) {
int rc;
BLOCK_SIGNALS;
BLOCK_CANCELLATIONS;
rc = __sig_killer(pt, sig, sic);
ALLOW_CANCELLATIONS;
ALLOW_SIGNALS;
return rc;
}
textwindows void __sig_generate(int sig, int sic) {
struct Dll *e;
struct PosixThread *pt, *mark = 0;
if (__sig_ignored(sig)) {
STRACE("ignoring %G", sig);
return;
}
if (__sighandrvas[sig] == (intptr_t)SIG_DFL) {
STRACE("terminating on %G due to no handler", sig);
__sig_terminate(sig);
}
pthread_spin_lock(&_pthread_lock);
for (e = dll_first(_pthread_list); e; e = dll_next(_pthread_list, e)) {
pt = POSIXTHREAD_CONTAINER(e);
if (atomic_load_explicit(&pt->status, memory_order_acquire) <
kPosixThreadTerminated &&
!(pt->tib->tib_sigmask & (1ull << (sig - 1)))) {
mark = pt;
break;
}
}
pthread_spin_unlock(&_pthread_lock);
if (mark) {
__sig_kill(mark, sig, sic);
} else {
STRACE("all threads block %G so adding to pending signals of process", sig);
__sig.pending |= sig;
}
}
static int __sig_crash_sig(struct NtExceptionPointers *ep, int *code) {
switch (ep->ExceptionRecord->ExceptionCode) {
case kNtSignalBreakpoint:
*code = TRAP_BRKPT;
return SIGTRAP;
case kNtSignalIllegalInstruction:
*code = ILL_ILLOPC;
return SIGILL;
case kNtSignalPrivInstruction:
*code = ILL_PRVOPC;
return SIGILL;
case kNtSignalGuardPage:
case kNtSignalInPageError:
case kNtStatusStackOverflow:
*code = SEGV_MAPERR;
return SIGSEGV;
case kNtSignalAccessViolation:
*code = SEGV_ACCERR;
return SIGSEGV;
case kNtSignalInvalidHandle:
case kNtSignalInvalidParameter:
case kNtSignalAssertionFailure:
*code = SI_USER;
return SIGABRT;
case kNtStatusIntegerOverflow:
*code = FPE_INTOVF;
return SIGFPE;
case kNtSignalFltDivideByZero:
*code = FPE_FLTDIV;
return SIGFPE;
case kNtSignalFltOverflow:
*code = FPE_FLTOVF;
return SIGFPE;
case kNtSignalFltUnderflow:
*code = FPE_FLTUND;
return SIGFPE;
case kNtSignalFltInexactResult:
*code = FPE_FLTRES;
return SIGFPE;
case kNtSignalFltDenormalOperand:
case kNtSignalFltInvalidOperation:
case kNtSignalFltStackCheck:
case kNtSignalIntegerDivideByZero:
case kNtSignalFloatMultipleFaults:
case kNtSignalFloatMultipleTraps:
*code = FPE_FLTINV;
return SIGFPE;
case kNtSignalDllNotFound:
case kNtSignalOrdinalNotFound:
case kNtSignalEntrypointNotFound:
case kNtSignalDllInitFailed:
*code = SI_KERNEL;
return SIGSYS;
default:
*code = ep->ExceptionRecord->ExceptionCode;
return SIGSEGV;
}
}
// abashed the devil stood, and felt how awful goodness is
__msabi unsigned __sig_crash(struct NtExceptionPointers *ep) {
int code, sig = __sig_crash_sig(ep, &code);
STRACE("win32 vectored exception 0x%08Xu raising %G "
"cosmoaddr2line %s %lx %s",
ep->ExceptionRecord->ExceptionCode, sig, program_invocation_name,
ep->ContextRecord->Rip,
DescribeBacktrace((struct StackFrame *)ep->ContextRecord->Rbp));
if (sig == SIGTRAP) {
ep->ContextRecord->Rip++;
if (__sig_ignored(sig)) {
return kNtExceptionContinueExecution;
}
}
struct PosixThread *pt = _pthread_self();
siginfo_t si = {.si_signo = sig,
.si_code = code,
.si_addr = ep->ExceptionRecord->ExceptionAddress};
unsigned rva = __sighandrvas[sig];
unsigned flags = __sighandflags[sig];
if (rva == (intptr_t)SIG_DFL || rva == (intptr_t)SIG_IGN) {
#ifndef TINY
intptr_t hStderr;
char sigbuf[21], s[128], *p;
hStderr = GetStdHandle(kNtStdErrorHandle);
p = stpcpy(s, "Terminating on uncaught ");
p = stpcpy(p, strsignal_r(sig, sigbuf));
p = stpcpy(p, ". Pass --strace and/or ShowCrashReports() for details.\n");
WriteFile(hStderr, s, p - s, 0, 0);
#endif
__sig_terminate(sig);
}
if (flags & SA_RESETHAND) {
STRACE("resetting %G handler", sig);
__sighandrvas[sig] = (int32_t)(intptr_t)SIG_DFL;
}
ucontext_t ctx = {0};
_ntcontext2linux(&ctx, ep->ContextRecord);
ctx.uc_sigmask.__bits[0] = pt->tib->tib_sigmask;
__sig_call(sig, &si, &ctx, rva, flags, pt->tib);
pt->tib->tib_sigmask = ctx.uc_sigmask.__bits[0];
_ntlinux2context(ep->ContextRecord, &ctx);
return kNtExceptionContinueExecution;
}
static textwindows int __sig_console_sig(uint32_t dwCtrlType) {
switch (dwCtrlType) {
case kNtCtrlCEvent:
return SIGINT;
case kNtCtrlBreakEvent:
return SIGQUIT;
case kNtCtrlCloseEvent:
case kNtCtrlLogoffEvent: // only received by services
case kNtCtrlShutdownEvent: // only received by services
return SIGHUP;
default:
return SIGSTKFLT;
}
}
__msabi textwindows dontinstrument bool32 __sig_console(uint32_t dwCtrlType) {
struct CosmoTib tls;
__bootstrap_tls(&tls, __builtin_frame_address(0));
__sig_generate(__sig_console_sig(dwCtrlType), SI_KERNEL);
return true;
}
static textwindows int __sig_checkem(atomic_ulong *sigs, struct CosmoTib *tib,
const char *thing, int id) {
bool handler_was_called = false;
uint64_t pending, masked, deliverable;
pending = atomic_load_explicit(sigs, memory_order_acquire);
masked = atomic_load_explicit(&tib->tib_sigmask, memory_order_acquire);
deliverable = pending & ~masked;
POLLTRACE("%s %d blocks %d sigs w/ %d pending and %d deliverable", thing, id,
popcnt(masked), popcnt(pending), popcnt(deliverable));
if (deliverable) {
for (int sig = 1; sig <= 64; ++sig) {
if ((deliverable & (1ull << (sig - 1))) &&
atomic_fetch_and(sigs, ~(1ull << (sig - 1))) & (1ull << (sig - 1))) {
handler_was_called |= __sig_raise(sig, SI_KERNEL);
}
}
}
return handler_was_called;
}
// returns 0 if no signal handlers were called, otherwise a bitmask
// consisting of `1` which means a signal handler was invoked which
// didn't have the SA_RESTART flag, and `2`, which means SA_RESTART
// handlers were called (or `3` if both were the case).
textwindows int __sig_check(void) {
bool handler_was_called = false;
struct CosmoTib *tib = __get_tls();
handler_was_called |=
__sig_checkem(&tib->tib_sigpending, tib, "tid", tib->tib_tid);
handler_was_called |= __sig_checkem(&__sig.pending, tib, "pid", getpid());
POLLTRACE("__sig_check() → %hhhd", handler_was_called);
return handler_was_called;
}
textstartup void __sig_init(void) {
if (!IsWindows()) return;
AddVectoredExceptionHandler(true, (void *)__sig_crash);
SetConsoleCtrlHandler((void *)__sig_console, true);
}
const void *const __sig_ctor[] initarray = {__sig_init};
#endif /* __x86_64__ */
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