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https://github.com/jart/cosmopolitan.git
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Implement signal handler tail recursion
GNU Make on Windows now appears to be working reliably. This change also fixes a bug where, after fork the Windows thread handle wasn't reset and that caused undefined behavior using SetThreadContext() with our signals
This commit is contained in:
Justine Tunney
parent
a657f3e878
commit
cdf556e7d2
15 changed files with 627 additions and 77 deletions
167
libc/calls/sig.c
167
libc/calls/sig.c
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@ -97,6 +97,32 @@ textwindows void __sig_delete(int sig) {
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ALLOW_SIGNALS;
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}
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static textwindows int __sig_getter(struct CosmoTib *tib, atomic_ulong *sigs) {
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int sig;
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sigset_t bit, pending, masked, deliverable;
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for (;;) {
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pending = atomic_load_explicit(sigs, memory_order_acquire);
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masked = atomic_load_explicit(&tib->tib_sigmask, memory_order_acquire);
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if ((deliverable = pending & ~masked)) {
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sig = _bsf(deliverable) + 1;
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bit = 1ull << (sig - 1);
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if (atomic_fetch_and_explicit(sigs, ~bit, memory_order_acq_rel) & bit) {
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return sig;
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}
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} else {
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return 0;
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}
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}
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}
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static textwindows int __sig_get(struct CosmoTib *tib) {
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int sig;
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if (!(sig = __sig_getter(tib, &tib->tib_sigpending))) {
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sig = __sig_getter(tib, &__sig.pending);
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}
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return sig;
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}
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static textwindows bool __sig_should_use_altstack(unsigned flags,
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struct CosmoTib *tib) {
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if (!(flags & SA_ONSTACK)) {
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@ -146,34 +172,49 @@ static textwindows sigaction_f __sig_handler(unsigned rva) {
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}
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textwindows int __sig_raise(int sig, int sic) {
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unsigned rva, flags;
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// create machine context object
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struct PosixThread *pt = _pthread_self();
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ucontext_t ctx = {.uc_sigmask = pt->tib->tib_sigmask};
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if (!__sig_start(pt, sig, &rva, &flags)) return 0;
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if (flags & SA_RESETHAND) {
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STRACE("resetting %G handler", sig);
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__sighandrvas[sig] = (int32_t)(intptr_t)SIG_DFL;
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}
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siginfo_t si = {.si_signo = sig, .si_code = sic};
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struct NtContext nc;
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nc.ContextFlags = kNtContextFull;
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GetThreadContext(GetCurrentThread(), &nc);
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_ntcontext2linux(&ctx, &nc);
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pt->tib->tib_sigmask |= __sighandmask[sig];
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if (!(flags & SA_NODEFER)) {
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pt->tib->tib_sigmask |= 1ull << (sig - 1);
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}
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NTTRACE("entering raise(%G) signal handler %t with mask %s → %s", sig,
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__sig_handler(rva), DescribeSigset(0, &ctx.uc_sigmask),
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DescribeSigset(0, (sigset_t *)&pt->tib->tib_sigmask));
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__sig_handler(rva)(sig, &si, &ctx);
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NTTRACE("leaving raise(%G) signal handler %t with mask %s → %s", sig,
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__sig_handler(rva),
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DescribeSigset(0, (sigset_t *)&pt->tib->tib_sigmask),
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DescribeSigset(0, &ctx.uc_sigmask));
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atomic_store_explicit(&pt->tib->tib_sigmask, ctx.uc_sigmask,
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memory_order_release);
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return (flags & SA_RESTART) ? 2 : 1;
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// process signal(s)
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int handler_was_called = 0;
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do {
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// start the signal
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unsigned rva, flags;
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if (__sig_start(pt, sig, &rva, &flags)) {
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if (flags & SA_RESETHAND) {
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STRACE("resetting %G handler", sig);
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__sighandrvas[sig] = (int32_t)(intptr_t)SIG_DFL;
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}
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// update the signal mask in preparation for signal handller
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sigset_t blocksigs = __sighandmask[sig];
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if (!(flags & SA_NODEFER)) blocksigs |= 1ull << (sig - 1);
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ctx.uc_sigmask = atomic_fetch_or_explicit(
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&pt->tib->tib_sigmask, blocksigs, memory_order_acq_rel);
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// call the user's signal handler
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char ssbuf[2][128];
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siginfo_t si = {.si_signo = sig, .si_code = sic};
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STRACE("__sig_raise(%G, %t) mask %s → %s", sig, __sig_handler(rva),
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(DescribeSigset)(ssbuf[0], 0, &ctx.uc_sigmask),
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(DescribeSigset)(ssbuf[1], 0, (sigset_t *)&pt->tib->tib_sigmask));
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__sig_handler(rva)(sig, &si, &ctx);
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(void)ssbuf;
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// restore the original signal mask
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atomic_store_explicit(&pt->tib->tib_sigmask, ctx.uc_sigmask,
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memory_order_release);
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handler_was_called |= (flags & SA_RESTART) ? 2 : 1;
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}
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sic = SI_KERNEL;
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} while ((sig = __sig_get(pt->tib)));
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return handler_was_called;
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}
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// cancels blocking operations being performed by signaled thread
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@ -220,17 +261,48 @@ textwindows void __sig_cancel(struct PosixThread *pt, int sig, unsigned flags) {
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WakeByAddressSingle(blocker);
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}
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// the user's signal handler callback is composed with this trampoline
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static textwindows wontreturn void __sig_tramp(struct SignalFrame *sf) {
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atomic_fetch_add_explicit(&__sig.count, 1, memory_order_relaxed);
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int sig = sf->si.si_signo;
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sigset_t blocksigs = __sighandmask[sig];
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if (!(sf->flags & SA_NODEFER)) blocksigs |= 1ull << (sig - 1);
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sf->ctx.uc_sigmask = atomic_fetch_or_explicit(
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&__get_tls()->tib_sigmask, blocksigs, memory_order_acq_rel);
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__sig_handler(sf->rva)(sig, &sf->si, &sf->ctx);
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atomic_store_explicit(&__get_tls()->tib_sigmask, sf->ctx.uc_sigmask,
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memory_order_release);
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__sig_restore(&sf->ctx);
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struct CosmoTib *tib = __get_tls();
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struct PosixThread *pt = (struct PosixThread *)tib->tib_pthread;
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for (;;) {
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atomic_fetch_add_explicit(&__sig.count, 1, memory_order_relaxed);
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// update the signal mask in preparation for signal handller
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sigset_t blocksigs = __sighandmask[sig];
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if (!(sf->flags & SA_NODEFER)) blocksigs |= 1ull << (sig - 1);
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sf->ctx.uc_sigmask = atomic_fetch_or_explicit(&tib->tib_sigmask, blocksigs,
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memory_order_acq_rel);
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// call the user's signal handler
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char ssbuf[2][128];
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STRACE("__sig_tramp(%G, %t) mask %s → %s", sig, __sig_handler(sf->rva),
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(DescribeSigset)(ssbuf[0], 0, &sf->ctx.uc_sigmask),
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(DescribeSigset)(ssbuf[1], 0, (sigset_t *)&tib->tib_sigmask));
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__sig_handler(sf->rva)(sig, &sf->si, &sf->ctx);
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(void)ssbuf;
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// restore the signal mask that was used by the interrupted code
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// this may have been modified by the signal handler in the callback
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atomic_store_explicit(&tib->tib_sigmask, sf->ctx.uc_sigmask,
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memory_order_release);
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// jump back into original code if there aren't any pending signals
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do {
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if (!(sig = __sig_get(tib))) {
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__sig_restore(&sf->ctx);
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}
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} while (!__sig_start(pt, sig, &sf->rva, &sf->flags));
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// tail recurse into another signal handler
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sf->si.si_signo = sig;
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sf->si.si_code = SI_KERNEL;
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if (sf->flags & SA_RESETHAND) {
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STRACE("resetting %G handler", sig);
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__sighandrvas[sig] = (int32_t)(intptr_t)SIG_DFL;
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}
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}
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}
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static int __sig_killer(struct PosixThread *pt, int sig, int sic) {
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@ -266,7 +338,7 @@ static int __sig_killer(struct PosixThread *pt, int sig, int sic) {
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if ((pt->tib->tib_sigmask & (1ull << (sig - 1))) ||
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!((uintptr_t)__executable_start <= nc.Rip &&
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nc.Rip < (uintptr_t)__privileged_start)) {
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STRACE("enqueing %G on %d", sig, _pthread_tid(pt));
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STRACE("enqueing %G on %d rip %p", sig, _pthread_tid(pt), nc.Rip);
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pt->tib->tib_sigpending |= 1ull << (sig - 1);
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ResumeThread(th);
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__sig_cancel(pt, sig, flags);
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@ -345,11 +417,11 @@ textwindows void __sig_generate(int sig, int sic) {
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if (mark) {
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STRACE("generating %G by killing %d", sig, _pthread_tid(mark));
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__sig_killer(mark, sig, sic);
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_pthread_unref(mark);
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} else {
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STRACE("all threads block %G so adding to pending signals of process", sig);
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__sig.pending |= 1ull << (sig - 1);
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}
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_pthread_unref(mark);
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ALLOW_SIGNALS;
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}
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@ -539,34 +611,17 @@ __msabi textwindows dontinstrument bool32 __sig_console(uint32_t dwCtrlType) {
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return true;
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}
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static textwindows int __sig_checker(atomic_ulong *sigs, struct CosmoTib *tib) {
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int sig, handler_was_called = 0;
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sigset_t bit, pending, masked, deliverable;
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pending = atomic_load_explicit(sigs, memory_order_acquire);
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masked = atomic_load_explicit(&tib->tib_sigmask, memory_order_acquire);
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if ((deliverable = pending & ~masked)) {
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do {
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sig = _bsf(deliverable) + 1;
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bit = 1ull << (sig - 1);
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if (atomic_fetch_and_explicit(sigs, ~bit, memory_order_acq_rel) & bit) {
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STRACE("found pending %G we can raise now", sig);
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handler_was_called |= __sig_raise(sig, SI_KERNEL);
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}
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} while ((deliverable &= ~bit));
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}
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return handler_was_called;
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}
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// returns 0 if no signal handlers were called, otherwise a bitmask
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// consisting of `1` which means a signal handler was invoked which
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// didn't have the SA_RESTART flag, and `2`, which means SA_RESTART
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// handlers were called (or `3` if both were the case).
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textwindows int __sig_check(void) {
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int handler_was_called = false;
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struct CosmoTib *tib = __get_tls();
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handler_was_called |= __sig_checker(&tib->tib_sigpending, tib);
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handler_was_called |= __sig_checker(&__sig.pending, tib);
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return handler_was_called;
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int sig;
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if ((sig = __sig_get(__get_tls()))) {
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return __sig_raise(sig, SI_KERNEL);
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} else {
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return 0;
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}
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}
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textstartup void __sig_init(void) {
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