Improve cancellations, randomness, and time

- Exhaustively document cancellation points
- Rename SIGCANCEL to SIGTHR just like BSDs
- Further improve POSIX thread cancellations
- Ensure asynchronous cancellations work correctly
- Elevate the quality of getrandom() and getentropy()
- Make futexes cancel correctly on OpenBSD 6.x and 7.x
- Add reboot.com and shutdown.com to examples directory
- Remove underscore prefix from awesome timespec_*() APIs
- Create assertions that help verify our cancellation points
- Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)

libc/runtime/cocmd.c

@@ -309,10 +309,10 @@ static int Usleep(void) {
   struct timespec t;
   if (n > 1) {
     f = 0;
-    t = _timespec_frommicros(atoi(args[1]));
+    t = timespec_frommicros(atoi(args[1]));
   } else {
     f = TIMER_ABSTIME;
-    t = _timespec_max;
+    t = timespec_max;
   }
   return clock_nanosleep(0, f, &t, 0);
 }

libc/runtime/cosmo.S

@@ -148,8 +148,10 @@ cosmo:	push	%rbp
 	or	$-1,%r8
 	xor	%r9d,%r9d
 	push	%rsi
+	push	%rsi
 	call	mmap
 	pop	%r8
+	pop	%r8
 	pop	%rsi
 	pop	%rdi
 	cmp	$-1,%rax

libc/runtime/ezmap.c

@@ -16,8 +16,8 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/intrin/safemacros.internal.h"
 #include "libc/calls/calls.h"
+#include "libc/intrin/safemacros.internal.h"
 #include "libc/limits.h"
 #include "libc/log/libfatal.internal.h"
 #include "libc/runtime/ezmap.internal.h"
@@ -26,6 +26,8 @@
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/prot.h"
 
+// TODO(jart): DELETE
+
 hidden int MapFileRead(const char *filename, struct MappedFile *mf) {
   mf->addr = MAP_FAILED;
   if ((mf->fd = open(filename, O_RDONLY)) != -1 &&

libc/runtime/fenv.c

@@ -1,41 +0,0 @@
-/*-*- 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 2021 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/runtime/fenv.h"
-
-/* TODO: implement these functions */
-
-int feclearexcept(int mask) {
-  return 0;
-}
-
-int fegetenv(fenv_t *envp) {
-  return 0;
-}
-
-int feraiseexcept(int mask) {
-  return 0;
-}
-
-int fetestexcept(int mask) {
-  return 0;
-}
-
-int fesetenv(const fenv_t *envp) {
-  return 0;
-}

libc/runtime/isdynamicexecutable.c

@@ -16,7 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/intrin/bits.h"
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/struct/stat.h"
 #include "libc/elf/def.h"
@@ -24,6 +24,7 @@
 #include "libc/elf/struct/ehdr.h"
 #include "libc/elf/struct/phdr.h"
 #include "libc/errno.h"
+#include "libc/intrin/bits.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sysv/consts/map.h"
 #include "libc/sysv/consts/o.h"
@@ -38,6 +39,7 @@ bool IsDynamicExecutable(const char *prog) {
   Elf64_Phdr *p;
   struct stat st;
   int i, fd, err;
+  BLOCK_CANCELLATIONS;
   fd = -1;
   err = errno;
   e = MAP_FAILED;
@@ -74,5 +76,6 @@ Finish:
   if (e != MAP_FAILED) munmap(e, st.st_size);
   if (fd != -1) close(fd);
   errno = err;
+  ALLOW_CANCELLATIONS;
   return res;
 }

libc/runtime/msync.c

@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/cp.internal.h"
 #include "libc/calls/syscall-nt.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
@@ -34,16 +35,22 @@
  * @param addr needs to be 4096-byte page aligned
  * @param flags needs MS_ASYNC or MS_SYNC and can have MS_INVALIDATE
  * @return 0 on success or -1 w/ errno
+ * @raise ECANCELED if thread was cancelled in masked mode
+ * @raise EINTR if we needed to block and a signal was delivered instead
  * @cancellationpoint
  */
 int msync(void *addr, size_t size, int flags) {
   int rc;
+  BEGIN_CANCELLATION_POINT;
+
   _unassert(((flags & MS_SYNC) ^ (flags & MS_ASYNC)) || !(MS_SYNC && MS_ASYNC));
   if (!IsWindows()) {
     rc = sys_msync(addr, size, flags);
   } else {
     rc = sys_msync_nt(addr, size, flags);
   }
+
+  END_CANCELLATION_POINT;
   STRACE("msync(%p, %'zu, %#x) → %d% m", addr, size, flags, rc);
   return rc;
 }

libc/runtime/opensymboltable.greg.c

@@ -17,8 +17,8 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
-#include "libc/intrin/strace.internal.h"
 #include "libc/dce.h"
 #include "libc/elf/def.h"
 #include "libc/elf/scalar.h"
@@ -27,6 +27,7 @@
 #include "libc/elf/struct/sym.h"
 #include "libc/errno.h"
 #include "libc/intrin/bits.h"
+#include "libc/intrin/strace.internal.h"
 #include "libc/limits.h"
 #include "libc/log/libfatal.internal.h"
 #include "libc/macros.internal.h"
@@ -100,12 +101,7 @@ static void GetImageRange(Elf64_Ehdr *elf, intptr_t *x, intptr_t *y) {
   if (y) *y = end;
 }
 
-/**
- * Maps debuggable binary into memory and indexes symbol addresses.
- *
- * @return object freeable with CloseSymbolTable(), or NULL w/ errno
- */
-struct SymbolTable *OpenSymbolTable(const char *filename) {
+static struct SymbolTable *OpenSymbolTableImpl(const char *filename) {
   int fd;
   void *map;
   long *stp;
@@ -200,3 +196,16 @@ SystemError:
   close(fd);
   return 0;
 }
+
+/**
+ * Maps debuggable binary into memory and indexes symbol addresses.
+ *
+ * @return object freeable with CloseSymbolTable(), or NULL w/ errno
+ */
+struct SymbolTable *OpenSymbolTable(const char *filename) {
+  struct SymbolTable *st;
+  BLOCK_CANCELLATIONS;
+  st = OpenSymbolTableImpl(filename);
+  ALLOW_CANCELLATIONS;
+  return st;
+}