Reduce stack virtual memory consumption on Linux

test/libc/intrin/stack_test.c

@@ -0,0 +1,75 @@
+/*-*- 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 2024 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/assert.h"
+#include "libc/calls/calls.h"
+#include "libc/calls/syscall-sysv.internal.h"
+#include "libc/cosmo.h"
+#include "libc/dce.h"
+#include "libc/errno.h"
+#include "libc/runtime/runtime.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/prot.h"
+#include "libc/testlib/testlib.h"
+
+// returns true if byte at memory address is readable
+bool readable(void *addr) {
+  return testlib_pokememory(addr);
+}
+
+// returns true if page is reserved by linux memory manager
+// it can be true for addresses that aren't listed in /proc/PID/maps
+bool occupied(void *addr) {
+  int olde = errno;
+  char *want = (char *)((uintptr_t)addr & -__pagesize);
+  char *got =
+      __sys_mmap(want, __pagesize, PROT_READ | PROT_WRITE,
+                 MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0, 0);
+  if (got == MAP_FAILED) {
+    unassert(errno == IsFreebsd() ? EINVAL : EEXIST);
+    errno = olde;
+    return true;
+  }
+  sys_munmap(got, __pagesize);
+  return got != want;
+}
+
+TEST(stack, test) {
+  if (IsWindows())
+    return;
+
+  void *vstackaddr;
+  size_t stacksize = 65536;
+  size_t guardsize = 4096;
+  unassert(!cosmo_stack_alloc(&stacksize, &guardsize, &vstackaddr));
+  char *stackaddr = vstackaddr;
+
+  /* check memory reservation */
+  unassert(occupied(stackaddr + stacksize - 1));  // top stack
+  unassert(occupied(stackaddr));                  // bot stack
+  unassert(occupied(stackaddr - 1));              // top guard
+  unassert(occupied(stackaddr - guardsize));      // bot guard
+
+  /* check memory accessibility */
+  unassert(readable(stackaddr + stacksize - 1));  // top stack
+  unassert(readable(stackaddr));                  // bot stack
+  unassert(!readable(stackaddr - 1));             // top guard
+  unassert(!readable(stackaddr - guardsize));     // bot guard
+
+  unassert(!cosmo_stack_free(stackaddr, stacksize, guardsize));
+}

test/libc/thread/pthread_cancel_test.c

@@ -19,6 +19,7 @@
 #include "libc/atomic.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/struct/sigaction.h"
+#include "libc/calls/struct/sigaltstack.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/kprintf.h"
@@ -27,6 +28,7 @@
 #include "libc/nexgen32e/nexgen32e.h"
 #include "libc/runtime/internal.h"
 #include "libc/runtime/runtime.h"
+#include "libc/runtime/sysconf.h"
 #include "libc/sysv/consts/sig.h"
 #include "libc/testlib/testlib.h"
 #include "libc/thread/thread.h"

test/libc/thread/pthread_create_test.c

@@ -70,6 +70,7 @@ void OnUsr1(int sig, siginfo_t *si, void *vctx) {
 
 void SetUpOnce(void) {
   cosmo_stack_setmaxstacks((_rand64() & 7) - 1);
+  cosmo_stack_setmaxstacks(100);
 }
 
 void SetUp(void) {