Fix pthread stacks with larger guard size

libc/intrin/describemapflags.c

@@ -30,7 +30,6 @@ const char *(DescribeMapFlags)(char buf[64], int x) {
       {MAP_SHARED, "SHARED"},                    //
       {MAP_FIXED, "FIXED"},                      //
       {MAP_FIXED_NOREPLACE, "FIXED_NOREPLACE"},  //
-      {MAP_GROWSDOWN, "GROWSDOWN"},              //
       {MAP_CONCEAL, "CONCEAL"},                  //
       {MAP_HUGETLB, "HUGETLB"},                  //
       {MAP_LOCKED, "LOCKED"},                    //

libc/intrin/describemapping.c

@@ -49,7 +49,6 @@ const char *(DescribeMapping)(char p[8], int prot, int flags) {
   DescribeProt(p, prot);
   p[3] = DescribeMapType(flags);
   p[4] = (flags & MAP_ANONYMOUS) ? 'a' : '-';
-  p[5] = (flags & MAP_GROWSDOWN) ? 'G' : '-';
   p[6] = (flags & MAP_FIXED) ? 'F' : '-';
   p[7] = 0;
   return p;

libc/intrin/pthread.h

@@ -85,7 +85,7 @@ typedef struct pthread_attr_s {
   char detachstate;
   size_t stacksize;
   size_t guardsize;
-  void *stackaddr;
+  char *stackaddr;
   int scope;
   int schedpolicy;
   int inheritsched;

libc/intrin/pthread_attr_init.c

@@ -30,8 +30,5 @@ int pthread_attr_init(pthread_attr_t *attr) {
       .stacksize = GetStackSize(),
       .guardsize = PAGESIZE,
   };
-  if (attr->stacksize >= 1048576) {
-    attr->guardsize = FRAMESIZE;
-  }
   return 0;
 }

libc/runtime/clone.c

@@ -595,9 +595,7 @@ int clone(void *func, void *stk, size_t stksz, int flags, void *arg, int *ptid,
              ((flags & CLONE_VM) && (stksz < PAGESIZE || (stksz & 15)))) {
     rc = einval();
   } else if (IsAsan() &&
-             ((stksz > PAGESIZE &&
+             (((flags & CLONE_SETTLS) && !__asan_is_valid(tls, 64)) ||
-               !__asan_is_valid((char *)stk + PAGESIZE, stksz - PAGESIZE)) ||
-              ((flags & CLONE_SETTLS) && !__asan_is_valid(tls, 64)) ||
               ((flags & CLONE_SETTLS) && !__asan_is_valid(tls, sizeof(long))) ||
               ((flags & CLONE_PARENT_SETTID) &&
                !__asan_is_valid(ptid, sizeof(*ptid))) ||

libc/sysv/consts/map.h

@@ -13,7 +13,6 @@ extern const int MAP_EXECUTABLE;
 extern const int MAP_FILE;
 extern const int MAP_FIXED;
 extern const int MAP_FIXED_NOREPLACE;
-extern const int MAP_GROWSDOWN;
 extern const int MAP_HASSEMAPHORE;
 extern const int MAP_HUGETLB;
 extern const int MAP_HUGE_MASK;
@@ -44,7 +43,6 @@ COSMOPOLITAN_C_END_
 #define MAP_DENYWRITE       SYMBOLIC(MAP_DENYWRITE)
 #define MAP_EXECUTABLE      SYMBOLIC(MAP_EXECUTABLE)
 #define MAP_FIXED_NOREPLACE SYMBOLIC(MAP_FIXED_NOREPLACE)
-#define MAP_GROWSDOWN       SYMBOLIC(MAP_GROWSDOWN)
 #define MAP_HASSEMAPHORE    SYMBOLIC(MAP_HASSEMAPHORE)
 #define MAP_HUGETLB         SYMBOLIC(MAP_HUGETLB)
 #define MAP_HUGE_MASK       SYMBOLIC(MAP_HUGE_MASK)

libc/thread/pthread_create.c

@@ -96,8 +96,8 @@ static int FixupCustomStackOnOpenbsd(pthread_attr_t *attr) {
   n = ROUNDDOWN(n, PAGESIZE);
   e = errno;
   if (__sys_mmap((void *)y, n, PROT_READ | PROT_WRITE,
-                 MAP_PRIVATE | MAP_ANON_OPENBSD | MAP_STACK_OPENBSD, -1, 0,
+                 MAP_PRIVATE | MAP_FIXED | MAP_ANON_OPENBSD | MAP_STACK_OPENBSD,
-                 0) != MAP_FAILED) {
+                 -1, 0, 0) == (void *)y) {
     attr->stackaddr = (void *)y;
     attr->stacksize = n;
     return 0;
@@ -215,8 +215,28 @@ int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
       _pthread_free(pt);
       return EINVAL;
     }
-    pt->attr.stackaddr = mmap(0, pt->attr.stacksize, PROT_READ | PROT_WRITE,
+    if (pt->attr.guardsize == PAGESIZE) {
-                              MAP_STACK | MAP_ANONYMOUS, -1, 0);
+      // user is wisely using smaller stacks with default guard size
+      pt->attr.stackaddr = mmap(0, pt->attr.stacksize, PROT_READ | PROT_WRITE,
+                                MAP_STACK | MAP_ANONYMOUS, -1, 0);
+    } else {
+      // user is tuning things, performance may suffer
+      pt->attr.stackaddr = mmap(0, pt->attr.stacksize, PROT_READ | PROT_WRITE,
+                                MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+      if (pt->attr.stackaddr != MAP_FAILED) {
+        if (IsOpenbsd() &&
+            __sys_mmap(
+                pt->attr.stackaddr, pt->attr.stacksize, PROT_READ | PROT_WRITE,
+                MAP_PRIVATE | MAP_FIXED | MAP_ANON_OPENBSD | MAP_STACK_OPENBSD,
+                -1, 0, 0) != pt->attr.stackaddr) {
+          notpossible;
+        }
+        if (pt->attr.guardsize && !IsWindows() &&
+            mprotect(pt->attr.stackaddr, pt->attr.guardsize, PROT_NONE)) {
+          notpossible;
+        }
+      }
+    }
     if (pt->attr.stackaddr == MAP_FAILED) {
       rc = errno;
       _pthread_free(pt);
@@ -227,27 +247,8 @@ int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
         return EAGAIN;
       }
     }
-    // mmap(MAP_STACK) creates a 4096 guard by default
+    if (IsAsan() && pt->attr.guardsize) {
-    if (pt->attr.guardsize != PAGESIZE) {
+      __asan_poison(pt->attr.stackaddr, pt->attr.guardsize, kAsanStackOverflow);
-      if (pt->attr.guardsize) {
-        // user requested special guard size
-        rc = mprotect(pt->attr.stackaddr, pt->attr.guardsize, PROT_NONE);
-      } else {
-        // user explicitly disabled guard page
-        rc = mprotect(pt->attr.stackaddr, PAGESIZE, PROT_READ | PROT_WRITE);
-      }
-      if (rc) {
-        notpossible;
-      }
-    }
-    if (IsAsan()) {
-      if (pt->attr.guardsize) {
-        __asan_poison(pt->attr.stackaddr, pt->attr.guardsize,
-                      kAsanStackOverflow);
-      }
-      __asan_poison((char *)pt->attr.stackaddr + pt->attr.stacksize -
-                        16 /* openbsd:stackbound */,
-                    16, kAsanStackOverflow);
     }
   }
 
@@ -267,7 +268,7 @@ int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
 
   // launch PosixThread(pt) in new thread
   if (clone(PosixThread, pt->attr.stackaddr,
-            pt->attr.stacksize - 16 /* openbsd:stackbound */,
+            pt->attr.stacksize - (IsOpenbsd() ? 16 : 0),
             CLONE_VM | CLONE_THREAD | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
                 CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
                 CLONE_CHILD_CLEARTID,

test/libc/thread/pthread_create_test.c

@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/calls/struct/sigaction.h"
 #include "libc/dce.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/intrin/pthread.h"
@@ -25,13 +26,31 @@
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/stack.h"
 #include "libc/sysv/consts/prot.h"
+#include "libc/sysv/consts/sa.h"
+#include "libc/sysv/consts/sig.h"
 #include "libc/testlib/ezbench.h"
 #include "libc/testlib/subprocess.h"
 #include "libc/testlib/testlib.h"
 #include "libc/thread/thread.h"
 
+void OnTrap(int sig, struct siginfo *si, void *vctx) {
+  struct ucontext *ctx = vctx;
+}
+
+void SetUp(void) {
+  struct sigaction sig = {.sa_sigaction = OnTrap, .sa_flags = SA_SIGINFO};
+  sigaction(SIGTRAP, &sig, 0);
+}
+
+void TriggerSignal(void) {
+  sched_yield();
+  DebugBreak();
+  sched_yield();
+}
+
 static void *Increment(void *arg) {
   ASSERT_EQ(gettid(), pthread_getthreadid_np());
+  TriggerSignal();
   return (void *)((uintptr_t)arg + 1);
 }
 
@@ -44,6 +63,7 @@ TEST(pthread_create, testCreateReturnJoin) {
 }
 
 static void *IncExit(void *arg) {
+  TriggerSignal();
   pthread_exit((void *)((uintptr_t)arg + 1));
 }
 
@@ -71,6 +91,7 @@ TEST(pthread_detach, testDetachUponCreation) {
 
 static void *CheckStack(void *arg) {
   char buf[1024 * 1024];
+  TriggerSignal();
   CheckLargeStackAllocation(buf, 1024 * 1024);
   return 0;
 }
@@ -85,6 +106,24 @@ TEST(pthread_detach, testBigStack) {
   ASSERT_EQ(0, pthread_join(id, 0));
 }
 
+static void *CheckStack2(void *arg) {
+  char buf[57244];
+  TriggerSignal();
+  CheckLargeStackAllocation(buf, sizeof(buf));
+  return 0;
+}
+
+TEST(pthread_detach, testBiggerGuardSize) {
+  pthread_t id;
+  pthread_attr_t attr;
+  ASSERT_EQ(0, pthread_attr_init(&attr));
+  ASSERT_EQ(0, pthread_attr_setstacksize(&attr, 65536));
+  ASSERT_EQ(0, pthread_attr_setguardsize(&attr, 8192));
+  ASSERT_EQ(0, pthread_create(&id, &attr, CheckStack2, 0));
+  ASSERT_EQ(0, pthread_attr_destroy(&attr));
+  ASSERT_EQ(0, pthread_join(id, 0));
+}
+
 TEST(pthread_detach, testCustomStack_withReallySmallSize) {
   char *stk;
   size_t siz;

third_party/libcxx/thread.cc

@@ -52,10 +52,6 @@
 #include "third_party/getopt/getopt.h"
 #endif // defined(__unix__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__CloudABI__) || defined(__Fuchsia__) || defined(__wasi__)
 
-#if defined(__NetBSD__)
-#pragma weak pthread_create // Do not create libpthread dependency
-#endif
-
 #if defined(_LIBCPP_WIN32API)
 #include "libc/nt/accounting.h"
 #include "libc/nt/automation.h"

tool/build/lib/xlat.c

@@ -372,7 +372,6 @@ int XlatMapFlags(int x) {
   if (x & 2) r |= MAP_PRIVATE;
   if (x & 16) r |= MAP_FIXED;
   if (x & 32) r |= MAP_ANONYMOUS;
-  if (x & 256) r |= MAP_GROWSDOWN;
   return r;
 }