Add pthread attributes and other libc functions

libc/thread/pthread_attr_setstack.c

@@ -0,0 +1,106 @@
+/*-*- 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/calls/calls.h"
+#include "libc/calls/syscall-sysv.internal.h"
+#include "libc/dce.h"
+#include "libc/errno.h"
+#include "libc/intrin/asan.internal.h"
+#include "libc/intrin/pthread.h"
+#include "libc/macros.internal.h"
+#include "libc/runtime/stack.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/prot.h"
+
+#define MAP_ANON_OPENBSD  0x1000
+#define MAP_STACK_OPENBSD 0x4000
+
+/**
+ * Configures custom allocated stack for thread, e.g.
+ *
+ *     pthread_t id;
+ *     pthread_attr_t attr;
+ *     pthread_attr_init(&attr);
+ *     pthread_attr_setstack(&attr, gc(malloc(GetStackSize())),
+ *                           GetStackSize());
+ *     pthread_create(&id, &attr, func, 0);
+ *     pthread_attr_destroy(&attr);
+ *     pthread_join(id, 0);
+ *
+ * Your stack must have at least `PTHREAD_STACK_MIN` bytes, which
+ * Cosmpolitan Libc defines as `GetStackSize()`. It's a link-time
+ * constant used by Actually Portable Executable that's 128 kb by
+ * default. See libc/runtime/stack.h for docs on your stack limit
+ * since the APE ELF phdrs are the one true source of truth here.
+ *
+ * Cosmpolitan Libc runtime magic (e.g. ftrace) and memory safety
+ * (e.g. kprintf) assumes that stack sizes are two-powers and are
+ * aligned to that two-power. Conformance isn't required since we
+ * say caveat emptor to those who don't maintain these invariants
+ *
+ * Unlike pthread_attr_setstacksize(), this function permits just
+ * about any parameters and will change the values and allocation
+ * as needed to conform to the mandatory requirements of the host
+ * operating system.
+ *
+ * @param stackaddr is address of stack allocated by caller, and
+ *     may be NULL in which case default behavior is restored
+ * @param stacksize is size of caller allocated stack
+ * @return 0 on success, or errno on error
+ * @raise EINVAL if parameters were unacceptable
+ * @see pthread_attr_setstacksize()
+ */
+int pthread_attr_setstack(pthread_attr_t *attr, void *stackaddr,
+                          size_t stacksize) {
+  if (!stackaddr) {
+    attr->stackaddr = 0;
+    attr->stacksize = 0;
+    return 0;
+  }
+  if (stacksize < PTHREAD_STACK_MIN ||
+      (IsAsan() && !__asan_is_valid(stackaddr, stacksize))) {
+    return EINVAL;
+  }
+  if (IsOpenbsd()) {
+    // OpenBSD: Only permits RSP to occupy memory that's been explicitly
+    // defined as stack memory. We need to squeeze the provided interval
+    // in order to successfully call mmap(), which will return EINVAL if
+    // these calculations should overflow.
+    size_t n;
+    int e, rc;
+    uintptr_t x, y;
+    n = stacksize;
+    x = (uintptr_t)stackaddr;
+    y = ROUNDUP(x, PAGESIZE);
+    n -= y - x;
+    n = ROUNDDOWN(n, PAGESIZE);
+    stackaddr = (void *)y;
+    stacksize = n;
+    e = errno;
+    if (__sys_mmap(stackaddr, stacksize, PROT_READ | PROT_WRITE,
+                   MAP_PRIVATE | MAP_ANON_OPENBSD | MAP_STACK_OPENBSD, -1, 0,
+                   0) == MAP_FAILED) {
+      rc = errno;
+      errno = e;
+      return rc;
+    }
+  }
+  attr->stackaddr = stackaddr;
+  attr->stacksize = stacksize;
+  return 0;
+}