Add phtread_setname_np() and pthread_getname_np()

libc/thread/pthread_getname_np.c

@@ -0,0 +1,118 @@
+/*-*- 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/fmt/itoa.h"
+#include "libc/intrin/asmflag.h"
+#include "libc/macros.internal.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/pr.h"
+#include "libc/thread/posixthread.internal.h"
+#include "libc/thread/thread.h"
+
+/**
+ * Gets name of thread registered with system, e.g.
+ *
+ *     char name[64];
+ *     pthread_getname_np(thread, name, sizeof(name));
+ *
+ * If the thread doesn't have a name, then empty string is returned.
+ * This implementation guarantees `buf` is always modified, even on
+ * error, and will always be nul-terminated. If `size` is 0 then this
+ * function returns 0. Your `buf` is also chomped to remove newlines.
+ *
+ * @return 0 on success, or errno on error
+ * @raise ERANGE if `size` wasn't large enough, in which case your
+ *     result will still be returned truncated if possible
+ * @raise ENOSYS on MacOS, Windows, FreeBSD, and OpenBSD
+ */
+int pthread_getname_np(pthread_t thread, char *name, size_t size) {
+  int e, fd, rc, tid, len;
+
+  if (!size) return 0;
+  bzero(name, size);
+  tid = ((struct PosixThread *)thread)->spawn.ptid;
+
+  if (IsLinux()) {
+    // TASK_COMM_LEN is 16 on Linux so we're just being paranoid.
+    char buf[256] = {0};
+    if (tid == gettid()) {
+      e = errno;
+      if (prctl(PR_GET_NAME, buf) == -1) {
+        rc = errno;
+        errno = e;
+        return rc;
+      }
+    } else {
+      char path[128], *p = path;
+      p = stpcpy(p, "/proc/self/task/");
+      p = FormatUint32(p, tid);
+      p = stpcpy(p, "/comm");
+      e = errno;
+      if ((fd = sys_open(path, O_RDONLY | O_CLOEXEC, 0)) == -1) {
+        rc = errno;
+        errno = e;
+        return rc;
+      }
+      rc = sys_read(fd, buf, sizeof(buf) - 1);
+      rc |= sys_close(fd);
+      if (rc == -1) {
+        rc = errno;
+        errno = e;
+        return rc;
+      }
+      _chomp(buf);
+    }
+    if ((len = strlen(buf))) {
+      memcpy(name, buf, MIN(len, size - 1));
+    }
+    if (len > size - 1) {
+      return ERANGE;
+    }
+    return 0;
+
+  } else if (IsNetbsd()) {
+    char cf;
+    int ax, dx;
+    // NetBSD doesn't document the subtleties of its nul-terminator
+    // behavior, so like Linux we shall take the paranoid approach.
+    asm volatile(CFLAG_ASM("syscall")
+                 : CFLAG_CONSTRAINT(cf), "=a"(ax), "=d"(dx)
+                 : "1"(324 /* _lwp_getname */), "D"(tid), "S"(name),
+                   "d"(size - 1)
+                 : "rcx", "r11", "memory");
+    if (!cf) {
+      // if size + our nul + kernel's nul is the buffer size, then we
+      // can't say with absolute confidence truncation didn't happen.
+      if (strlen(name) + 1 + 1 <= size) {
+        return 0;
+      } else {
+        return ERANGE;
+      }
+    } else {
+      return ax;
+    }
+
+  } else {
+    return ENOSYS;
+  }
+}