[libc][POSIX][unistd] Implement gethostname

libc/config/linux/aarch64/entrypoints.txt

@@ -327,6 +327,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.getcwd
     libc.src.unistd.getentropy
     libc.src.unistd.geteuid
+    libc.src.unistd.gethostname
     libc.src.unistd.getpid
     libc.src.unistd.getppid
     libc.src.unistd.getsid

libc/config/linux/riscv/entrypoints.txt

@@ -324,6 +324,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.ftruncate
     libc.src.unistd.getcwd
     libc.src.unistd.geteuid
+    libc.src.unistd.gethostname
     libc.src.unistd.getpid
     libc.src.unistd.getppid
     libc.src.unistd.getsid

libc/config/linux/x86_64/entrypoints.txt

@@ -326,6 +326,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.getcwd
     libc.src.unistd.getentropy
     libc.src.unistd.geteuid
+    libc.src.unistd.gethostname
     libc.src.unistd.getpid
     libc.src.unistd.getppid
     libc.src.unistd.getsid

libc/include/unistd.yaml

@@ -141,6 +141,13 @@ functions:
     return_type: uid_t
     arguments:
       - type: void
+  - name: gethostname
+    standards:
+      - POSIX
+    return_type: int
+    arguments:
+      - type: char *
+      - type: size_t
   - name: getopt
     standards:
       - POSIX

libc/src/unistd/CMakeLists.txt

@@ -111,6 +111,13 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.getcwd
 )
 
+add_entrypoint_object(
+  gethostname
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.gethostname
+)
+
 add_entrypoint_object(
   getpid
   ALIAS

libc/src/unistd/gethostname.h

@@ -0,0 +1,22 @@
+//===-- Implementation header for gethostname -------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_UNISTD_GETHOSTNAME_H
+#define LLVM_LIBC_SRC_UNISTD_GETHOSTNAME_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/unistd_macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int gethostname(char *name, size_t len);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_UNISTD_GETHOSTNAME_H

libc/src/unistd/linux/CMakeLists.txt

@@ -193,6 +193,22 @@ add_entrypoint_object(
     libc.src.errno.errno
 )
 
+add_entrypoint_object(
+  gethostname
+  SRCS
+    gethostname.cpp
+  HDRS
+    ../gethostname.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.include.sys_syscall
+    libc.include.sys_utsname
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+    libc.src.string.strlen
+    libc.src.string.strncpy
+)
+
 add_entrypoint_object(
   geteuid
   SRCS

libc/src/unistd/linux/gethostname.cpp

@@ -0,0 +1,60 @@
+//===-- Linux implementation of gethostname -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/gethostname.h"
+
+#include "hdr/types/size_t.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+#include "src/errno/libc_errno.h"
+#include "src/string/strlen.h"
+#include "src/string/strncpy.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+#include <sys/utsname.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+// Matching the behavior of glibc version 2.2 and later.
+// Copies up to len bytes from the returned nodename field into name.
+LLVM_LIBC_FUNCTION(int, gethostname, (char *name, size_t len)) {
+  // Check for invalid pointer
+  if (name == nullptr) {
+    libc_errno = EFAULT;
+    return -1;
+  }
+
+  struct utsname unameData;
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_uname, &unameData);
+
+  // Checks if the length of the nodename was greater than or equal to len, and
+  // if it is, then the function returns -1 with errno set to ENAMETOOLONG. In
+  // this case, a terminating null byte is not included in the returned name.
+  if (strlen(unameData.nodename) >= len) {
+    strncpy(name, unameData.nodename, len);
+    libc_errno = ENAMETOOLONG;
+    return -1;
+  }
+
+  // If the size of the array name is not large enough (less than the size of
+  // nodename with null termination), then anything might happen. In this case,
+  // what happens to the array name will be determined by the implementation of
+  // LIBC_NAMESPACE_DECL::strncpy
+  strncpy(name, unameData.nodename, len);
+
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/test/src/unistd/CMakeLists.txt

@@ -374,6 +374,17 @@ add_libc_unittest(
     libc.src.unistd.unlinkat
 )
 
+add_libc_unittest(
+  gethostname_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    gethostname_test.cpp
+  DEPENDS
+    libc.src.unistd.gethostname
+    libc.src.errno.errno
+)
+
 add_libc_unittest(
   getpid_test
   SUITE

libc/test/src/unistd/gethostname_test.cpp

@@ -0,0 +1,28 @@
+//===-- Unittests for gethostname -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/errno/libc_errno.h"
+#include "src/unistd/gethostname.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcGetHostNameTest, GetCurrHostName) {
+  char hostbuffer[1024];
+  int ret = LIBC_NAMESPACE::gethostname(hostbuffer, sizeof(hostbuffer));
+  ASSERT_NE(ret, -1);
+  ASSERT_ERRNO_SUCCESS();
+
+  ret = LIBC_NAMESPACE::gethostname(hostbuffer, 0);
+  ASSERT_EQ(ret, -1);
+  ASSERT_ERRNO_EQ(ENAMETOOLONG);
+
+  // test for invalid pointer
+  char *nptr = nullptr;
+  ret = LIBC_NAMESPACE::gethostname(nptr, 1);
+  ASSERT_EQ(ret, -1);
+  ASSERT_ERRNO_EQ(EFAULT);
+}