Implement gethostname

Matching the behavior of glibc version 2.2 and later.

If the size of the array name is not large enough, then anything might happen.
In this case, what happens to the array name
will be determined by the implementation of LIBC_NAMESPACE_DECL::strncpy

Signed-off-by: ZakyHermawan <[email protected]>

Author: ZakyHermawan

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 +1,62 @@
+//===-- 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/string/strlen.h"
+#include "src/string/strncpy.h"
+#include "src/errno/libc_errno.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);
+}