[libc] Add a minimal implementation of the POSIX fork function.

A very simple and minimal implementation of fork is added. Future
changes will add more functionality to satisfy POSIX and Linux
requirements.

An implementation of wait and a few support macros in sys/wait.h
have also been added to help with testing the fork function.

Reviewed By: lntue, michaelrj

Differential Revision: https://reviews.llvm.org/D135131

6 files changed, 76 insertions, 0 deletions

diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 70bf4d663f70..3998d7228e68 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -174,6 +174,7 @@ add_gen_header(
     .llvm_libc_common_h
     .llvm-libc-macros.file_seek_macros
     .llvm-libc-macros.unistd_macros
+    .llvm-libc-types.off_t
     .llvm-libc-types.pid_t
     .llvm-libc-types.size_t
     .llvm-libc-types.ssize_t
@@ -273,6 +274,16 @@ add_gen_header(
     .llvm-libc-types.struct_utsname
 )
 
+add_gen_header(
+  sys_wait
+  DEF_FILE sys/wait.h.def
+  GEN_HDR sys/wait.h
+  DEPENDS
+    .llvm_libc_common_h
+    .llvm-libc-macros.sys_wait_macros
+    .llvm-libc-types.pid_t
+)
+
 if(NOT LLVM_LIBC_FULL_BUILD)
   # We don't install headers in non-fullbuild mode.
   return()
diff --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index fbf8cef92dcd..740802cd4429 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -47,6 +47,14 @@ add_header(
 )
 
 add_header(
+  sys_wait_macros
+  HDR
+    sys-wait-macros.h
+  DEPENDS
+    .linux.sys_wait_macros
+)
+
+add_header(
   time_macros
   HDR
     time-macros.h
diff --git a/libc/include/llvm-libc-macros/linux/CMakeLists.txt b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
index e0dcb7c9058b..cf6fe04d28d6 100644
--- a/libc/include/llvm-libc-macros/linux/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
@@ -17,6 +17,12 @@ add_header(
 )
 
 add_header(
+  sys_wait_macros
+  HDR
+    sys-wait-macros.h
+)
+
+add_header(
   time_macros
   HDR
     time-macros.h
diff --git a/libc/include/llvm-libc-macros/linux/sys-wait-macros.h b/libc/include/llvm-libc-macros/linux/sys-wait-macros.h
new file mode 100644
index 000000000000..5b5ad22ecae1
--- /dev/null
+++ b/libc/include/llvm-libc-macros/linux/sys-wait-macros.h
@@ -0,0 +1,17 @@
+//===-- Definition of macros from sys/wait.h ------------------------------===//
+//
+// 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_MACROS_LINUX_SYS_WAIT_MACROS_H
+#define __LLVM_LIBC_MACROS_LINUX_SYS_WAIT_MACROS_H
+
+// Wait status info macros
+#define WTERMSIG(status) (((status)&0x7F))
+#define WIFEXITED(status) (WTERMSIG(status) == 0)
+#define WEXITSTATUS(status) (((status)&0xFF00) >> 8)
+
+#endif // __LLVM_LIBC_MACROS_LINUX_SYS_WAIT_MACROS_H
diff --git a/libc/include/llvm-libc-macros/sys-wait-macros.h b/libc/include/llvm-libc-macros/sys-wait-macros.h
new file mode 100644
index 000000000000..ea58fccecaff
--- /dev/null
+++ b/libc/include/llvm-libc-macros/sys-wait-macros.h
@@ -0,0 +1,16 @@
+//===-- Macros defined in sys/wait.h header file --------------------------===//
+//
+// 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_MACROS_SYS_WAIT_MACROS_H
+#define __LLVM_LIBC_MACROS_SYS_WAIT_MACROS_H
+
+#ifdef __linux__
+#include "linux/sys-wait-macros.h"
+#endif
+
+#endif // __LLVM_LIBC_MACROS_SYS_WAIT_MACROS_H
diff --git a/libc/include/sys/wait.h.def b/libc/include/sys/wait.h.def
new file mode 100644
index 000000000000..b4fcce4d1652
--- /dev/null
+++ b/libc/include/sys/wait.h.def
@@ -0,0 +1,18 @@
+//===-- POSIX header wait.h -----------------------------------------------===//
+//
+// 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_SYS_WAIT_H
+#define LLVM_LIBC_SYS_WAIT_H
+
+#include <__llvm-libc-common.h>
+
+#include <llvm-libc-macros/sys-wait-macros.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_SYS_WAIT_H