[libc-commits] [libc] e3638e8 - [libc] Add a minimal implementation of the POSIX fork function.
Siva Chandra Reddy via libc-commits
libc-commits at lists.llvm.org
Tue Oct 4 12:12:31 PDT 2022
Author: Siva Chandra Reddy
Date: 2022-10-04T19:12:08Z
New Revision: e3638e83db086e77243d0673a4ce8a0b4b330d42
URL: https://github.com/llvm/llvm-project/commit/e3638e83db086e77243d0673a4ce8a0b4b330d42
DIFF: https://github.com/llvm/llvm-project/commit/e3638e83db086e77243d0673a4ce8a0b4b330d42.diff
LOG: [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
Added:
libc/include/llvm-libc-macros/linux/sys-wait-macros.h
libc/include/llvm-libc-macros/sys-wait-macros.h
libc/include/sys/wait.h.def
libc/src/sys/wait/CMakeLists.txt
libc/src/sys/wait/linux/CMakeLists.txt
libc/src/sys/wait/linux/wait.cpp
libc/src/sys/wait/wait.h
libc/src/unistd/fork.h
libc/src/unistd/linux/fork.cpp
libc/test/integration/src/unistd/CMakeLists.txt
libc/test/integration/src/unistd/fork_test.cpp
Modified:
libc/config/linux/api.td
libc/config/linux/x86_64/entrypoints.txt
libc/include/CMakeLists.txt
libc/include/llvm-libc-macros/CMakeLists.txt
libc/include/llvm-libc-macros/linux/CMakeLists.txt
libc/spec/posix.td
libc/src/sys/CMakeLists.txt
libc/src/unistd/CMakeLists.txt
libc/src/unistd/linux/CMakeLists.txt
libc/test/integration/src/CMakeLists.txt
Removed:
################################################################################
diff --git a/libc/config/linux/api.td b/libc/config/linux/api.td
index bd60cb1a572fe..8496b29455d65 100644
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -271,6 +271,10 @@ def SysStatAPI : PublicAPI<"sys/stat.h"> {
"struct timespec", "blksize_t", "blkcnt_t", "struct stat"];
}
+def SysWaitAPI : PublicAPI<"sys/wait.h"> {
+ let Types = ["pid_t"];
+}
+
def SysSendfileAPI : PublicAPI<"sys/sendfile.h"> {
let Types = ["off_t", "size_t", "ssize_t"];
}
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 42da9adf83070..c7e6c733bf743 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -129,6 +129,9 @@ set(TARGET_LIBC_ENTRYPOINTS
# sys/utsname.h entrypoints
libc.src.sys.utsname.uname
+ # sys/wait.h entrypoints
+ libc.src.sys.wait.wait
+
# unistd.h entrypoints
libc.src.unistd.access
libc.src.unistd.chdir
@@ -401,6 +404,9 @@ if(LLVM_LIBC_FULL_BUILD)
libc.src.time.mktime
libc.src.time.nanosleep
libc.src.time.clock_gettime
+
+ # unistd.h entrypoints
+ libc.src.unistd.fork
)
endif()
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 70bf4d663f70a..3998d7228e681 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 fbf8cef92dcdb..740802cd44293 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -46,6 +46,14 @@ add_header(
.linux.sys_resource_macros
)
+add_header(
+ sys_wait_macros
+ HDR
+ sys-wait-macros.h
+ DEPENDS
+ .linux.sys_wait_macros
+)
+
add_header(
time_macros
HDR
diff --git a/libc/include/llvm-libc-macros/linux/CMakeLists.txt b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
index e0dcb7c9058bc..cf6fe04d28d68 100644
--- a/libc/include/llvm-libc-macros/linux/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
@@ -16,6 +16,12 @@ add_header(
sys-stat-macros.h
)
+add_header(
+ sys_wait_macros
+ HDR
+ sys-wait-macros.h
+)
+
add_header(
time_macros
HDR
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 0000000000000..5b5ad22ecae14
--- /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 0000000000000..ea58fccecaffb
--- /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 0000000000000..b4fcce4d16529
--- /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
diff --git a/libc/spec/posix.td b/libc/spec/posix.td
index 3f31723c43d79..47e71e9cc567d 100644
--- a/libc/spec/posix.td
+++ b/libc/spec/posix.td
@@ -342,6 +342,11 @@ def POSIX : StandardSpec<"POSIX"> {
RetValSpec<IntType>,
[ArgSpec<IntType>]
>,
+ FunctionSpec<
+ "fork",
+ RetValSpec<PidT>,
+ [ArgSpec<VoidType>]
+ >,
FunctionSpec<
"fsync",
RetValSpec<IntType>,
@@ -963,6 +968,20 @@ def POSIX : StandardSpec<"POSIX"> {
]
>;
+ HeaderSpec SysWait = HeaderSpec<
+ "sys/wait.h",
+ [], // Macros
+ [PidT],
+ [], // Enumerations
+ [
+ FunctionSpec<
+ "wait",
+ RetValSpec<PidT>,
+ [ArgSpec<IntPtr>]
+ >
+ ]
+ >;
+
let Headers = [
CType,
Dirent,
@@ -976,6 +995,7 @@ def POSIX : StandardSpec<"POSIX"> {
SysResource,
SysStat,
SysUtsName,
+ SysWait,
Time,
UniStd,
String
diff --git a/libc/src/sys/CMakeLists.txt b/libc/src/sys/CMakeLists.txt
index 7e6ab887b3107..f8e25cc8d4e54 100644
--- a/libc/src/sys/CMakeLists.txt
+++ b/libc/src/sys/CMakeLists.txt
@@ -3,3 +3,4 @@ add_subdirectory(resource)
add_subdirectory(sendfile)
add_subdirectory(stat)
add_subdirectory(utsname)
+add_subdirectory(wait)
diff --git a/libc/src/sys/wait/CMakeLists.txt b/libc/src/sys/wait/CMakeLists.txt
new file mode 100644
index 0000000000000..9731d7daa361a
--- /dev/null
+++ b/libc/src/sys/wait/CMakeLists.txt
@@ -0,0 +1,10 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+ add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+ wait
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.wait
+)
diff --git a/libc/src/sys/wait/linux/CMakeLists.txt b/libc/src/sys/wait/linux/CMakeLists.txt
new file mode 100644
index 0000000000000..88e6f34fba692
--- /dev/null
+++ b/libc/src/sys/wait/linux/CMakeLists.txt
@@ -0,0 +1,13 @@
+add_entrypoint_object(
+ wait
+ SRCS
+ wait.cpp
+ HDRS
+ ../wait.h
+ DEPENDS
+ libc.include.errno
+ libc.include.sys_wait
+ libc.include.sys_syscall
+ libc.src.__support.OSUtil.osutil
+ libc.src.errno.errno
+)
diff --git a/libc/src/sys/wait/linux/wait.cpp b/libc/src/sys/wait/linux/wait.cpp
new file mode 100644
index 0000000000000..91300f2f2f464
--- /dev/null
+++ b/libc/src/sys/wait/linux/wait.cpp
@@ -0,0 +1,34 @@
+//===-- Linux implementation of wait --------------------------------------===//
+//
+// 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/sys/wait/wait.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers.
+#include <sys/wait.h>
+
+namespace __llvm_libc {
+
+// The implementation of wait here is very minimal. We will add more
+// functionality and standard compliance in future.
+
+LLVM_LIBC_FUNCTION(pid_t, wait, (int *wait_status)) {
+ pid_t pid = __llvm_libc::syscall_impl(SYS_wait4, -1, wait_status, 0, 0);
+ if (pid < 0) {
+ // Error case, a child process was not created.
+ errno = -pid;
+ return -1;
+ }
+
+ return pid;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/sys/wait/wait.h b/libc/src/sys/wait/wait.h
new file mode 100644
index 0000000000000..d49fb21d9b728
--- /dev/null
+++ b/libc/src/sys/wait/wait.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for wait --------------------------*- 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_SYS_WAIT_WAIT_H
+#define LLVM_LIBC_SRC_SYS_WAIT_WAIT_H
+
+#include <sys/wait.h>
+
+namespace __llvm_libc {
+
+pid_t wait(int *waitstatus);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SYS_WAIT_WAIT_H
diff --git a/libc/src/unistd/CMakeLists.txt b/libc/src/unistd/CMakeLists.txt
index 1e54f4cd4d351..a460b5d18055f 100644
--- a/libc/src/unistd/CMakeLists.txt
+++ b/libc/src/unistd/CMakeLists.txt
@@ -51,6 +51,13 @@ add_entrypoint_object(
.${LIBC_TARGET_OS}.fchdir
)
+add_entrypoint_object(
+ fork
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.fork
+)
+
add_entrypoint_object(
fsync
ALIAS
diff --git a/libc/src/unistd/fork.h b/libc/src/unistd/fork.h
new file mode 100644
index 0000000000000..8d591dd8667c5
--- /dev/null
+++ b/libc/src/unistd/fork.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for fork --------------------------*- 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_FORK_H
+#define LLVM_LIBC_SRC_UNISTD_FORK_H
+
+#include <unistd.h>
+
+namespace __llvm_libc {
+
+pid_t fork();
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_FORK_H
diff --git a/libc/src/unistd/linux/CMakeLists.txt b/libc/src/unistd/linux/CMakeLists.txt
index 0bbde7a102ab6..a3f7ef4187f01 100644
--- a/libc/src/unistd/linux/CMakeLists.txt
+++ b/libc/src/unistd/linux/CMakeLists.txt
@@ -90,6 +90,21 @@ add_entrypoint_object(
libc.src.errno.errno
)
+add_entrypoint_object(
+ fork
+ SRCS
+ fork.cpp
+ HDRS
+ ../fork.h
+ DEPENDS
+ libc.include.errno
+ libc.include.unistd
+ libc.include.sys_syscall
+ libc.src.__support.OSUtil.osutil
+ libc.src.__support.threads.thread
+ libc.src.errno.errno
+)
+
add_entrypoint_object(
fsync
SRCS
diff --git a/libc/src/unistd/linux/fork.cpp b/libc/src/unistd/linux/fork.cpp
new file mode 100644
index 0000000000000..c51eaeec0d85e
--- /dev/null
+++ b/libc/src/unistd/linux/fork.cpp
@@ -0,0 +1,49 @@
+//===-- Linux implementation of fork --------------------------------------===//
+//
+// 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/fork.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/__support/threads/thread.h" // For thread self object
+
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+// The implementation of fork here is very minimal. We will add more
+// functionality and standard compliance in future.
+
+LLVM_LIBC_FUNCTION(pid_t, fork, (void)) {
+#ifdef SYS_fork
+ pid_t ret = __llvm_libc::syscall_impl(SYS_fork);
+#elif defined(SYS_clone)
+ pid_t ret = __llvm_libc::syscall_impl(SYS_clone, SIGCHLD, 0);
+#else
+#error "SYS_fork or SYS_clone not available."
+#endif
+ if (ret == 0) {
+ // Return value is 0 in the child process.
+ // The child is created with a single thread whose self object will be a
+ // copy of parent process' thread which called fork. So, we have to fix up
+ // the child process' self object with the new process' tid.
+ self.attrib->tid = __llvm_libc::syscall_impl(SYS_gettid);
+ return 0;
+ }
+
+ if (ret < 0) {
+ // Error case, a child process was not created.
+ errno = -ret;
+ return -1;
+ }
+
+ return ret;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/test/integration/src/CMakeLists.txt b/libc/test/integration/src/CMakeLists.txt
index 01662b9104383..c86cd178a3ce6 100644
--- a/libc/test/integration/src/CMakeLists.txt
+++ b/libc/test/integration/src/CMakeLists.txt
@@ -3,3 +3,4 @@ add_subdirectory(pthread)
add_subdirectory(stdio)
add_subdirectory(stdlib)
add_subdirectory(threads)
+add_subdirectory(unistd)
diff --git a/libc/test/integration/src/unistd/CMakeLists.txt b/libc/test/integration/src/unistd/CMakeLists.txt
new file mode 100644
index 0000000000000..624f911cc9357
--- /dev/null
+++ b/libc/test/integration/src/unistd/CMakeLists.txt
@@ -0,0 +1,20 @@
+add_custom_target(unistd-integration-tests)
+add_dependencies(libc-integration-tests unistd-integration-tests)
+
+add_integration_test(
+ fork_test
+ SUITE
+ unistd-integration-tests
+ SRCS
+ fork_test.cpp
+ LOADER
+ libc.loader.linux.crt1
+ DEPENDS
+ libc.include.errno
+ libc.include.signal
+ libc.include.sys_wait
+ libc.include.unistd
+ libc.src.signal.raise
+ libc.src.sys.wait.wait
+ libc.src.unistd.fork
+)
diff --git a/libc/test/integration/src/unistd/fork_test.cpp b/libc/test/integration/src/unistd/fork_test.cpp
new file mode 100644
index 0000000000000..0cf89f00b8729
--- /dev/null
+++ b/libc/test/integration/src/unistd/fork_test.cpp
@@ -0,0 +1,49 @@
+//===-- Unittests for fork ------------------------------------------------===//
+//
+// 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/signal/raise.h"
+#include "src/sys/wait/wait.h"
+#include "src/unistd/fork.h"
+
+#include "utils/IntegrationTest/test.h"
+
+#include <errno.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+void fork_and_wait_normal_exit() {
+ pid_t pid = __llvm_libc::fork();
+ if (pid == 0)
+ return; // Just end without any thing special.
+ ASSERT_TRUE(pid > 0);
+ int status;
+ pid_t cpid = __llvm_libc::wait(&status);
+ ASSERT_TRUE(cpid > 0);
+ ASSERT_EQ(cpid, pid);
+ ASSERT_TRUE(WIFEXITED(status));
+}
+
+void fork_and_wait_signal_exit() {
+ pid_t pid = __llvm_libc::fork();
+ if (pid == 0)
+ __llvm_libc::raise(SIGUSR1);
+ ASSERT_TRUE(pid > 0);
+ int status;
+ pid_t cpid = __llvm_libc::wait(&status);
+ ASSERT_TRUE(cpid > 0);
+ ASSERT_EQ(cpid, pid);
+ ASSERT_FALSE(WIFEXITED(status));
+ ASSERT_TRUE(WTERMSIG(status) == SIGUSR1);
+}
+
+TEST_MAIN(int argc, char **argv, char **envp) {
+ fork_and_wait_normal_exit();
+ fork_and_wait_signal_exit();
+ return 0;
+}
More information about the libc-commits
mailing list