[libc][POSIX][unistd] implement getsid

libc/config/linux/aarch64/entrypoints.txt

@@ -329,6 +329,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.geteuid
     libc.src.unistd.getpid
     libc.src.unistd.getppid
+    libc.src.unistd.getsid
     libc.src.unistd.gettid
     libc.src.unistd.getuid
     libc.src.unistd.isatty

libc/config/linux/riscv/entrypoints.txt

@@ -326,6 +326,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.geteuid
     libc.src.unistd.getpid
     libc.src.unistd.getppid
+    libc.src.unistd.getsid
     libc.src.unistd.gettid
     libc.src.unistd.getuid
     libc.src.unistd.isatty

libc/config/linux/x86_64/entrypoints.txt

@@ -328,6 +328,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.geteuid
     libc.src.unistd.getpid
     libc.src.unistd.getppid
+    libc.src.unistd.getsid
     libc.src.unistd.gettid
     libc.src.unistd.getuid
     libc.src.unistd.isatty

libc/include/unistd.yaml

@@ -161,6 +161,12 @@ functions:
     return_type: int
     arguments:
       - type: void
+  - name: getsid
+    standards:
+      - POSIX
+    return_type: pid_t
+    arguments:
+      - type: pid_t
   - name: gettid
     standards:
       - Linux

libc/src/unistd/CMakeLists.txt

@@ -125,6 +125,13 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.getppid
 )
 
+add_entrypoint_object(
+  getsid
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.getsid
+)
+
 add_entrypoint_object(
   geteuid
   ALIAS

libc/src/unistd/getsid.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for getsid ------------------------*- 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_GETSID_H
+#define LLVM_LIBC_SRC_UNISTD_GETSID_H
+
+#include "hdr/types/pid_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+pid_t getsid(pid_t);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_UNISTD_GETSID_H

libc/src/unistd/linux/CMakeLists.txt

@@ -235,6 +235,19 @@ add_entrypoint_object(
     libc.src.__support.OSUtil.osutil
 )
 
+add_entrypoint_object(
+  getsid
+  SRCS
+    getsid.cpp
+  HDRS
+    ../getsid.h
+  DEPENDS
+    libc.hdr.types.pid_t
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
 add_entrypoint_object(
   getuid
   SRCS

libc/src/unistd/linux/getsid.cpp

@@ -0,0 +1,29 @@
+//===-- Linux implementation of getsid-------------------------------------===//
+//
+// 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/getsid.h"
+
+#include "hdr/types/pid_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 <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(pid_t, getsid, (pid_t pid)) {
+  pid_t ret = LIBC_NAMESPACE::syscall_impl<pid_t>(SYS_getsid, pid);
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/test/src/unistd/CMakeLists.txt

@@ -394,6 +394,16 @@ add_libc_unittest(
     libc.src.unistd.getppid
 )
 
+add_libc_unittest(
+  getsid_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    getsid_test.cpp
+  DEPENDS
+    libc.src.unistd.getsid
+)
+
 add_libc_unittest(
   getuid_test
   SUITE

libc/test/src/unistd/getsid_test.cpp

@@ -0,0 +1,21 @@
+//===-- Unittests for getsid ----------------------------------------------===//
+//
+// 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/getsid.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcGetPidTest, GetCurrSID) {
+  pid_t sid = LIBC_NAMESPACE::getsid(0);
+  ASSERT_NE(sid, -1);
+  ASSERT_ERRNO_SUCCESS();
+
+  pid_t nonexist_sid = LIBC_NAMESPACE::getsid(999999);
+  ASSERT_EQ(nonexist_sid, -1);
+  ASSERT_ERRNO_FAILURE();
+}