[libc] Implement process_mrelease.

libc/config/linux/aarch64/entrypoints.txt

@@ -252,6 +252,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.munlockall
     libc.src.sys.mman.munmap
     libc.src.sys.mman.remap_file_pages
+    libc.src.sys.mman.process_mrelease
     libc.src.sys.mman.posix_madvise
     libc.src.sys.mman.shm_open
     libc.src.sys.mman.shm_unlink

libc/config/linux/riscv/entrypoints.txt

@@ -251,6 +251,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.munmap
     libc.src.sys.mman.remap_file_pages
     libc.src.sys.mman.posix_madvise
+    libc.src.sys.mman.process_mrelease
     libc.src.sys.mman.shm_open
     libc.src.sys.mman.shm_unlink
 

libc/config/linux/x86_64/entrypoints.txt

@@ -252,6 +252,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.munmap
     libc.src.sys.mman.remap_file_pages
     libc.src.sys.mman.posix_madvise
+    libc.src.sys.mman.process_mrelease
     libc.src.sys.mman.shm_open
     libc.src.sys.mman.shm_unlink
 

libc/include/sys/syscall.h.def

@@ -2349,5 +2349,12 @@
 #define SYS_writev __NR_writev
 #endif
 
+#ifdef __NR_process_mrelease
+#define SYS_process_mrelease __NR_process_mrelease
+#endif
+
+#ifdef __NR_pidfd_open
+#define SYS_pidfd_open __NR_pidfd_open
+#endif
 
 #endif // LLVM_LIBC_SYS_SYSCALL_H

libc/newhdrgen/yaml/sys/mman.yaml

@@ -132,3 +132,10 @@ functions:
     return_type: int
     arguments:
       - type: const char *
+  - name: process_mrelease
+    standards:
+      - Linux
+    return_type: int
+    arguments:
+      - type: int
+      - type: unsigned int

libc/spec/linux.td

@@ -112,6 +112,12 @@ def Linux : StandardSpec<"Linux"> {
             ArgSpec<IntType>,
             ArgSpec<SizeTType>,
             ArgSpec<IntType>,
+        FunctionSpec<
+          "process_mrelease",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>,
+            ArgSpec<UnsignedIntType>
           ]
         >,
         FunctionSpec<

libc/src/sys/mman/CMakeLists.txt

@@ -113,3 +113,9 @@ add_entrypoint_object(
   DEPENDS
     .${LIBC_TARGET_OS}.mremap
 )
+
+add_entrypoint_object(
+  process_mrelease 
+  ALIAS 
+  DEPENDS
+    .${LIBC_TARGET_OS}.process_mrelease)

libc/src/sys/mman/linux/CMakeLists.txt

@@ -36,7 +36,6 @@ add_entrypoint_object(
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
-
 add_entrypoint_object(
   munmap
   SRCS
@@ -214,3 +213,14 @@ add_entrypoint_object(
     libc.src.unistd.unlink
     .shm_common
 )
+
+add_entrypoint_object(
+  process_mrelease
+  SRCS
+    process_mrelease.cpp
+  HDRS
+    ../process_mrelease.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno)

libc/src/sys/mman/linux/process_mrelease.cpp

@@ -0,0 +1,33 @@
+//===---------- Linux implementation of the mrelease function -----------===//
+//
+// 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/mman/process_mrelease.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 <linux/param.h> // For EXEC_PAGESIZE.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, process_mrelease, (int pidfd, unsigned int flags)) {
+  long ret =
+      LIBC_NAMESPACE::syscall_impl<int>(SYS_process_mrelease, pidfd, flags);
+
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return libc_errno;
+  }
+
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/mman/process_mrelease.h

@@ -0,0 +1,22 @@
+//===-- Implementation header for process_mrelease  function -----------------*-
+// 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_MMAN_PROCESS_MRELEASE_H
+#define LLVM_LIBC_SRC_SYS_MMAN_PROCESS_MRELEASE_H
+
+#include "src/__support/macros/config.h"
+#include <sys/mman.h> // For size_t and off_t
+
+namespace LIBC_NAMESPACE_DECL {
+
+int process_mrelease(int pidfd, unsigned int flags);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_PROCESS_MRELEASE_H

libc/test/src/sys/mman/linux/CMakeLists.txt

@@ -181,3 +181,21 @@ add_libc_unittest(
     libc.hdr.fcntl_macros
     libc.test.UnitTest.ErrnoSetterMatcher
 )
+
+add_libc_unittest(
+  process_mrelease_test
+  SUITE
+    libc_sys_mman_unittests
+  SRCS
+    process_mrelease_test.cpp
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.errno.errno
+    libc.src.sys.mman.process_mrelease
+    libc.src.unistd.close
+    libc.src.signal.kill
+    libc.include.signal
+    libc.src.stdlib.exit
+    libc.src.__support.OSUtil.osutil
+    libc.src.__support.threads.sleep)

libc/test/src/sys/mman/linux/process_mrelease_test.cpp

@@ -0,0 +1,72 @@
+//===-- Unittests for process_mrelease
+//-------------------------------------===//
+//
+// 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/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/threads/sleep.h"
+#include "src/errno/libc_errno.h"
+#include "src/signal/kill.h"
+#include "src/stdlib/exit.h"
+#include "src/sys/mman/process_mrelease.h"
+#include "src/unistd/close.h"
+#include "src/unistd/fork.h"
+#include "test/UnitTest/LibcTest.h"
+
+#include <sys/syscall.h>
+
+int pidfd_open(pid_t pid, unsigned int flags) {
+  return LIBC_NAMESPACE::syscall_impl(SYS_pidfd_open, pid, flags);
+}
+
+TEST(LlvmLibcMProcessMReleaseTest, NoError) {
+  pid_t child_pid = fork();
+  EXPECT_GE(child_pid, 0);
+
+  if (child_pid == 0) {
+    // Child process: wait a bit then exit gracefully.
+    LIBC_NAMESPACE::sleep_briefly();
+    LIBC_NAMESPACE::exit(0);
+  } else {
+    // Parent process: wait a bit and then kill the child.
+    // Give child process some time to start.
+    LIBC_NAMESPACE::sleep_briefly();
+    int pidfd = pidfd_open(child_pid, 0);
+    EXPECT_GE(pidfd, 0);
+
+    // Send SIGKILL to child process
+    LIBC_NAMESPACE::kill(child_pid, SIGKILL);
+
+    EXPECT_EQ(LIBC_NAMESPACE::process_mrelease(pidfd, 0), 0);
+
+    LIBC_NAMESPACE::close(pidfd);
+  }
+}
+
+TEST(LlvmLibcMProcessMReleaseTest, ErrorNotKilled) {
+  pid_t child_pid = fork();
+  EXPECT_GE(child_pid, 0);
+
+  if (child_pid == 0) {
+    // Child process: wait a bit then exit gracefully.
+    LIBC_NAMESPACE::sleep_briefly();
+    LIBC_NAMESPACE::exit(0);
+  } else {
+    // Give child process some time to start.
+    LIBC_NAMESPACE::sleep_briefly();
+    int pidfd = pidfd_open(child_pid, 0);
+    EXPECT_GE(pidfd, 0);
+
+    ASSERT_EQ(LIBC_NAMESPACE::process_mrelease(pidfd, 0), EINVAL);
+
+    LIBC_NAMESPACE::close(pidfd);
+  }
+}
+
+TEST(LlvmLibcMProcessMReleaseTest, ErrorNonExistingPidfd) {
+
+  ASSERT_EQ(LIBC_NAMESPACE::process_mrelease(12345, 0), EBADF);
+}