[libc] (reland #117503) Implement process_mrelease (#117851)

This PR implements process_mrelease.
A previous PR was merged #117503, but failed on merge due to an issue in
the tests. Namely the failing tests were comparing against return type
as opposed to errno. This is fixed in this PR.

Author: moar55

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 -1;
+  }
+
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/mman/process_mrelease.h

@@ -0,0 +1,21 @@
+//===-- 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 +181,23 @@ 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.UnitTest.ErrnoSetterMatcher
+)

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

@@ -0,0 +1,74 @@
+//===-- 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/ErrnoSetterMatcher.h"
+#include "test/UnitTest/LibcTest.h"
+
+#include <sys/syscall.h>
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+
+int pidfd_open(pid_t pid, unsigned int flags) {
+  return LIBC_NAMESPACE::syscall_impl(SYS_pidfd_open, pid, flags);
+}
+
+TEST(LlvmLibcProcessMReleaseTest, 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_THAT(LIBC_NAMESPACE::process_mrelease(pidfd, 0), Succeeds());
+
+    LIBC_NAMESPACE::close(pidfd);
+  }
+}
+
+TEST(LlvmLibcProcessMReleaseTest, 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);
+
+    EXPECT_THAT(LIBC_NAMESPACE::process_mrelease(pidfd, 0), Fails(EINVAL));
+
+    LIBC_NAMESPACE::close(pidfd);
+  }
+}
+
+TEST(LlvmLibcProcessMReleaseTest, ErrorNonExistingPidfd) {
+  EXPECT_THAT(LIBC_NAMESPACE::process_mrelease(-1, 0), Fails(EBADF));
+}