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[libc][mman] Implement msync (#84700)
Implement `msync` as specified in: 1. https://www.man7.org/linux/man-pages/man2/msync.2.html 2. https://pubs.opengroup.org/onlinepubs/9699919799/
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‎libc/config/linux/aarch64/entrypoints.txt‎

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@@ -185,6 +185,7 @@ set(TARGET_LIBC_ENTRYPOINTS
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libc.src.sys.mman.munlock
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libc.src.sys.mman.mlockall
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libc.src.sys.mman.munlockall
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libc.src.sys.mman.msync
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# sys/random.h entrypoints
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libc.src.sys.random.getrandom

‎libc/config/linux/riscv/entrypoints.txt‎

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@@ -190,6 +190,7 @@ set(TARGET_LIBC_ENTRYPOINTS
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libc.src.sys.mman.munlock
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libc.src.sys.mman.mlockall
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libc.src.sys.mman.munlockall
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libc.src.sys.mman.msync
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# sys/random.h entrypoints
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libc.src.sys.random.getrandom

‎libc/config/linux/x86_64/entrypoints.txt‎

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@@ -228,6 +228,7 @@ set(TARGET_LIBC_ENTRYPOINTS
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libc.src.sys.mman.munlock
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libc.src.sys.mman.mlockall
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libc.src.sys.mman.munlockall
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libc.src.sys.mman.msync
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# sys/random.h entrypoints
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libc.src.sys.random.getrandom

‎libc/spec/posix.td‎

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@@ -309,6 +309,11 @@ def POSIX : StandardSpec<"POSIX"> {
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RetValSpec<IntType>,
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[ArgSpec<VoidType>]
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>,
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FunctionSpec<
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"msync",
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RetValSpec<IntType>,
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[ArgSpec<VoidPtr>, ArgSpec<SizeTType>, ArgSpec<IntType>]
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>,
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]
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>;
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‎libc/src/sys/mman/CMakeLists.txt‎

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@@ -78,3 +78,10 @@ add_entrypoint_object(
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DEPENDS
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.${LIBC_TARGET_OS}.munlockall
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)
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add_entrypoint_object(
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msync
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ALIAS
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DEPENDS
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.${LIBC_TARGET_OS}.msync
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)

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

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@@ -139,3 +139,16 @@ add_entrypoint_object(
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libc.src.__support.OSUtil.osutil
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libc.src.errno.errno
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)
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add_entrypoint_object(
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msync
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SRCS
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msync.cpp
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HDRS
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../msync.h
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DEPENDS
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libc.include.sys_mman
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libc.include.sys_syscall
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libc.src.__support.OSUtil.osutil
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libc.src.errno.errno
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)

‎libc/src/sys/mman/linux/msync.cpp‎

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//===---------- Linux implementation of the msync function ----------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "src/sys/mman/msync.h"
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#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
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#include "src/errno/libc_errno.h"
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#include <sys/syscall.h> // For syscall numbers.
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namespace LIBC_NAMESPACE {
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LLVM_LIBC_FUNCTION(int, msync, (void *addr, size_t len, int flags)) {
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long ret = syscall_impl(SYS_msync, cpp::bit_cast<long>(addr), len, flags);
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if (ret < 0) {
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libc_errno = static_cast<int>(-ret);
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return -1;
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}
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return 0;
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}
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} // namespace LIBC_NAMESPACE

‎libc/src/sys/mman/msync.h‎

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//===-- Implementation header for msync function ----------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SRC_SYS_MMAN_MSYNC_H
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#define LLVM_LIBC_SRC_SYS_MMAN_MSYNC_H
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#include <sys/mman.h>
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#include <sys/syscall.h>
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namespace LIBC_NAMESPACE {
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int msync(void *addr, size_t len, int flags);
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} // namespace LIBC_NAMESPACE
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#endif // LLVM_LIBC_SRC_SYS_MMAN_MSYNC_H

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

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@@ -107,3 +107,23 @@ add_libc_unittest(
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libc.src.unistd.sysconf
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libc.test.UnitTest.ErrnoSetterMatcher
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)
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add_libc_unittest(
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msync_test
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SUITE
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libc_sys_mman_unittests
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SRCS
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msync_test.cpp
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DEPENDS
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libc.include.sys_mman
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libc.include.unistd
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libc.src.errno.errno
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libc.src.sys.mman.mmap
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libc.src.sys.mman.munmap
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libc.src.sys.mman.msync
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libc.src.sys.mman.mincore
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libc.src.sys.mman.mlock
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libc.src.sys.mman.munlock
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libc.src.unistd.sysconf
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libc.test.UnitTest.ErrnoSetterMatcher
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)

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

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//===-- Unittests for msync -----------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "src/errno/libc_errno.h"
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#include "src/sys/mman/mlock.h"
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#include "src/sys/mman/mmap.h"
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#include "src/sys/mman/msync.h"
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#include "src/sys/mman/munlock.h"
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#include "src/sys/mman/munmap.h"
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#include "src/unistd/sysconf.h"
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#include "test/UnitTest/ErrnoSetterMatcher.h"
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#include "test/UnitTest/LibcTest.h"
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#include "test/UnitTest/Test.h"
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using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
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struct PageHolder {
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size_t size;
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void *addr;
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PageHolder()
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: size(LIBC_NAMESPACE::sysconf(_SC_PAGESIZE)),
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addr(LIBC_NAMESPACE::mmap(nullptr, size, PROT_READ | PROT_WRITE,
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MAP_ANONYMOUS | MAP_PRIVATE, -1, 0)) {}
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~PageHolder() {
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if (addr != MAP_FAILED)
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LIBC_NAMESPACE::munmap(addr, size);
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}
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char &operator[](size_t i) { return reinterpret_cast<char *>(addr)[i]; }
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bool is_valid() { return addr != MAP_FAILED; }
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};
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TEST(LlvmLibcMsyncTest, UnMappedMemory) {
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EXPECT_THAT(LIBC_NAMESPACE::msync(nullptr, 1024, MS_SYNC), Fails(ENOMEM));
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EXPECT_THAT(LIBC_NAMESPACE::msync(nullptr, 1024, MS_ASYNC), Fails(ENOMEM));
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}
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TEST(LlvmLibcMsyncTest, LockedPage) {
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PageHolder page;
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ASSERT_TRUE(page.is_valid());
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ASSERT_THAT(LIBC_NAMESPACE::mlock(page.addr, page.size), Succeeds());
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EXPECT_THAT(
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LIBC_NAMESPACE::msync(page.addr, page.size, MS_SYNC | MS_INVALIDATE),
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Fails(EBUSY));
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ASSERT_THAT(LIBC_NAMESPACE::munlock(page.addr, page.size), Succeeds());
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EXPECT_THAT(LIBC_NAMESPACE::msync(page.addr, page.size, MS_SYNC), Succeeds());
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}
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TEST(LlvmLibcMsyncTest, UnalignedAddress) {
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PageHolder page;
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ASSERT_TRUE(page.is_valid());
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EXPECT_THAT(LIBC_NAMESPACE::msync(&page[1], page.size - 1, MS_SYNC),
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Fails(EINVAL));
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}
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TEST(LlvmLibcMsyncTest, InvalidFlag) {
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PageHolder page;
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ASSERT_TRUE(page.is_valid());
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EXPECT_THAT(LIBC_NAMESPACE::msync(page.addr, page.size, MS_SYNC | MS_ASYNC),
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Fails(EINVAL));
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EXPECT_THAT(LIBC_NAMESPACE::msync(page.addr, page.size, -1), Fails(EINVAL));
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}

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