[libc-commits] [libc] [libc] Add Linux mman extension remap_file_pages. (PR #110307)
Aly ElAshram via libc-commits
libc-commits at lists.llvm.org
Tue Oct 1 09:32:18 PDT 2024
https://github.com/AlyElashram updated https://github.com/llvm/llvm-project/pull/110307
>From 50bf5e92716bfca96c311da021dace6688f98fcd Mon Sep 17 00:00:00 2001
From: Aly Elashram <alyahelashram at gmail.com>
Date: Fri, 27 Sep 2024 20:46:11 +0300
Subject: [PATCH 1/5] - Create remap_file_pages wrapper for the linux sys call.
- Add UnitTest for remap_file_pages - Add function to libc/spec/linux.td -
Add Function spec to mman.yaml
---
libc/newhdrgen/yaml/sys/mman.yaml | 10 +++
libc/spec/linux.td | 11 +++
libc/src/sys/mman/CMakeLists.txt | 7 ++
libc/src/sys/mman/linux/CMakeLists.txt | 13 ++++
libc/src/sys/mman/linux/remap_file_pages.cpp | 44 +++++++++++
libc/src/sys/mman/remap_file_pages.h | 21 ++++++
libc/test/src/sys/mman/linux/CMakeLists.txt | 17 +++++
.../sys/mman/linux/remap_file_pages_test.cpp | 74 +++++++++++++++++++
8 files changed, 197 insertions(+)
create mode 100644 libc/src/sys/mman/linux/remap_file_pages.cpp
create mode 100644 libc/src/sys/mman/remap_file_pages.h
create mode 100644 libc/test/src/sys/mman/linux/remap_file_pages_test.cpp
diff --git a/libc/newhdrgen/yaml/sys/mman.yaml b/libc/newhdrgen/yaml/sys/mman.yaml
index 272e7e2af16aaf..2f5f199bddec83 100644
--- a/libc/newhdrgen/yaml/sys/mman.yaml
+++ b/libc/newhdrgen/yaml/sys/mman.yaml
@@ -98,6 +98,16 @@ functions:
- type: void *
- type: size_t
- type: int
+ - name: remap_file_pages
+ standards:
+ - LINUX
+ return_type: int
+ arguments:
+ - type: void *
+ - type: size_t
+ - type: int
+ - type: size_t
+ - type: int
- name: shm_open
standards:
- POSIX
diff --git a/libc/spec/linux.td b/libc/spec/linux.td
index 395c2a6fe853a7..4aaf18b0803f3d 100644
--- a/libc/spec/linux.td
+++ b/libc/spec/linux.td
@@ -103,6 +103,17 @@ def Linux : StandardSpec<"Linux"> {
ArgSpec<UnsignedIntType>,
]
>,
+ FunctionSpec<
+ "remap_file_pages",
+ RetValSpec<IntType>,
+ [
+ ArgSpec<VoidPtr>,
+ ArgSpec<SizeTType>,
+ ArgSpec<IntType>,
+ ArgSpec<SizeTType>,
+ ArgSpec<IntType>,
+ ]
+ >,
] // Functions
>;
diff --git a/libc/src/sys/mman/CMakeLists.txt b/libc/src/sys/mman/CMakeLists.txt
index 9c74202a09f035..4ea43e14be0297 100644
--- a/libc/src/sys/mman/CMakeLists.txt
+++ b/libc/src/sys/mman/CMakeLists.txt
@@ -86,6 +86,13 @@ add_entrypoint_object(
.${LIBC_TARGET_OS}.msync
)
+add_entrypoint_object(
+ remap_file_pages
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.remap_file_pages
+)
+
add_entrypoint_object(
shm_open
ALIAS
diff --git a/libc/src/sys/mman/linux/CMakeLists.txt b/libc/src/sys/mman/linux/CMakeLists.txt
index 00f4f0e64ec06b..f673d47ba96aef 100644
--- a/libc/src/sys/mman/linux/CMakeLists.txt
+++ b/libc/src/sys/mman/linux/CMakeLists.txt
@@ -153,6 +153,19 @@ add_entrypoint_object(
libc.src.errno.errno
)
+add_entrypoint_object(
+ remap_file_pages
+ SRCS
+ remap_file_pages.cpp.cpp
+ HDRS
+ ../remap_file_pages.h.h
+ DEPENDS
+ libc.include.sys_mman
+ libc.include.sys_syscall
+ libc.src.__support.OSUtil.osutil
+ libc.src.errno.errno
+)
+
add_header_library(
shm_common
HDRS
diff --git a/libc/src/sys/mman/linux/remap_file_pages.cpp b/libc/src/sys/mman/linux/remap_file_pages.cpp
new file mode 100644
index 00000000000000..074d24d7c9b435
--- /dev/null
+++ b/libc/src/sys/mman/linux/remap_file_pages.cpp
@@ -0,0 +1,44 @@
+//===----- Linux implementation of the POSIX remap_file_pages 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/remap_file_pages.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 {
+
+// This function is currently linux only. It has to be refactored suitably if
+// remap_file_pages is to be supported on non-linux operating systems also.
+LLVM_LIBC_FUNCTION(int, remap_file_pages,
+ (void *addr, size_t size, int prot, size_t pgoff, int flags))
+ {
+#ifdef SYS_remap_file_pages
+ long syscall_number = SYS_remap_file_pages;
+#else
+#error "remap_file_pages syscall is not available."
+#endif
+
+
+ int ret = LIBC_NAMESPACE::syscall_impl<int>(
+ syscall_number, reinterpret_cast<long>(addr), size, prot, pgoff, flags);
+
+ // A negative return value indicates an error with the magnitude of the
+ // value being the error code.
+ if (ret < 0) {
+ libc_errno = ret;
+ return -1;
+ }
+
+ return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
\ No newline at end of file
diff --git a/libc/src/sys/mman/remap_file_pages.h b/libc/src/sys/mman/remap_file_pages.h
new file mode 100644
index 00000000000000..cfb540fd904140
--- /dev/null
+++ b/libc/src/sys/mman/remap_file_pages.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for remap_file_pages 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_REMAP_FILE_PAGES_H
+#define LLVM_LIBC_SRC_SYS_MMAN_REMAP_FILE_PAGES_H
+
+#include "src/__support/macros/config.h"
+#include <sys/mman.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+int remap_file_pages(void *addr, size_t size, int prot, size_t pgoff, int flags);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif //LLVM_LIBC_SRC_SYS_MMAN_REMAP_FILE_PAGES_H
diff --git a/libc/test/src/sys/mman/linux/CMakeLists.txt b/libc/test/src/sys/mman/linux/CMakeLists.txt
index b63c76f4306fac..3718f732b425f6 100644
--- a/libc/test/src/sys/mman/linux/CMakeLists.txt
+++ b/libc/test/src/sys/mman/linux/CMakeLists.txt
@@ -128,6 +128,23 @@ add_libc_unittest(
libc.test.UnitTest.ErrnoSetterMatcher
)
+add_libc_unittest(
+ remap_file_pages_test
+ SUITE
+ libc_sys_mman_unittests
+ SRCS
+ remap_file_pages_test.cpp
+ DEPENDS
+ libc.include.sys_mman
+ libc.src.unistd.sysconf
+ libc.test.UnitTest.Test
+ libc.test.UnitTest.ErrnoSetterMatcher
+ libc.src.sys.mman.remap_file_pages
+ libc.src.errno.errno
+ libc.src.sys.mman.mmap
+ libc.src.sys.mman.munmap
+)
+
add_libc_unittest(
shm_test
SUITE
diff --git a/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp b/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp
new file mode 100644
index 00000000000000..270ae4b6701e97
--- /dev/null
+++ b/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp
@@ -0,0 +1,74 @@
+//===-- Unittests for remap_file_pages ------------------------------------===//
+//
+// 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/sys/mman/mmap.h"
+#include "src/sys/mman/munmap.h"
+#include "src/sys/mman/remap_file_pages.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "src/unistd/sysconf.h"
+
+#include <sys/mman.h>
+
+
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+TEST(LlvmLibcRemapFilePagesTest, NoError) {
+ size_t page_size = sysconf(_SC_PAGE_SIZE);
+ ASSERT_GT(page_size, size_t(0));
+
+ // First, allocate some memory using mmap
+ size_t alloc_size = 2 * page_size;
+ LIBC_NAMESPACE::libc_errno = 0;
+ void *addr = LIBC_NAMESPACE::mmap(nullptr, alloc_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ ASSERT_ERRNO_SUCCESS();
+ EXPECT_NE(addr, MAP_FAILED);
+
+ // Reset error number for the new function
+ LIBC_NAMESPACE::libc_errno = 0;
+
+ // Now try to remap the pages
+ EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(addr, page_size, PROT_READ, page_size, 0),
+ Succeeds());
+
+ // Reset error number for the new function
+ LIBC_NAMESPACE::libc_errno = 0;
+
+ // Clean up
+ EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, alloc_size), Succeeds());
+}
+
+TEST(LlvmLibcRemapFilePagesTest, ErrorInvalidFlags) {
+ size_t page_size = sysconf(_SC_PAGESIZE);
+ ASSERT_GT(page_size, size_t(0));
+
+ void *addr = LIBC_NAMESPACE::mmap(nullptr, page_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ ASSERT_NE(addr, MAP_FAILED);
+
+ // Try to remap pages with an invalid flag MAP_PRIVATE
+ EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(addr, page_size, PROT_READ, 0, MAP_PRIVATE),
+ Fails(EINVAL));
+
+ // Clean up
+ EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, page_size), Succeeds());
+}
+
+TEST(LlvmLibcRemapFilePagesTest, ErrorInvalidAddress) {
+ size_t page_size = sysconf(_SC_PAGESIZE);
+ ASSERT_GT(page_size, size_t(0));
+
+ // Use an address that we haven't mapped
+ void *invalid_addr = reinterpret_cast<void*>(0x12345000);
+
+ EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(invalid_addr, page_size, PROT_READ, 0, 0),
+ Fails(EINVAL));
+}
\ No newline at end of file
>From 5a8891ad6dbd23317f226a2995230f6c8011b674 Mon Sep 17 00:00:00 2001
From: Aly Elashram <alyahelashram at gmail.com>
Date: Sat, 28 Sep 2024 02:43:14 +0300
Subject: [PATCH 2/5] fixup! - Create remap_file_pages wrapper for the linux
sys call. - Add UnitTest for remap_file_pages - Add function to
libc/spec/linux.td - Add Function spec to mman.yaml
---
libc/newhdrgen/yaml/sys/mman.yaml | 2 +-
libc/src/sys/mman/linux/remap_file_pages.cpp | 22 ++++++++-----------
libc/src/sys/mman/remap_file_pages.h | 7 +++---
.../sys/mman/linux/remap_file_pages_test.cpp | 16 ++++++++------
4 files changed, 23 insertions(+), 24 deletions(-)
diff --git a/libc/newhdrgen/yaml/sys/mman.yaml b/libc/newhdrgen/yaml/sys/mman.yaml
index 2f5f199bddec83..7c4fb1ef09e791 100644
--- a/libc/newhdrgen/yaml/sys/mman.yaml
+++ b/libc/newhdrgen/yaml/sys/mman.yaml
@@ -100,7 +100,7 @@ functions:
- type: int
- name: remap_file_pages
standards:
- - LINUX
+ - Linux
return_type: int
arguments:
- type: void *
diff --git a/libc/src/sys/mman/linux/remap_file_pages.cpp b/libc/src/sys/mman/linux/remap_file_pages.cpp
index 074d24d7c9b435..46e0f8b150ae51 100644
--- a/libc/src/sys/mman/linux/remap_file_pages.cpp
+++ b/libc/src/sys/mman/linux/remap_file_pages.cpp
@@ -1,4 +1,4 @@
-//===----- Linux implementation of the POSIX remap_file_pages function ----===//
+//===------- Linux implementation of the remap_file_pages function --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
@@ -6,31 +6,27 @@
//
//===----------------------------------------------------------------------===//
-#include <src/sys/mman/remap_file_pages.h>
+#include "src/sys/mman/remap_file_pages.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.
+#include <sys/syscall.h> // For syscall numbers.
namespace LIBC_NAMESPACE_DECL {
-// This function is currently linux only. It has to be refactored suitably if
-// remap_file_pages is to be supported on non-linux operating systems also.
LLVM_LIBC_FUNCTION(int, remap_file_pages,
- (void *addr, size_t size, int prot, size_t pgoff, int flags))
- {
+ (void *addr, size_t size, int prot, size_t pgoff,
+ int flags)) {
#ifdef SYS_remap_file_pages
- long syscall_number = SYS_remap_file_pages;
+ int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_remap_file_pages,
+ reinterpret_cast<long>(addr),
+ size, prot, pgoff, flags);
#else
#error "remap_file_pages syscall is not available."
#endif
-
- int ret = LIBC_NAMESPACE::syscall_impl<int>(
- syscall_number, reinterpret_cast<long>(addr), size, prot, pgoff, flags);
-
// A negative return value indicates an error with the magnitude of the
// value being the error code.
if (ret < 0) {
@@ -41,4 +37,4 @@ LLVM_LIBC_FUNCTION(int, remap_file_pages,
return 0;
}
-} // namespace LIBC_NAMESPACE_DECL
\ No newline at end of file
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/remap_file_pages.h b/libc/src/sys/mman/remap_file_pages.h
index cfb540fd904140..518502960d5cf1 100644
--- a/libc/src/sys/mman/remap_file_pages.h
+++ b/libc/src/sys/mman/remap_file_pages.h
@@ -10,12 +10,13 @@
#define LLVM_LIBC_SRC_SYS_MMAN_REMAP_FILE_PAGES_H
#include "src/__support/macros/config.h"
-#include <sys/mman.h>
+#include <stddef.h>
namespace LIBC_NAMESPACE_DECL {
-int remap_file_pages(void *addr, size_t size, int prot, size_t pgoff, int flags);
+int remap_file_pages(void *addr, size_t size, int prot, size_t pgoff,
+ int flags);
} // namespace LIBC_NAMESPACE_DECL
-#endif //LLVM_LIBC_SRC_SYS_MMAN_REMAP_FILE_PAGES_H
+#endif // LLVM_LIBC_SRC_SYS_MMAN_REMAP_FILE_PAGES_H
diff --git a/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp b/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp
index 270ae4b6701e97..069303232d0b9d 100644
--- a/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp
+++ b/libc/test/src/sys/mman/linux/remap_file_pages_test.cpp
@@ -10,13 +10,12 @@
#include "src/sys/mman/mmap.h"
#include "src/sys/mman/munmap.h"
#include "src/sys/mman/remap_file_pages.h"
+#include "src/unistd/sysconf.h"
#include "test/UnitTest/ErrnoSetterMatcher.h"
#include "test/UnitTest/Test.h"
-#include "src/unistd/sysconf.h"
#include <sys/mman.h>
-
using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
@@ -36,7 +35,8 @@ TEST(LlvmLibcRemapFilePagesTest, NoError) {
LIBC_NAMESPACE::libc_errno = 0;
// Now try to remap the pages
- EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(addr, page_size, PROT_READ, page_size, 0),
+ EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(addr, page_size, PROT_READ,
+ page_size, 0),
Succeeds());
// Reset error number for the new function
@@ -55,7 +55,8 @@ TEST(LlvmLibcRemapFilePagesTest, ErrorInvalidFlags) {
ASSERT_NE(addr, MAP_FAILED);
// Try to remap pages with an invalid flag MAP_PRIVATE
- EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(addr, page_size, PROT_READ, 0, MAP_PRIVATE),
+ EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(addr, page_size, PROT_READ, 0,
+ MAP_PRIVATE),
Fails(EINVAL));
// Clean up
@@ -67,8 +68,9 @@ TEST(LlvmLibcRemapFilePagesTest, ErrorInvalidAddress) {
ASSERT_GT(page_size, size_t(0));
// Use an address that we haven't mapped
- void *invalid_addr = reinterpret_cast<void*>(0x12345000);
+ void *invalid_addr = reinterpret_cast<void *>(0x12345000);
- EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(invalid_addr, page_size, PROT_READ, 0, 0),
+ EXPECT_THAT(LIBC_NAMESPACE::remap_file_pages(invalid_addr, page_size,
+ PROT_READ, 0, 0),
Fails(EINVAL));
-}
\ No newline at end of file
+}
>From 17d7626ae3b3a2f1d49fa9f6e63ba263982bcd4f Mon Sep 17 00:00:00 2001
From: Aly Elashram <alyahelashram at gmail.com>
Date: Tue, 1 Oct 2024 01:04:25 +0300
Subject: [PATCH 3/5] fixup! - Create remap_file_pages wrapper for the linux
sys call. - Add UnitTest for remap_file_pages - Add function to
libc/spec/linux.td - Add Function spec to mman.yaml
---
libc/config/linux/aarch64/entrypoints.txt | 1 +
libc/config/linux/riscv/entrypoints.txt | 1 +
libc/config/linux/x86_64/entrypoints.txt | 1 +
3 files changed, 3 insertions(+)
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 64fbe1a250c0ba..0031883c98ac83 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -250,6 +250,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sys.mman.munlock
libc.src.sys.mman.munlockall
libc.src.sys.mman.munmap
+ libc.src.sys.mman.remap_file_pages
libc.src.sys.mman.posix_madvise
libc.src.sys.mman.shm_open
libc.src.sys.mman.shm_unlink
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index ff3d821c664c5b..8a32407b3c6dc7 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -249,6 +249,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sys.mman.munlock
libc.src.sys.mman.munlockall
libc.src.sys.mman.munmap
+ libc.src.sys.mman.remap_file_pages
libc.src.sys.mman.posix_madvise
libc.src.sys.mman.shm_open
libc.src.sys.mman.shm_unlink
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index dd658af3bfb674..4de278f07b6afe 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -249,6 +249,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sys.mman.munlock
libc.src.sys.mman.munlockall
libc.src.sys.mman.munmap
+ libc.src.sys.mman.remap_file_pages
libc.src.sys.mman.posix_madvise
libc.src.sys.mman.shm_open
libc.src.sys.mman.shm_unlink
>From cbc1c339bddb5578501cc623e82afe3049fbc11f Mon Sep 17 00:00:00 2001
From: AlyElashram <alyahelashram at gmail.com>
Date: Tue, 1 Oct 2024 01:22:02 +0300
Subject: [PATCH 4/5] Remove extra file extensions
---
libc/src/sys/mman/linux/CMakeLists.txt | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libc/src/sys/mman/linux/CMakeLists.txt b/libc/src/sys/mman/linux/CMakeLists.txt
index f673d47ba96aef..11188254cfbd45 100644
--- a/libc/src/sys/mman/linux/CMakeLists.txt
+++ b/libc/src/sys/mman/linux/CMakeLists.txt
@@ -156,9 +156,9 @@ add_entrypoint_object(
add_entrypoint_object(
remap_file_pages
SRCS
- remap_file_pages.cpp.cpp
+ remap_file_pages.cpp
HDRS
- ../remap_file_pages.h.h
+ ../remap_file_pages.h
DEPENDS
libc.include.sys_mman
libc.include.sys_syscall
>From 0caed2f96f666673cfb4f11129a1bdf33af4eb1a Mon Sep 17 00:00:00 2001
From: AlyElashram <alyahelashram at gmail.com>
Date: Tue, 1 Oct 2024 19:32:04 +0300
Subject: [PATCH 5/5] - Remove extra file extensions - return the negative of
the return value
---
libc/src/sys/mman/linux/remap_file_pages.cpp | 2 +-
libc/test/src/sys/mman/linux/CMakeLists.txt | 1 -
2 files changed, 1 insertion(+), 2 deletions(-)
diff --git a/libc/src/sys/mman/linux/remap_file_pages.cpp b/libc/src/sys/mman/linux/remap_file_pages.cpp
index 46e0f8b150ae51..f616e1915ecc5e 100644
--- a/libc/src/sys/mman/linux/remap_file_pages.cpp
+++ b/libc/src/sys/mman/linux/remap_file_pages.cpp
@@ -30,7 +30,7 @@ LLVM_LIBC_FUNCTION(int, remap_file_pages,
// A negative return value indicates an error with the magnitude of the
// value being the error code.
if (ret < 0) {
- libc_errno = ret;
+ libc_errno = -ret;
return -1;
}
diff --git a/libc/test/src/sys/mman/linux/CMakeLists.txt b/libc/test/src/sys/mman/linux/CMakeLists.txt
index 3718f732b425f6..6c8e86be9ceaa3 100644
--- a/libc/test/src/sys/mman/linux/CMakeLists.txt
+++ b/libc/test/src/sys/mman/linux/CMakeLists.txt
@@ -137,7 +137,6 @@ add_libc_unittest(
DEPENDS
libc.include.sys_mman
libc.src.unistd.sysconf
- libc.test.UnitTest.Test
libc.test.UnitTest.ErrnoSetterMatcher
libc.src.sys.mman.remap_file_pages
libc.src.errno.errno
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