[libc] Implement faccessat #161065
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[libc] Implement faccessat #161065
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@llvm/pr-subscribers-libc Author: Marcell Leleszi (mleleszi) Changes#160404
Full diff: https://github.com/llvm/llvm-project/pull/161065.diff 11 Files Affected:
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index ae8deabc97407..cfb77911f3c2d 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -325,6 +325,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.unistd.dup2
libc.src.unistd.dup3
libc.src.unistd.execve
+ libc.src.unistd.faccessat
libc.src.unistd.fchdir
libc.src.unistd.fpathconf
libc.src.unistd.fsync
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index bf2ad4a40ca11..87b78a337b875 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -331,6 +331,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.unistd.dup2
libc.src.unistd.dup3
libc.src.unistd.execve
+ libc.src.unistd.faccessat
libc.src.unistd.fchdir
libc.src.unistd.fpathconf
libc.src.unistd.fsync
diff --git a/libc/include/llvm-libc-macros/linux/fcntl-macros.h b/libc/include/llvm-libc-macros/linux/fcntl-macros.h
index aec8a0d2da0b5..74d406f742f38 100644
--- a/libc/include/llvm-libc-macros/linux/fcntl-macros.h
+++ b/libc/include/llvm-libc-macros/linux/fcntl-macros.h
@@ -61,6 +61,9 @@
// Allow empty relative pathname.
#define AT_EMPTY_PATH 0x1000
+// Perform access checks using the effective user and group IDs.
+#define AT_EACCESS 0x200
+
// Values of SYS_fcntl commands.
#define F_DUPFD 0
#define F_GETFD 1
diff --git a/libc/include/unistd.yaml b/libc/include/unistd.yaml
index 3ba3ec71c25ce..2ff86eafaf550 100644
--- a/libc/include/unistd.yaml
+++ b/libc/include/unistd.yaml
@@ -96,6 +96,15 @@ functions:
- type: const char *
- type: __exec_argv_t
- type: __exec_envp_t
+ - name: faccessat
+ standards:
+ - POSIX
+ return_type: int
+ arguments:
+ - type: int
+ - type: const char *
+ - type: int
+ - type: int
- name: fchdir
standards:
- POSIX
diff --git a/libc/src/unistd/CMakeLists.txt b/libc/src/unistd/CMakeLists.txt
index c66a3a4d0ed76..78c3bf8442fab 100644
--- a/libc/src/unistd/CMakeLists.txt
+++ b/libc/src/unistd/CMakeLists.txt
@@ -55,6 +55,13 @@ add_entrypoint_object(
.${LIBC_TARGET_OS}.dup3
)
+add_entrypoint_object(
+ faccessat
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.faccessat
+)
+
add_entrypoint_object(
fchdir
ALIAS
diff --git a/libc/src/unistd/faccessat.h b/libc/src/unistd/faccessat.h
new file mode 100644
index 0000000000000..578c22faff258
--- /dev/null
+++ b/libc/src/unistd/faccessat.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for faccessat ------------------------*- 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_FACCESSAT_H
+#define LLVM_LIBC_SRC_UNISTD_FACCESSAT_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int faccessat(int fd, const char *path, int amode, int flag);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_UNISTD_FACCESSAT_H
diff --git a/libc/src/unistd/linux/CMakeLists.txt b/libc/src/unistd/linux/CMakeLists.txt
index 2d510f32d287d..0b67417475b71 100644
--- a/libc/src/unistd/linux/CMakeLists.txt
+++ b/libc/src/unistd/linux/CMakeLists.txt
@@ -80,6 +80,20 @@ add_entrypoint_object(
libc.src.errno.errno
)
+add_entrypoint_object(
+ faccessat
+ SRCS
+ faccessat.cpp
+ HDRS
+ ../faccessat.h
+ DEPENDS
+ libc.hdr.fcntl_macros
+ libc.include.unistd
+ libc.include.sys_syscall
+ libc.src.__support.OSUtil.osutil
+ libc.src.errno.errno
+)
+
add_entrypoint_object(
fchdir
SRCS
diff --git a/libc/src/unistd/linux/access.cpp b/libc/src/unistd/linux/access.cpp
index 55cd6adca779d..f06eec5a8db6a 100644
--- a/libc/src/unistd/linux/access.cpp
+++ b/libc/src/unistd/linux/access.cpp
@@ -23,7 +23,7 @@ LLVM_LIBC_FUNCTION(int, access, (const char *path, int mode)) {
int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_access, path, mode);
#elif defined(SYS_faccessat)
int ret =
- LIBC_NAMESPACE::syscall_impl<int>(SYS_faccessat, AT_FDCWD, path, mode, 0);
+ LIBC_NAMESPACE::syscall_impl<int>(SYS_faccessat, AT_FDCWD, path, mode);
#else
#error "access and faccessat syscalls not available."
#endif
diff --git a/libc/src/unistd/linux/faccessat.cpp b/libc/src/unistd/linux/faccessat.cpp
new file mode 100644
index 0000000000000..f6efd9a887999
--- /dev/null
+++ b/libc/src/unistd/linux/faccessat.cpp
@@ -0,0 +1,38 @@
+//===-- Linux implementation of faccessat
+//------------------------------------===//
+//
+// 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/faccessat.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "hdr/fcntl_macros.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, faccessat,
+ (int fd, const char *path, int amode, int flag)) {
+#ifdef SYS_faccessat2
+ int ret =
+ LIBC_NAMESPACE::syscall_impl<int>(SYS_faccessat2, fd, path, amode, flag);
+#else
+#error "faccessat2 syscall is not available."
+#endif
+
+ if (ret < 0) {
+ libc_errno = -ret;
+ return -1;
+ }
+ return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/unistd/CMakeLists.txt b/libc/test/src/unistd/CMakeLists.txt
index 6630a7ef15e53..e03e4be7b0936 100644
--- a/libc/test/src/unistd/CMakeLists.txt
+++ b/libc/test/src/unistd/CMakeLists.txt
@@ -93,6 +93,28 @@ add_libc_unittest(
libc.test.UnitTest.ErrnoSetterMatcher
)
+add_libc_unittest(
+ faccessat_test
+ SUITE
+ libc_unistd_unittests
+ SRCS
+ faccessat_test.cpp
+ DEPENDS
+ libc.include.unistd
+ libc.src.__support.CPP.string
+ libc.src.sys.stat.mkdir
+ libc.src.errno.errno
+ libc.src.fcntl.open
+ libc.src.unistd.faccessat
+ libc.src.unistd.close
+ libc.src.unistd.symlink
+ libc.src.unistd.unlink
+ libc.src.unistd.unlinkat
+ libc.src.unistd.rmdir
+ libc.test.UnitTest.ErrnoCheckingTest
+ libc.test.UnitTest.ErrnoSetterMatcher
+)
+
add_libc_unittest(
fchdir_test
SUITE
diff --git a/libc/test/src/unistd/faccessat_test.cpp b/libc/test/src/unistd/faccessat_test.cpp
new file mode 100644
index 0000000000000..2dff0b21cccfb
--- /dev/null
+++ b/libc/test/src/unistd/faccessat_test.cpp
@@ -0,0 +1,172 @@
+//===-- Unittests for faccessat -------------------------------------------===//
+//
+// 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/CPP/string.h"
+#include "src/fcntl/open.h"
+#include "src/sys/stat/mkdir.h"
+#include "src/unistd/close.h"
+#include "src/unistd/faccessat.h"
+#include "src/unistd/rmdir.h"
+#include "src/unistd/symlink.h"
+#include "src/unistd/unlink.h"
+#include "src/unistd/unlinkat.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+namespace {
+
+namespace cpp = LIBC_NAMESPACE::cpp;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+using LlvmLibcFaccessatTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcFaccessatTest, WithAtFdcwd) {
+ // Test access checks on a file with AT_FDCWD and no flags, equivalent to
+ // access().
+ constexpr const char *FILENAME = "faccessat_basic.test";
+ auto TEST_FILE = libc_make_test_file_path(FILENAME);
+
+ // Check permissions on a file with full permissions
+ int fd = LIBC_NAMESPACE::open(TEST_FILE, O_WRONLY | O_CREAT, S_IRWXU);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(fd, 0);
+ ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, F_OK, 0),
+ Succeeds(0));
+ ASSERT_THAT(
+ LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, X_OK | W_OK | R_OK, 0),
+ Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::unlink(TEST_FILE), Succeeds(0));
+
+ // Check permissions on a file with execute-only permission
+ fd = LIBC_NAMESPACE::open(TEST_FILE, O_WRONLY | O_CREAT, S_IXUSR);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(fd, 0);
+ ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, F_OK, 0),
+ Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, X_OK, 0),
+ Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, R_OK, 0),
+ Fails(EACCES));
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, W_OK, 0),
+ Fails(EACCES));
+ ASSERT_THAT(LIBC_NAMESPACE::unlink(TEST_FILE), Succeeds(0));
+
+ // Check permissions on a non existent file
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, F_OK, 0),
+ Fails(ENOENT));
+}
+
+TEST_F(LlvmLibcFaccessatTest, RelativePathWithDirFD) {
+ // Check permissions on a file releative to dir_fd
+ const cpp::string DIRNAME = "faccessat_dir";
+ const cpp::string FILENAME = "relative_file.txt";
+
+ auto TEST_DIR = libc_make_test_file_path(DIRNAME.data());
+ ASSERT_THAT(LIBC_NAMESPACE::mkdir(TEST_DIR, S_IRWXU), Succeeds(0));
+
+ int dir_fd = LIBC_NAMESPACE::open(TEST_DIR, O_RDONLY | O_DIRECTORY);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(dir_fd, 0);
+
+ auto FULL_FILE_PATH =
+ libc_make_test_file_path((DIRNAME + "/" + FILENAME).data());
+ int fd = LIBC_NAMESPACE::open(FULL_FILE_PATH, O_WRONLY | O_CREAT, S_IRWXU);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(fd, 0);
+ ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+
+ ASSERT_THAT(
+ LIBC_NAMESPACE::faccessat(dir_fd, FILENAME.data(), R_OK | W_OK, 0),
+ Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::unlinkat(dir_fd, FILENAME.data(), 0),
+ Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::close(dir_fd), Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::rmdir(TEST_DIR), Succeeds(0));
+}
+
+TEST_F(LlvmLibcFaccessatTest, SymlinkNoFollow) {
+ // Check permissions on a symlink itself, not what it links to
+ constexpr const char *TARGET = "faccessat_target";
+ constexpr const char *SYMLINK = "faccessat_link";
+ auto TEST_TARGET = libc_make_test_file_path(TARGET);
+ auto TEST_SYMLINK = libc_make_test_file_path(SYMLINK);
+
+ int fd = LIBC_NAMESPACE::open(TEST_TARGET, O_WRONLY | O_CREAT, 0);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(fd, 0);
+ ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::symlink(TARGET, TEST_SYMLINK), Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_SYMLINK, R_OK, 0),
+ Fails(EACCES));
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_SYMLINK, F_OK,
+ AT_SYMLINK_NOFOLLOW),
+ Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::unlink(TEST_SYMLINK), Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::unlink(TEST_TARGET), Succeeds(0));
+}
+
+TEST_F(LlvmLibcFaccessatTest, AtEaccess) {
+ // With AT_EACCESS, faccessat checks permissions using the effective user ID,
+ // but the effective and real user ID will be the same here and changing that
+ // is not feasible in a test, so this is just a basic sanity check.
+ constexpr const char *FILENAME = "faccessat_eaccess.test";
+ auto TEST_FILE = libc_make_test_file_path(FILENAME);
+
+ int fd = LIBC_NAMESPACE::open(TEST_FILE, O_WRONLY | O_CREAT, S_IRWXU);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(fd, 0);
+ ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, TEST_FILE, X_OK | W_OK | R_OK,
+ AT_EACCESS),
+ Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::unlink(TEST_FILE), Succeeds(0));
+}
+
+TEST_F(LlvmLibcFaccessatTest, AtEmptyPath) {
+ constexpr const char *FILENAME = "faccessat_atemptypath.test";
+ auto TEST_FILE = libc_make_test_file_path(FILENAME);
+
+ int fd = LIBC_NAMESPACE::open(TEST_FILE, O_WRONLY | O_CREAT, S_IRWXU);
+ ASSERT_ERRNO_SUCCESS();
+ ASSERT_GT(fd, 0);
+
+ // Check permissions on the file referred to by fd
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(fd, "", F_OK, AT_EMPTY_PATH),
+ Succeeds(0));
+ ASSERT_THAT(
+ LIBC_NAMESPACE::faccessat(fd, "", X_OK | W_OK | R_OK, AT_EMPTY_PATH),
+ Succeeds(0));
+
+ ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::unlink(TEST_FILE), Succeeds(0));
+
+ // Check permissions on the current working directory
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, "", F_OK, AT_EMPTY_PATH),
+ Succeeds(0));
+ ASSERT_THAT(LIBC_NAMESPACE::faccessat(AT_FDCWD, "", X_OK | W_OK | R_OK,
+ AT_EMPTY_PATH),
+ Succeeds(0));
+}
+
+} // namespace
|
Yes, can you merge please, I don't think I can merge yet |
michaelrj-google
approved these changes
Oct 2, 2025
|
@mleleszi Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR. Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues. How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/104/builds/32643 Here is the relevant piece of the build log for the reference |
mahesh-attarde
pushed a commit
to mahesh-attarde/llvm-project
that referenced
this pull request
Oct 3, 2025
llvm#160404 - Implement POSIX function "faccessat" - Remove redundant param in facessat syscall in access implementation, faccessat syscall does not take a flags arg
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#160404