[libc-commits] [libc] f5cbbb9 - [libc] Add implementation of POSIX setrlimit and getrlimit functions.

Siva Chandra Reddy via libc-commits libc-commits at lists.llvm.org
Fri Sep 16 13:50:44 PDT 2022 

Author: Siva Chandra Reddy
Date: 2022-09-16T20:50:28Z
New Revision: f5cbbb998826bc84cbebd12f890622b3ec3184fe

URL: https://github.com/llvm/llvm-project/commit/f5cbbb998826bc84cbebd12f890622b3ec3184fe
DIFF: https://github.com/llvm/llvm-project/commit/f5cbbb998826bc84cbebd12f890622b3ec3184fe.diff

LOG: [libc] Add implementation of POSIX setrlimit and getrlimit functions.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D134016

Added: 
    libc/include/llvm-libc-macros/linux/sys-resource-macros.h
    libc/include/llvm-libc-macros/sys-resource-macros.h
    libc/include/llvm-libc-types/rlim_t.h
    libc/include/llvm-libc-types/struct_rlimit_t.h
    libc/include/sys/resource.h.def
    libc/src/sys/resource/CMakeLists.txt
    libc/src/sys/resource/getrlimit.h
    libc/src/sys/resource/linux/CMakeLists.txt
    libc/src/sys/resource/linux/getrlimit.cpp
    libc/src/sys/resource/linux/setrlimit.cpp
    libc/src/sys/resource/setrlimit.h
    libc/test/src/sys/resource/CMakeLists.txt
    libc/test/src/sys/resource/getrlimit_setrlimit_test.cpp
    libc/test/src/sys/resource/testdata/CMakeLists.txt

Modified: 
    libc/config/linux/api.td
    libc/config/linux/x86_64/entrypoints.txt
    libc/include/CMakeLists.txt
    libc/include/llvm-libc-macros/CMakeLists.txt
    libc/include/llvm-libc-macros/linux/CMakeLists.txt
    libc/include/llvm-libc-types/CMakeLists.txt
    libc/spec/posix.td
    libc/src/sys/CMakeLists.txt
    libc/test/src/sys/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/libc/config/linux/api.td b/libc/config/linux/api.td
index 92b42ffbed885..a77a4b5a9d9b7 100644
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -271,6 +271,10 @@ def UniStdAPI : PublicAPI<"unistd.h"> {
   let Types = ["off_t", "size_t", "ssize_t"];
 }
 
+def SysResourceAPI : PublicAPI<"sys/resource.h"> {
+  let Types = ["rlim_t", "struct rlimit_t"];
+}
+
 def SysStatAPI : PublicAPI<"sys/stat.h"> {
   let Types = ["mode_t"];
 }

diff  --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 620f86920ffd2..750670e25a80a 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -101,6 +101,10 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap
 
+    # sys/resource.h entrypoints
+    libc.src.sys.resource.getrlimit
+    libc.src.sys.resource.setrlimit
+
     # sys/sendfile entrypoints
     libc.src.sys.sendfile.sendfile
 

diff  --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 1a31bd8463a57..412c130bf58a9 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -203,6 +203,17 @@ add_gen_header(
     .llvm-libc-types.ssize_t
 )
 
+add_gen_header(
+  sys_resource
+  DEF_FILE sys/resource.h.def
+  GEN_HDR sys/resource.h
+  DEPENDS
+    .llvm_libc_common_h
+    .llvm-libc-macros.sys_resource_macros
+    .llvm-libc-types.rlim_t
+    .llvm-libc-types.struct_rlimit_t
+)
+
 add_gen_header(
   sys_stat
   DEF_FILE sys/stat.h.def

diff  --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index 4d19ed6c092df..1a53b535dadba 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -22,6 +22,14 @@ add_header(
     .linux.sys_stat_macros
 )
 
+add_header(
+  sys_resource_macros
+  HDR
+    sys-resource-macros.h
+  DEPENDS
+    .linux.sys_resource_macros
+)
+
 add_header(
   unistd_macros
   HDR

diff  --git a/libc/include/llvm-libc-macros/linux/CMakeLists.txt b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
index 199f9b6edc330..3fb9efcbfdf71 100644
--- a/libc/include/llvm-libc-macros/linux/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
@@ -10,6 +10,12 @@ add_header(
     sys-stat-macros.h
 )
 
+add_header(
+  sys_resource_macros
+  HDR
+    sys-resource-macros.h
+)
+
 add_header(
   unistd_macros
   HDR

diff  --git a/libc/include/llvm-libc-macros/linux/sys-resource-macros.h b/libc/include/llvm-libc-macros/linux/sys-resource-macros.h
new file mode 100644
index 0000000000000..dd265530ada26
--- /dev/null
+++ b/libc/include/llvm-libc-macros/linux/sys-resource-macros.h
@@ -0,0 +1,26 @@
+//===-- Macros defined in sys/resource.h header file ----------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#define RLIMIT_CPU 0
+#define RLIMIT_FSIZE 1
+#define RLIMIT_DATA 2
+#define RLIMIT_STACK 3
+#define RLIMIT_CORE 4
+#define RLIMIT_RSS 5
+#define RLIMIT_NPROC 6
+#define RLIMIT_NOFILE 7
+#define RLIMIT_MEMLOCK 8
+#define RLIMIT_AS 9
+#define RLIMIT_LOCKS 10
+#define RLIMIT_SIGPENDING 11
+#define RLIMIT_MSGQUEUE 12
+#define RLIMIT_NICE 13
+#define RLIMIT_RTPRIO 14
+#define RLIMIT_RTTIME 15
+
+#define RLIM_INFINITY (~0UL)

diff  --git a/libc/include/llvm-libc-macros/sys-resource-macros.h b/libc/include/llvm-libc-macros/sys-resource-macros.h
new file mode 100644
index 0000000000000..d85bdde07cf80
--- /dev/null
+++ b/libc/include/llvm-libc-macros/sys-resource-macros.h
@@ -0,0 +1,16 @@
+//===-- Macros defined in sys/resource.h header file ----------------------===//
+//
+// 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_MACROS_SYS_RESOURCE_MACROS_H
+#define __LLVM_LIBC_MACROS_SYS_RESOURCE_MACROS_H
+
+#ifdef __unix__
+#include "linux/sys-resource-macros.h"
+#endif
+
+#endif // __LLVM_LIBC_MACROS_SYS_RESOURCE_MACROS_H

diff  --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index b0f520b8425fb..bf7be2517affa 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -31,6 +31,8 @@ add_header(pthread_key_t HDR pthread_key_t.h)
 add_header(pthread_mutex_t HDR pthread_mutex_t.h DEPENDS .__futex_word .__mutex_type)
 add_header(pthread_t HDR pthread_t.h DEPENDS .__thread_type)
 add_header(pthread_mutexattr_t HDR pthread_mutexattr_t.h)
+add_header(rlim_t HDR rlim_t.h)
+add_header(struct_rlimit_t HDR struct_rlimit_t.h DEPENDS .rlim_t)
 add_header(ssize_t HDR ssize_t.h)
 add_header(struct_dirent HDR struct_dirent.h DEPENDS .ino_t .off_t)
 add_header(struct_sigaction HDR struct_sigaction.h)

diff  --git a/libc/include/llvm-libc-types/rlim_t.h b/libc/include/llvm-libc-types/rlim_t.h
new file mode 100644
index 0000000000000..467a715c31df3
--- /dev/null
+++ b/libc/include/llvm-libc-types/rlim_t.h
@@ -0,0 +1,14 @@
+//===-- Definition of type rlim_t -----------------------------------------===//
+//
+// 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_TYPES_RLIM_T_H__
+#define __LLVM_LIBC_TYPES_RLIM_T_H__
+
+typedef unsigned long rlim_t;
+
+#endif // __LLVM_LIBC_TYPES_RLIM_T_H__

diff  --git a/libc/include/llvm-libc-types/struct_rlimit_t.h b/libc/include/llvm-libc-types/struct_rlimit_t.h
new file mode 100644
index 0000000000000..1b546239b6235
--- /dev/null
+++ b/libc/include/llvm-libc-types/struct_rlimit_t.h
@@ -0,0 +1,19 @@
+//===-- Definition of type rlimit_t ---------------------------------------===//
+//
+// 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_TYPES_RLIMIT_T_H__
+#define __LLVM_LIBC_TYPES_RLIMIT_T_H__
+
+#include <llvm-libc-types/rlim_t.h>
+
+struct rlimit_t {
+  rlim_t rlim_cur;
+  rlim_t rlim_max;
+};
+
+#endif // __LLVM_LIBC_TYPES_RLIMIT_T_H__

diff  --git a/libc/include/sys/resource.h.def b/libc/include/sys/resource.h.def
new file mode 100644
index 0000000000000..31132d3b26087
--- /dev/null
+++ b/libc/include/sys/resource.h.def
@@ -0,0 +1,18 @@
+//===-- POSIX header resource.h -------------------------------------------===//
+//
+// 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_SYS_RESOURCE_H
+#define LLVM_LIBC_SYS_RESOURCE_H
+
+#include <__llvm-libc-common.h>
+
+#include <llvm-libc-macros/sys-resource-macros.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_SYS_RESOURCE_H

diff  --git a/libc/spec/posix.td b/libc/spec/posix.td
index b0520dbfcb2bd..f7d71434069d5 100644
--- a/libc/spec/posix.td
+++ b/libc/spec/posix.td
@@ -465,6 +465,29 @@ def POSIX : StandardSpec<"POSIX"> {
     ]
   >;
 
+  NamedType RLimTType = NamedType<"rlim_t">;
+  NamedType StructRLimitTType = NamedType<"struct rlimit_t">;
+  PtrType StructRLimitPtr = PtrType<StructRLimitTType>;
+  ConstType ConstStructRLimitPtr = ConstType<StructRLimitTType>;
+  HeaderSpec SysResource = HeaderSpec<
+    "sys/resource.h",
+    [], // Macros
+    [RLimTType, StructRLimitTType], // Types
+    [], // Enumerations
+    [
+        FunctionSpec<
+          "getrlimit",
+          RetValSpec<IntType>,
+          [ArgSpec<StructRLimitPtr>]
+        >,
+        FunctionSpec<
+          "setrlimit",
+          RetValSpec<IntType>,
+          [ArgSpec<ConstStructRLimitPtr>]
+        >,
+    ]
+  >;
+
   HeaderSpec SysStat = HeaderSpec<
     "sys/stat.h",
     [], // Macros
@@ -764,6 +787,7 @@ def POSIX : StandardSpec<"POSIX"> {
     StdIO,
     StdLib,
     SysMMan,
+    SysResource,
     SysStat,
     UniStd,
     String

diff  --git a/libc/src/sys/CMakeLists.txt b/libc/src/sys/CMakeLists.txt
index 36d0cdf47cbb1..5239aa84da46f 100644
--- a/libc/src/sys/CMakeLists.txt
+++ b/libc/src/sys/CMakeLists.txt
@@ -1,3 +1,4 @@
 add_subdirectory(mman)
+add_subdirectory(resource)
 add_subdirectory(sendfile)
 add_subdirectory(stat)

diff  --git a/libc/src/sys/resource/CMakeLists.txt b/libc/src/sys/resource/CMakeLists.txt
new file mode 100644
index 0000000000000..8319b6399650c
--- /dev/null
+++ b/libc/src/sys/resource/CMakeLists.txt
@@ -0,0 +1,17 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+  getrlimit
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.getrlimit
+)
+
+add_entrypoint_object(
+  setrlimit
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.setrlimit
+)

diff  --git a/libc/src/sys/resource/getrlimit.h b/libc/src/sys/resource/getrlimit.h
new file mode 100644
index 0000000000000..e8449684d881e
--- /dev/null
+++ b/libc/src/sys/resource/getrlimit.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for getrlimit ---------------------*- 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_STAT_GETRLIMIT_H
+#define LLVM_LIBC_SRC_SYS_STAT_GETRLIMIT_H
+
+#include <sys/resource.h>
+
+namespace __llvm_libc {
+
+int getrlimit(int resource, struct rlimit_t *lim);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SYS_STAT_GETRLIMIT_H

diff  --git a/libc/src/sys/resource/linux/CMakeLists.txt b/libc/src/sys/resource/linux/CMakeLists.txt
new file mode 100644
index 0000000000000..19f3901c98a29
--- /dev/null
+++ b/libc/src/sys/resource/linux/CMakeLists.txt
@@ -0,0 +1,25 @@
+add_entrypoint_object(
+  getrlimit
+  SRCS
+    getrlimit.cpp
+  HDRS
+    ../getrlimit.h
+  DEPENDS
+    libc.include.sys_resource
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  setrlimit
+  SRCS
+    setrlimit.cpp
+  HDRS
+    ../setrlimit.h
+  DEPENDS
+    libc.include.sys_resource
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

diff  --git a/libc/src/sys/resource/linux/getrlimit.cpp b/libc/src/sys/resource/linux/getrlimit.cpp
new file mode 100644
index 0000000000000..2b42a13436a18
--- /dev/null
+++ b/libc/src/sys/resource/linux/getrlimit.cpp
@@ -0,0 +1,29 @@
+//===-- Linux implementation of getrlimit ---------------------------------===//
+//
+// 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/resource/getrlimit.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <sys/resource.h> // For struct rlimit_t
+#include <sys/syscall.h>  // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, getrlimit, (int res, struct rlimit_t *limits)) {
+  long ret = __llvm_libc::syscall(SYS_prlimit64, 0, res, nullptr, limits);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

diff  --git a/libc/src/sys/resource/linux/setrlimit.cpp b/libc/src/sys/resource/linux/setrlimit.cpp
new file mode 100644
index 0000000000000..43d843f228ed8
--- /dev/null
+++ b/libc/src/sys/resource/linux/setrlimit.cpp
@@ -0,0 +1,29 @@
+//===-- Linux implementation of setrlimit ---------------------------------===//
+//
+// 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/resource/setrlimit.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <sys/resource.h> // For struct rlimit_t
+#include <sys/syscall.h>  // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, setrlimit, (int res, const struct rlimit_t *limits)) {
+  long ret = __llvm_libc::syscall(SYS_prlimit64, 0, res, limits, nullptr);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

diff  --git a/libc/src/sys/resource/setrlimit.h b/libc/src/sys/resource/setrlimit.h
new file mode 100644
index 0000000000000..ba48e824edaa5
--- /dev/null
+++ b/libc/src/sys/resource/setrlimit.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for setrlimit ---------------------*- 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_STAT_SETRLIMIT_H
+#define LLVM_LIBC_SRC_SYS_STAT_SETRLIMIT_H
+
+#include <sys/resource.h>
+
+namespace __llvm_libc {
+
+int setrlimit(int resource, const struct rlimit_t *lim);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SYS_STAT_SETRLIMIT_H

diff  --git a/libc/test/src/sys/CMakeLists.txt b/libc/test/src/sys/CMakeLists.txt
index 36d0cdf47cbb1..5239aa84da46f 100644
--- a/libc/test/src/sys/CMakeLists.txt
+++ b/libc/test/src/sys/CMakeLists.txt
@@ -1,3 +1,4 @@
 add_subdirectory(mman)
+add_subdirectory(resource)
 add_subdirectory(sendfile)
 add_subdirectory(stat)

diff  --git a/libc/test/src/sys/resource/CMakeLists.txt b/libc/test/src/sys/resource/CMakeLists.txt
new file mode 100644
index 0000000000000..574a4dc8d64c0
--- /dev/null
+++ b/libc/test/src/sys/resource/CMakeLists.txt
@@ -0,0 +1,20 @@
+add_libc_testsuite(libc_sys_resource_unittests)
+
+add_subdirectory(testdata)
+
+add_libc_unittest(
+  getrlimit_setrlimit_test
+  SUITE
+    libc_sys_resource_unittests
+  SRCS
+    getrlimit_setrlimit_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.fcntl
+    libc.include.sys_resource
+    libc.src.fcntl.open
+    libc.src.sys.resource.getrlimit
+    libc.src.sys.resource.setrlimit
+    libc.src.unistd.close
+    libc.src.unistd.unlink
+)

diff  --git a/libc/test/src/sys/resource/getrlimit_setrlimit_test.cpp b/libc/test/src/sys/resource/getrlimit_setrlimit_test.cpp
new file mode 100644
index 0000000000000..c4265f0be42eb
--- /dev/null
+++ b/libc/test/src/sys/resource/getrlimit_setrlimit_test.cpp
@@ -0,0 +1,77 @@
+//===-- Unittests for getrlimit and setrlimit -----------------------------===//
+//
+// 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_view.h"
+#include "src/fcntl/open.h"
+#include "src/sys/resource/getrlimit.h"
+#include "src/sys/resource/setrlimit.h"
+#include "src/unistd/close.h"
+#include "src/unistd/unlink.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+#include <errno.h>
+#include <sys/resource.h>
+
+TEST(LlvmLibcResourceLimitsTest, SetNoFileLimit) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+
+  // The test strategy is to first create initialize two file descriptors
+  // successfully. Next, close the files and set the file descriptor limit
+  // to 4. This will allow us to open one of those file but not the other.
+
+  constexpr const char *TEST_FILE1 = "testdata/resource_limits1.test";
+  constexpr const char *TEST_FILE2 = "testdata/resource_limits2.test";
+  errno = 0;
+
+  int fd1 = __llvm_libc::open(TEST_FILE1, O_CREAT | O_WRONLY, S_IRWXU);
+  ASSERT_GT(fd1, 0);
+  ASSERT_EQ(errno, 0);
+  int fd2 = __llvm_libc::open(TEST_FILE2, O_CREAT | O_WRONLY, S_IRWXU);
+  ASSERT_GT(fd2, 0);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_THAT(__llvm_libc::close(fd1), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::close(fd2), Succeeds(0));
+
+  struct rlimit_t limits {
+    4, 4
+  };
+  ASSERT_THAT(__llvm_libc::setrlimit(RLIMIT_NOFILE, &limits), Succeeds(0));
+
+  // One can now only open one of the files successfully.
+  fd1 = __llvm_libc::open(TEST_FILE1, O_RDONLY);
+  ASSERT_GT(fd1, 0);
+  ASSERT_EQ(errno, 0);
+  fd2 = __llvm_libc::open(TEST_FILE2, O_RDONLY);
+  ASSERT_LT(fd2, 0);
+  ASSERT_NE(errno, 0);
+
+  errno = 0;
+  ASSERT_THAT(__llvm_libc::close(fd1), Succeeds(0));
+
+  fd2 = __llvm_libc::open(TEST_FILE2, O_RDONLY);
+  ASSERT_GT(fd2, 0);
+  ASSERT_EQ(errno, 0);
+  fd1 = __llvm_libc::open(TEST_FILE1, O_RDONLY);
+  ASSERT_LT(fd1, 0);
+  ASSERT_NE(errno, 0);
+
+  errno = 0;
+  ASSERT_THAT(__llvm_libc::close(fd2), Succeeds(0));
+
+  ASSERT_THAT(__llvm_libc::unlink(TEST_FILE1), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::unlink(TEST_FILE2), Succeeds(0));
+
+  struct rlimit_t current_limits;
+  ASSERT_THAT(__llvm_libc::getrlimit(RLIMIT_NOFILE, &current_limits),
+              Succeeds(0));
+  ASSERT_EQ(current_limits.rlim_cur, rlim_t(4));
+  ASSERT_EQ(current_limits.rlim_max, rlim_t(4));
+}

diff  --git a/libc/test/src/sys/resource/testdata/CMakeLists.txt b/libc/test/src/sys/resource/testdata/CMakeLists.txt
new file mode 100644
index 0000000000000..e69de29bb2d1d

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