[llvm] [libc] [libc] add epoll_wait functions (PR #79515)

via llvm-commits llvm-commits at lists.llvm.org
Thu Jan 25 14:27:33 PST 2024


https://github.com/michaelrj-google created https://github.com/llvm/llvm-project/pull/79515

The epoll_wait functions are syscall wrappers that were requested by
upstream users. This patch adds them, as well as their header and types.

The tests are currently incomplete since they require epoll_create to
properly test epoll_wait. That will be added in a followup patch since
this one is already very large.


>From dca91e3bdef2fa5839384efc04835c2fb4999151 Mon Sep 17 00:00:00 2001
From: Michael Jones <michaelrj at google.com>
Date: Thu, 25 Jan 2024 13:49:13 -0800
Subject: [PATCH] [libc] add epoll_wait functions

The epoll_wait functions are syscall wrappers that were requested by
upstream users. This patch adds them, as well as their header and types.

The tests are currently incomplete since they require epoll_create to
properly test epoll_wait. That will be added in a followup patch since
this one is already very large.
---
 libc/config/linux/api.td                      | 12 ++-
 libc/config/linux/syscall_numbers.h.inc       |  4 +
 libc/config/linux/x86_64/entrypoints.txt      |  5 ++
 libc/config/linux/x86_64/headers.txt          |  1 +
 libc/include/CMakeLists.txt                   | 11 +++
 libc/include/llvm-libc-types/CMakeLists.txt   |  2 +
 .../llvm-libc-types/struct_epoll_data.h       | 21 +++++
 .../llvm-libc-types/struct_epoll_event.h      | 19 +++++
 libc/include/sys/epoll.h.def                  | 16 ++++
 libc/spec/gnu_ext.td                          |  4 +-
 libc/spec/linux.td                            | 77 +++++++++++++++++++
 libc/src/sys/CMakeLists.txt                   |  1 +
 libc/src/sys/epoll/CMakeLists.txt             | 24 ++++++
 libc/src/sys/epoll/epoll_pwait.h              | 23 ++++++
 libc/src/sys/epoll/epoll_pwait2.h             | 24 ++++++
 libc/src/sys/epoll/epoll_wait.h               | 21 +++++
 libc/src/sys/epoll/linux/CMakeLists.txt       | 41 ++++++++++
 libc/src/sys/epoll/linux/epoll_pwait.cpp      | 38 +++++++++
 libc/src/sys/epoll/linux/epoll_pwait2.cpp     | 40 ++++++++++
 libc/src/sys/epoll/linux/epoll_wait.cpp       | 35 +++++++++
 libc/test/src/sys/CMakeLists.txt              |  1 +
 libc/test/src/sys/epoll/CMakeLists.txt        |  3 +
 libc/test/src/sys/epoll/linux/CMakeLists.txt  | 39 ++++++++++
 .../src/sys/epoll/linux/epoll_pwait2_test.cpp | 20 +++++
 .../src/sys/epoll/linux/epoll_pwait_test.cpp  | 20 +++++
 .../src/sys/epoll/linux/epoll_wait_test.cpp   | 20 +++++
 .../llvm-project-overlay/libc/BUILD.bazel     | 32 ++++++++
 .../libc/test/src/sys/epoll/BUILD.bazel       | 35 +++++++++
 28 files changed, 584 insertions(+), 5 deletions(-)
 create mode 100644 libc/include/llvm-libc-types/struct_epoll_data.h
 create mode 100644 libc/include/llvm-libc-types/struct_epoll_event.h
 create mode 100644 libc/include/sys/epoll.h.def
 create mode 100644 libc/src/sys/epoll/CMakeLists.txt
 create mode 100644 libc/src/sys/epoll/epoll_pwait.h
 create mode 100644 libc/src/sys/epoll/epoll_pwait2.h
 create mode 100644 libc/src/sys/epoll/epoll_wait.h
 create mode 100644 libc/src/sys/epoll/linux/CMakeLists.txt
 create mode 100644 libc/src/sys/epoll/linux/epoll_pwait.cpp
 create mode 100644 libc/src/sys/epoll/linux/epoll_pwait2.cpp
 create mode 100644 libc/src/sys/epoll/linux/epoll_wait.cpp
 create mode 100644 libc/test/src/sys/epoll/CMakeLists.txt
 create mode 100644 libc/test/src/sys/epoll/linux/CMakeLists.txt
 create mode 100644 libc/test/src/sys/epoll/linux/epoll_pwait2_test.cpp
 create mode 100644 libc/test/src/sys/epoll/linux/epoll_pwait_test.cpp
 create mode 100644 libc/test/src/sys/epoll/linux/epoll_wait_test.cpp
 create mode 100644 utils/bazel/llvm-project-overlay/libc/test/src/sys/epoll/BUILD.bazel

diff --git a/libc/config/linux/api.td b/libc/config/linux/api.td
index 85f6b59264eb06d..b8fe16cc0c79ea3 100644
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -1,11 +1,11 @@
 include "config/public_api.td"
 
-include "spec/bsd_ext.td"
-include "spec/gnu_ext.td"
+include "spec/stdc.td"
+include "spec/posix.td"
 include "spec/linux.td"
+include "spec/gnu_ext.td"
+include "spec/bsd_ext.td"
 include "spec/llvm_libc_ext.td"
-include "spec/posix.td"
-include "spec/stdc.td"
 
 def AssertMacro : MacroDef<"assert"> {
   let Defn = [{
@@ -242,6 +242,10 @@ def SysUtsNameAPI : PublicAPI<"sys/utsname.h"> {
   let Types = ["struct utsname"];
 }
 
+def SysEpollAPI : PublicAPI<"sys/epoll.h"> {
+  let Types = ["struct epoll_event", "struct epoll_data", "sigset_t", "struct timespec"];
+}
+
 def SpawnAPI : PublicAPI<"spawn.h"> {
   let Types = ["mode_t", "pid_t", "posix_spawnattr_t", "posix_spawn_file_actions_t"];
 }
diff --git a/libc/config/linux/syscall_numbers.h.inc b/libc/config/linux/syscall_numbers.h.inc
index 5bbb08878ef9df9..9f910c5f9042a81 100644
--- a/libc/config/linux/syscall_numbers.h.inc
+++ b/libc/config/linux/syscall_numbers.h.inc
@@ -258,6 +258,10 @@
 #define SYS_epoll_pwait __NR_epoll_pwait
 #endif
 
+#ifdef __NR_epoll_pwait2
+#define SYS_epoll_pwait2 __NR_epoll_pwait2
+#endif
+
 #ifdef __NR_epoll_wait
 #define SYS_epoll_wait __NR_epoll_wait
 #endif
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 5b43188e75cd744..00a847160cda9f7 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -136,6 +136,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.scanf
     libc.src.stdio.fscanf
 
+    # sys/epoll.h entrypoints
+    libc.src.sys.epoll.epoll_wait
+    libc.src.sys.epoll.epoll_pwait
+    libc.src.sys.epoll.epoll_pwait2
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.madvise
     libc.src.sys.mman.mmap
diff --git a/libc/config/linux/x86_64/headers.txt b/libc/config/linux/x86_64/headers.txt
index d103176897a74a8..e2bea1fb31f36df 100644
--- a/libc/config/linux/x86_64/headers.txt
+++ b/libc/config/linux/x86_64/headers.txt
@@ -29,6 +29,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.arpa_inet
 
     libc.include.sys_auxv
+    libc.include.sys_epoll
     libc.include.sys_ioctl
     libc.include.sys_mman
     libc.include.sys_prctl
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 89fffd1022758ea..24e50fb6a47e019 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -332,6 +332,17 @@ add_gen_header(
     .llvm-libc-macros.sys_auxv_macros
 )
 
+add_gen_header(
+  sys_epoll
+  DEF_FILE sys/epoll.h.def
+  GEN_HDR sys/epoll.h
+  DEPENDS
+    .llvm_libc_common_h
+    .llvm-libc-types.struct_epoll_event
+    .llvm-libc-types.struct_epoll_data
+    .llvm-libc-types.sigset_t
+)
+
 add_gen_header(
   sys_ioctl
   DEF_FILE sys/ioctl.h.def
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index 500900ffa0bbb05..6f004d2d6469705 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -96,3 +96,5 @@ add_header(rpc_opcodes_t HDR rpc_opcodes_t.h)
 add_header(ACTION HDR ACTION.h)
 add_header(ENTRY HDR ENTRY.h)
 add_header(struct_hsearch_data HDR struct_hsearch_data.h)
+add_header(struct_epoll_event HDR struct_epoll_event.h)
+add_header(struct_epoll_data HDR struct_epoll_data.h)
diff --git a/libc/include/llvm-libc-types/struct_epoll_data.h b/libc/include/llvm-libc-types/struct_epoll_data.h
new file mode 100644
index 000000000000000..c363171089f116f
--- /dev/null
+++ b/libc/include/llvm-libc-types/struct_epoll_data.h
@@ -0,0 +1,21 @@
+//===-- Definition of epoll_data type -------------------------------------===//
+//
+// 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_EPOLL_DATA_H__
+#define __LLVM_LIBC_TYPES_EPOLL_DATA_H__
+
+union epoll_data {
+  void *ptr;
+  int fd;
+  __UINT32_TYPE__ u32;
+  __UINT64_TYPE__ u64;
+};
+
+typedef union epoll_data epoll_data_t;
+
+#endif // __LLVM_LIBC_TYPES_EPOLL_DATA_H__
diff --git a/libc/include/llvm-libc-types/struct_epoll_event.h b/libc/include/llvm-libc-types/struct_epoll_event.h
new file mode 100644
index 000000000000000..425dd51e030cc1c
--- /dev/null
+++ b/libc/include/llvm-libc-types/struct_epoll_event.h
@@ -0,0 +1,19 @@
+//===-- Definition of epoll_event type ------------------------------------===//
+//
+// 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_EPOLL_EVENT_H__
+#define __LLVM_LIBC_TYPES_EPOLL_EVENT_H__
+
+#include <llvm-libc-types/epoll_data.h>
+
+typedef struct epoll_event {
+  __UINT32_TYPE__ events;
+  epoll_data_t data;
+};
+
+#endif // __LLVM_LIBC_TYPES_EPOLL_EVENT_H__
diff --git a/libc/include/sys/epoll.h.def b/libc/include/sys/epoll.h.def
new file mode 100644
index 000000000000000..490fad91db3c3a5
--- /dev/null
+++ b/libc/include/sys/epoll.h.def
@@ -0,0 +1,16 @@
+//===-- Linux header epoll.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_EPOLL_H
+#define LLVM_LIBC_SYS_EPOLL_H
+
+#include <__llvm-libc-common.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_SYS_EPOLL_H
diff --git a/libc/spec/gnu_ext.td b/libc/spec/gnu_ext.td
index cb0407c84d4e212..1b1b35b4d028be0 100644
--- a/libc/spec/gnu_ext.td
+++ b/libc/spec/gnu_ext.td
@@ -238,7 +238,9 @@ def GnuExtensions : StandardSpec<"GNUExtensions"> {
       [], // Macros
       [], // Types
       [], // Enumerations
-      []  // Functions
+      [
+        //TODO: Add getauxval here
+      ]  // Functions
   >;
 
   HeaderSpec SendFile = HeaderSpec<
diff --git a/libc/spec/linux.td b/libc/spec/linux.td
index eab0a987b920cd9..9fa8734db7eba66 100644
--- a/libc/spec/linux.td
+++ b/libc/spec/linux.td
@@ -1,3 +1,8 @@
+def StructEpollEvent : NamedType<"struct epoll_event">;
+def StructEpollEventPtr : PtrType<StructEpollEvent>;
+
+def StructEpollData : NamedType<"struct epoll_data">;
+
 def Linux : StandardSpec<"Linux"> {
   HeaderSpec Errno = HeaderSpec<
       "errno.h",
@@ -137,6 +142,77 @@ def Linux : StandardSpec<"Linux"> {
       []  // Functions
   >;
 
+
+  HeaderSpec SysEpoll = HeaderSpec<
+      "sys/epoll.h",
+      [], // Macros
+      [
+        StructEpollEvent,
+        StructEpollData,
+        SigSetType,
+        StructTimeSpec,
+      ], // Types
+      [], // Enumerations
+      [
+        FunctionSpec<
+          "epoll_create",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>
+          ]
+        >,
+        FunctionSpec<
+          "epoll_create1",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>
+          ]
+        >,
+        FunctionSpec<
+          "epoll_ctl",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>,
+            ArgSpec<IntType>,
+            ArgSpec<IntType>,
+            ArgSpec<StructEpollEventPtr>
+          ]
+        >,
+        FunctionSpec<
+          "epoll_wait",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>,
+            ArgSpec<StructEpollEventPtr>,
+            ArgSpec<IntType>,
+            ArgSpec<IntType>
+          ]
+        >,
+        FunctionSpec<
+          "epoll_pwait",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>,
+            ArgSpec<StructEpollEventPtr>,
+            ArgSpec<IntType>,
+            ArgSpec<IntType>,
+            ArgSpec<SigSetPtrType>
+          ]
+        >,
+        FunctionSpec<
+          "epoll_pwait2",
+          RetValSpec<IntType>,
+          [
+            ArgSpec<IntType>,
+            ArgSpec<StructEpollEventPtr>,
+            ArgSpec<IntType>,
+            ArgSpec<ConstStructTimeSpecPtr>,
+            ArgSpec<SigSetPtrType>
+          ]
+        >,
+      ]  // Functions
+  >;
+
   HeaderSpec Signal = HeaderSpec<
       "signal.h",
       [
@@ -181,6 +257,7 @@ def Linux : StandardSpec<"Linux"> {
 
   let Headers = [
     Errno,
+    SysEpoll,
     SysMMan,
     SysPrctl,
     SysRandom,
diff --git a/libc/src/sys/CMakeLists.txt b/libc/src/sys/CMakeLists.txt
index 81098294176ad5b..57ea7b4beaca1bf 100644
--- a/libc/src/sys/CMakeLists.txt
+++ b/libc/src/sys/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_subdirectory(auxv)
+add_subdirectory(epoll)
 add_subdirectory(mman)
 add_subdirectory(random)
 add_subdirectory(resource)
diff --git a/libc/src/sys/epoll/CMakeLists.txt b/libc/src/sys/epoll/CMakeLists.txt
new file mode 100644
index 000000000000000..d4991a238e2a77f
--- /dev/null
+++ b/libc/src/sys/epoll/CMakeLists.txt
@@ -0,0 +1,24 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+  epoll_wait
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.epoll_wait
+)
+
+add_entrypoint_object(
+  epoll_pwait
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.epoll_pwait
+)
+
+add_entrypoint_object(
+  epoll_pwait2
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.epoll_pwait2
+)
diff --git a/libc/src/sys/epoll/epoll_pwait.h b/libc/src/sys/epoll/epoll_pwait.h
new file mode 100644
index 000000000000000..f4042cc9888f677
--- /dev/null
+++ b/libc/src/sys/epoll/epoll_pwait.h
@@ -0,0 +1,23 @@
+//===-- Implementation header for epoll_pwait 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_EPOLL_EPOLL_PWAIT_H
+#define LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_PWAIT_H
+
+#include <signal.h>    // For sigset_t
+#include <sys/epoll.h> // For epoll_event
+
+namespace LIBC_NAMESPACE {
+
+// TODO: sigmask should be nullable
+int epoll_pwait(int epfd, struct epoll_event *events, int maxevents,
+                int timeout, const sigset_t *sigmask);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_PWAIT_H
diff --git a/libc/src/sys/epoll/epoll_pwait2.h b/libc/src/sys/epoll/epoll_pwait2.h
new file mode 100644
index 000000000000000..17ea4b2c226a6b2
--- /dev/null
+++ b/libc/src/sys/epoll/epoll_pwait2.h
@@ -0,0 +1,24 @@
+//===-- Implementation header for epoll_pwait2 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_EPOLL_EPOLL_PWAIT2_H
+#define LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_PWAIT2_H
+
+#include <signal.h>    // For sigset_t
+#include <sys/epoll.h> // For epoll_event
+#include <time.h>      // For timespec
+
+namespace LIBC_NAMESPACE {
+
+// TODO: sigmask and timeout should be nullable
+int epoll_pwait2(int epfd, struct epoll_event *events, int maxevents,
+                 const struct timespec *timeout, const sigset_t *sigmask);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_PWAIT2_H
diff --git a/libc/src/sys/epoll/epoll_wait.h b/libc/src/sys/epoll/epoll_wait.h
new file mode 100644
index 000000000000000..b8f768aabf16d6d
--- /dev/null
+++ b/libc/src/sys/epoll/epoll_wait.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for epoll_wait 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_EPOLL_EPOLL_WAIT_H
+#define LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_WAIT_H
+
+#include <sys/epoll.h> // For epoll_event
+
+namespace LIBC_NAMESPACE {
+
+int epoll_wait(int epfd, struct epoll_event *events, int maxevents,
+               int timeout);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_WAIT_H
diff --git a/libc/src/sys/epoll/linux/CMakeLists.txt b/libc/src/sys/epoll/linux/CMakeLists.txt
new file mode 100644
index 000000000000000..a27905d962dc57e
--- /dev/null
+++ b/libc/src/sys/epoll/linux/CMakeLists.txt
@@ -0,0 +1,41 @@
+add_entrypoint_object(
+  epoll_wait
+  SRCS
+    epoll_wait.cpp
+  HDRS
+    ../epoll_wait.h
+  DEPENDS
+    libc.include.sys_epoll
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  epoll_pwait
+  SRCS
+    epoll_pwait.cpp
+  HDRS
+    ../epoll_pwait.h
+  DEPENDS
+    libc.include.sys_epoll
+    libc.include.signal
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  epoll_pwait2
+  SRCS
+    epoll_pwait2.cpp
+  HDRS
+    ../epoll_pwait2.h
+  DEPENDS
+    libc.include.sys_epoll
+    libc.include.signal
+    libc.include.time
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
diff --git a/libc/src/sys/epoll/linux/epoll_pwait.cpp b/libc/src/sys/epoll/linux/epoll_pwait.cpp
new file mode 100644
index 000000000000000..e3a7b6e0393bdd6
--- /dev/null
+++ b/libc/src/sys/epoll/linux/epoll_pwait.cpp
@@ -0,0 +1,38 @@
+//===---------- Linux implementation of the epoll_pwait 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/epoll/epoll_pwait.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "src/errno/libc_errno.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+#include <signal.h> // For sigset_t
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, epoll_pwait,
+                   (int epfd, struct epoll_event *events, int maxevents,
+                    int timeout, const sigset_t *sigmask)) {
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_epoll_pwait, epfd, reinterpret_cast<long>(events), maxevents, timeout,
+      reinterpret_cast<long>(sigmask), sizeof(sigset_t));
+
+  // 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
diff --git a/libc/src/sys/epoll/linux/epoll_pwait2.cpp b/libc/src/sys/epoll/linux/epoll_pwait2.cpp
new file mode 100644
index 000000000000000..25ca0ae06f4402d
--- /dev/null
+++ b/libc/src/sys/epoll/linux/epoll_pwait2.cpp
@@ -0,0 +1,40 @@
+//===---------- Linux implementation of the epoll_pwait2 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/epoll/epoll_pwait2.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "src/errno/libc_errno.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+#include <signal.h> // For sigset_t
+#include <time.h>   // For timespec
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, epoll_pwait2,
+                   (int epfd, struct epoll_event *events, int maxevents,
+                    const struct timespec *timeout, const sigset_t *sigmask)) {
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_epoll_pwait2, epfd, reinterpret_cast<long>(events), maxevents,
+      reinterpret_cast<long>(timeout), reinterpret_cast<long>(sigmask),
+      sizeof(sigset_t));
+
+  // 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
diff --git a/libc/src/sys/epoll/linux/epoll_wait.cpp b/libc/src/sys/epoll/linux/epoll_wait.cpp
new file mode 100644
index 000000000000000..b305575e099f212
--- /dev/null
+++ b/libc/src/sys/epoll/linux/epoll_wait.cpp
@@ -0,0 +1,35 @@
+//===---------- Linux implementation of the epoll_wait 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/epoll/epoll_wait.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "src/errno/libc_errno.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, epoll_wait,
+                   (int epfd, struct epoll_event *events, int maxevents,
+                    int timeout)) {
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_epoll_wait, epfd, reinterpret_cast<long>(events), maxevents, timeout);
+
+  // 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
diff --git a/libc/test/src/sys/CMakeLists.txt b/libc/test/src/sys/CMakeLists.txt
index c7095456383b300..7f228e709046d0a 100644
--- a/libc/test/src/sys/CMakeLists.txt
+++ b/libc/test/src/sys/CMakeLists.txt
@@ -9,3 +9,4 @@ add_subdirectory(utsname)
 add_subdirectory(wait)
 add_subdirectory(prctl)
 add_subdirectory(auxv)
+add_subdirectory(epoll)
diff --git a/libc/test/src/sys/epoll/CMakeLists.txt b/libc/test/src/sys/epoll/CMakeLists.txt
new file mode 100644
index 000000000000000..b4bbe81c92ff2eb
--- /dev/null
+++ b/libc/test/src/sys/epoll/CMakeLists.txt
@@ -0,0 +1,3 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${LIBC_TARGET_OS})
+endif()
diff --git a/libc/test/src/sys/epoll/linux/CMakeLists.txt b/libc/test/src/sys/epoll/linux/CMakeLists.txt
new file mode 100644
index 000000000000000..e346af2328db212
--- /dev/null
+++ b/libc/test/src/sys/epoll/linux/CMakeLists.txt
@@ -0,0 +1,39 @@
+add_custom_target(libc_sys_epoll_unittests)
+add_libc_unittest(
+  epoll_wait_test
+  SUITE
+    libc_sys_epoll_unittests
+  SRCS
+    epoll_wait_test.cpp
+  DEPENDS
+    libc.include.sys_epoll
+    libc.src.errno.errno
+    libc.src.sys.epoll.epoll_wait
+    libc.test.UnitTest.ErrnoSetterMatcher
+)
+
+add_libc_unittest(
+  epoll_pwait_test
+  SUITE
+    libc_sys_epoll_unittests
+  SRCS
+    epoll_pwait_test.cpp
+  DEPENDS
+    libc.include.sys_epoll
+    libc.src.errno.errno
+    libc.src.sys.epoll.epoll_pwait
+    libc.test.UnitTest.ErrnoSetterMatcher
+)
+
+add_libc_unittest(
+  epoll_pwait2_test
+  SUITE
+    libc_sys_epoll_unittests
+  SRCS
+    epoll_pwait2_test.cpp
+  DEPENDS
+    libc.include.sys_epoll
+    libc.src.errno.errno
+    libc.src.sys.epoll.epoll_pwait2
+    libc.test.UnitTest.ErrnoSetterMatcher
+)
diff --git a/libc/test/src/sys/epoll/linux/epoll_pwait2_test.cpp b/libc/test/src/sys/epoll/linux/epoll_pwait2_test.cpp
new file mode 100644
index 000000000000000..83fe12bb8eb6574
--- /dev/null
+++ b/libc/test/src/sys/epoll/linux/epoll_pwait2_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for epoll_pwait2 ----------------------------------------===//
+//
+// 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/epoll/epoll_pwait2.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+
+TEST(LlvmLibcEpollWaitTest, Basic) {
+  EXPECT_THAT(LIBC_NAMESPACE::epoll_pwait2(-1, nullptr, 0, nullptr, nullptr),
+              returns(EQ(-1ul)).with_errno(EQ(EINVAL)));
+}
+
+// TODO: Complete these tests when epoll_create is implemented.
diff --git a/libc/test/src/sys/epoll/linux/epoll_pwait_test.cpp b/libc/test/src/sys/epoll/linux/epoll_pwait_test.cpp
new file mode 100644
index 000000000000000..217facbfcebb9d0
--- /dev/null
+++ b/libc/test/src/sys/epoll/linux/epoll_pwait_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for epoll_pwait -----------------------------------------===//
+//
+// 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/epoll/epoll_pwait.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+
+TEST(LlvmLibcEpollWaitTest, Basic) {
+  EXPECT_THAT(LIBC_NAMESPACE::epoll_pwait(-1, nullptr, 0, 0, nullptr),
+              returns(EQ(-1ul)).with_errno(EQ(EINVAL)));
+}
+
+// TODO: Complete these tests when epoll_create is implemented.
diff --git a/libc/test/src/sys/epoll/linux/epoll_wait_test.cpp b/libc/test/src/sys/epoll/linux/epoll_wait_test.cpp
new file mode 100644
index 000000000000000..57fef3f690b6242
--- /dev/null
+++ b/libc/test/src/sys/epoll/linux/epoll_wait_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for epoll_wait ------------------------------------------===//
+//
+// 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/epoll/epoll_wait.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+
+TEST(LlvmLibcEpollWaitTest, Basic) {
+  EXPECT_THAT(LIBC_NAMESPACE::epoll_wait(-1, nullptr, 0, 0),
+              returns(EQ(-1ul)).with_errno(EQ(EINVAL)));
+}
+
+// TODO: Complete these tests when epoll_create is implemented.
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index e601fa7e4377d4a..3b8ce044b7fc7d0 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2942,3 +2942,35 @@ libc_function(
         ":vfprintf_internal",
     ],
 )
+
+############################## sys/epoll targets ###############################
+
+libc_function(
+    name = "epoll_wait",
+    srcs = ["src/sys/epoll/linux/epoll_wait.cpp"],
+    hdrs = ["src/sys/epoll/epoll_wait.h"],
+    deps = [
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
+
+libc_function(
+    name = "epoll_pwait",
+    srcs = ["src/sys/epoll/linux/epoll_pwait.cpp"],
+    hdrs = ["src/sys/epoll/epoll_pwait.h"],
+    deps = [
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
+
+libc_function(
+    name = "epoll_pwait2",
+    srcs = ["src/sys/epoll/linux/epoll_pwait2.cpp"],
+    hdrs = ["src/sys/epoll/epoll_pwait2.h"],
+    deps = [
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/sys/epoll/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/sys/epoll/BUILD.bazel
new file mode 100644
index 000000000000000..e0afce60e6bc2fc
--- /dev/null
+++ b/utils/bazel/llvm-project-overlay/libc/test/src/sys/epoll/BUILD.bazel
@@ -0,0 +1,35 @@
+# This file is licensed 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
+
+# Tests for LLVM libc string.h functions.
+
+load("//libc/test:libc_test_rules.bzl", "libc_test")
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+libc_test(
+    name = "epoll_wait_test",
+    srcs = ["linux/epoll_wait_test.cpp"],
+    libc_function_deps = [
+        "//libc:epoll_wait",
+    ],
+)
+
+libc_test(
+    name = "epoll_pwait_test",
+    srcs = ["linux/epoll_pwait_test.cpp"],
+    libc_function_deps = [
+        "//libc:epoll_pwait",
+    ],
+)
+
+libc_test(
+    name = "epoll_pwait2_test",
+    srcs = ["linux/epoll_pwait2_test.cpp"],
+    libc_function_deps = [
+        "//libc:epoll_pwait2",
+    ],
+)



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