[libc-commits] [libc] [llvm] [libc] add remaining epoll functions, pipe (PR #84587)

via libc-commits libc-commits at lists.llvm.org
Fri Mar 8 16:28:16 PST 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Michael Jones (michaelrj-google)

<details>
<summary>Changes</summary>

The epoll_wait functions need the rest of the epoll functions (create,
ctl) to be available to actually test them, as well as pipe to create a
usable file descriptor. This patch adds epoll_create, epoll_create1,
epoll_ctl, and pipe. These have tests, and the tests for epoll_wait,
epoll_pwait, and epoll_pwait2 (currently disabled) are updated to use
these newly available functions.


---

Patch is 37.26 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/84587.diff


34 Files Affected:

- (modified) libc/config/linux/x86_64/entrypoints.txt (+4) 
- (modified) libc/include/CMakeLists.txt (+1) 
- (modified) libc/include/llvm-libc-macros/CMakeLists.txt (+6) 
- (modified) libc/include/llvm-libc-macros/linux/CMakeLists.txt (+6) 
- (added) libc/include/llvm-libc-macros/linux/sys-epoll-macros.h (+38) 
- (added) libc/include/llvm-libc-macros/sys-epoll-macros.h (+16) 
- (modified) libc/include/sys/epoll.h.def (+1) 
- (modified) libc/spec/posix.td (+5) 
- (modified) libc/src/sys/epoll/CMakeLists.txt (+21) 
- (added) libc/src/sys/epoll/epoll_create.h (+18) 
- (added) libc/src/sys/epoll/epoll_create1.h (+18) 
- (added) libc/src/sys/epoll/epoll_ctl.h (+25) 
- (modified) libc/src/sys/epoll/linux/CMakeLists.txt (+37) 
- (added) libc/src/sys/epoll/linux/epoll_create.cpp (+39) 
- (added) libc/src/sys/epoll/linux/epoll_create1.cpp (+31) 
- (added) libc/src/sys/epoll/linux/epoll_ctl.cpp (+38) 
- (modified) libc/src/sys/epoll/linux/epoll_pwait.cpp (+3-3) 
- (modified) libc/src/sys/epoll/linux/epoll_pwait2.cpp (+3-3) 
- (modified) libc/src/sys/epoll/linux/epoll_wait.cpp (+3-2) 
- (modified) libc/src/unistd/CMakeLists.txt (+7) 
- (modified) libc/src/unistd/linux/CMakeLists.txt (+13) 
- (added) libc/src/unistd/linux/pipe.cpp (+33) 
- (added) libc/src/unistd/pipe.h (+18) 
- (modified) libc/test/src/sys/epoll/linux/CMakeLists.txt (+57) 
- (added) libc/test/src/sys/epoll/linux/epoll_create1_test.cpp (+32) 
- (added) libc/test/src/sys/epoll/linux/epoll_create_test.cpp (+22) 
- (added) libc/test/src/sys/epoll/linux/epoll_ctl_test.cpp (+44) 
- (modified) libc/test/src/sys/epoll/linux/epoll_pwait2_test.cpp (+37-5) 
- (modified) libc/test/src/sys/epoll/linux/epoll_pwait_test.cpp (+34-5) 
- (modified) libc/test/src/sys/epoll/linux/epoll_wait_test.cpp (+31-4) 
- (modified) libc/test/src/unistd/CMakeLists.txt (+15) 
- (added) libc/test/src/unistd/pipe_test.cpp (+26) 
- (modified) utils/bazel/llvm-project-overlay/libc/BUILD.bazel (+44) 
- (modified) utils/bazel/llvm-project-overlay/libc/test/src/sys/epoll/BUILD.bazel (+41) 


``````````diff
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 27c9a42934c240..46eeaa7f1d15ae 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -194,6 +194,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.fscanf
 
     # sys/epoll.h entrypoints
+    libc.src.sys.epoll.epoll_create
+    libc.src.sys.epoll.epoll_create1
+    libc.src.sys.epoll.epoll_ctl
     libc.src.sys.epoll.epoll_wait
     libc.src.sys.epoll.epoll_pwait
     # TODO: Need to check if pwait2 is available before providing.
@@ -280,6 +283,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.link
     libc.src.unistd.linkat
     libc.src.unistd.lseek
+    libc.src.unistd.pipe
     libc.src.unistd.pread
     libc.src.unistd.pwrite
     libc.src.unistd.read
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 9090b3bca01e0d..3b6bd212b4fad3 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -369,6 +369,7 @@ add_gen_header(
     .llvm-libc-types.struct_epoll_event
     .llvm-libc-types.struct_epoll_data
     .llvm-libc-types.sigset_t
+    .llvm-libc-macros.sys_epoll_macros
 )
 
 add_gen_header(
diff --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index 157b786aa7e815..ea49c8662f9cd3 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -137,6 +137,12 @@ add_macro_header(
     sys-auxv-macros.h
 )
 
+add_macro_header(
+  sys_epoll_macros
+  HDR
+    sys-epoll-macros.h
+)
+
 add_macro_header(
   sys_ioctl_macros
   HDR
diff --git a/libc/include/llvm-libc-macros/linux/CMakeLists.txt b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
index d934c3a0fca6f8..4ee429d1db166a 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(
     sched-macros.h
 )
 
+add_header(
+  sys_epoll_macros
+  HDR
+    sys-epoll-macros.h
+)
+
 add_header(
   sys_ioctl_macros
   HDR
diff --git a/libc/include/llvm-libc-macros/linux/sys-epoll-macros.h b/libc/include/llvm-libc-macros/linux/sys-epoll-macros.h
new file mode 100644
index 00000000000000..59fb2c23ce9426
--- /dev/null
+++ b/libc/include/llvm-libc-macros/linux/sys-epoll-macros.h
@@ -0,0 +1,38 @@
+//===-- Macros defined in sys/epoll.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_LINUX_SYS_EPOLL_MACROS_H
+#define LLVM_LIBC_MACROS_LINUX_SYS_EPOLL_MACROS_H
+
+#include "llvm-libc-macros/linux/fcntl-macros.h"
+
+// TODO: Do we need to define these?
+
+#define EPOLL_CLOEXEC O_CLOEXEC
+
+#define EPOLL_CTL_ADD 1
+#define EPOLL_CTL_DEL 2
+#define EPOLL_CTL_MOD 3
+
+#define EPOLLIN 0x1
+#define EPOLLPRI 0x2
+#define EPOLLOUT 0x4
+#define EPOLLERR 0x8
+#define EPOLLHUP 0x10
+#define EPOLLRDNORM 0x40
+#define EPOLLRDBAND 0x80
+#define EPOLLWRNORM 0x100
+#define EPOLLWRBAND 0x200
+#define EPOLLMSG 0x400
+#define EPOLLRDHUP 0x2000
+#define EPOLLEXCLUSIVE 0x10000000
+#define EPOLLWAKEUP 0x20000000
+#define EPOLLONESHOT 0x40000000
+#define EPOLLET 0x80000000
+
+#endif // LLVM_LIBC_MACROS_LINUX_SYS_EPOLL_MACROS_H
diff --git a/libc/include/llvm-libc-macros/sys-epoll-macros.h b/libc/include/llvm-libc-macros/sys-epoll-macros.h
new file mode 100644
index 00000000000000..8212df252b8e7e
--- /dev/null
+++ b/libc/include/llvm-libc-macros/sys-epoll-macros.h
@@ -0,0 +1,16 @@
+//===-- Macros defined in sys/epoll.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_EPOLL_MACROS_H
+#define LLVM_LIBC_MACROS_SYS_EPOLL_MACROS_H
+
+#ifdef __linux__
+#include "linux/sys-epoll-macros.h"
+#endif
+
+#endif // LLVM_LIBC_MACROS_SYS_EPOLL_MACROS_H
diff --git a/libc/include/sys/epoll.h.def b/libc/include/sys/epoll.h.def
index 490fad91db3c3a..9579eada248fab 100644
--- a/libc/include/sys/epoll.h.def
+++ b/libc/include/sys/epoll.h.def
@@ -10,6 +10,7 @@
 #define LLVM_LIBC_SYS_EPOLL_H
 
 #include <__llvm-libc-common.h>
+#include <llvm-libc-macros/sys-epoll-macros.h>
 
 %%public_api()
 
diff --git a/libc/spec/posix.td b/libc/spec/posix.td
index 70be692e208a88..7cfa208948dd47 100644
--- a/libc/spec/posix.td
+++ b/libc/spec/posix.td
@@ -548,6 +548,11 @@ def POSIX : StandardSpec<"POSIX"> {
           RetValSpec<OffTType>,
           [ArgSpec<IntType>, ArgSpec<OffTType>, ArgSpec<IntType>]
         >,
+        FunctionSpec<
+          "pipe",
+          RetValSpec<IntType>,
+          [ArgSpec<IntPtr>] //TODO: make this int[2]
+        >,
         FunctionSpec<
           "pread",
           RetValSpec<SSizeTType>,
diff --git a/libc/src/sys/epoll/CMakeLists.txt b/libc/src/sys/epoll/CMakeLists.txt
index d4991a238e2a77..e785f535bf0cfb 100644
--- a/libc/src/sys/epoll/CMakeLists.txt
+++ b/libc/src/sys/epoll/CMakeLists.txt
@@ -2,6 +2,27 @@ if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
 endif()
 
+add_entrypoint_object(
+  epoll_create
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.epoll_create
+)
+
+add_entrypoint_object(
+  epoll_create1
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.epoll_create1
+)
+
+add_entrypoint_object(
+  epoll_ctl
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.epoll_ctl
+)
+
 add_entrypoint_object(
   epoll_wait
   ALIAS
diff --git a/libc/src/sys/epoll/epoll_create.h b/libc/src/sys/epoll/epoll_create.h
new file mode 100644
index 00000000000000..a1eeabd567e4c8
--- /dev/null
+++ b/libc/src/sys/epoll/epoll_create.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for epoll_create 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_CREATE_H
+#define LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_CREATE_H
+
+namespace LIBC_NAMESPACE {
+
+int epoll_create(int size);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_CREATE_H
diff --git a/libc/src/sys/epoll/epoll_create1.h b/libc/src/sys/epoll/epoll_create1.h
new file mode 100644
index 00000000000000..70f446b5926608
--- /dev/null
+++ b/libc/src/sys/epoll/epoll_create1.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for epoll_create1 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_CREATE1_H
+#define LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_CREATE1_H
+
+namespace LIBC_NAMESPACE {
+
+int epoll_create1(int flags);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_CREATE1_H
diff --git a/libc/src/sys/epoll/epoll_ctl.h b/libc/src/sys/epoll/epoll_ctl.h
new file mode 100644
index 00000000000000..06f8f530cf39c1
--- /dev/null
+++ b/libc/src/sys/epoll/epoll_ctl.h
@@ -0,0 +1,25 @@
+//===-- Implementation header for epoll_ctl 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_CTL_H
+#define LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_CTL_H
+
+// TODO: Use this include once the include headers are also using quotes.
+// #include "include/llvm-libc-types/sigset_t.h"
+// #include "include/llvm-libc-types/struct_epoll_event.h"
+
+#include <sys/epoll.h>
+
+namespace LIBC_NAMESPACE {
+
+// TODO: event should be nullable
+int epoll_ctl(int epfd, int op, int fd, epoll_event *event);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_EPOLL_EPOLL_CTL_H
diff --git a/libc/src/sys/epoll/linux/CMakeLists.txt b/libc/src/sys/epoll/linux/CMakeLists.txt
index a27905d962dc57..ab3000b58992ec 100644
--- a/libc/src/sys/epoll/linux/CMakeLists.txt
+++ b/libc/src/sys/epoll/linux/CMakeLists.txt
@@ -1,3 +1,40 @@
+add_entrypoint_object(
+  epoll_create
+  SRCS
+    epoll_create.cpp
+  HDRS
+    ../epoll_create.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  epoll_create1
+  SRCS
+    epoll_create1.cpp
+  HDRS
+    ../epoll_create1.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  epoll_ctl
+  SRCS
+    epoll_ctl.cpp
+  HDRS
+    ../epoll_ctl.h
+  DEPENDS
+    libc.include.sys_epoll
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
 add_entrypoint_object(
   epoll_wait
   SRCS
diff --git a/libc/src/sys/epoll/linux/epoll_create.cpp b/libc/src/sys/epoll/linux/epoll_create.cpp
new file mode 100644
index 00000000000000..382320edca7353
--- /dev/null
+++ b/libc/src/sys/epoll/linux/epoll_create.cpp
@@ -0,0 +1,39 @@
+//===---------- Linux implementation of the epoll_create 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_create.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_create, (int size)) {
+#ifdef SYS_epoll_create
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_epoll_create, size);
+#elif defined(SYS_epoll_create1)
+  // TODO: Silence warning for size being unused.
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_epoll_create1, 0);
+#else
+#error                                                                         \
+    "epoll_create and epoll_create1 are unavailable. Unable to build epoll_create."
+#endif
+
+  // 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 ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/sys/epoll/linux/epoll_create1.cpp b/libc/src/sys/epoll/linux/epoll_create1.cpp
new file mode 100644
index 00000000000000..30f1a9910274d0
--- /dev/null
+++ b/libc/src/sys/epoll/linux/epoll_create1.cpp
@@ -0,0 +1,31 @@
+//===---------- Linux implementation of the epoll_create1 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_create1.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_create1, (int flags)) {
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_epoll_create1, 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 ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/sys/epoll/linux/epoll_ctl.cpp b/libc/src/sys/epoll/linux/epoll_ctl.cpp
new file mode 100644
index 00000000000000..2835dfc6f3a244
--- /dev/null
+++ b/libc/src/sys/epoll/linux/epoll_ctl.cpp
@@ -0,0 +1,38 @@
+//===---------- Linux implementation of the epoll_ctl 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_ctl.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.
+
+// TODO: Use this include once the include headers are also using quotes.
+// #include "include/llvm-libc-types/struct_epoll_event.h"
+
+#include <sys/epoll.h>
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, epoll_ctl,
+                   (int epfd, int op, int fd, epoll_event *event)) {
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_epoll_ctl, epfd, op, fd,
+                                              reinterpret_cast<long>(event));
+
+  // 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 ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/sys/epoll/linux/epoll_pwait.cpp b/libc/src/sys/epoll/linux/epoll_pwait.cpp
index ee1b4e66e98444..4c4c6425bc16f2 100644
--- a/libc/src/sys/epoll/linux/epoll_pwait.cpp
+++ b/libc/src/sys/epoll/linux/epoll_pwait.cpp
@@ -10,7 +10,6 @@
 
 #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.
 
@@ -19,6 +18,7 @@
 // #include "include/llvm-libc-types/struct_epoll_event.h"
 
 #include <sys/epoll.h>
+#include <signal.h> // for NSIG
 
 namespace LIBC_NAMESPACE {
 
@@ -27,7 +27,7 @@ LLVM_LIBC_FUNCTION(int, epoll_pwait,
                     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));
+      reinterpret_cast<long>(sigmask), NSIG / 8);
 
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
@@ -36,7 +36,7 @@ LLVM_LIBC_FUNCTION(int, epoll_pwait,
     return -1;
   }
 
-  return 0;
+  return ret;
 }
 
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/sys/epoll/linux/epoll_pwait2.cpp b/libc/src/sys/epoll/linux/epoll_pwait2.cpp
index 671dede2a1058d..4fea4a6bc83b1e 100644
--- a/libc/src/sys/epoll/linux/epoll_pwait2.cpp
+++ b/libc/src/sys/epoll/linux/epoll_pwait2.cpp
@@ -10,7 +10,6 @@
 
 #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.
 
@@ -20,6 +19,7 @@
 // #include "include/llvm-libc-types/struct_timespec.h"
 
 #include <sys/epoll.h>
+#include <signal.h> // for NSIG
 
 namespace LIBC_NAMESPACE {
 
@@ -29,7 +29,7 @@ LLVM_LIBC_FUNCTION(int, epoll_pwait2,
   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));
+      NSIG / 8);
 
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
@@ -38,7 +38,7 @@ LLVM_LIBC_FUNCTION(int, epoll_pwait2,
     return -1;
   }
 
-  return 0;
+  return ret;
 }
 
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/sys/epoll/linux/epoll_wait.cpp b/libc/src/sys/epoll/linux/epoll_wait.cpp
index 0c43edf7645454..514306f0a076f4 100644
--- a/libc/src/sys/epoll/linux/epoll_wait.cpp
+++ b/libc/src/sys/epoll/linux/epoll_wait.cpp
@@ -18,6 +18,7 @@
 // #include "include/llvm-libc-types/struct_epoll_event.h"
 
 #include <sys/epoll.h>
+#include <signal.h> // for NSIG
 
 namespace LIBC_NAMESPACE {
 
@@ -30,7 +31,7 @@ LLVM_LIBC_FUNCTION(int, epoll_wait,
 #elif defined(SYS_epoll_pwait)
   int ret = LIBC_NAMESPACE::syscall_impl<int>(
       SYS_epoll_pwait, epfd, reinterpret_cast<long>(events), maxevents, timeout,
-      reinterpret_cast<long>(nullptr), sizeof(sigset_t));
+      reinterpret_cast<long>(nullptr), NSIG / 8);
 #else
 #error "epoll_wait and epoll_pwait are unavailable. Unable to build epoll_wait."
 #endif
@@ -41,7 +42,7 @@ LLVM_LIBC_FUNCTION(int, epoll_wait,
     return -1;
   }
 
-  return 0;
+  return ret;
 }
 
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/unistd/CMakeLists.txt b/libc/src/unistd/CMakeLists.txt
index e22b0e1872caa1..368c4f0328eda2 100644
--- a/libc/src/unistd/CMakeLists.txt
+++ b/libc/src/unistd/CMakeLists.txt
@@ -149,6 +149,13 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.lseek
 )
 
+add_entrypoint_object(
+  pipe
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pipe
+)
+
 add_entrypoint_object(
   pread
   ALIAS
diff --git a/libc/src/unistd/linux/CMakeLists.txt b/libc/src/unistd/linux/CMakeLists.txt
index df85d44e9e9edc..7d831f9c29c74f 100644
--- a/libc/src/unistd/linux/CMakeLists.txt
+++ b/libc/src/unistd/linux/CMakeLists.txt
@@ -273,6 +273,19 @@ add_entrypoint_object(
     libc.src.errno.errno
 )
 
+add_entrypoint_object(
+  pipe
+  SRCS
+    pipe.cpp
+  HDRS
+    ../pipe.h
+  DEPENDS
+    libc.include.unistd
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
 add_entrypoint_object(
   pread
   SRCS
diff --git a/libc/src/unistd/linux/pipe.cpp b/libc/src/unistd/linux/pipe.cpp
new file mode 100644
index 00000000000000..b4e8b9b7d9c85e
--- /dev/null
+++ b/libc/src/unistd/linux/pipe.cpp
@@ -0,0 +1,33 @@
+//===-- Linux implementation of pipe --------------------------------------===//
+//
+// 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/pipe.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, pipe, (int pipefd[2])) {
+#ifdef SYS_pipe
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_pipe,
+                                              reinterpret_cast<long>(pipefd));
+#elif defined(SYS_pipe2)
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_pipe2, reinterpret_cast<long>(pipefd), 0);
+#endif
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/unistd/pipe.h b/libc/src/unistd/pipe.h
new file mode 100644
index 00000000000000..0e20bb49c05849
--- /dev/null
+++ b/libc/src/unistd/pipe.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for pipe --------------------------*- 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_PIPE_H
+#define LLVM_LIBC_SRC_UNISTD_PIPE_H
+
+namespace LIBC_NAMESPACE {
+
+int pipe(int pipefd[2]);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_UNISTD_PIPE_H
diff --git a/libc/test/src/sys/epoll/linux/CMakeLists.txt b/libc/test/src/sys/epoll...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/84587


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