[DFSan] Add custom wrapper for epoll_wait.

The wrapper clears shadow for any events written.

Reviewed By: stephan.yichao.zhao

Differential Revision: https://reviews.llvm.org/D92891

Author: morehouse

compiler-rt/lib/dfsan/dfsan_custom.cpp

@@ -11,12 +11,6 @@
 // This file defines the custom functions listed in done_abilist.txt.
 //===----------------------------------------------------------------------===//
 
-#include "sanitizer_common/sanitizer_common.h"
-#include "sanitizer_common/sanitizer_internal_defs.h"
-#include "sanitizer_common/sanitizer_linux.h"
-
-#include "dfsan/dfsan.h"
-
 #include <arpa/inet.h>
 #include <assert.h>
 #include <ctype.h>
@@ -32,6 +26,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/epoll.h>
 #include <sys/resource.h>
 #include <sys/select.h>
 #include <sys/stat.h>
@@ -40,6 +35,11 @@
 #include <time.h>
 #include <unistd.h>
 
+#include "dfsan/dfsan.h"
+#include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_internal_defs.h"
+#include "sanitizer_common/sanitizer_linux.h"
+
 using namespace __dfsan;
 
 #define CALL_WEAK_INTERCEPTOR_HOOK(f, ...)                                     \
@@ -715,6 +715,18 @@ int __dfsw_getpwuid_r(id_t uid, struct passwd *pwd,
   return ret;
 }
 
+SANITIZER_INTERFACE_ATTRIBUTE
+int __dfsw_epoll_wait(int epfd, struct epoll_event *events, int maxevents,
+                      int timeout, dfsan_label epfd_label,
+                      dfsan_label events_label, dfsan_label maxevents_label,
+                      dfsan_label timeout_label, dfsan_label *ret_label) {
+  int ret = epoll_wait(epfd, events, maxevents, timeout);
+  if (ret > 0)
+    dfsan_set_label(0, events, ret * sizeof(*events));
+  *ret_label = 0;
+  return ret;
+}
+
 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_poll(struct pollfd *fds, nfds_t nfds, int timeout,
                 dfsan_label dfs_label, dfsan_label nfds_label,

compiler-rt/lib/dfsan/done_abilist.txt

@@ -184,6 +184,7 @@ fun:uselocale=discard
 fun:calloc=custom
 fun:clock_gettime=custom
 fun:dlopen=custom
+fun:epoll_wait=custom
 fun:fgets=custom
 fun:fstat=custom
 fun:getcwd=custom

compiler-rt/test/dfsan/custom.cpp

@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <strings.h>
+#include <sys/epoll.h>
 #include <sys/resource.h>
 #include <sys/select.h>
 #include <sys/stat.h>
@@ -638,6 +639,46 @@ void test_getpwuid_r() {
   ASSERT_READ_ZERO_LABEL(&pwd, 4);
 }
 
+void test_epoll_wait() {
+  // Set up a pipe to monitor with epoll.
+  int pipe_fds[2];
+  int ret = pipe(pipe_fds);
+  assert(ret != -1);
+
+  // Configure epoll to monitor the pipe.
+  int epfd = epoll_create1(0);
+  assert(epfd != -1);
+  struct epoll_event event;
+  event.events = EPOLLIN;
+  event.data.fd = pipe_fds[0];
+  ret = epoll_ctl(epfd, EPOLL_CTL_ADD, pipe_fds[0], &event);
+  assert(ret != -1);
+
+  // Test epoll_wait when no events have occurred.
+  event = {};
+  dfsan_set_label(i_label, &event, sizeof(event));
+  ret = epoll_wait(epfd, &event, /*maxevents=*/1, /*timeout=*/0);
+  assert(ret == 0);
+  assert(event.events == 0);
+  assert(event.data.fd == 0);
+  ASSERT_ZERO_LABEL(ret);
+  ASSERT_READ_LABEL(&event, sizeof(event), i_label);
+
+  // Test epoll_wait when an event occurs.
+  write(pipe_fds[1], "x", 1);
+  ret = epoll_wait(epfd, &event, /*maxevents=*/1, /*timeout=*/0);
+  assert(ret == 1);
+  assert(event.events == EPOLLIN);
+  assert(event.data.fd == pipe_fds[0]);
+  ASSERT_ZERO_LABEL(ret);
+  ASSERT_READ_ZERO_LABEL(&event, sizeof(event));
+
+  // Clean up.
+  close(epfd);
+  close(pipe_fds[0]);
+  close(pipe_fds[1]);
+}
+
 void test_poll() {
   struct pollfd fd;
   fd.fd = 0;
@@ -1027,6 +1068,7 @@ int main(void) {
   test_dfsan_set_write_callback();
   test_dl_iterate_phdr();
   test_dlopen();
+  test_epoll_wait();
   test_fgets();
   test_fstat();
   test_get_current_dir_name();