[compiler-rt] [rtsan] Add ioctl interceptor (PR #117569)

[via llvm-commits]

================
@@ -373,6 +375,57 @@ class RtsanOpenedFileTest : public RtsanFileTest {
   int fd = -1;
 };
 
+TEST(TestRtsanInterceptors, IoctlDiesWhenRealtime) {
+  auto Func = []() { ioctl(0, FIONREAD); };
+  ExpectRealtimeDeath(Func, "ioctl");
+  ExpectNonRealtimeSurvival(Func);
+}
+
+TEST_F(RtsanOpenedFileTest, IoctlBehavesWithOutputArg) {
+  int arg{};
+  ioctl(GetOpenFd(), FIONREAD, &arg);
+
+  EXPECT_THAT(arg, Ge(0));
+}
+
+TEST(TestRtsanInterceptors, IoctlBehavesWithOutputPointer) {
+  // These initial checks just see if we CAN run these tests.
+  // If we can't (can't open a socket, or can't find an interface, just
+  // gracefully skip.
+  int sock = socket(AF_INET, SOCK_STREAM, 0);
+  if (sock == -1) {
+    perror("socket");
+    GTEST_SKIP();
+    return;
+  }
+
+  struct ifaddrs *ifaddr = nullptr;
+  if (getifaddrs(&ifaddr) == -1 || ifaddr == nullptr) {
+    perror("getifaddrs");
+    close(sock);
+    GTEST_SKIP();
+    return;
+  }
+
+  struct ifreq ifr {};
+  strncpy(ifr.ifr_name, ifaddr->ifa_name, IFNAMSIZ - 1);
+
+  int retval = ioctl(sock, SIOCGIFADDR, &ifr);
+  if (retval == -1) {
+    perror("ioctl");
+    close(sock);
+    freeifaddrs(ifaddr);
+    ASSERT_TRUE(false) << "ioctl failed";
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davidtrevelyan wrote:

Could replace `ASSERT_TRUE(false)` with `FAIL()`, and `return` underneath is also not needed

https://github.com/llvm/llvm-project/pull/117569