1 files changed, 31 insertions, 2 deletions
diff --git a/test/syscalls/linux/pty.cc b/test/syscalls/linux/pty.cc
index 99a0df235..f9392b9e0 100644
--- a/test/syscalls/linux/pty.cc
+++ b/test/syscalls/linux/pty.cc
@@ -70,6 +70,8 @@ constexpr absl::Duration kTimeout = absl::Seconds(20);
 // The maximum line size in bytes returned per read from a pty file.
 constexpr int kMaxLineSize = 4096;
 
+constexpr char kMasterPath[] = "/dev/ptmx";
+
 // glibc defines its own, different, version of struct termios. We care about
 // what the kernel does, not glibc.
 #define KERNEL_NCCS 19
@@ -362,6 +364,12 @@ PosixErrorOr<size_t> PollAndReadFd(int fd, void* buf, size_t count,
     ssize_t n =
         ReadFd(fd, static_cast<char*>(buf) + completed, count - completed);
     if (n < 0) {
+      if (errno == EAGAIN) {
+        // Linux sometimes returns EAGAIN from this read, despite the fact that
+        // poll returned success. Let's just do what do as we are told and try
+        // again.
+        continue;
+      }
       return PosixError(errno, "read failed");
     }
     completed += n;
@@ -376,9 +384,25 @@ PosixErrorOr<size_t> PollAndReadFd(int fd, void* buf, size_t count,
   return PosixError(ETIMEDOUT, "Poll timed out");
 }
 
+TEST(PtyTrunc, Truncate) {
+  // Opening PTYs with O_TRUNC shouldn't cause an error, but calls to
+  // (f)truncate should.
+  FileDescriptor master =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(kMasterPath, O_RDWR | O_TRUNC));
+  int n = ASSERT_NO_ERRNO_AND_VALUE(SlaveID(master));
+  std::string spath = absl::StrCat("/dev/pts/", n);
+  FileDescriptor slave =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(spath, O_RDWR | O_NONBLOCK | O_TRUNC));
+
+  EXPECT_THAT(truncate(kMasterPath, 0), SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(truncate(spath.c_str(), 0), SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(ftruncate(master.get(), 0), SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(ftruncate(slave.get(), 0), SyscallFailsWithErrno(EINVAL));
+}
+
 TEST(BasicPtyTest, StatUnopenedMaster) {
   struct stat s;
-  ASSERT_THAT(stat("/dev/ptmx", &s), SyscallSucceeds());
+  ASSERT_THAT(stat(kMasterPath, &s), SyscallSucceeds());
 
   EXPECT_EQ(s.st_rdev, makedev(TTYAUX_MAJOR, kPtmxMinor));
   EXPECT_EQ(s.st_size, 0);
@@ -610,6 +634,11 @@ TEST_F(PtyTest, TermiosAffectsSlave) {
 // Verify this by setting ICRNL (which rewrites input \r to \n) and verify that
 // it has no effect on the master.
 TEST_F(PtyTest, MasterTermiosUnchangable) {
+  struct kernel_termios master_termios = {};
+  EXPECT_THAT(ioctl(master_.get(), TCGETS, &master_termios), SyscallSucceeds());
+  master_termios.c_lflag |= ICRNL;
+  EXPECT_THAT(ioctl(master_.get(), TCSETS, &master_termios), SyscallSucceeds());
+
   char c = '\r';
   ASSERT_THAT(WriteFd(slave_.get(), &c, 1), SyscallSucceedsWithValue(1));
 
@@ -1108,7 +1137,7 @@ TEST_F(PtyTest, SwitchTwiceMultiline) {
   std::string kExpected = "GO\nBLUE\n!";
 
   // Write each line.
-  for (std::string input : kInputs) {
+  for (const std::string& input : kInputs) {
     ASSERT_THAT(WriteFd(master_.get(), input.c_str(), input.size()),
                 SyscallSucceedsWithValue(input.size()));
   }