From 4af0789caf1080e06c756d3076930bb8077b72cf Mon Sep 17 00:00:00 2001
From: Kyle Huey <khuey@kylehuey.com>
Date: Thu, 27 Mar 2025 13:41:51 -0700
Subject: [PATCH] Support TCGETS2 and TCSETS2.

Fixes #2430
---
 src/record_syscall.cc | 19 +++++++++++++++++++
 src/test/ioctl_tty.c  | 29 +++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/record_syscall.cc b/src/record_syscall.cc
index 45ba46c90be..faf86af0e6f 100644
--- a/src/record_syscall.cc
+++ b/src/record_syscall.cc
@@ -103,6 +103,23 @@
 
 using namespace std;
 
+// The kernel header that defines this conflicts badly with glibc headers
+// so we define it ourselves.
+// NB: We need this struct defined so that the preprocessor macro for
+// TCGETS2 will evaluate. But we use IOCTL_MASK_SIZE on it and we use
+// the size from the tracee to determine how many bytes to record, so
+// we don't actually depend on this being *accurate*.
+struct termios2 {
+  tcflag_t c_iflag;
+  tcflag_t c_oflag;
+  tcflag_t c_cflag;
+  tcflag_t c_lflag;
+  cc_t c_line;
+  cc_t c_cc[19];
+  speed_t c_ispeed;
+  speed_t c_ospeed;
+};
+
 namespace rr {
 
 union _semun {
@@ -1943,6 +1960,7 @@ static Switchable prepare_ioctl(RecordTask* t,
       case IOCTL_MASK_SIZE(TUNSETIFINDEX):
       case IOCTL_MASK_SIZE(TUNSETVNETLE):
       case IOCTL_MASK_SIZE(TUNSETVNETBE):
+      case IOCTL_MASK_SIZE(TCSETS2):
         return PREVENT_SWITCH;
       case IOCTL_MASK_SIZE(USBDEVFS_GETDRIVER):
         // Reads and writes its parameter despite not having the _IOC_READ bit.
@@ -2078,6 +2096,7 @@ static Switchable prepare_ioctl(RecordTask* t,
     case IOCTL_MASK_SIZE(OTPGETREGIONINFO):
     case IOCTL_MASK_SIZE(ECCGETLAYOUT):
     case IOCTL_MASK_SIZE(ECCGETSTATS):
+    case IOCTL_MASK_SIZE(TCGETS2):
       syscall_state.reg_parameter(3, size);
       return PREVENT_SWITCH;
 
diff --git a/src/test/ioctl_tty.c b/src/test/ioctl_tty.c
index 98ee07d8289..17ca3d4c8f6 100644
--- a/src/test/ioctl_tty.c
+++ b/src/test/ioctl_tty.c
@@ -2,10 +2,26 @@
 
 #include "util.h"
 
+/* We have to define termios2 ourselves. See
+ * https://github.com/npat-efault/picocom/blob/1acf1ddabaf3576b4023c4f6f09c5a3e4b086fb8/termios2.txt
+ * for the long explanation.
+ */
+struct termios2 {
+  tcflag_t c_iflag;
+  tcflag_t c_oflag;
+  tcflag_t c_cflag;
+  tcflag_t c_lflag;
+  cc_t c_line;
+  cc_t c_cc[19];
+  speed_t c_ispeed;
+  speed_t c_ospeed;
+};
+
 int main(void) {
   int fd;
   int ret;
   struct termios* tc;
+  struct termios2* tc2;
   struct termio* tio;
   pid_t* pgrp;
   int* navail;
@@ -94,6 +110,19 @@ int main(void) {
   VERIFY_GUARD(nread);
   atomic_printf("FIONREAD returned nread=%d\n", *nread);
 
+  ALLOCATE_GUARD(tc2, 'i');
+  test_assert(0 == ioctl(fd, TCGETS2, tc));
+  VERIFY_GUARD(tc2);
+  atomic_printf("TCGETS2 returned { iflag=0x%x, oflag=0x%x, cflag=0x%x, "
+                "lflag=0x%x, ispeed=%d, ospeed=%d }\n",
+                tc2->c_iflag, tc2->c_oflag, tc2->c_cflag, tc2->c_lflag,
+                tc2->c_ispeed, tc2->c_ospeed);
+  test_assert(0 == ioctl(fd, TCSETS2, tc2));
+
+  // NB: leaving the TCSETS2 as the last word seems to mess up the terminal,
+  // so fix it.
+  test_assert(0 == ioctl(fd, TCSETS, tc));
+
   atomic_puts("EXIT-SUCCESS");
   return 0;
 }