[libc] Add termios.h and the implementation of functions declared in it.

[sivachandra]

Suppress a compiler warning.

[lntue]

libc/src/termios/linux/CMakeLists.txt

4

nit: we *use* different

[michaelrj]

libc/src/termios/linux/cfsetispeed.cpp

21

nit: if it is

libc/src/termios/linux/cfsetospeed.cpp

21

same as above

libc/test/src/termios/termios_test.cpp

49

this will fail on the buildbot, you need to put the rest of the test inside an if(fd > 0) clause, similar to how isatty_test.cpp does it.

[sivachandra]

Fix typos.

[sivachandra]

libc/test/src/termios/termios_test.cpp

49

Can we try once more on the bot? If it fails, I will add a conditional here.

[michaelrj]

libc/test/src/termios/termios_test.cpp

49

SGTM

libc/config/linux/api.td

 
 def SysUtsNameAPI : PublicAPI<"sys/utsname.h"> {
   let Types = ["struct utsname"];
 }
 
 def SpawnAPI : PublicAPI<"spawn.h"> {
   let Types = ["mode_t", "pid_t", "posix_spawnattr_t", "posix_spawn_file_actions_t"];
 }
+
+def TermiosAPI : PublicAPI<"termios.h"> {
+  let Types = ["cc_t", "pid_t", "speed_t", "struct termios", "tcflag_t"];
+}

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     # sys/utsname.h entrypoints
     libc.src.sys.utsname.uname
 
     # sys/wait.h entrypoints
     libc.src.sys.wait.wait
     libc.src.sys.wait.wait4
     libc.src.sys.wait.waitpid
 
+    # termios.h entrypoints
+    libc.src.termios.cfgetispeed
+    libc.src.termios.cfgetospeed
+    libc.src.termios.cfsetispeed
+    libc.src.termios.cfsetospeed
+    libc.src.termios.tcgetattr
+    libc.src.termios.tcgetsid
+    libc.src.termios.tcdrain
+    libc.src.termios.tcflow
+    libc.src.termios.tcflush
+    libc.src.termios.tcsendbreak
+    libc.src.termios.tcsetattr
+
     # unistd.h entrypoints
     libc.src.unistd.access
     libc.src.unistd.chdir
     libc.src.unistd.close
     libc.src.unistd.dup
     libc.src.unistd.dup2
     libc.src.unistd.dup3
     libc.src.unistd.execve

libc/include/CMakeLists.txt

add_gen_header(
   GEN_HDR sys/wait.h
   DEPENDS
     .llvm_libc_common_h
     .llvm-libc-macros.sys_wait_macros
     .llvm-libc-types.pid_t
     .llvm-libc-types.struct_rusage
 )
 
+add_gen_header(
+  termios
+  DEF_FILE termios.h.def
+  GEN_HDR termios.h
+  DEPENDS
+    .llvm_libc_common_h
+    .llvm-libc-macros.termios_macros
+    .llvm-libc-types.cc_t
+    .llvm-libc-types.speed_t
+    .llvm-libc-types.struct_termios
+    .llvm-libc-types.tcflag_t
+)
+
 if(NOT LLVM_LIBC_FULL_BUILD)
   # We don't install headers in non-fullbuild mode.
   return()
 endif()
 
 function(get_all_install_header_targets out_var)
   set(all_deps ${ARGN})
   foreach(target IN LISTS ARGN)

libc/include/llvm-libc-macros/CMakeLists.txt

add_header(
   sys_wait_macros
   HDR
     sys-wait-macros.h
   DEPENDS
     .linux.sys_wait_macros
 )
 
 add_header(
+  termios_macros
+  HDR
+    termios-macros.h
+  DEPENDS
+    .linux.termios_macros
+)
+
+add_header(
   time_macros
   HDR
     time-macros.h
   DEPENDS
     .linux.time_macros
 )
 
 add_header(
   unistd_macros
   HDR
     unistd-macros.h
   DEPENDS
     .linux.unistd_macros
 )

libc/include/llvm-libc-macros/linux/CMakeLists.txt

HDR
     unistd-macros.h
 )
 
 add_header(
   signal_macros
   HDR
     signal-macros.h
 )
+
+add_header(
+  termios_macros
+  HDR
+    termios-macros.h
+)

libc/include/llvm-libc-macros/linux/termios-macros.h

+//===-- Definition of macros from termios.h -------------------------------===//
+//
+// 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_TERMIOS_MACROS_H
+#define __LLVM_LIBC_MACROS_LINUX_TERMIOS_MACROS_H
+
+// Below are generic definitions of symbolic bit-masks, modes etc. They serve
+// most architectures including x86_64, aarch64 but have to be adjusted for few
+// architectures MIPS.
+
+#define NCCS 32
+
+// Bit-masks for the c_iflag field of struct termios.
+#define IGNBRK 0000001  // Ignore break condition
+#define BRKINT 0000002  // Signal interrupt on break
+#define IGNPAR 0000004  // Ignore characters with parity errors
+#define PARMRK 0000010  // Mark parity and framing errors
+#define INPCK 0000020   // Enable input parity check
+#define ISTRIP 0000040  // Strip 8th bit off characters
+#define INLCR 0000100   // Map NL to CR on input
+#define IGNCR 0000200   // Ignore CR
+#define ICRNL 0000400   // Map CR to NL on input
+#define IUCLC 0001000   // Map uppercase characters to lowercase on input
+#define IXON 0002000    // Enable start/stop output control
+#define IXANY 0004000   // Enable any character to restart output
+#define IXOFF 0010000   // Enable start/stop input control
+#define IMAXBEL 0020000 // Ring bell when input queue is full
+#define IUTF8 0040000   // Input is UTF8 (not in POSIX)
+
+// Bit-masks for the c_oflag field of struct termios.
+#define OPOST 0000001  // Post-process output
+#define OLCUC 0000002  // Map lowercase characters to uppercase on output
+#define ONLCR 0000004  // Map NL to CR-NL on output
+#define OCRNL 0000010  // Map CR to NL on output
+#define ONOCR 0000020  // No CR output at column 0
+#define ONLRET 0000040 // NL performs CR function
+#define OFILL 0000100  // Use fill characters for delay
+#define OFDEL 0000200  // Fill is DEL
+#define NLDLY 0000400  // Select newline delays
+#define NL0 0000000    // Newline type 0
+#define NL1 0000400    // Newline type 1
+#define CRDLY 0003000  // Select carriage-return delays
+#define CR0 0000000    // Carriage-return delay type 0
+#define CR1 0001000    // Carriage-return delay type 1
+#define CR2 0002000    // Carriage-return delay type 2
+#define CR3 0003000    // Carriage-return delay type 3
+#define TABDLY 0014000 // Select horizontal-tab delays
+#define TAB0 0000000   // Horizontal-tab delay type 0
+#define TAB1 0004000   // Horizontal-tab delay type 1
+#define TAB2 0010000   // Horizontal-tab delay type 2
+#define TAB3 0014000   // Expand tabs to spaces
+#define BSDLY 0020000  // Select backspace delays
+#define BS0 0000000    // Backspace-delay type 0
+#define BS1 0020000    // Backspace-delay type 1
+#define FFDLY 0100000  // Select form-feed delays
+#define FF0 0000000    // Form-feed delay type 0
+#define FF1 0100000    // Form-feed delay type 1
+#define VTDLY 0040000  // Select vertical-tab delays
+#define VT0 0000000    // Vertical-tab delay type 0
+#define VT1 0040000    // Vertical-tab delay type 1
+#define XTABS 0014000
+
+// Symbolic subscripts for the c_cc array.
+#define VINTR 0
+#define VQUIT 1
+#define VERASE 2
+#define VKILL 3
+#define VEOF 4
+#define VTIME 5
+#define VMIN 6
+#define VSWTC 7
+#define VSTART 8
+#define VSTOP 9
+#define VSUSP 10
+#define VEOL 11
+#define VREPRINT 12
+#define VDISCARD 13
+#define VWERASE 14
+#define VLNEXT 15
+#define VEOL2 16
+
+// Baud rate related definitions
+#define CBAUD 000000010017  // Baud speed mask
+#define CBAUDX 000000010000 // Extra baud speed mask
+#define CIBAUD 002003600000
+#define CMSPAR 010000000000
+#define CRTSCTS 020000000000
+// Baud rates with values representable by the speed_t type.
+#define B0 0000000 // Implies hang-up
+// A symbol B<NN+> below indicates a baud rate of <NN+>.
+#define B50 0000001
+#define B75 0000002
+#define B110 0000003
+#define B134 0000004
+#define B150 0000005
+#define B200 0000006
+#define B300 0000007
+#define B600 0000010
+#define B1200 0000011
+#define B1800 0000012
+#define B2400 0000013
+#define B4800 0000014
+#define B9600 0000015
+#define B19200 0000016
+#define B38400 0000017
+// Extra baud rates
+#define B57600 0010001
+#define B115200 0010002
+#define B230400 0010003
+#define B460800 0010004
+#define B500000 0010005
+#define B576000 0010006
+#define B921600 0010007
+#define B1000000 0010010
+#define B1152000 0010011
+#define B1500000 0010012
+#define B2000000 0010013
+#define B2500000 0010014
+#define B3000000 0010015
+#define B3500000 0010016
+#define B4000000 0010017
+
+// Control mode bits for use in the c_cflag field of struct termios.
+#define CSIZE 0000060 // Mask for character size bits
+#define CS5 0000000
+#define CS6 0000020
+#define CS7 0000040
+#define CS8 0000060
+#define CSTOPB 0000100 // Send two bits, else one
+#define CREAD 0000200  // Enable receiver
+#define PARENB 0000400 // Parity enable
+#define PARODD 0001000 // Odd parity, else even
+#define HUPCL 0002000  // Hang up on last close
+#define CLOCAL 0004000 // Ignore modem status lines
+
+// Local mode bits for use in the c_lflag field of struct termios.
+#define ISIG 0000001   // Enable signals
+#define ICANON 0000002 // Canonical input (erase and kill processing)
+#define ECHO 0000010   // Enable echo
+#define ECHOE 0000020  // Echo erase character as error-correcting backspace
+#define ECHOK 0000040  // Echo KILL
+#define ECHONL 0000100 // Echo NL
+#define NOFLSH 0000200 // Disable flush after interrupt or quit
+#define TOSTOP 0000400 // Send SIGTTOU for background output
+
+// Attribute selection
+#define TCSANOW 0   // Change attributes immediately
+#define TCSADRAIN 1 // Change attributes when output has drained
+#define TCSAFLUSH 2 // Same as TCSADRAIN and flush pending Output
+
+// Symbolic constants for use with tcflush function.
+#define TCIFLUSH 0  // Flush pending input
+#define TCIOFLUSH 1 // Flush pending input and unstransmitted output
+#define TCOFLUSH 2  // Flush unstransmitted output
+
+// Symbolic constantf for use with tcflow function.
+#define TCOOFF 0 // Transmit a STOP character, intended to suspend input data
+#define TCOON 1  // Transmit a START character, intended to restart input data
+#define TCIOFF 2 // Suspend output
+#define TCION 3  // Restart output
+
+#endif // __LLVM_LIBC_MACROS_LINUX_TERMIOS_MACROS_H

libc/include/llvm-libc-macros/termios-macros.h

+//===-- Macros defined in termios.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_TERMIOS_MACROS_H
+#define __LLVM_LIBC_MACROS_TERMIOS_MACROS_H
+
+#ifdef __linux__
+#include "linux/termios-macros.h"
+#endif
+
+#endif // __LLVM_LIBC_MACROS_TERMIOS_MACROS_H

libc/include/llvm-libc-types/CMakeLists.txt

 add_header(__pthread_once_func_t HDR __pthread_once_func_t.h)
 add_header(__pthread_start_t HDR __pthread_start_t.h)
 add_header(__pthread_tss_dtor_t HDR __pthread_tss_dtor_t.h)
 add_header(__qsortcompare_t HDR __qsortcompare_t.h)
 add_header(__sighandler_t HDR __sighandler_t.h)
 add_header(__thread_type HDR __thread_type.h)
 add_header(blkcnt_t HDR blkcnt_t.h)
 add_header(blksize_t HDR blksize_t.h)
+add_header(cc_t HDR cc_t.h)
 add_header(clockid_t HDR clockid_t.h)
 add_header(cnd_t HDR cnd_t.h)
 add_header(cookie_io_functions_t HDR cookie_io_functions_t.h DEPENDS .off64_t)
 add_header(cpu_set_t HDR cpu_set_t.h)
 add_header(double_t HDR double_t.h)
 add_header(DIR HDR DIR.h)
 add_header(dev_t HDR dev_t.h)
 add_header(div_t HDR div_t.h)

 )
 add_header(struct_tm HDR struct_tm.h)
 add_header(struct_utsname HDR struct_utsname.h)
 add_header(thrd_start_t HDR thrd_start_t.h)
 add_header(thrd_t HDR thrd_t.h DEPENDS .__thread_type)
 add_header(tss_t HDR tss_t.h)
 add_header(tss_dtor_t HDR tss_dtor_t.h)
 add_header(__atexithandler_t HDR __atexithandler_t.h)
+add_header(speed_t HDR speed_t.h)
+add_header(tcflag_t HDR tcflag_t.h)
+add_header(struct_termios HDR struct_termios.h DEPENDS .cc_t .speed_t .tcflag_t)

libc/include/llvm-libc-types/cc_t.h

+//===-- Definition of cc_t type -------------------------------------------===//
+//
+// 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_TYPES_CC_T_H__
+#define __LLVM_LIBC_TYPES_CC_T_H__
+
+typedef unsigned char cc_t;
+
+#endif // __LLVM_LIBC_TYPES_CC_T_H__

libc/include/llvm-libc-types/speed_t.h

+//===-- Definition of speed_t type ----------------------------------------===//
+//
+// 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_TYPES_SPEED_T_H__
+#define __LLVM_LIBC_TYPES_SPEED_T_H__
+
+typedef unsigned int speed_t;
+
+#endif // __LLVM_LIBC_TYPES_SPEED_T_H__

libc/include/llvm-libc-types/struct_termios.h

+//===-- Definition of struct termios --------------------------------------===//
+//
+// 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_TYPES_STRUCT_TERMIOS_H__
+#define __LLVM_LIBC_TYPES_STRUCT_TERMIOS_H__
+
+#include <llvm-libc-types/cc_t.h>
+#include <llvm-libc-types/speed_t.h>
+#include <llvm-libc-types/tcflag_t.h>
+
+struct termios {
+  tcflag_t c_iflag; // Input mode flags
+  tcflag_t c_oflag; // Output mode flags
+  tcflag_t c_cflag; // Control mode flags
+  tcflag_t c_lflag; // Local mode flags
+#ifdef __linux__
+  cc_t c_line; // Line discipline
+#endif         // __linux__
+  // NCCS is defined in llvm-libc-macros/termios-macros.h.
+  cc_t c_cc[NCCS]; // Control characters
+#ifdef __linux__
+  speed_t c_ispeed; // Input speed
+  speed_t c_ospeed; // output speed
+#endif              // __linux__
+};
+
+#endif // __LLVM_LIBC_TYPES_STRUCT_TERMIOS_H__

libc/include/llvm-libc-types/tcflag_t.h

+//===-- Definition of tcflag_t type ---------------------------------------===//
+//
+// 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_TYPES_TCFLAG_T_H__
+#define __LLVM_LIBC_TYPES_TCFLAG_T_H__
+
+typedef unsigned int tcflag_t;
+
+#endif // __LLVM_LIBC_TYPES_TCFLAG_T_H__

libc/include/termios.h.def

+//===-- C standard library header termios.h -------------------------------===//
+//
+// 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_TERMIOS_H
+#define LLVM_LIBC_TERMIOS_H
+
+#include <__llvm-libc-common.h>
+#include <llvm-libc-macros/termios-macros.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_TERMIOS_H

libc/spec/posix.td

 def PosixSpawnFileActionsT : NamedType<"posix_spawn_file_actions_t">;
 def PosixSpawnFileActionsTPtr : PtrType<PosixSpawnFileActionsT>;
 def ConstPosixSpawnFileActionsTPtr : ConstType<PosixSpawnFileActionsTPtr>;
 def PosixSpawnFileActionsTRestrictedPtr : RestrictedPtrType<PosixSpawnFileActionsT>;
 
 def PosixSpawnAttrT : NamedType<"posix_spawnattr_t">;
 def RestrictedPosixSpawnAttrTPtrType : RestrictedPtrType<PosixSpawnAttrT>;
 
+def CcT : NamedType<"cc_t">;
+def SpeedT : NamedType<"speed_t">;
+def StructTermios : NamedType<"struct termios">;
+def StructTermiosPtr : PtrType<StructTermios>;
+def ConstStructTermiosPtr : ConstType<StructTermiosPtr>;
+def TcFlagT : NamedType<"tcflag_t">;
+
 def POSIX : StandardSpec<"POSIX"> {
   PtrType CharPtr = PtrType<CharType>;
   RestrictedPtrType RestrictedCharPtr = RestrictedPtrType<CharType>;
   RestrictedPtrType CharRestrictedDoublePtr = RestrictedPtrType<CharPtr>;
   ConstType ConstCharPtr = ConstType<CharPtr>;
   ConstType ConstRestrictedCharPtr = ConstType<RestrictedCharPtr>;
 
   NamedType ModeTType = NamedType<"mode_t">;
[
         RetValSpec<IntType>,
         [ArgSpec<RestrictedPidTPtr>, ArgSpec<ConstCharRestrictedPtr>,
          ArgSpec<PosixSpawnFileActionsTPtr>, ArgSpec<RestrictedPosixSpawnAttrTPtrType>,
          ArgSpec<ConstCharRestrictedPtrPtr>, ArgSpec<ConstCharRestrictedPtrPtr>]
       >,
     ]
   >;
 
+  HeaderSpec Termios = HeaderSpec<
+    "termios.h",
+    [
+      Macro<"NCCS">,
+    ],
+    [CcT, PidT, SpeedT, StructTermios, TcFlagT], // Types
+    [], // Enumerations
+    [
+      FunctionSpec<
+        "cfgetispeed",
+        RetValSpec<SpeedT>,
+        [ArgSpec<ConstStructTermiosPtr>]
+      >,
+      FunctionSpec<
+        "cfgetospeed",
+        RetValSpec<SpeedT>,
+        [ArgSpec<ConstStructTermiosPtr>]
+      >,
+      FunctionSpec<
+        "cfsetispeed",
+        RetValSpec<SpeedT>,
+        [ArgSpec<StructTermiosPtr>, ArgSpec<SpeedT>]
+      >,
+      FunctionSpec<
+        "cfsetospeed",
+        RetValSpec<SpeedT>,
+        [ArgSpec<StructTermiosPtr>, ArgSpec<SpeedT>]
+      >,
+      FunctionSpec<
+        "tcdrain",
+        RetValSpec<IntType>,
+        [ArgSpec<IntType>]
+      >,
+      FunctionSpec<
+        "tcflow",
+        RetValSpec<IntType>,
+        [ArgSpec<IntType>, ArgSpec<IntType>]
+      >,
+      FunctionSpec<
+        "tcflush",
+        RetValSpec<IntType>,
+        [ArgSpec<IntType>, ArgSpec<IntType>]
+      >,
+      FunctionSpec<
+        "tcgetattr",
+        RetValSpec<IntType>,
+        [ArgSpec<IntType>, ArgSpec<StructTermiosPtr>]
+      >,
+      FunctionSpec<
+        "tcgetsid",
+        RetValSpec<PidT>,
+        [ArgSpec<IntType>]
+      >,
+      FunctionSpec<
+        "tcsendbreak",
+        RetValSpec<IntType>,
+        [ArgSpec<IntType>, ArgSpec<IntType>]
+      >,
+      FunctionSpec<
+        "tcsetattr",
+        RetValSpec<IntType>,
+        [ArgSpec<IntType>, ArgSpec<IntType>, ArgSpec<StructTermiosPtr>]
+      >,
+    ]
+  >;
+
   let Headers = [
     CType,
     Dirent,
     Errno,
     FCntl,
     PThread,
     Signal,
     Spawn,
     StdIO,
     StdLib,
     SysIOctl,
     SysMMan,
     SysResource,
     SysStat,
     SysUtsName,
     SysWait,
     Time,
+    Termios,
     UniStd,
     String
   ];
 }

libc/src/CMakeLists.txt

 add_subdirectory(stdio)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(dirent)
   add_subdirectory(fcntl)
   add_subdirectory(pthread)
   add_subdirectory(sched)
   add_subdirectory(sys)
+  add_subdirectory(termios)
   add_subdirectory(unistd)
 endif()
 
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
 # The signal API is currently disabled as signal.h is incorrect.
 # since assert uses the signal API, we disable assert also.
 # add_subdirectory(assert)
 add_subdirectory(signal)
 add_subdirectory(spawn)
 add_subdirectory(threads)
 add_subdirectory(time)

libc/src/termios/CMakeLists.txt

+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+  cfgetispeed
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.cfgetispeed
+)
+
+add_entrypoint_object(
+  cfsetispeed
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.cfsetispeed
+)
+
+add_entrypoint_object(
+  cfgetospeed
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.cfgetospeed
+)
+
+add_entrypoint_object(
+  cfsetospeed
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.cfsetospeed
+)
+
+add_entrypoint_object(
+  tcgetsid
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcgetsid
+)
+
+add_entrypoint_object(
+  tcdrain
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcdrain
+)
+
+add_entrypoint_object(
+  tcflow
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcflow
+)
+
+add_entrypoint_object(
+  tcflush
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcflush
+)
+
+add_entrypoint_object(
+  tcsendbreak
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcsendbreak
+)
+
+add_entrypoint_object(
+  tcgetattr
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcgetattr
+)
+
+add_entrypoint_object(
+  tcsetattr
+  ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.tcsetattr
+)

libc/src/termios/cfgetispeed.h

+//===-- Implementation header for cfgetispeed -------------------*- 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_CFGETISPEED_H
+#define LLVM_LIBC_SRC_UNISTD_CFGETISPEED_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+speed_t cfgetispeed(const struct termios *t);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_CFGETISPEED_H

libc/src/termios/cfgetospeed.h

+//===-- Implementation header for cfgetospeed -------------------*- 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_CFGETOSPEED_H
+#define LLVM_LIBC_SRC_UNISTD_CFGETOSPEED_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+speed_t cfgetospeed(const struct termios *t);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_CFGETOSPEED_H

libc/src/termios/cfsetispeed.h

+//===-- Implementation header for cfsetispeed -------------------*- 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_CFSETISPEED_H
+#define LLVM_LIBC_SRC_UNISTD_CFSETISPEED_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int cfsetispeed(struct termios *t, speed_t speed);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_CFSETISPEED_H

libc/src/termios/cfsetospeed.h

+//===-- Implementation header for cfsetospeed -------------------*- 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_CFSETOSPEED_H
+#define LLVM_LIBC_SRC_UNISTD_CFSETOSPEED_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int cfsetospeed(struct termios *t, speed_t speed);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_CFSETOSPEED_H

libc/src/termios/linux/CMakeLists.txt

+# There is no difference between input and output speeds on Linux.
+# However, since POSIX requires separate functions for setting and getting
+# of the input and output speeds, we use different entrypoints wiht the
+# same getter/setter logic.
+add_entrypoint_object(
+  cfgetispeed
+  SRCS
+    cfgetispeed.cpp
+  HDRS
+    ../cfgetispeed.h
+  DEPENDS
+    libc.include.termios
+)
+
+add_entrypoint_object(
+  cfsetispeed
+  SRCS
+    cfsetispeed.cpp
+  HDRS
+    ../cfsetispeed.h
+  DEPENDS
+    libc.include.termios
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  cfgetospeed
+  SRCS
+    cfgetospeed.cpp
+  HDRS
+    ../cfgetospeed.h
+  DEPENDS
+    libc.include.termios
+)
+
+add_entrypoint_object(
+  cfsetospeed
+  SRCS
+    cfsetospeed.cpp
+  HDRS
+    ../cfsetospeed.h
+  DEPENDS
+    libc.include.termios
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  tcgetsid
+  SRCS
+    tcgetsid.cpp
+  HDRS
+    ../tcgetsid.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  tcdrain
+  SRCS
+    tcdrain.cpp
+  HDRS
+    ../tcdrain.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  tcflush
+  SRCS
+    tcflush.cpp
+  HDRS
+    ../tcflush.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  tcflow
+  SRCS
+    tcflow.cpp
+  HDRS
+    ../tcflow.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  tcsendbreak
+  SRCS
+    tcsendbreak.cpp
+  HDRS
+    ../tcsendbreak.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_header_library(
+  kernel_termios
+  HDRS
+    kernel_termios.h
+)
+
+add_entrypoint_object(
+  tcgetattr
+  SRCS
+    tcgetattr.cpp
+  HDRS
+    ../tcgetattr.h
+  DEPENDS
+    .kernel_termios
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  tcsetattr
+  SRCS
+    tcsetattr.cpp
+  HDRS
+    ../tcsetattr.h
+  DEPENDS
+    .kernel_termios
+    libc.include.sys_syscall
+    libc.include.termios
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

libc/src/termios/linux/cfgetispeed.cpp

+//===-- Linux implementation of cfgetispeed -------------------------------===//
+//
+// 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/termios/cfgetispeed.h"
+
+#include "src/__support/common.h"
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(speed_t, cfgetispeed, (const struct termios *t)) {
+  return t->c_cflag & CBAUD;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/cfgetospeed.cpp

+//===-- Linux implementation of cfgetospeed -------------------------------===//
+//
+// 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/termios/cfgetospeed.h"
+
+#include "src/__support/common.h"
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(speed_t, cfgetospeed, (const struct termios *t)) {
+  return t->c_cflag & CBAUD;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/cfsetispeed.cpp

+//===-- Linux implementation of cfsetispeed -------------------------------===//
+//
+// 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/termios/cfsetispeed.h"
+
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, cfsetispeed, (struct termios * t, speed_t speed)) {
+  constexpr speed_t NOT_SPEED_MASK = ~speed_t(CBAUD);
+  // A speed value is valid only if it is equal to one of the B<NN+> values.
+  if (t == nullptr || ((speed & NOT_SPEED_MASK) != 0)) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  t->c_cflag = (t->c_cflag & NOT_SPEED_MASK) | speed;
+  t->c_ispeed = speed;
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/cfsetospeed.cpp

+//===-- Linux implementation of cfsetospeed -------------------------------===//
+//
+// 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/termios/cfsetospeed.h"
+
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, cfsetospeed, (struct termios * t, speed_t speed)) {
+  constexpr speed_t NOT_SPEED_MASK = ~speed_t(CBAUD);
+  // A speed value is valid only if it is equal to one of the B<NN+> values.
+  if (t == nullptr || ((speed & NOT_SPEED_MASK) != 0)) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  t->c_cflag = (t->c_cflag & NOT_SPEED_MASK) | speed;
+  t->c_ospeed = speed;
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/kernel_termios.h

+//===-- Definition of kernel's version of struct termios --------*- 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_TERMIOS_LINUX_KERNEL_TERMIOS_H
+#define LLVM_LIBC_SRC_TERMIOS_LINUX_KERNEL_TERMIOS_H
+
+#include <stddef.h>
+#include <termios.h>
+
+namespace __llvm_libc {
+
+// The kernel's struct termios is different from the libc's struct termios. The
+// kernel's syscalls expect the size and layout of its definition of struct
+// termios. So, we define a flavor of struct termios which matches that of the
+// kernel so that we can translate between the libc version and the kernel
+// version when passing struct termios objects to syscalls.
+
+// NOTE: The definitions here are generic definitions valid for most target
+// architectures including x86_64 and aarch64. Definitions on some architectures
+// deviate from these generic definitions. Adjustments have to be made for those
+// architectures.
+
+constexpr size_t KERNEL_NCCS = 19;
+
+struct kernel_termios {
+  tcflag_t c_iflag;
+  tcflag_t c_oflag;
+  tcflag_t c_cflag;
+  tcflag_t c_lflag;
+  cc_t c_line;
+  cc_t c_cc[KERNEL_NCCS];
+};
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TERMIOS_LINUX_KERNEL_TERMIOS_H

libc/src/termios/linux/tcdrain.cpp

+//===-- Linux implementation of tcdrain -----------------------------------===//
+//
+// 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/termios/tcdrain.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, tcdrain, (int fd)) {
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, TCSBRK, 1);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/tcflow.cpp

+//===-- Linux implementation of tcflow -----------------------------------===//
+//
+// 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/termios/tcflow.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, tcflow, (int fd, int action)) {
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, TCXONC, action);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/tcflush.cpp

+//===-- Linux implementation of tcflush -----------------------------------===//
+//
+// 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/termios/tcflush.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, tcflush, (int fd, int queue_selector)) {
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, TCFLSH, queue_selector);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/tcgetattr.cpp

+//===-- Linux implementation of tcgetattr ---------------------------------===//
+//
+// 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/termios/tcgetattr.h"
+#include "kernel_termios.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, tcgetattr, (int fd, struct termios *t)) {
+  __llvm_libc::kernel_termios kt;
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, TCGETS, &kt);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  t->c_iflag = kt.c_iflag;
+  t->c_oflag = kt.c_oflag;
+  t->c_cflag = kt.c_cflag;
+  t->c_lflag = kt.c_lflag;
+  t->c_ispeed = kt.c_cflag & CBAUD;
+  t->c_ospeed = kt.c_cflag & CBAUD;
+
+  size_t nccs = KERNEL_NCCS <= NCCS ? KERNEL_NCCS : NCCS;
+  for (size_t i = 0; i < nccs; ++i)
+    t->c_cc[i] = kt.c_cc[i];
+  if (NCCS > nccs) {
+    for (size_t i = nccs; i < NCCS; ++i)
+      t->c_cc[i] = 0;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/tcgetsid.cpp

+//===-- Linux implementation of tcgetsid ----------------------------------===//
+//
+// 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/termios/tcgetsid.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(pid_t, tcgetsid, (int fd)) {
+  pid_t sid;
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, TIOCGSID, &sid);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return sid;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/tcsendbreak.cpp

+//===-- Linux implementation of tcsendbreak -------------------------------===//
+//
+// 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/termios/tcsendbreak.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(pid_t, tcsendbreak, (int fd, int /* unused duration */)) {
+  // POSIX leaves the behavior for non-zero duration implementation dependent.
+  // Which means that the behavior can be the same as it is when duration is
+  // zero. So, we just pass zero to the syscall.
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, TCSBRK, 0);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/linux/tcsetattr.cpp

+//===-- Linux implementation of tcsetattr ---------------------------------===//
+//
+// 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/termios/tcsetattr.h"
+#include "kernel_termios.h"
+
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+
+#include <asm/ioctls.h> // Safe to include without the risk of name pollution.
+#include <errno.h>
+#include <sys/syscall.h> // For syscall numbers
+#include <termios.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, tcsetattr,
+                   (int fd, int actions, const struct termios *t)) {
+  struct kernel_termios kt;
+  long cmd;
+
+  switch (actions) {
+  case TCSANOW:
+    cmd = TCSETS;
+    break;
+  case TCSADRAIN:
+    cmd = TCSETSW;
+    break;
+  case TCSAFLUSH:
+    cmd = TCSETSF;
+    break;
+  default:
+    errno = EINVAL;
+    return -1;
+  }
+
+  kt.c_iflag = t->c_iflag;
+  kt.c_oflag = t->c_oflag;
+  kt.c_cflag = t->c_cflag;
+  kt.c_lflag = t->c_lflag;
+  size_t nccs = KERNEL_NCCS <= NCCS ? KERNEL_NCCS : NCCS;
+  for (size_t i = 0; i < nccs; ++i)
+    kt.c_cc[i] = t->c_cc[i];
+  if (nccs < KERNEL_NCCS) {
+    for (size_t i = nccs; i < KERNEL_NCCS; ++i)
+      kt.c_cc[i] = 0;
+  }
+
+  long ret = __llvm_libc::syscall_impl(SYS_ioctl, fd, cmd, &kt);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/termios/tcdrain.h

+//===-- Implementation header for tcdrain -----------------------*- 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_TCDRAIN_H
+#define LLVM_LIBC_SRC_UNISTD_TCDRAIN_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int tcdrain(int fd);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_TCDRAIN_H

libc/src/termios/tcflow.h

+//===-- Implementation header for tcflow ------------------------*- 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_TCFLOW_H
+#define LLVM_LIBC_SRC_UNISTD_TCFLOW_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int tcflow(int fd, int action);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_TCFLOW_H

libc/src/termios/tcflush.h

+//===-- Implementation header for tcflush -----------------------*- 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_TCFLUSH_H
+#define LLVM_LIBC_SRC_UNISTD_TCFLUSH_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int tcflush(int fd, int queue_selector);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_TCFLUSH_H

libc/src/termios/tcgetattr.h

+//===-- Implementation header for tcgetattr ---------------------*- 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_TERMIOS_TCGETATTR_H
+#define LLVM_LIBC_SRC_TERMIOS_TCGETATTR_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int tcgetattr(int fd, struct termios *t);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TERMIOS_TCGETATTR_H

libc/src/termios/tcgetsid.h

+//===-- Implementation header for tcgetsid ----------------------*- 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_TERMIOS_TCGETSID_H
+#define LLVM_LIBC_SRC_TERMIOS_TCGETSID_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+pid_t tcgetsid(int fd);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TERMIOS_TCGETSID_H

libc/src/termios/tcsendbreak.h

+//===-- Implementation header for tcsendbreak -------------------*- 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_TCSENDBREAK_H
+#define LLVM_LIBC_SRC_UNISTD_TCSENDBREAK_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int tcsendbreak(int fd, int duration);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_TCSENDBREAK_H

libc/src/termios/tcsetattr.h

+//===-- Implementation header for tcsetattr ---------------------*- 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_TERMIOS_TCSETATTR_H
+#define LLVM_LIBC_SRC_TERMIOS_TCSETATTR_H
+
+#include <termios.h>
+
+namespace __llvm_libc {
+
+int tcsetattr(int fd, int actions, const struct termios *t);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TERMIOS_TCSETATTR_H

libc/test/src/CMakeLists.txt

 add_subdirectory(string)
 add_subdirectory(stdlib)
 add_subdirectory(stdio)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(fcntl)
   add_subdirectory(sched)
   add_subdirectory(sys)
+  add_subdirectory(termios)
   add_subdirectory(unistd)
 endif()
 
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
 add_subdirectory(dirent)

libc/test/src/termios/CMakeLists.txt

+add_libc_testsuite(libc_termios_unittests)
+
+add_libc_unittest(
+  termios_test
+  SUITE
+    libc_termios_unittests
+  SRCS
+    termios_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.termios
+    libc.src.fcntl.open
+    libc.src.termios.cfgetispeed
+    libc.src.termios.cfgetospeed
+    libc.src.termios.cfsetispeed
+    libc.src.termios.cfsetospeed
+    libc.src.termios.tcgetattr
+    libc.src.termios.tcgetsid
+    libc.src.termios.tcsetattr
+    libc.src.unistd.close
+    libc.test.errno_setter_matcher
+)

libc/test/src/termios/termios_test.cpp

+//===-- Unittests for a bunch of functions in termios.h -------------------===//
+//
+// 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/fcntl/open.h"
+#include "src/termios/cfgetispeed.h"
+#include "src/termios/cfgetospeed.h"
+#include "src/termios/cfsetispeed.h"
+#include "src/termios/cfsetospeed.h"
+#include "src/termios/tcgetattr.h"
+#include "src/termios/tcgetsid.h"
+#include "src/termios/tcsetattr.h"
+#include "src/unistd/close.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+#include <errno.h>
+#include <termios.h>
+
+using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+
+// We just list a bunch of smoke tests here as it is not possible to
+// test functionality at the least because we want to run the tests
+// from ninja/make which change the terminal behavior.
+
+TEST(LlvmLibcTermiosTest, SpeedSmokeTest) {
+  struct termios t;
+  errno = 0;
+  ASSERT_THAT(__llvm_libc::cfsetispeed(&t, B50), Succeeds(0));
+  ASSERT_EQ(__llvm_libc::cfgetispeed(&t), speed_t(B50));
+  ASSERT_THAT(__llvm_libc::cfsetospeed(&t, B75), Succeeds(0));
+  ASSERT_EQ(__llvm_libc::cfgetospeed(&t), speed_t(B75));
+
+  errno = 0;
+  ASSERT_THAT(__llvm_libc::cfsetispeed(&t, ~CBAUD), Fails(EINVAL));
+  errno = 0;
+  ASSERT_THAT(__llvm_libc::cfsetospeed(&t, ~CBAUD), Fails(EINVAL));
+}
+
+TEST(LlvmLibcTermiosTest, GetAttrSmokeTest) {
+  struct termios t;
+  errno = 0;
+  int fd = __llvm_libc::open("/dev/tty", O_RDONLY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  ASSERT_THAT(__llvm_libc::tcgetattr(fd, &t), Succeeds(0));
+  ASSERT_EQ(__llvm_libc::close(fd), 0);
+}
+
+TEST(LlvmLibcTermiosTest, TcGetSidSmokeTest) {
+  int fd = __llvm_libc::open("/dev/tty", O_RDONLY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  ASSERT_GT(__llvm_libc::tcgetsid(fd), pid_t(0));
+  ASSERT_EQ(__llvm_libc::close(fd), 0);
+}