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/* Copyright (C) 1993-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <termios_internals.h>
#define static_assert_equal(x,y) _Static_assert ((x) == (y), #x " != " #y)
/* Set the state of FD to *TERMIOS_P. */
int
__tcsetattr (int fd, int optional_actions, const struct termios *termios_p)
{
struct termios2 k_termios;
struct termios2 k_termios_old;
unsigned long cmd;
int retval, old_retval;
memset (&k_termios, 0, sizeof k_termios);
k_termios.c_iflag = termios_p->c_iflag;
k_termios.c_oflag = termios_p->c_oflag;
k_termios.c_cflag = termios_p->c_cflag;
k_termios.c_lflag = termios_p->c_lflag;
k_termios.c_line = termios_p->c_line;
k_termios.c_ospeed = termios_p->c_ospeed;
k_termios.c_ispeed = termios_p->c_ispeed;
___termios2_canonicalize_speeds (&k_termios);
copy_c_cc (k_termios.c_cc, _TERMIOS2_NCCS, termios_p->c_cc, NCCS);
/*
* Choose the proper ioctl number to invoke.
*
* Alpha got TCSETS2 late (Linux 4.20), but has the same structure
* format, and it only needs TCSETS2 if either it needs to use
* __BOTHER or split speed. All other architectures have TCSETS2 as
* far back as the current glibc supports. Calling TCSETS with
* __BOTHER causes unpredictable results on old Alpha kernels and
* could even crash them.
*/
static_assert_equal(TCSADRAIN, TCSANOW + 1);
static_assert_equal(TCSAFLUSH, TCSANOW + 2);
static_assert_equal(TCSETSW2, TCSETS2 + 1);
static_assert_equal(TCSETSF2, TCSETS2 + 2);
static_assert_equal(TCSETSW, TCSETS + 1);
static_assert_equal(TCSETSF, TCSETS + 2);
cmd = (long)optional_actions - TCSANOW;
if (cmd > 2)
return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
if (__ASSUME_TERMIOS2 ||
k_termios.c_ospeed != k_termios.c_ispeed ||
cbaud (k_termios.c_cflag) == __BOTHER)
{
cmd += TCSETS2;
}
else
{
cmd += TCSETS;
k_termios.c_cflag &= ~CIBAUD;
}
/* Preserve the previous termios state if we can. */
if (__ASSUME_TERMIOS2)
old_retval = INLINE_SYSCALL_CALL (ioctl, fd, TCGETS2, &k_termios_old);
else
old_retval = INLINE_SYSCALL_CALL (ioctl, fd, TCGETS, &k_termios_old);
retval = INLINE_SYSCALL_CALL (ioctl, fd, cmd, &k_termios);
/* The Linux kernel silently ignores the invalid c_cflag on pty.
We have to check it here, and return an error. But if some other
setting was successfully changed, POSIX requires us to report
success. */
if ((retval == 0) && (old_retval == 0))
{
int save = errno;
if (__ASSUME_TERMIOS2)
retval = INLINE_SYSCALL_CALL (ioctl, fd, TCGETS2, &k_termios);
else
retval = INLINE_SYSCALL_CALL (ioctl, fd, TCGETS, &k_termios);
if (retval)
{
/* We cannot verify if the setting is ok. We don't return
an error (?). */
__set_errno (save);
retval = 0;
}
else if ((k_termios_old.c_oflag != k_termios.c_oflag) ||
(k_termios_old.c_lflag != k_termios.c_lflag) ||
(k_termios_old.c_line != k_termios.c_line) ||
(k_termios_old.c_iflag != k_termios.c_iflag))
{
/* Some other setting was successfully changed, which
means we should not return an error. */
__set_errno (save);
retval = 0;
}
else if ((k_termios_old.c_cflag & ~(PARENB | CREAD | CSIZE)) !=
(k_termios.c_cflag & ~(PARENB | CREAD | CSIZE)))
{
/* Some other c_cflag setting was successfully changed, which
means we should not return an error. */
__set_errno (save);
retval = 0;
}
else if ((termios_p->c_cflag & (PARENB | CREAD))
!= (k_termios.c_cflag & (PARENB | CREAD))
|| ((termios_p->c_cflag & CSIZE)
&& (termios_p->c_cflag & CSIZE)
!= (k_termios.c_cflag & CSIZE)))
{
/* It looks like the Linux kernel silently changed the
PARENB/CREAD/CSIZE bits in c_cflag. Report it as an
error. */
__set_errno (EINVAL);
retval = -1;
}
}
return retval;
}
libc_hidden_def (__tcsetattr)
#if _HAVE_STRUCT_OLD_TERMIOS && _TERMIOS_OLD_COMPAT
versioned_symbol (libc, __tcsetattr, tcsetattr, GLIBC_2_42);
/* Legacy version for shorter struct termios without speed fields */
int
attribute_compat_text_section
__old_tcsetattr (int fd, int optional_actions, const old_termios_t *termios_p)
{
struct termios new_termios;
memset (&new_termios, 0, sizeof (new_termios));
new_termios.c_iflag = termios_p->c_iflag;
new_termios.c_oflag = termios_p->c_oflag;
new_termios.c_cflag = termios_p->c_cflag;
new_termios.c_lflag = termios_p->c_lflag;
new_termios.c_line = termios_p->c_line;
copy_c_cc(new_termios.c_cc, NCCS, termios_p->c_cc, OLD_NCCS);
return __tcsetattr (fd, optional_actions, &new_termios);
}
compat_symbol (libc, __old_tcsetattr, tcsetattr, GLIBC_2_0);
#else
weak_alias (__tcsetattr, tcsetattr)
#endif
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