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8d999a6993
After getting more experience with the various broken direct-to-ioctl termios2 hacks using Fedora 43 beta, I have found a fair number of cases where the software would fail to set, or clear CIBAUD for non-split-speed operation. Thus it seems will help improve compatibility to clear the kernel-side version of c_cflag & CIBAUD (having the same meaning to the Linux kernel as the speed 0 has for cfsetibaud(), i.e. force the input speed to equal the output speed) for non-split-speed operation, rather than having it explicitly equal the output speed in CBAUD. When writing the code that went into glibc 2.42 I had considered this issue, and had to make an educated guess which way would be more likely to break fewer things. Unfortunately, it appears I guessed wrong. A third option would be to *always* set CIBAUD to __BOTHER, even for the standard baud rates. However, that is an even bigger departure from legacy behavior, whereas this variant mostly preserves current behavior in terms of under what conditions buggy utilities will continue to work. This change is in tcsetattr() rather than ___termios2_canonicalize_speeds(), as it should not be run for tcgetattr(); that would break split speed support for the legacy interface versions of cfgetispeed() and cfsetispeed(). [ v2: fixed comment style ] Resolves: BZ #33340 Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
110 lines
3.7 KiB
C
110 lines
3.7 KiB
C
/* Copyright (C) 1993-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <termios_internals.h>
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#define static_assert_equal(x,y) _Static_assert ((x) == (y), #x " != " #y)
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/* Set the state of FD to *TERMIOS_P. */
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int
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__tcsetattr (int fd, int optional_actions, const struct termios *termios_p)
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{
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struct termios2 k_termios;
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unsigned long cmd;
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memset (&k_termios, 0, sizeof k_termios);
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k_termios.c_iflag = termios_p->c_iflag;
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k_termios.c_oflag = termios_p->c_oflag;
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k_termios.c_cflag = termios_p->c_cflag;
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k_termios.c_lflag = termios_p->c_lflag;
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k_termios.c_line = termios_p->c_line;
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k_termios.c_ospeed = termios_p->c_ospeed;
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k_termios.c_ispeed = termios_p->c_ispeed;
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___termios2_canonicalize_speeds (&k_termios);
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copy_c_cc (k_termios.c_cc, _TERMIOS2_NCCS, termios_p->c_cc, NCCS);
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static_assert_equal(TCSADRAIN, TCSANOW + 1);
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static_assert_equal(TCSAFLUSH, TCSANOW + 2);
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static_assert_equal(TCSETSW2, TCSETS2 + 1);
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static_assert_equal(TCSETSF2, TCSETS2 + 2);
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static_assert_equal(TCSETSW, TCSETS + 1);
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static_assert_equal(TCSETSF, TCSETS + 2);
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cmd = (long)optional_actions - TCSANOW;
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if (cmd > 2)
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
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/* For compatibility with broken workaround hacks for the lack
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of arbitrary speed support in previous versions of glibc,
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clear CIBAUD if only one speed is used.
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This is also necessary for the Alpha compatibility hack below. */
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if (k_termios.c_ospeed == k_termios.c_ispeed)
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k_termios.c_cflag &= ~CIBAUD;
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/* Choose the proper ioctl number to invoke.
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Alpha got TCSETS2 late (Linux 4.20), but has the same structure
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format, and it only needs TCSETS2 if either it needs to use
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__BOTHER or split speed. All other architectures have TCSETS2 as
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far back as the current glibc supports. Calling TCSETS with
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__BOTHER causes unpredictable results on old Alpha kernels and
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could even crash them. */
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if (__ASSUME_TERMIOS2 ||
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k_termios.c_ospeed != k_termios.c_ispeed ||
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cbaud (k_termios.c_cflag) == __BOTHER)
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cmd += TCSETS2;
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else
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cmd += TCSETS;
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return INLINE_SYSCALL_CALL (ioctl, fd, cmd, &k_termios);
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}
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libc_hidden_def (__tcsetattr)
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#if _HAVE_STRUCT_OLD_TERMIOS && _TERMIOS_OLD_COMPAT
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versioned_symbol (libc, __tcsetattr, tcsetattr, GLIBC_2_42);
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/* Legacy version for shorter struct termios without speed fields */
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int
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attribute_compat_text_section
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__old_tcsetattr (int fd, int optional_actions, const old_termios_t *termios_p)
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{
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struct termios new_termios;
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memset (&new_termios, 0, sizeof (new_termios));
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new_termios.c_iflag = termios_p->c_iflag;
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new_termios.c_oflag = termios_p->c_oflag;
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new_termios.c_cflag = termios_p->c_cflag;
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new_termios.c_lflag = termios_p->c_lflag;
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new_termios.c_line = termios_p->c_line;
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copy_c_cc(new_termios.c_cc, NCCS, termios_p->c_cc, OLD_NCCS);
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return __tcsetattr (fd, optional_actions, &new_termios);
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}
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compat_symbol (libc, __old_tcsetattr, tcsetattr, GLIBC_2_0);
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#else
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weak_alias (__tcsetattr, tcsetattr)
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#endif
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