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linux: implement arbitrary and split speeds in termios
Linux has supported arbitrary speeds and split speeds in the kernel since 2008 on all platforms except Alpha (fixed in 2020), but glibc was never updated to match. This is further complicated by POSIX uses of macros for the cf[gs]et[io]speed interfaces, rather than plain numbers, as it really ought to have. On most platforms, the glibc ABI includes the c_[io]speed fields in struct termios, but they are incorrectly used. On MIPS and SPARC, they are entirely missing. For backwards compatibility, the kernel will still use the legacy speed fields unless they are set to BOTHER, and will use the legacy output speed as the input speed if the latter is 0 (== B0). However, the specific encoding used is visible to user space applications, including ones other than the one running. - SPARC and MIPS get a new struct termios, and tc[gs]etattr() is versioned accordingly. However, the new struct termios is set to be a strict extension of the old one, which means that cf* interfaces other than the speed-related ones do not need versioning. - The Bxxx constants are redefined as equivalent to their integer values and the legacy Bxxx constants are renamed __Bxxx. - cf[gs]et[io]speed() and cfsetspeed() are versioned accordingly. - tcgetattr() and cfset[io]speed() are adjusted to always keep the c_[io]speed fields correct (unlike earlier versions), but to canonicalize the representation to ALSO configure the legacy fields if a valid legacy representation exists. - tcsetattr(), too, canonicalizes the representation in this way before passing it to the kernel, to maximize compatibility with older applications/tools. - The old IBAUD0 hack is removed; it is no longer necessary since even the legacy c_cflag baud rate fields have had separate input values for a long time. Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This commit is contained in:
H. Peter Anvin (Intel)
committed by
Adhemerval Zanella
Adhemerval Zanella
parent
5f54d8bc48
commit
5cf101a85a
@@ -15,67 +15,94 @@
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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 <errno.h>
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#include <string.h>
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#include <termios.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sysdep.h>
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/* The difference here is that the termios structure used in the
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kernel is not the same as we use in the libc. Therefore we must
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translate it here. */
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#include <kernel_termios.h>
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/* This is a gross hack around a kernel bug. If the cfsetispeed functions
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is called with the SPEED argument set to zero this means use the same
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speed as for output. But we don't have independent input and output
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speeds and therefore cannot record this.
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We use an unused bit in the `c_iflag' field to keep track of this
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use of `cfsetispeed'. The value here must correspond to the one used
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in `speed.c'. */
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#define IBAUD0 020000000000
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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 __kernel_termios k_termios;
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unsigned long int cmd;
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struct termios2 k_termios;
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unsigned long cmd;
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switch (optional_actions)
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{
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case TCSANOW:
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cmd = TCSETS;
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break;
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case TCSADRAIN:
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cmd = TCSETSW;
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break;
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case TCSAFLUSH:
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cmd = TCSETSF;
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break;
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default:
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
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}
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memset (&k_termios, 0, sizeof k_termios);
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k_termios.c_iflag = termios_p->c_iflag & ~IBAUD0;
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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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#if _HAVE_C_ISPEED && _HAVE_STRUCT_TERMIOS_C_ISPEED
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k_termios.c_ispeed = termios_p->c_ispeed;
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#endif
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#if _HAVE_C_OSPEED && _HAVE_STRUCT_TERMIOS_C_OSPEED
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k_termios.c_ospeed = termios_p->c_ospeed;
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#endif
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memcpy (&k_termios.c_cc[0], &termios_p->c_cc[0],
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__KERNEL_NCCS * sizeof (cc_t));
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k_termios.c_line = termios_p->c_line;
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return INLINE_SYSCALL (ioctl, 3, fd, cmd, &k_termios);
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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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/*
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* Choose the proper ioctl number to invoke.
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*
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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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*/
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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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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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{
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cmd += TCSETS2;
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}
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else
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{
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cmd += TCSETS;
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k_termios.c_cflag &= ~CIBAUD;
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}
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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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