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Short description: Fedora-specific workaround for kernel pty bug.
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Author(s): Fedora glibc team <glibc@lists.fedoraproject.org>
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Origin: PATCH
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Upstream status: not-submitted
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This is a Fedora-specific workaround for a kernel bug where calling
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ioctl on a pty will silently ignore the invalid c_cflag. The
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workaround is to use TCGETS to verify the setting matches. This is
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not upstream and needs to either be removed or submitted upstream
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after analysis.
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Index: b/sysdeps/unix/sysv/linux/tcsetattr.c
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===================================================================
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--- a/sysdeps/unix/sysv/linux/tcsetattr.c
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+++ b/sysdeps/unix/sysv/linux/tcsetattr.c
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@@ -45,6 +45,7 @@ __tcsetattr (int fd, int optional_action
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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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+ int retval;
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switch (optional_actions)
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{
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@@ -75,7 +76,36 @@ __tcsetattr (int fd, int optional_action
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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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- return INLINE_SYSCALL (ioctl, 3, fd, cmd, &k_termios);
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+ retval = INLINE_SYSCALL (ioctl, 3, fd, cmd, &k_termios);
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+
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+ if (retval == 0 && cmd == TCSETS)
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+ {
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+ /* The Linux kernel has a bug which silently ignore the invalid
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+ c_cflag on pty. We have to check it here. */
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+ int save = errno;
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+ retval = INLINE_SYSCALL (ioctl, 3, fd, TCGETS, &k_termios);
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+ if (retval)
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+ {
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+ /* We cannot verify if the setting is ok. We don't return
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+ an error (?). */
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+ __set_errno (save);
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+ retval = 0;
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+ }
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+ else if ((termios_p->c_cflag & (PARENB | CREAD))
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+ != (k_termios.c_cflag & (PARENB | CREAD))
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+ || ((termios_p->c_cflag & CSIZE)
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+ && ((termios_p->c_cflag & CSIZE)
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+ != (k_termios.c_cflag & CSIZE))))
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+ {
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+ /* It looks like the Linux kernel silently changed the
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+ PARENB/CREAD/CSIZE bits in c_cflag. Report it as an
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+ error. */
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+ __set_errno (EINVAL);
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+ retval = -1;
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+ }
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+ }
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+
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+ return retval;
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}
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weak_alias (__tcsetattr, tcsetattr)
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libc_hidden_def (tcsetattr)
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