On Wed, Apr 13, 2005 at 07:50:03AM -0500, Bruce Dubbs wrote: > In any case, we are getting closer. I did follow the book precisely and > took the option of not changing anything in the console configuration. > This worked in the past. It would certainly be easy enough to throw in > a "stty sane" or "stty erase ^?" in /etc/profile, but the question now > is why is that necessary?
None of your boot scripts (or your login scripts) set stty erase ^H, correct? You never know... stty seems to pull those settings in from a tcgetattr() call. The "struct termios" that that call fills in, has the ^H character code set in the c_cc[VERASE] element (this defines which keycode acts as the "erase" keycode). tcgetattr() is part of glibc. glibc's sysdeps/unix/sysv/linux/tcgetattr.c file defines tcgetattr() as a weak alias for __tcgetattr, which basically calls the TCGETS ioctl on the passed-in file handle. In the kernel, in drivers/char/tty_ioctl.c, that ioctl value translates real_tty->termios into a user-space version, and copies it into the passed-in buffer. real_tty's value depends on whether the tty that gets passed into the ioctl handler is a pseudo-terminal master, or something else. If it's a PTY master, then real_tty is its "link" (presumably the PTY slave, though I don't know that for sure). Otherwise, real_tty is the tty_struct that was passed in. (This is all happening in drivers/char/tty_ioctl.c, function n_tty_ioctl.) Beyond that, I get lost in the kernel. I *think* the tty_struct that gets passed in depends on the line discipline (I can't find any promising callers of n_tty_ioctl, and the only other promising reference to it is the spot that sets it as the ioctl handler for the N_TTY line discipline, which seems to be the "standard" TTY line discipline). I also know that ->termios has to be initialized somewhere (when the line discipline is opened? doesn't seem to be it though), but I can't figure out where. Did you say you were using some kind of framebuffer console? Does it help at all if you change that, or did you try that already?
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