I took a good hard look at the locking and it appears the locking on vt_pid
is the console semaphore. Every modified path is called under the console
semaphore except reset_vc when it is called from fn_SAK or do_SAK both of
which appear to be in interrupt context. In addition I need to be careful
because in the presence of an oops the console_sem may be arbitrarily
dropped.
Which leads me to conclude the current locking is inadequate for my needs.
Given the weird cases we could hit because of oops printing instead of
introducing an extra spin lock to protect the data and keep the pid to
signal and the signal to send in sync, I have opted to use xchg on just the
struct pid * pointer instead.
Due to console_sem we will stay in sync between vt_pid and vt_mode except
for a small window during a SAK, or oops handling. SAK handling should
kill any user space process that care, and oops handling we are broken
anyway. Besides the worst that can happen is that I try to send the wrong
signal.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This is such a rare path it took me a while to figure out how to test
this after soring out the locking.
This patch does several things.
- The variables used are moved into a structure and declared in vt_kern.h
- A spinlock is added so we don't have SMP races updating the values.
- Instead of raw pid_t value a struct_pid is used to guard against
pid wrap around issues, if the daemon to spawn a new console dies.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The current kernel serializes console resizes but does not serialize the
resize against the tty structure updates. This means that while two
parallel resizes cannot mess up the console you can get incorrect results
reported.
Secondly while doing this I added vc_lock_resize() to lock and resize the
console. This leaves all knowledge of the console_sem in the vt/console
driver and kicks it out of the tty layer, which is good
Thirdly while doing this I decided I couldn't stand "disallocate" any
longer so I switched it to "deallocate".
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When reading /dev/vcsa while a font with more than 256 characters is
loaded, one of the attribute bits records the 9th bit of the character.
But depending on the console driver (vgacon or fbcon for instance), that's
bit 3 or bit 0. And there is no way for userland to know that, thus no way
for userland to safely grab the screen content. So here is a (tested)
patch:
Add a VT_GETHIFONTMASK ioctl for knowing which bit is the 9th bit for VC
text (vc_hi_font_mask field of the vc_data structure).
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Mikael Pettersson <mikpe@csd.uu.se> noted that the current 2.6-git (and 2.4)
patch to disallow KDSKBSENT for unpriviledged users should be less restrictive
allowing reading of current function key string entry, but not writing.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Because people can play games reprogramming keys and leaving traps for the
next user of the console.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This code uses the x86 (non-AMD-ELAN) value of CLOCK_TICK_RATE instead of
CLOCK_TICK_RATE itself, which is wrong for other archs.
Signed-off-by: Emmanuel Colbus <emmanuel.colbus@ensimag.imag.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Convert most of the current code that uses _NSIG directly to instead use
valid_signal(). This avoids gcc -W warnings and off-by-one errors.
Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Eric W. Biederman