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uterm: vt: add fake-vt logic for debugging

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This adds a very limited non-multi-seat-capable fake-VT logic. If you use
this in production it will break your multi-seat systems so do not use it
except for debugging.

On SIGUSR1 we activate fake VTs and on SIGUSR2 we deactivate them. The
signals must be sent from a priviledged process. Kernel signals are
ignored.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
This commit is contained in:
David Herrmann 2012-08-12 11:18:48 +02:00
parent 4f3cd2eecd
commit f084da1852
1 changed files with 35 additions and 0 deletions
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35
src/uterm_vt.c
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@ -353,6 +353,36 @@ static int real_deactivate(struct uterm_vt *vt)
return -EINPROGRESS;
}
/*
* Fake VT:
* For systems without CONFIG_VT or for all seats that have no real VTs (which
* is all seats except seat0), we support a fake-VT mechanism. This machanism is
* only used for debugging and should not be used in production.
* The Fake-VT reacts on SIGUSR1 and SIGUSR2 similar to the real-vt and
* activates or deactivates the VT. However, this is a global mechanism as all
* fake VTs listen to the same signals. Therefore, this is not really multi-seat
* safe.
* TODO: Replace this with a proper multi-seat-capable fake-VT mechanism.
*/
static void fake_enter(struct uterm_vt *vt, struct signalfd_siginfo *info)
{
if (info->ssi_code != SI_USER)
return;
log_debug("activating fake VT due to SIGUSR1");
vt_call(vt, UTERM_VT_ACTIVATE);
}
static void fake_leave(struct uterm_vt *vt, struct signalfd_siginfo *info)
{
if (info->ssi_code != SI_USER)
return;
log_debug("deactivating fake VT due to SIGUSR2");
vt_call(vt, UTERM_VT_DEACTIVATE);
}
static bool check_vt_support(void)
{
if (!access("/dev/tty", F_OK))
@ -366,6 +396,7 @@ static void vt_idle_event(struct ev_eloop *eloop, void *unused, void *data)
struct uterm_vt *vt = data;
ev_eloop_unregister_idle_cb(eloop, vt_idle_event, data);
log_debug("activating fake VT on startup");
vt_call(vt, UTERM_VT_ACTIVATE);
}
@ -376,6 +407,8 @@ static void vt_sigusr1(struct ev_eloop *eloop, struct signalfd_siginfo *info,
if (vt->mode == UTERM_VT_REAL)
real_enter(vt, info);
else if (vt->mode == UTERM_VT_FAKE)
fake_enter(vt, info);
}
static void vt_sigusr2(struct ev_eloop *eloop, struct signalfd_siginfo *info,
@ -385,6 +418,8 @@ static void vt_sigusr2(struct ev_eloop *eloop, struct signalfd_siginfo *info,
if (vt->mode == UTERM_VT_REAL)
real_leave(vt, info);
else if (vt->mode == UTERM_VT_FAKE)
fake_leave(vt, info);
}
int uterm_vt_allocate(struct uterm_vt_master *vtm,