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entry: Add support for TIF_NOTIFY_SIGNAL

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Add TIF_NOTIFY_SIGNAL handling in the generic entry code, which if set,
will return true if signal_pending() is used in a wait loop. That causes an
exit of the loop so that notify_signal tracehooks can be run. If the wait
loop is currently inside a system call, the system call is restarted once
task_work has been processed.

In preparation for only having arch_do_signal() handle syscall restarts if
_TIF_SIGPENDING isn't set, rename it to arch_do_signal_or_restart().  Pass
in a boolean that tells the architecture specific signal handler if it
should attempt to get a signal, or just process a potential syscall
restart.

For !CONFIG_GENERIC_ENTRY archs, add the TIF_NOTIFY_SIGNAL handling to
get_signal(). This is done to minimize the needed architecture changes to
support this feature.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20201026203230.386348-3-axboe@kernel.dk
This commit is contained in:
Jens Axboe 2020-10-26 14:32:28 -06:00 • committed by Thomas Gleixner
parent 5c251e9dc0
commit 12db8b6900
8 changed files with 77 additions and 11 deletions
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14
kernel/entry/common.c
View file

@ -109,7 +109,15 @@ static __always_inline void exit_to_user_mode(void)
}
/* Workaround to allow gradual conversion of architecture code */
void __weak arch_do_signal(struct pt_regs *regs) { }
void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
{
if (ti_work & _TIF_NOTIFY_SIGNAL)
tracehook_notify_signal();
arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
}
static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
unsigned long ti_work)
@ -131,8 +139,8 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
if (ti_work & _TIF_PATCH_PENDING)
klp_update_patch_state(current);
if (ti_work & _TIF_SIGPENDING)
arch_do_signal(regs);
if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
handle_signal_work(regs, ti_work);
if (ti_work & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);

3
kernel/entry/kvm.c
View file

@ -8,6 +8,9 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
do {
int ret;
if (ti_work & _TIF_NOTIFY_SIGNAL)
tracehook_notify_signal();
if (ti_work & _TIF_SIGPENDING) {
kvm_handle_signal_exit(vcpu);
return -EINTR;