This is a note to let you know that I've just added the patch titled
entry: Add support for TIF_NOTIFY_SIGNAL
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
entry-add-support-for-tif_notify_signal.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d02e3fa856542e39531f7f0910389b334cd9b1f3 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxxxxx>
Date: Mon, 26 Oct 2020 14:32:28 -0600
Subject: entry: Add support for TIF_NOTIFY_SIGNAL
From: Jens Axboe <axboe@xxxxxxxxx>
[ Upstream commit 12db8b690010ccfadf9d0b49a1e1798e47dbbe1a ]
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@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20201026203230.386348-3-axboe@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/signal.c | 4 ++--
include/linux/entry-common.h | 11 ++++++++---
include/linux/entry-kvm.h | 4 ++--
include/linux/sched/signal.h | 11 ++++++++++-
include/linux/tracehook.h | 27 +++++++++++++++++++++++++++
kernel/entry/common.c | 14 +++++++++++---
kernel/entry/kvm.c | 3 +++
kernel/signal.c | 14 ++++++++++++++
8 files changed, 77 insertions(+), 11 deletions(-)
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -798,11 +798,11 @@ static inline unsigned long get_nr_resta
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
-void arch_do_signal(struct pt_regs *regs)
+void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
{
struct ksignal ksig;
- if (get_signal(&ksig)) {
+ if (has_signal && get_signal(&ksig)) {
/* Whee! Actually deliver the signal. */
handle_signal(&ksig, regs);
return;
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -37,6 +37,10 @@
# define _TIF_UPROBE (0)
#endif
+#ifndef _TIF_NOTIFY_SIGNAL
+# define _TIF_NOTIFY_SIGNAL (0)
+#endif
+
/*
* TIF flags handled in syscall_enter_from_user_mode()
*/
@@ -69,7 +73,7 @@
#define EXIT_TO_USER_MODE_WORK \
(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
- _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | \
+ _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \
ARCH_EXIT_TO_USER_MODE_WORK)
/**
@@ -259,12 +263,13 @@ static __always_inline void arch_exit_to
#endif
/**
- * arch_do_signal - Architecture specific signal delivery function
+ * arch_do_signal_or_restart - Architecture specific signal delivery function
* @regs: Pointer to currents pt_regs
+ * @has_signal: actual signal to handle
*
* Invoked from exit_to_user_mode_loop().
*/
-void arch_do_signal(struct pt_regs *regs);
+void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal);
/**
* arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit()
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -11,8 +11,8 @@
# define ARCH_XFER_TO_GUEST_MODE_WORK (0)
#endif
-#define XFER_TO_GUEST_MODE_WORK \
- (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
+#define XFER_TO_GUEST_MODE_WORK \
+ (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL | \
_TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)
struct kvm_vcpu;
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -361,6 +361,15 @@ static inline int task_sigpending(struct
static inline int signal_pending(struct task_struct *p)
{
+#if defined(TIF_NOTIFY_SIGNAL)
+ /*
+ * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same
+ * behavior in terms of ensuring that we break out of wait loops
+ * so that notify signal callbacks can be processed.
+ */
+ if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
+ return 1;
+#endif
return task_sigpending(p);
}
@@ -508,7 +517,7 @@ extern int set_user_sigmask(const sigset
static inline void restore_saved_sigmask_unless(bool interrupted)
{
if (interrupted)
- WARN_ON(!test_thread_flag(TIF_SIGPENDING));
+ WARN_ON(!signal_pending(current));
else
restore_saved_sigmask();
}
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -198,4 +198,31 @@ static inline void tracehook_notify_resu
blkcg_maybe_throttle_current();
}
+/*
+ * called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This
+ * is currently used by TWA_SIGNAL based task_work, which requires breaking
+ * wait loops to ensure that task_work is noticed and run.
+ */
+static inline void tracehook_notify_signal(void)
+{
+#if defined(TIF_NOTIFY_SIGNAL)
+ clear_thread_flag(TIF_NOTIFY_SIGNAL);
+ smp_mb__after_atomic();
+ if (current->task_works)
+ task_work_run();
+#endif
+}
+
+/*
+ * Called when we have work to process from exit_to_user_mode_loop()
+ */
+static inline void set_notify_signal(struct task_struct *task)
+{
+#if defined(TIF_NOTIFY_SIGNAL)
+ if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
+ !wake_up_state(task, TASK_INTERRUPTIBLE))
+ kick_process(task);
+#endif
+}
+
#endif /* <linux/tracehook.h> */
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -135,7 +135,15 @@ static __always_inline void exit_to_user
}
/* 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)
@@ -157,8 +165,8 @@ static unsigned long exit_to_user_mode_l
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) {
tracehook_notify_resume(regs);
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -8,6 +8,9 @@ static int xfer_to_guest_mode_work(struc
do {
int ret;
+ if (ti_work & _TIF_NOTIFY_SIGNAL)
+ tracehook_notify_signal();
+
if (ti_work & _TIF_SIGPENDING) {
kvm_handle_signal_exit(vcpu);
return -EINTR;
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2520,6 +2520,20 @@ bool get_signal(struct ksignal *ksig)
struct signal_struct *signal = current->signal;
int signr;
+ /*
+ * For non-generic architectures, check for TIF_NOTIFY_SIGNAL so
+ * that the arch handlers don't all have to do it. If we get here
+ * without TIF_SIGPENDING, just exit after running signal work.
+ */
+#ifdef TIF_NOTIFY_SIGNAL
+ if (!IS_ENABLED(CONFIG_GENERIC_ENTRY)) {
+ if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+ tracehook_notify_signal();
+ if (!task_sigpending(current))
+ return false;
+ }
+#endif
+
if (unlikely(uprobe_deny_signal()))
return false;
Patches currently in stable-queue which might be from axboe@xxxxxxxxx are
queue-5.10/x86-process-setup-io_threads-more-like-normal-user-space-threads.patch
queue-5.10/powerpc-add-support-for-tif_notify_signal.patch
queue-5.10/eventfd-provide-a-eventfd_signal_mask-helper.patch
queue-5.10/fs-provide-locked-helper-variant-of-close_fd_get_file.patch
queue-5.10/relay-fix-type-mismatch-when-allocating-memory-in-re.patch
queue-5.10/eventfd-change-int-to-__u64-in-eventfd_signal-ifndef.patch
queue-5.10/io_uring-pass-in-epoll_uring_wake-for-eventfd-signaling-and-wakeups.patch
queue-5.10/blk-mq-fix-possible-memleak-when-register-hctx-faile.patch
queue-5.10/fix-handling-of-nd-depth-on-lookup_cached-failures-in-try_to_unlazy.patch
queue-5.10/net-provide-__sys_shutdown_sock-that-takes-a-socket.patch
queue-5.10/task_work-unconditionally-run-task_work-from-get_signal.patch
queue-5.10/openrisc-add-support-for-tif_notify_signal.patch
queue-5.10/signal-add-task_sigpending-helper.patch
queue-5.10/net-remove-cmsg-restriction-from-io_uring-based-send-recvmsg-calls.patch
queue-5.10/alpha-add-support-for-tif_notify_signal.patch
queue-5.10/nios32-add-support-for-tif_notify_signal.patch
queue-5.10/ia64-don-t-call-handle_signal-unless-there-s-actually-a-signal-queued.patch
queue-5.10/task_work-remove-legacy-twa_signal-path.patch
queue-5.10/revert-proc-don-t-allow-async-path-resolution-of-proc-self-components.patch
queue-5.10/m68k-add-support-for-tif_notify_signal.patch
queue-5.10/s390-add-support-for-tif_notify_signal.patch
queue-5.10/um-add-support-for-tif_notify_signal.patch
queue-5.10/tools-headers-uapi-sync-openat2.h-with-the-kernel-sources.patch
queue-5.10/kernel-provide-create_io_thread-helper.patch
queue-5.10/iov_iter-add-helper-to-save-iov_iter-state.patch
queue-5.10/arc-unbork-5.11-bootup-fix-snafu-in-_tif_notify_signal-handling.patch
queue-5.10/arch-ensure-parisc-powerpc-handle-pf_io_worker-in-copy_thread.patch
queue-5.10/csky-add-support-for-tif_notify_signal.patch
queue-5.10/arm-add-support-for-tif_notify_signal.patch
queue-5.10/kernel-stop-masking-signals-in-create_io_thread.patch
queue-5.10/fs-expose-lookup_cached-through-openat2-resolve_cached.patch
queue-5.10/task_work-add-helper-for-more-targeted-task_work-canceling.patch
queue-5.10/nds32-add-support-for-tif_notify_signal.patch
queue-5.10/signal-kill-jobctl_task_work.patch
queue-5.10/hexagon-add-support-for-tif_notify_signal.patch
queue-5.10/sh-add-support-for-tif_notify_signal.patch
queue-5.10/riscv-add-support-for-tif_notify_signal.patch
queue-5.10/h8300-add-support-for-tif_notify_signal.patch
queue-5.10/io_uring-import-5.15-stable-io_uring.patch
queue-5.10/sparc-add-support-for-tif_notify_signal.patch
queue-5.10/blktrace-fix-output-non-blktrace-event-when-blk_clas.patch
queue-5.10/eventpoll-add-epoll_uring_wake-poll-wakeup-flag.patch
queue-5.10/parisc-add-support-for-tif_notify_signal.patch
queue-5.10/entry-add-support-for-tif_notify_signal.patch
queue-5.10/x86-wire-up-tif_notify_signal.patch
queue-5.10/task_work-use-tif_notify_signal-if-available.patch
queue-5.10/drbd-fix-an-invalid-memory-access-caused-by-incorrec.patch
queue-5.10/kernel-don-t-call-do_exit-for-pf_io_worker-threads.patch
queue-5.10/kernel-allow-fork-with-tif_notify_signal-pending.patch
queue-5.10/pata_ipx4xx_cf-fix-unsigned-comparison-with-less-tha.patch
queue-5.10/mips-add-support-for-tif_notify_signal.patch
queue-5.10/xtensa-add-support-for-tif_notify_signal.patch
queue-5.10/c6x-add-support-for-tif_notify_signal.patch
queue-5.10/microblaze-add-support-for-tif_notify_signal.patch
queue-5.10/net-add-accept-helper-not-installing-fd.patch
queue-5.10/ia64-add-support-for-tif_notify_signal.patch
queue-5.10/arm64-add-support-for-tif_notify_signal.patch
queue-5.10/arc-add-support-for-tif_notify_signal.patch
queue-5.10/revert-proc-don-t-allow-async-path-resolution-of-proc-thread-self-components.patch
queue-5.10/fs-make-do_renameat2-take-struct-filename.patch
queue-5.10/kernel-remove-checking-for-tif_notify_signal.patch
queue-5.10/arch-setup-pf_io_worker-threads-like-pf_kthread.patch
queue-5.10/nvme-pci-fix-mempool-alloc-size.patch
queue-5.10/fs-add-support-for-lookup_cached.patch
