[PATCH 08/13] task_work: Call tracehook_notify_signal from get_signal on all architectures

Eric W. Biederman
2022-03-09T16:44:48Z

Always handle TIF_NOTIFY_SIGNAL in get_signal. With commit 35d0b389f3b2
("task_work: unconditionally run task_work from get_signal()") always
calling task_wofffffffrk_run all of the work of tracehook_notify_signal is
already happening except clearing TIF_NOTIFY_SIGNAL.

Factor clear_notify_signal out of tracehook_notify_signal and use it in
get_signal so that get_signal only needs one call of trask_work_run.

To keep the semantics in sync update xfer_to_guest_mode_work (which
does not call get_signal) to call tracehook_notify_signal if either
_TIF_SIGPENDING or _TIF_NOTIFY_SIGNAL.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
arch/s390/kernel/signal.c | 4 ++--
arch/x86/kernel/signal.c | 4 ++--
include/linux/entry-common.h | 2 +-
include/linux/tracehook.h | 9 +++++++--
kernel/entry/common.c | 12 ++----------
kernel/entry/kvm.c | 2 +-
kernel/signal.c | 14 +++-----------
7 files changed, 18 insertions(+), 29 deletions(-)

diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 307f5d99514d..ea9e5e8182cd 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -453,7 +453,7 @@ static void handle_signal(struct ksignal *ksig, sigset_t *oldset,
* stack-frames in one go after that.
*/

-void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
+void arch_do_signal_or_restart(struct pt_regs *regs)
{
struct ksignal ksig;
sigset_t *oldset = sigmask_to_save();
@@ -466,7 +466,7 @@ void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
current->thread.system_call =
test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;

- if (has_signal && get_signal(&ksig)) {
+ if (get_signal(&ksig)) {
/* Whee! Actually deliver the signal. */
if (current->thread.system_call) {
regs->int_code = current->thread.system_call;
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index ec71e06ae364..de3d5b5724d8 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -861,11 +861,11 @@ static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
-void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
+void arch_do_signal_or_restart(struct pt_regs *regs)
{
struct ksignal ksig;

- if (has_signal && get_signal(&ksig)) {
+ if (get_signal(&ksig)) {
/* Whee! Actually deliver the signal. */
handle_signal(&ksig, regs);
return;
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 9efbdda61f7a..3537fd25f14e 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -257,7 +257,7 @@ static __always_inline void arch_exit_to_user_mode(void) { }
*
* Invoked from exit_to_user_mode_loop().
*/
-void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal);
+void arch_do_signal_or_restart(struct pt_regs *regs);

/**
* exit_to_user_mode - Fixup state when exiting to user mode
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index fa834a22e86e..b44a7820c468 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -106,6 +106,12 @@ static inline void tracehook_notify_resume(struct pt_regs *regs)
rseq_handle_notify_resume(NULL, regs);
}

+static inline void clear_notify_signal(void)
+{
+ clear_thread_flag(TIF_NOTIFY_SIGNAL);
+ smp_mb__after_atomic();
+}
+
/*
* 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
@@ -113,8 +119,7 @@ static inline void tracehook_notify_resume(struct pt_regs *regs)
*/
static inline void tracehook_notify_signal(void)
{
- clear_thread_flag(TIF_NOTIFY_SIGNAL);
- smp_mb__after_atomic();
+ clear_notify_signal();
if (task_work_pending(current))
task_work_run();
}
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index f0b1daa1e8da..79eaf9b4b10d 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -139,15 +139,7 @@ void noinstr exit_to_user_mode(void)
}

/* Workaround to allow gradual conversion of architecture code */
-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);
-}
+void __weak arch_do_signal_or_restart(struct pt_regs *regs) { }

static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
unsigned long ti_work)
@@ -170,7 +162,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
klp_update_patch_state(current);

if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
- handle_signal_work(regs, ti_work);
+ arch_do_signal_or_restart(regs);

if (ti_work & _TIF_NOTIFY_RESUME)
tracehook_notify_resume(regs);
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 96d476e06c77..cabf36a489e4 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -8,7 +8,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
do {
int ret;

- if (ti_work & _TIF_NOTIFY_SIGNAL)
+ if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
tracehook_notify_signal();

if (ti_work & _TIF_SIGPENDING) {
diff --git a/kernel/signal.c b/kernel/signal.c
index 3b4cf25fb9b3..8632b88982c9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2626,20 +2626,12 @@ bool get_signal(struct ksignal *ksig)
struct signal_struct *signal = current->signal;
int signr;

+ clear_notify_signal();
if (unlikely(task_work_pending(current)))
task_work_run();

- /*
- * 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.
- */
- if (!IS_ENABLED(CONFIG_GENERIC_ENTRY)) {
- if (test_thread_flag(TIF_NOTIFY_SIGNAL))
- tracehook_notify_signal();
- if (!task_sigpending(current))
- return false;
- }
+ if (!task_sigpending(current))
+ return false;

if (unlikely(uprobe_deny_signal()))
return false;
--
2.29.2