[PATCH 1/2] entry: move the exit path to header files

Sven Schnelle
2023-05-16T13:40:06Z

In order to allow inlining the generic entry C functions,
move them to include/linux/entry-common.h.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
---
include/linux/entry-common.h | 182 ++++++++++++++++++++++++++++++++++-
kernel/entry/common.c | 168 --------------------------------
2 files changed, 179 insertions(+), 171 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index d95ab85f96ba..b409fbcbd3ac 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -7,8 +7,13 @@
#include <linux/syscalls.h>
#include <linux/seccomp.h>
#include <linux/sched.h>
-
+#include <linux/livepatch.h>
#include <asm/entry-common.h>
+#include <linux/context_tracking.h>
+#include <linux/resume_user_mode.h>
+#include <linux/tick.h>
+
+#include <trace/events/syscalls.h>

/*
* Define dummy _TIF work flags if not defined by the architecture or for
@@ -291,7 +296,7 @@ void exit_to_user_mode(void);
* make the final state transitions. Interrupts must stay disabled between
* return from this function and the invocation of exit_to_user_mode().
*/
-void syscall_exit_to_user_mode_work(struct pt_regs *regs);
+static void syscall_exit_to_user_mode_work(struct pt_regs *regs);

/**
* syscall_exit_to_user_mode - Handle work before returning to user mode
@@ -350,7 +355,7 @@ void irqentry_enter_from_user_mode(struct pt_regs *regs);
* Interrupt exit is not invoking #1 which is the syscall specific one time
* work.
*/
-void irqentry_exit_to_user_mode(struct pt_regs *regs);
+static void irqentry_exit_to_user_mode(struct pt_regs *regs);

#ifndef irqentry_state
/**
@@ -465,4 +470,175 @@ irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
*/
void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);

+static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
+ unsigned long ti_work)
+{
+ /*
+ * Before returning to user space ensure that all pending work
+ * items have been completed.
+ */
+ while (ti_work & EXIT_TO_USER_MODE_WORK) {
+
+ local_irq_enable_exit_to_user(ti_work);
+
+ if (ti_work & _TIF_NEED_RESCHED)
+ schedule();
+
+ if (ti_work & _TIF_UPROBE)
+ uprobe_notify_resume(regs);
+
+ if (ti_work & _TIF_PATCH_PENDING)
+ klp_update_patch_state(current);
+
+ if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
+ arch_do_signal_or_restart(regs);
+
+ if (ti_work & _TIF_NOTIFY_RESUME)
+ resume_user_mode_work(regs);
+
+ /* Architecture specific TIF work */
+ arch_exit_to_user_mode_work(regs, ti_work);
+
+ /*
+ * Disable interrupts and reevaluate the work flags as they
+ * might have changed while interrupts and preemption was
+ * enabled above.
+ */
+ local_irq_disable_exit_to_user();
+
+ /* Check if any of the above work has queued a deferred wakeup */
+ tick_nohz_user_enter_prepare();
+
+ ti_work = read_thread_flags();
+ }
+
+ /* Return the latest work state for arch_exit_to_user_mode() */
+ return ti_work;
+}
+
+
+static void exit_to_user_mode_prepare(struct pt_regs *regs)
+{
+ unsigned long ti_work;
+
+ lockdep_assert_irqs_disabled();
+
+ /* Flush pending rcuog wakeup before the last need_resched() check */
+ tick_nohz_user_enter_prepare();
+
+ ti_work = read_thread_flags();
+ if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
+ ti_work = exit_to_user_mode_loop(regs, ti_work);
+
+ arch_exit_to_user_mode_prepare(regs, ti_work);
+
+ /* Ensure that the address limit is intact and no locks are held */
+ addr_limit_user_check();
+ kmap_assert_nomap();
+ lockdep_assert_irqs_disabled();
+ lockdep_sys_exit();
+}
+
+/*
+ * If SYSCALL_EMU is set, then the only reason to report is when
+ * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
+ * instruction has been already reported in syscall_enter_from_user_mode().
+ */
+static inline bool report_single_step(unsigned long work)
+{
+ if (work & SYSCALL_WORK_SYSCALL_EMU)
+ return false;
+
+ return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
+}
+
+static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
+{
+ bool step;
+
+ /*
+ * If the syscall was rolled back due to syscall user dispatching,
+ * then the tracers below are not invoked for the same reason as
+ * the entry side was not invoked in syscall_trace_enter(): The ABI
+ * of these syscalls is unknown.
+ */
+ if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
+ if (unlikely(current->syscall_dispatch.on_dispatch)) {
+ current->syscall_dispatch.on_dispatch = false;
+ return;
+ }
+ }
+
+ audit_syscall_exit(regs);
+
+ if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
+ trace_sys_exit(regs, syscall_get_return_value(current, regs));
+
+ step = report_single_step(work);
+ if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
+ ptrace_report_syscall_exit(regs, step);
+}
+
+/*
+ * Syscall specific exit to user mode preparation. Runs with interrupts
+ * enabled.
+ */
+static __always_inline void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
+{
+ unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
+ unsigned long nr = syscall_get_nr(current, regs);
+
+ CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
+
+ if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
+ if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
+ local_irq_enable();
+ }
+
+ rseq_syscall(regs);
+
+ /*
+ * Do one-time syscall specific work. If these work items are
+ * enabled, we want to run them exactly once per syscall exit with
+ * interrupts enabled.
+ */
+ if (unlikely(work & SYSCALL_WORK_EXIT))
+ syscall_exit_work(regs, work);
+}
+
+static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
+{
+ syscall_exit_to_user_mode_prepare(regs);
+ local_irq_disable_exit_to_user();
+ exit_to_user_mode_prepare(regs);
+}
+
+static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
+{
+ __syscall_exit_to_user_mode_work(regs);
+}
+
+/* See comment for exit_to_user_mode() in entry-common.h */
+static __always_inline void __exit_to_user_mode(void)
+{
+ instrumentation_begin();
+ trace_hardirqs_on_prepare();
+ lockdep_hardirqs_on_prepare();
+ instrumentation_end();
+
+ user_enter_irqoff();
+ arch_exit_to_user_mode();
+ lockdep_hardirqs_on(CALLER_ADDR0);
+}
+
+
+static __always_inline void irqentry_exit_to_user_mode(struct pt_regs *regs)
+{
+ instrumentation_begin();
+ exit_to_user_mode_prepare(regs);
+ instrumentation_end();
+ __exit_to_user_mode();
+}
+
+
#endif
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index be61332c66b5..66af971c3fe4 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -123,19 +123,6 @@ noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
instrumentation_end();
}

-/* See comment for exit_to_user_mode() in entry-common.h */
-static __always_inline void __exit_to_user_mode(void)
-{
- instrumentation_begin();
- trace_hardirqs_on_prepare();
- lockdep_hardirqs_on_prepare();
- instrumentation_end();
-
- user_enter_irqoff();
- arch_exit_to_user_mode();
- lockdep_hardirqs_on(CALLER_ADDR0);
-}
-
void noinstr exit_to_user_mode(void)
{
__exit_to_user_mode();
@@ -144,153 +131,6 @@ 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) { }

-static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
- unsigned long ti_work)
-{
- /*
- * Before returning to user space ensure that all pending work
- * items have been completed.
- */
- while (ti_work & EXIT_TO_USER_MODE_WORK) {
-
- local_irq_enable_exit_to_user(ti_work);
-
- if (ti_work & _TIF_NEED_RESCHED)
- schedule();
-
- if (ti_work & _TIF_UPROBE)
- uprobe_notify_resume(regs);
-
- if (ti_work & _TIF_PATCH_PENDING)
- klp_update_patch_state(current);
-
- if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
- arch_do_signal_or_restart(regs);
-
- if (ti_work & _TIF_NOTIFY_RESUME)
- resume_user_mode_work(regs);
-
- /* Architecture specific TIF work */
- arch_exit_to_user_mode_work(regs, ti_work);
-
- /*
- * Disable interrupts and reevaluate the work flags as they
- * might have changed while interrupts and preemption was
- * enabled above.
- */
- local_irq_disable_exit_to_user();
-
- /* Check if any of the above work has queued a deferred wakeup */
- tick_nohz_user_enter_prepare();
-
- ti_work = read_thread_flags();
- }
-
- /* Return the latest work state for arch_exit_to_user_mode() */
- return ti_work;
-}
-
-static void exit_to_user_mode_prepare(struct pt_regs *regs)
-{
- unsigned long ti_work;
-
- lockdep_assert_irqs_disabled();
-
- /* Flush pending rcuog wakeup before the last need_resched() check */
- tick_nohz_user_enter_prepare();
-
- ti_work = read_thread_flags();
- if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
- ti_work = exit_to_user_mode_loop(regs, ti_work);
-
- arch_exit_to_user_mode_prepare(regs, ti_work);
-
- /* Ensure that the address limit is intact and no locks are held */
- addr_limit_user_check();
- kmap_assert_nomap();
- lockdep_assert_irqs_disabled();
- lockdep_sys_exit();
-}
-
-/*
- * If SYSCALL_EMU is set, then the only reason to report is when
- * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
- * instruction has been already reported in syscall_enter_from_user_mode().
- */
-static inline bool report_single_step(unsigned long work)
-{
- if (work & SYSCALL_WORK_SYSCALL_EMU)
- return false;
-
- return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
-}
-
-static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
-{
- bool step;
-
- /*
- * If the syscall was rolled back due to syscall user dispatching,
- * then the tracers below are not invoked for the same reason as
- * the entry side was not invoked in syscall_trace_enter(): The ABI
- * of these syscalls is unknown.
- */
- if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
- if (unlikely(current->syscall_dispatch.on_dispatch)) {
- current->syscall_dispatch.on_dispatch = false;
- return;
- }
- }
-
- audit_syscall_exit(regs);
-
- if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
- trace_sys_exit(regs, syscall_get_return_value(current, regs));
-
- step = report_single_step(work);
- if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
- ptrace_report_syscall_exit(regs, step);
-}
-
-/*
- * Syscall specific exit to user mode preparation. Runs with interrupts
- * enabled.
- */
-static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
-{
- unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
- unsigned long nr = syscall_get_nr(current, regs);
-
- CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
-
- if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
- if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
- local_irq_enable();
- }
-
- rseq_syscall(regs);
-
- /*
- * Do one-time syscall specific work. If these work items are
- * enabled, we want to run them exactly once per syscall exit with
- * interrupts enabled.
- */
- if (unlikely(work & SYSCALL_WORK_EXIT))
- syscall_exit_work(regs, work);
-}
-
-static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
-{
- syscall_exit_to_user_mode_prepare(regs);
- local_irq_disable_exit_to_user();
- exit_to_user_mode_prepare(regs);
-}
-
-void syscall_exit_to_user_mode_work(struct pt_regs *regs)
-{
- __syscall_exit_to_user_mode_work(regs);
-}
-
__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
{
instrumentation_begin();
@@ -304,14 +144,6 @@ noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
__enter_from_user_mode(regs);
}

-noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
-{
- instrumentation_begin();
- exit_to_user_mode_prepare(regs);
- instrumentation_end();
- __exit_to_user_mode();
-}
-
noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
{
irqentry_state_t ret = {
--
2.39.2