linux-stable/kernel/entry/common.c
Frederic Weisbecker f268c3737e tick/nohz: Only check for RCU deferred wakeup on user/guest entry when needed
Checking for and processing RCU-nocb deferred wakeup upon user/guest
entry is only relevant when nohz_full runs on the local CPU, otherwise
the periodic tick should take care of it.

Make sure we don't needlessly pollute these fast-paths as a -3%
performance regression on a will-it-scale.per_process_ops has been
reported so far.

Fixes: 47b8ff194c (entry: Explicitly flush pending rcuog wakeup before last rescheduling point)
Fixes: 4ae7dc97f7 (entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point)
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210527113441.465489-1-frederic@kernel.org
2021-05-31 10:14:49 +02:00

479 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#include <linux/highmem.h>
#include <linux/livepatch.h>
#include <linux/audit.h>
#include <linux/tick.h>
#include "common.h"
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
/* See comment for enter_from_user_mode() in entry-common.h */
static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
{
arch_check_user_regs(regs);
lockdep_hardirqs_off(CALLER_ADDR0);
CT_WARN_ON(ct_state() != CONTEXT_USER);
user_exit_irqoff();
instrumentation_begin();
trace_hardirqs_off_finish();
instrumentation_end();
}
void noinstr enter_from_user_mode(struct pt_regs *regs)
{
__enter_from_user_mode(regs);
}
static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
{
if (unlikely(audit_context())) {
unsigned long args[6];
syscall_get_arguments(current, regs, args);
audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
}
}
static long syscall_trace_enter(struct pt_regs *regs, long syscall,
unsigned long work)
{
long ret = 0;
/*
* Handle Syscall User Dispatch. This must comes first, since
* the ABI here can be something that doesn't make sense for
* other syscall_work features.
*/
if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
if (syscall_user_dispatch(regs))
return -1L;
}
/* Handle ptrace */
if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
ret = arch_syscall_enter_tracehook(regs);
if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
return -1L;
}
/* Do seccomp after ptrace, to catch any tracer changes. */
if (work & SYSCALL_WORK_SECCOMP) {
ret = __secure_computing(NULL);
if (ret == -1L)
return ret;
}
/* Either of the above might have changed the syscall number */
syscall = syscall_get_nr(current, regs);
if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
trace_sys_enter(regs, syscall);
syscall_enter_audit(regs, syscall);
return ret ? : syscall;
}
static __always_inline long
__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
{
unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
if (work & SYSCALL_WORK_ENTER)
syscall = syscall_trace_enter(regs, syscall, work);
return syscall;
}
long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
{
return __syscall_enter_from_user_work(regs, syscall);
}
noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
{
long ret;
__enter_from_user_mode(regs);
instrumentation_begin();
local_irq_enable();
ret = __syscall_enter_from_user_work(regs, syscall);
instrumentation_end();
return ret;
}
noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
{
__enter_from_user_mode(regs);
instrumentation_begin();
local_irq_enable();
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(CALLER_ADDR0);
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();
}
/* 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);
}
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))
handle_signal_work(regs, ti_work);
if (ti_work & _TIF_NOTIFY_RESUME) {
tracehook_notify_resume(regs);
rseq_handle_notify_resume(NULL, 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_ONCE(current_thread_info()->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 = READ_ONCE(current_thread_info()->flags);
lockdep_assert_irqs_disabled();
/* Flush pending rcuog wakeup before the last need_resched() check */
tick_nohz_user_enter_prepare();
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)
arch_syscall_exit_tracehook(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();
__syscall_exit_to_user_mode_work(regs);
instrumentation_end();
__exit_to_user_mode();
}
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 = {
.exit_rcu = false,
};
if (user_mode(regs)) {
irqentry_enter_from_user_mode(regs);
return ret;
}
/*
* If this entry hit the idle task invoke rcu_irq_enter() whether
* RCU is watching or not.
*
* Interrupts can nest when the first interrupt invokes softirq
* processing on return which enables interrupts.
*
* Scheduler ticks in the idle task can mark quiescent state and
* terminate a grace period, if and only if the timer interrupt is
* not nested into another interrupt.
*
* Checking for rcu_is_watching() here would prevent the nesting
* interrupt to invoke rcu_irq_enter(). If that nested interrupt is
* the tick then rcu_flavor_sched_clock_irq() would wrongfully
* assume that it is the first interrupt and eventually claim
* quiescent state and end grace periods prematurely.
*
* Unconditionally invoke rcu_irq_enter() so RCU state stays
* consistent.
*
* TINY_RCU does not support EQS, so let the compiler eliminate
* this part when enabled.
*/
if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
/*
* If RCU is not watching then the same careful
* sequence vs. lockdep and tracing is required
* as in irqentry_enter_from_user_mode().
*/
lockdep_hardirqs_off(CALLER_ADDR0);
rcu_irq_enter();
instrumentation_begin();
trace_hardirqs_off_finish();
instrumentation_end();
ret.exit_rcu = true;
return ret;
}
/*
* If RCU is watching then RCU only wants to check whether it needs
* to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
* already contains a warning when RCU is not watching, so no point
* in having another one here.
*/
lockdep_hardirqs_off(CALLER_ADDR0);
instrumentation_begin();
rcu_irq_enter_check_tick();
trace_hardirqs_off_finish();
instrumentation_end();
return ret;
}
void irqentry_exit_cond_resched(void)
{
if (!preempt_count()) {
/* Sanity check RCU and thread stack */
rcu_irq_exit_check_preempt();
if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
WARN_ON_ONCE(!on_thread_stack());
if (need_resched())
preempt_schedule_irq();
}
}
#ifdef CONFIG_PREEMPT_DYNAMIC
DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
#endif
noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
{
lockdep_assert_irqs_disabled();
/* Check whether this returns to user mode */
if (user_mode(regs)) {
irqentry_exit_to_user_mode(regs);
} else if (!regs_irqs_disabled(regs)) {
/*
* If RCU was not watching on entry this needs to be done
* carefully and needs the same ordering of lockdep/tracing
* and RCU as the return to user mode path.
*/
if (state.exit_rcu) {
instrumentation_begin();
/* Tell the tracer that IRET will enable interrupts */
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
instrumentation_end();
rcu_irq_exit();
lockdep_hardirqs_on(CALLER_ADDR0);
return;
}
instrumentation_begin();
if (IS_ENABLED(CONFIG_PREEMPTION)) {
#ifdef CONFIG_PREEMPT_DYNAMIC
static_call(irqentry_exit_cond_resched)();
#else
irqentry_exit_cond_resched();
#endif
}
/* Covers both tracing and lockdep */
trace_hardirqs_on();
instrumentation_end();
} else {
/*
* IRQ flags state is correct already. Just tell RCU if it
* was not watching on entry.
*/
if (state.exit_rcu)
rcu_irq_exit();
}
}
irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
{
irqentry_state_t irq_state;
irq_state.lockdep = lockdep_hardirqs_enabled();
__nmi_enter();
lockdep_hardirqs_off(CALLER_ADDR0);
lockdep_hardirq_enter();
rcu_nmi_enter();
instrumentation_begin();
trace_hardirqs_off_finish();
ftrace_nmi_enter();
instrumentation_end();
return irq_state;
}
void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
{
instrumentation_begin();
ftrace_nmi_exit();
if (irq_state.lockdep) {
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
}
instrumentation_end();
rcu_nmi_exit();
lockdep_hardirq_exit();
if (irq_state.lockdep)
lockdep_hardirqs_on(CALLER_ADDR0);
__nmi_exit();
}