blob: dab71ceb4c360ec9ed17b5ab1d83c0672554f036 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#include <linux/livepatch.h>
#include <linux/audit.h>
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
/**
* enter_from_user_mode - Establish state when coming from user mode
*
* Syscall/interrupt entry disables interrupts, but user mode is traced as
* interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
*
* 1) Tell lockdep that interrupts are disabled
* 2) Invoke context tracking if enabled to reactivate RCU
* 3) Trace interrupts off state
*/
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();
}
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 ti_work)
{
long ret = 0;
/* Handle ptrace */
if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
ret = arch_syscall_enter_tracehook(regs);
if (ret || (ti_work & _TIF_SYSCALL_EMU))
return -1L;
}
/* Do seccomp after ptrace, to catch any tracer changes. */
if (ti_work & _TIF_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(ti_work & _TIF_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 ti_work;
ti_work = READ_ONCE(current_thread_info()->flags);
if (ti_work & SYSCALL_ENTER_WORK)
syscall = syscall_trace_enter(regs, syscall, ti_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;
trace_printk("syscall: Enter from user\n");
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();
}
/**
* exit_to_user_mode - Fixup state when exiting to user mode
*
* Syscall/interupt exit enables interrupts, but the kernel state is
* interrupts disabled when this is invoked. Also tell RCU about it.
*
* 1) Trace interrupts on state
* 2) Invoke context tracking if enabled to adjust RCU state
* 3) Invoke architecture specific last minute exit code, e.g. speculation
* mitigations, etc.
* 4) Tell lockdep that interrupts are enabled
*/
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);
}
/* Workaround to allow gradual conversion of architecture code */
void __weak arch_do_signal(struct pt_regs *regs) { }
unsigned long exit_to_user_get_work(void)
{
unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
if (IS_ENABLED(CONFIG_SCHED_CORE) && !sched_core_kernel_protected())
return ti_work;
#ifdef CONFIG_SCHED_CORE
ti_work &= EXIT_TO_USER_MODE_WORK;
if ((ti_work & _TIF_UNSAFE_RET) == ti_work) {
sched_core_unsafe_exit();
if (sched_core_wait_till_safe(EXIT_TO_USER_MODE_WORK)) {
sched_core_unsafe_enter(); /* not exiting to user yet. */
}
}
return READ_ONCE(current_thread_info()->flags);
#endif
}
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)
arch_do_signal(regs);
if (ti_work & _TIF_NOTIFY_RESUME) {
clear_thread_flag(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();
ti_work = exit_to_user_get_work();
}
/* 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();
ti_work = exit_to_user_get_work();
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();
lockdep_assert_irqs_disabled();
lockdep_sys_exit();
}
#ifndef _TIF_SINGLESTEP
static inline bool report_single_step(unsigned long ti_work)
{
return false;
}
#else
/*
* If TIF_SYSCALL_EMU is set, then the only reason to report is when
* TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
* instruction has been already reported in syscall_enter_from_usermode().
*/
#define SYSEMU_STEP (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU)
static inline bool report_single_step(unsigned long ti_work)
{
return (ti_work & SYSEMU_STEP) == _TIF_SINGLESTEP;
}
#endif
static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
{
bool step;
audit_syscall_exit(regs);
if (ti_work & _TIF_SYSCALL_TRACEPOINT)
trace_sys_exit(regs, syscall_get_return_value(current, regs));
step = report_single_step(ti_work);
if (step || ti_work & _TIF_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)
{
u32 cached_flags = READ_ONCE(current_thread_info()->flags);
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(cached_flags & SYSCALL_EXIT_WORK))
syscall_exit_work(regs, cached_flags);
}
__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
{
instrumentation_begin();
syscall_exit_to_user_mode_prepare(regs);
local_irq_disable_exit_to_user();
exit_to_user_mode_prepare(regs);
instrumentation_end();
trace_printk("syscall: Entering exit_to_user_mode\n");
exit_to_user_mode();
trace_printk("syscall: Leaving exit_to_user_mode\n");
}
noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
{
trace_printk("irq: Enter from user\n");
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();
trace_printk("irq: Entering exit_to_user_mode\n");
exit_to_user_mode();
trace_printk("irq: Leaving exit_to_user_mode\n");
}
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.
*
* Interupts 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 interupt and eventually claim
* quiescient 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 irq_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.
*/
instrumentation_begin();
rcu_irq_enter_check_tick();
/* Use the combo lockdep/tracing function */
trace_hardirqs_off();
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();
}
}
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))
irqentry_exit_cond_resched();
/* 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();
}
}