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kernel/entry/common.c
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// SPDX-License-Identifier: GPL-2.0 #include <linux/context_tracking.h> #include <linux/entry-common.h> |
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#include <linux/livepatch.h> #include <linux/audit.h> |
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#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; } |
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/* Either of the above might have changed the syscall number */ syscall = syscall_get_nr(current, regs); |
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if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT)) trace_sys_enter(regs, syscall); syscall_enter_audit(regs, syscall); |
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return ret ? : syscall; |
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} |
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static __always_inline long __syscall_enter_from_user_work(struct pt_regs *regs, long syscall) |
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{ unsigned long ti_work; |
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ti_work = READ_ONCE(current_thread_info()->flags); if (ti_work & SYSCALL_ENTER_WORK) syscall = syscall_trace_enter(regs, syscall, ti_work); |
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return syscall; } |
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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(); } |
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/** * 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) { } 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) { |
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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 = 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(); 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 |
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* instruction has been already reported in syscall_enter_from_user_mode(). |
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*/ #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(); exit_to_user_mode(); } |
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noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs) { enter_from_user_mode(regs); } |
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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(); } |
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noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs) |
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{ 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. * |
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* Checking for rcu_is_watching() here would prevent the nesting |
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* 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. */ |
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lockdep_hardirqs_off(CALLER_ADDR0); |
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instrumentation_begin(); rcu_irq_enter_check_tick(); |
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trace_hardirqs_off_finish(); |
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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(); } } |
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noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state) |
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{ 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(); } } |