The following commit has been merged into the x86/entry branch of tip: Commit-ID: eadb831607477ba774b3314bdc956331b41817d6 Gitweb: https://git.kernel.org/tip/eadb831607477ba774b3314bdc956331b41817d6 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Thu, 26 Mar 2020 16:28:52 +01:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Tue, 19 May 2020 16:03:57 +02:00 x86/entry/common: Provide idtentry_enter/exit() Provide functions which handle the low level entry and exit similar to enter/exit from user mode. Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Acked-by: Andy Lutomirski <luto@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200505134904.457578656@xxxxxxxxxxxxx --- arch/x86/entry/common.c | 99 +++++++++++++++++++++++++++++++- arch/x86/include/asm/idtentry.h | 3 +- 2 files changed, 102 insertions(+) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index e4f9f5f..9ebe334 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -510,3 +510,102 @@ SYSCALL_DEFINE0(ni_syscall) { return -ENOSYS; } + +/** + * idtentry_enter - Handle state tracking on idtentry + * @regs: Pointer to pt_regs of interrupted context + * + * Invokes: + * - lockdep irqflag state tracking as low level ASM entry disabled + * interrupts. + * + * - Context tracking if the exception hit user mode. + * + * - RCU notification if the exception hit kernel mode. + * + * - The hardirq tracer to keep the state consistent as low level ASM + * entry disabled interrupts. + */ +void noinstr idtentry_enter(struct pt_regs *regs) +{ + if (user_mode(regs)) { + enter_from_user_mode(); + } else { + lockdep_hardirqs_off(CALLER_ADDR0); + rcu_irq_enter(); + instrumentation_begin(); + trace_hardirqs_off_prepare(); + instrumentation_end(); + } +} + +/** + * idtentry_exit - Common code to handle return from exceptions + * @regs: Pointer to pt_regs (exception entry regs) + * + * Depending on the return target (kernel/user) this runs the necessary + * preemption and work checks if possible and required and returns to + * the caller with interrupts disabled and no further work pending. + * + * This is the last action before returning to the low level ASM code which + * just needs to return to the appropriate context. + * + * Invoked by all exception/interrupt IDTENTRY handlers which are not + * returning through the paranoid exit path (all except NMI, #DF and the IST + * variants of #MC and #DB) and are therefore on the thread stack. + */ +void noinstr idtentry_exit(struct pt_regs *regs) +{ + lockdep_assert_irqs_disabled(); + + /* Check whether this returns to user mode */ + if (user_mode(regs)) { + prepare_exit_to_usermode(regs); + } else if (regs->flags & X86_EFLAGS_IF) { + /* Check kernel preemption, if enabled */ + if (IS_ENABLED(CONFIG_PREEMPTION)) { + /* + * This needs to be done very carefully. + * idtentry_enter() invoked rcu_irq_enter(). This + * needs to be undone before scheduling. + * + * Preemption is disabled inside of RCU idle + * sections. When the task returns from + * preempt_schedule_irq(), RCU is still watching. + * + * rcu_irq_exit_preempt() has additional state + * checking if CONFIG_PROVE_RCU=y + */ + if (!preempt_count()) { + if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) + WARN_ON_ONCE(!on_thread_stack()); + instrumentation_begin(); + rcu_irq_exit_preempt(); + if (need_resched()) + preempt_schedule_irq(); + /* Covers both tracing and lockdep */ + trace_hardirqs_on(); + instrumentation_end(); + return; + } + } + /* + * If preemption is disabled then this needs to be done + * carefully with respect to RCU. The exception might come + * from a RCU idle section in the idle task due to the fact + * that safe_halt() enables interrupts. So this needs the + * same ordering of lockdep/tracing and RCU as the return + * to user mode path. + */ + 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); + } else { + /* IRQ flags state is correct already. Just tell RCU */ + rcu_irq_exit(); + } +} diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index bbd81e2..2adfd80 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -7,6 +7,9 @@ #ifndef __ASSEMBLY__ +void idtentry_enter(struct pt_regs *regs); +void idtentry_exit(struct pt_regs *regs); + /** * DECLARE_IDTENTRY - Declare functions for simple IDT entry points * No error code pushed by hardware
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