diff options
| -rw-r--r-- | arch/x86/entry/common.c | 112 |
1 files changed, 111 insertions, 1 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 9a327ee..febc530 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -207,6 +207,7 @@ long syscall_trace_enter(struct pt_regs *regs) return syscall_trace_enter_phase2(regs, arch, phase1_result); } +/* Deprecated. */ void syscall_trace_leave(struct pt_regs *regs) { bool step; @@ -237,8 +238,117 @@ void syscall_trace_leave(struct pt_regs *regs) user_enter(); } +static struct thread_info *pt_regs_to_thread_info(struct pt_regs *regs) +{ + unsigned long top_of_stack = + (unsigned long)(regs + 1) + TOP_OF_KERNEL_STACK_PADDING; + return (struct thread_info *)(top_of_stack - THREAD_SIZE); +} + +/* Called with IRQs disabled. */ +__visible void prepare_exit_to_usermode(struct pt_regs *regs) +{ + if (WARN_ON(!irqs_disabled())) + local_irq_disable(); + + /* + * In order to return to user mode, we need to have IRQs off with + * none of _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_USER_RETURN_NOTIFY, + * _TIF_UPROBE, or _TIF_NEED_RESCHED set. Several of these flags + * can be set at any time on preemptable kernels if we have IRQs on, + * so we need to loop. Disabling preemption wouldn't help: doing the + * work to clear some of the flags can sleep. + */ + while (true) { + u32 cached_flags = + READ_ONCE(pt_regs_to_thread_info(regs)->flags); + + if (!(cached_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | + _TIF_UPROBE | _TIF_NEED_RESCHED))) + break; + + /* We have work to do. */ + local_irq_enable(); + + if (cached_flags & _TIF_NEED_RESCHED) + schedule(); + + if (cached_flags & _TIF_UPROBE) + uprobe_notify_resume(regs); + + /* deal with pending signal delivery */ + if (cached_flags & _TIF_SIGPENDING) + do_signal(regs); + + if (cached_flags & _TIF_NOTIFY_RESUME) { + clear_thread_flag(TIF_NOTIFY_RESUME); + tracehook_notify_resume(regs); + } + + if (cached_flags & _TIF_USER_RETURN_NOTIFY) + fire_user_return_notifiers(); + + /* Disable IRQs and retry */ + local_irq_disable(); + } + + user_enter(); +} + +/* + * Called with IRQs on and fully valid regs. Returns with IRQs off in a + * state such that we can immediately switch to user mode. + */ +__visible void syscall_return_slowpath(struct pt_regs *regs) +{ + struct thread_info *ti = pt_regs_to_thread_info(regs); + u32 cached_flags = READ_ONCE(ti->flags); + bool step; + + CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + + if (WARN(irqs_disabled(), "syscall %ld left IRQs disabled", + regs->orig_ax)) + local_irq_enable(); + + /* + * First do one-time work. If these work items are enabled, we + * want to run them exactly once per syscall exit with IRQs on. + */ + if (cached_flags & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | + _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)) { + audit_syscall_exit(regs); + + if (cached_flags & _TIF_SYSCALL_TRACEPOINT) + trace_sys_exit(regs, regs->ax); + + /* + * If TIF_SYSCALL_EMU is set, we only get here because of + * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP). + * We already reported this syscall instruction in + * syscall_trace_enter(). + */ + step = unlikely( + (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU)) + == _TIF_SINGLESTEP); + if (step || cached_flags & _TIF_SYSCALL_TRACE) + tracehook_report_syscall_exit(regs, step); + } + +#ifdef CONFIG_COMPAT + /* + * Compat syscalls set TS_COMPAT. Make sure we clear it before + * returning to user mode. + */ + ti->status &= ~TS_COMPAT; +#endif + + local_irq_disable(); + prepare_exit_to_usermode(regs); +} + /* - * notification of userspace execution resumption + * Deprecated notification of userspace execution resumption * - triggered by the TIF_WORK_MASK flags */ __visible void |
