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-rw-r--r--arch/x86/entry/common.c112
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
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