Hi Andy,
I am really sorry for delay.
This is on top of the recent change from Kees, right? Could me remind me
where can I found the tree this series based on? So that I could actually
apply these changes...
On 07/21, Andy Lutomirski wrote:
>
> +long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
> + unsigned long phase1_result)
> {
> long ret = 0;
> + u32 work = ACCESS_ONCE(current_thread_info()->flags) &
> + _TIF_WORK_SYSCALL_ENTRY;
> +
> + BUG_ON(regs != task_pt_regs(current));
>
> user_exit();
>
> @@ -1458,17 +1562,20 @@ long syscall_trace_enter(struct pt_regs *regs)
> * do_debug() and we need to set it again to restore the user
> * state. If we entered on the slow path, TF was already set.
> */
> - if (test_thread_flag(TIF_SINGLESTEP))
> + if (work & _TIF_SINGLESTEP)
> regs->flags |= X86_EFLAGS_TF;
This looks suspicious, but perhaps I misread this change.
If I understand correctly, syscall_trace_enter() can avoid _phase2() above.
But we should always call user_exit() unconditionally?
And we should always set X86_EFLAGS_TF if TIF_SINGLESTEP? IIRC, TF can be
actually cleared on a 32bit kernel if we step over sysenter insn?
Oleg.
