On Fri, 2018-08-31 at 17:01 +0200, Jann Horn wrote:
> Is there a reason why all the code in this patch isn't #ifdef'ed
> away
> on builds that don't support CET? It looks like the CET handler is
> hooked up to the IDT conditionally, but the handler code is always
> built?
Yes, in idt.c, it should have been:
#ifdef CONFIG_X86_64
INTG(X86_TRAP_CP, control_protection),
#endif
I will fix it.
> > +dotraplinkage void
> > +do_control_protection(struct pt_regs *regs, long error_code)
> > +{
> > + struct task_struct *tsk;
> > +
> > + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't
> > wake RCU");
> > + if (notify_die(DIE_TRAP, "control protection fault", regs,
> > + error_code, X86_TRAP_CP, SIGSEGV) ==
> > NOTIFY_STOP)
> > + return;
> > + cond_local_irq_enable(regs);
> > +
> > + if (!user_mode(regs))
> > + die("kernel control protection fault", regs,
> > error_code);
> > +
> > + if (!static_cpu_has(X86_FEATURE_SHSTK) &&
> > + !static_cpu_has(X86_FEATURE_IBT))
> > + WARN_ONCE(1, "CET is disabled but got control "
> > + "protection fault\n");
> > +
> > + tsk = current;
> > + tsk->thread.error_code = error_code;
> > + tsk->thread.trap_nr = X86_TRAP_CP;
> > +
> > + if (show_unhandled_signals && unhandled_signal(tsk,
> > SIGSEGV) &&
> > + printk_ratelimit()) {
> > + unsigned int max_err;
> > +
> > + max_err = ARRAY_SIZE(control_protection_err) - 1;
> > + if ((error_code < 0) || (error_code > max_err))
> > + error_code = 0;
> > + pr_info("%s[%d] control protection ip:%lx sp:%lx
> > error:%lx(%s)",
> > + tsk->comm, task_pid_nr(tsk),
> > + regs->ip, regs->sp, error_code,
> > + control_protection_err[error_code]);
> > + print_vma_addr(" in ", regs->ip);
> Shouldn't this be using KERN_CONT, like other callers of
> print_vma_addr(), to get the desired output?
I will change it.
