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Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu Subject: Re: [PATCH v15 04/26] x86/cet: Add control-protection fault handler Message-ID: <20201126184933.GF31565@zn.tnic> References: <20201110162211.9207-1-yu-cheng.yu@intel.com> <20201110162211.9207-5-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201110162211.9207-5-yu-cheng.yu@intel.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Nov 10, 2020 at 08:21:49AM -0800, Yu-cheng Yu wrote: > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index e19df6cde35d..6c21c1e92605 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -598,6 +598,65 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) > cond_local_irq_disable(regs); > } > > +#ifdef CONFIG_X86_CET > +static const char * const control_protection_err[] = { > + "unknown", > + "near-ret", > + "far-ret/iret", > + "endbranch", > + "rstorssp", > + "setssbsy", > +}; > + > +/* > + * When a control protection exception occurs, send a signal > + * to the responsible application. Currently, control > + * protection is only enabled for the user mode. This > + * exception should not come from the kernel mode. > + */ Make that 80 cols wide. > +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection) > +{ > + struct task_struct *tsk; > + > + if (notify_die(DIE_TRAP, "control protection fault", regs, > + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) > + return; What is the intent here, notifiers can prevent the machine from printing the CP error below? > + cond_local_irq_enable(regs); > + > + if (!user_mode(regs)) > + die("kernel control protection fault", regs, error_code); Let's write that more explicitly: die("Unexpected/unsupported control protection fault"... > + > + if (!static_cpu_has(X86_FEATURE_SHSTK) && > + !static_cpu_has(X86_FEATURE_IBT)) Why static_cpu_has? > + WARN_ONCE(1, "CET is disabled but got control protection fault\n"); "Control protection fault with CET support disabled\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; > + unsigned long ssp; > + > + max_err = ARRAY_SIZE(control_protection_err) - 1; > + if ((error_code < 0) || (error_code > max_err)) > + error_code = 0; <---- newline here. > + rdmsrl(MSR_IA32_PL3_SSP, ssp); > + pr_info("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)", > + tsk->comm, task_pid_nr(tsk), > + regs->ip, regs->sp, ssp, error_code, > + control_protection_err[error_code]); > + print_vma_addr(KERN_CONT " in ", regs->ip); > + pr_cont("\n"); > + } ... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette