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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 , "Michael Kerrisk (man-pages)" Subject: Re: [PATCH v17 06/26] x86/cet: Add control-protection fault handler Message-ID: <20210119120425.GI27433@zn.tnic> References: <20201229213053.16395-1-yu-cheng.yu@intel.com> <20201229213053.16395-7-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201229213053.16395-7-yu-cheng.yu@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Tue, Dec 29, 2020 at 01:30:33PM -0800, Yu-cheng Yu wrote: > @@ -606,6 +606,65 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) > cond_local_irq_disable(regs); > } > > +#ifdef CONFIG_X86_CET_USER > +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. > + */ There's no "the user mode" or "the kernel mode" - just "user mode" or "kernel mode". > +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection) > +{ > + struct task_struct *tsk; > + > + if (!user_mode(regs)) { > + if (notify_die(DIE_TRAP, "control protection fault", regs, > + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) > + return; > + die("Upexpected/unsupported kernel control protection fault", regs, error_code); Isn't the machine supposed to panic() here and do no further progress? > + } > + > + cond_local_irq_enable(regs); > + > + if (!boot_cpu_has(X86_FEATURE_CET)) > + WARN_ONCE(1, "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()) { WARNING: Prefer printk_ratelimited or pr__ratelimited to printk_ratelimit #136: FILE: arch/x86/kernel/traps.c:645: + printk_ratelimit()) { Still not using checkpatch? > + 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; > + > + rdmsrl(MSR_IA32_PL3_SSP, ssp); > + pr_info("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)", If anything, all this stuff should be pr_emerg(). > + 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"); > + } > + > + force_sig_fault(SIGSEGV, SEGV_CPERR, > + (void __user *)uprobe_get_trap_addr(regs)); > + cond_local_irq_disable(regs); > +} > +#endif > + > static bool do_int3(struct pt_regs *regs) > { > int res; > diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h > index d2597000407a..1c2ea91284a0 100644 > --- a/include/uapi/asm-generic/siginfo.h > +++ b/include/uapi/asm-generic/siginfo.h > @@ -231,7 +231,8 @@ typedef struct siginfo { > #define SEGV_ADIPERR 7 /* Precise MCD exception */ > #define SEGV_MTEAERR 8 /* Asynchronous ARM MTE error */ > #define SEGV_MTESERR 9 /* Synchronous ARM MTE exception */ > -#define NSIGSEGV 9 > +#define SEGV_CPERR 10 /* Control protection fault */ > +#define NSIGSEGV 10 This looks like it needs documentation in this manpage: https://www.man7.org/linux/man-pages/man2/sigaction.2.html + Michael. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette