From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A524FECDFB8 for ; Thu, 19 Jul 2018 23:23:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D6BD20673 for ; Thu, 19 Jul 2018 23:23:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D6BD20673 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731074AbeGTAIX (ORCPT ); Thu, 19 Jul 2018 20:08:23 -0400 Received: from terminus.zytor.com ([198.137.202.136]:58839 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730659AbeGTAIX (ORCPT ); Thu, 19 Jul 2018 20:08:23 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w6JNM1KE2451265 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 19 Jul 2018 16:22:01 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w6JNM1r52451262; Thu, 19 Jul 2018 16:22:01 -0700 Date: Thu, 19 Jul 2018 16:22:01 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Joerg Roedel Message-ID: Cc: dave.hansen@intel.com, brgerst@gmail.com, bp@alien8.de, gregkh@linuxfoundation.org, torvalds@linux-foundation.org, pavel@ucw.cz, jpoimboe@redhat.com, jkosina@suse.cz, will.deacon@arm.com, dhgutteridge@sympatico.ca, luto@kernel.org, eduval@amazon.com, llong@redhat.com, peterz@infradead.org, boris.ostrovsky@oracle.com, linux-kernel@vger.kernel.org, David.Laight@aculab.com, hpa@zytor.com, tglx@linutronix.de, jroedel@suse.de, jgross@suse.com, aarcange@redhat.com, mingo@kernel.org, dvlasenk@redhat.com Reply-To: hpa@zytor.com, jroedel@suse.de, jgross@suse.com, tglx@linutronix.de, boris.ostrovsky@oracle.com, peterz@infradead.org, llong@redhat.com, David.Laight@aculab.com, linux-kernel@vger.kernel.org, dvlasenk@redhat.com, mingo@kernel.org, aarcange@redhat.com, brgerst@gmail.com, bp@alien8.de, dave.hansen@intel.com, luto@kernel.org, eduval@amazon.com, dhgutteridge@sympatico.ca, gregkh@linuxfoundation.org, pavel@ucw.cz, torvalds@linux-foundation.org, will.deacon@arm.com, jpoimboe@redhat.com, jkosina@suse.cz In-Reply-To: <1531906876-13451-8-git-send-email-joro@8bytes.org> References: <1531906876-13451-8-git-send-email-joro@8bytes.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/entry/32: Enter the kernel via trampoline stack Git-Commit-ID: 45d7b255747c21fc4b1f5043bee0754d39c3bdbf X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 45d7b255747c21fc4b1f5043bee0754d39c3bdbf Gitweb: https://git.kernel.org/tip/45d7b255747c21fc4b1f5043bee0754d39c3bdbf Author: Joerg Roedel AuthorDate: Wed, 18 Jul 2018 11:40:44 +0200 Committer: Thomas Gleixner CommitDate: Fri, 20 Jul 2018 01:11:37 +0200 x86/entry/32: Enter the kernel via trampoline stack Use the entry-stack as a trampoline to enter the kernel. The entry-stack is already in the cpu_entry_area and will be mapped to userspace when PTI is enabled. Signed-off-by: Joerg Roedel Signed-off-by: Thomas Gleixner Tested-by: Pavel Machek Cc: "H . Peter Anvin" Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Dave Hansen Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Jiri Kosina Cc: Boris Ostrovsky Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli Cc: Waiman Long Cc: "David H . Gutteridge" Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-8-git-send-email-joro@8bytes.org --- arch/x86/entry/entry_32.S | 119 ++++++++++++++++++++++++++++++++------- arch/x86/include/asm/switch_to.h | 14 ++++- arch/x86/kernel/asm-offsets.c | 1 + arch/x86/kernel/cpu/common.c | 5 +- arch/x86/kernel/process.c | 2 - arch/x86/kernel/process_32.c | 2 - 6 files changed, 115 insertions(+), 28 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 7251c4f3e99e..fea49ec345ba 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -154,7 +154,7 @@ #endif /* CONFIG_X86_32_LAZY_GS */ -.macro SAVE_ALL pt_regs_ax=%eax +.macro SAVE_ALL pt_regs_ax=%eax switch_stacks=0 cld PUSH_GS pushl %fs @@ -173,6 +173,12 @@ movl $(__KERNEL_PERCPU), %edx movl %edx, %fs SET_KERNEL_GS %edx + + /* Switch to kernel stack if necessary */ +.if \switch_stacks > 0 + SWITCH_TO_KERNEL_STACK +.endif + .endm /* @@ -269,6 +275,73 @@ .Lend_\@: #endif /* CONFIG_X86_ESPFIX32 */ .endm + + +/* + * Called with pt_regs fully populated and kernel segments loaded, + * so we can access PER_CPU and use the integer registers. + * + * We need to be very careful here with the %esp switch, because an NMI + * can happen everywhere. If the NMI handler finds itself on the + * entry-stack, it will overwrite the task-stack and everything we + * copied there. So allocate the stack-frame on the task-stack and + * switch to it before we do any copying. + */ +.macro SWITCH_TO_KERNEL_STACK + + ALTERNATIVE "", "jmp .Lend_\@", X86_FEATURE_XENPV + + /* Are we on the entry stack? Bail out if not! */ + movl PER_CPU_VAR(cpu_entry_area), %ecx + addl $CPU_ENTRY_AREA_entry_stack + SIZEOF_entry_stack, %ecx + subl %esp, %ecx /* ecx = (end of entry_stack) - esp */ + cmpl $SIZEOF_entry_stack, %ecx + jae .Lend_\@ + + /* Load stack pointer into %esi and %edi */ + movl %esp, %esi + movl %esi, %edi + + /* Move %edi to the top of the entry stack */ + andl $(MASK_entry_stack), %edi + addl $(SIZEOF_entry_stack), %edi + + /* Load top of task-stack into %edi */ + movl TSS_entry2task_stack(%edi), %edi + + /* Bytes to copy */ + movl $PTREGS_SIZE, %ecx + +#ifdef CONFIG_VM86 + testl $X86_EFLAGS_VM, PT_EFLAGS(%esi) + jz .Lcopy_pt_regs_\@ + + /* + * Stack-frame contains 4 additional segment registers when + * coming from VM86 mode + */ + addl $(4 * 4), %ecx + +.Lcopy_pt_regs_\@: +#endif + + /* Allocate frame on task-stack */ + subl %ecx, %edi + + /* Switch to task-stack */ + movl %edi, %esp + + /* + * We are now on the task-stack and can safely copy over the + * stack-frame + */ + shrl $2, %ecx + cld + rep movsl + +.Lend_\@: +.endm + /* * %eax: prev task * %edx: next task @@ -469,7 +542,7 @@ ENTRY(entry_SYSENTER_32) pushl $__USER_CS /* pt_regs->cs */ pushl $0 /* pt_regs->ip = 0 (placeholder) */ pushl %eax /* pt_regs->orig_ax */ - SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */ + SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest, stack already switched */ /* * SYSENTER doesn't filter flags, so we need to clear NT, AC @@ -580,7 +653,8 @@ ENDPROC(entry_SYSENTER_32) ENTRY(entry_INT80_32) ASM_CLAC pushl %eax /* pt_regs->orig_ax */ - SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */ + + SAVE_ALL pt_regs_ax=$-ENOSYS switch_stacks=1 /* save rest */ /* * User mode is traced as though IRQs are on, and the interrupt gate @@ -677,7 +751,8 @@ END(irq_entries_start) common_interrupt: ASM_CLAC addl $-0x80, (%esp) /* Adjust vector into the [-256, -1] range */ - SAVE_ALL + + SAVE_ALL switch_stacks=1 ENCODE_FRAME_POINTER TRACE_IRQS_OFF movl %esp, %eax @@ -685,16 +760,16 @@ common_interrupt: jmp ret_from_intr ENDPROC(common_interrupt) -#define BUILD_INTERRUPT3(name, nr, fn) \ -ENTRY(name) \ - ASM_CLAC; \ - pushl $~(nr); \ - SAVE_ALL; \ - ENCODE_FRAME_POINTER; \ - TRACE_IRQS_OFF \ - movl %esp, %eax; \ - call fn; \ - jmp ret_from_intr; \ +#define BUILD_INTERRUPT3(name, nr, fn) \ +ENTRY(name) \ + ASM_CLAC; \ + pushl $~(nr); \ + SAVE_ALL switch_stacks=1; \ + ENCODE_FRAME_POINTER; \ + TRACE_IRQS_OFF \ + movl %esp, %eax; \ + call fn; \ + jmp ret_from_intr; \ ENDPROC(name) #define BUILD_INTERRUPT(name, nr) \ @@ -926,16 +1001,20 @@ common_exception: pushl %es pushl %ds pushl %eax + movl $(__USER_DS), %eax + movl %eax, %ds + movl %eax, %es + movl $(__KERNEL_PERCPU), %eax + movl %eax, %fs pushl %ebp pushl %edi pushl %esi pushl %edx pushl %ecx pushl %ebx + SWITCH_TO_KERNEL_STACK ENCODE_FRAME_POINTER cld - movl $(__KERNEL_PERCPU), %ecx - movl %ecx, %fs UNWIND_ESPFIX_STACK GS_TO_REG %ecx movl PT_GS(%esp), %edi # get the function address @@ -943,9 +1022,6 @@ common_exception: movl $-1, PT_ORIG_EAX(%esp) # no syscall to restart REG_TO_PTGS %ecx SET_KERNEL_GS %ecx - movl $(__USER_DS), %ecx - movl %ecx, %ds - movl %ecx, %es TRACE_IRQS_OFF movl %esp, %eax # pt_regs pointer CALL_NOSPEC %edi @@ -964,6 +1040,7 @@ ENTRY(debug) */ ASM_CLAC pushl $-1 # mark this as an int + SAVE_ALL ENCODE_FRAME_POINTER xorl %edx, %edx # error code 0 @@ -999,6 +1076,7 @@ END(debug) */ ENTRY(nmi) ASM_CLAC + #ifdef CONFIG_X86_ESPFIX32 pushl %eax movl %ss, %eax @@ -1066,7 +1144,8 @@ END(nmi) ENTRY(int3) ASM_CLAC pushl $-1 # mark this as an int - SAVE_ALL + + SAVE_ALL switch_stacks=1 ENCODE_FRAME_POINTER TRACE_IRQS_OFF xorl %edx, %edx # zero error code diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index eb5f7999a893..8bc2f70b452e 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -89,13 +89,23 @@ static inline void refresh_sysenter_cs(struct thread_struct *thread) /* This is used when switching tasks or entering/exiting vm86 mode. */ static inline void update_sp0(struct task_struct *task) { - /* On x86_64, sp0 always points to the entry trampoline stack, which is constant: */ + /* sp0 always points to the entry trampoline stack, which is constant: */ #ifdef CONFIG_X86_32 - load_sp0(task->thread.sp0); + if (static_cpu_has(X86_FEATURE_XENPV)) + load_sp0(task->thread.sp0); + else + this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); #else + /* + * x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That + * doesn't work on x86-32 because sp1 and + * cpu_current_top_of_stack have different values (because of + * the non-zero stack-padding on 32bit). + */ if (static_cpu_has(X86_FEATURE_XENPV)) load_sp0(task_top_of_stack(task)); #endif + } #endif /* _ASM_X86_SWITCH_TO_H */ diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c index a1e16286a832..01de31db300d 100644 --- a/arch/x86/kernel/asm-offsets.c +++ b/arch/x86/kernel/asm-offsets.c @@ -103,6 +103,7 @@ void common(void) { OFFSET(CPU_ENTRY_AREA_entry_trampoline, cpu_entry_area, entry_trampoline); OFFSET(CPU_ENTRY_AREA_entry_stack, cpu_entry_area, entry_stack_page); DEFINE(SIZEOF_entry_stack, sizeof(struct entry_stack)); + DEFINE(MASK_entry_stack, (~(sizeof(struct entry_stack) - 1))); /* Offset for sp0 and sp1 into the tss_struct */ OFFSET(TSS_sp0, tss_struct, x86_tss.sp0); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index eb4cb3efd20e..43a927eb9c09 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1804,11 +1804,12 @@ void cpu_init(void) enter_lazy_tlb(&init_mm, curr); /* - * Initialize the TSS. Don't bother initializing sp0, as the initial - * task never enters user mode. + * Initialize the TSS. sp0 points to the entry trampoline stack + * regardless of what task is running. */ set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss); load_TR_desc(); + load_sp0((unsigned long)(cpu_entry_stack(cpu) + 1)); load_mm_ldt(&init_mm); diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 30ca2d1a9231..c93fcfdf1673 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -57,14 +57,12 @@ __visible DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw) = { */ .sp0 = (1UL << (BITS_PER_LONG-1)) + 1, -#ifdef CONFIG_X86_64 /* * .sp1 is cpu_current_top_of_stack. The init task never * runs user code, but cpu_current_top_of_stack should still * be well defined before the first context switch. */ .sp1 = TOP_OF_INIT_STACK, -#endif #ifdef CONFIG_X86_32 .ss0 = __KERNEL_DS, diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index ec62cc77388d..0ae659de21eb 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -290,8 +290,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) this_cpu_write(cpu_current_top_of_stack, (unsigned long)task_stack_page(next_p) + THREAD_SIZE); - /* SYSENTER reads the task-stack from tss.sp1 */ - this_cpu_write(cpu_tss_rw.x86_tss.sp1, next_p->thread.sp0); /* * Restore %gs if needed (which is common)