Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753544AbdCVVeA (ORCPT ); Wed, 22 Mar 2017 17:34:00 -0400 Received: from mail.kernel.org ([198.145.29.136]:42768 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753070AbdCVVdM (ORCPT ); Wed, 22 Mar 2017 17:33:12 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Borislav Petkov , Boris Ostrovsky , Juergen Gross , Thomas Garnier , Andy Lutomirski Subject: [PATCH 7/7] x86/boot/32: Rewrite test_wp_bit() Date: Wed, 22 Mar 2017 14:32:35 -0700 Message-Id: <79e844a7bb0da929fcf89f4b14d3552cf1ce672b.1490218061.git.luto@kernel.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4937 Lines: 163 This code seems to be very old and has gotten only minor updates. Nowadays we have a shiny function probe_kernel_write() that does more or less exactly what we need. Use it. While we're at it, remove cpuinfo_x86::wp_works_ok, since we panic on kernels where wp doesn't work okay. Signed-off-by: Andy Lutomirski --- arch/x86/include/asm/processor.h | 2 -- arch/x86/kernel/cpu/proc.c | 5 ++--- arch/x86/kernel/setup.c | 2 -- arch/x86/mm/init_32.c | 44 ++++++++-------------------------------- arch/x86/xen/enlighten.c | 1 - 5 files changed, 11 insertions(+), 43 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index edf42c4ac8c8..2c7695c9c684 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -90,8 +90,6 @@ struct cpuinfo_x86 { __u8 x86_model; __u8 x86_mask; #ifdef CONFIG_X86_32 - char wp_works_ok; /* It doesn't on 386's */ - /* Problems on some 486Dx4's and old 386's: */ char rfu; char pad0; diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c index 18ca99f2798b..6df621ae62a7 100644 --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -31,14 +31,13 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) "fpu\t\t: %s\n" "fpu_exception\t: %s\n" "cpuid level\t: %d\n" - "wp\t\t: %s\n", + "wp\t\t: yes\n", static_cpu_has_bug(X86_BUG_FDIV) ? "yes" : "no", static_cpu_has_bug(X86_BUG_F00F) ? "yes" : "no", static_cpu_has_bug(X86_BUG_COMA) ? "yes" : "no", static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no", static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no", - c->cpuid_level, - c->wp_works_ok ? "yes" : "no"); + c->cpuid_level); } #else static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 56b1177155db..462b7c69443d 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -175,11 +175,9 @@ static struct resource bss_resource = { #ifdef CONFIG_X86_32 /* cpu data as detected by the assembly code in head.S */ struct cpuinfo_x86 new_cpu_data = { - .wp_works_ok = -1, }; /* common cpu data for all cpus */ struct cpuinfo_x86 boot_cpu_data __read_mostly = { - .wp_works_ok = -1, }; EXPORT_SYMBOL(boot_cpu_data); diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 5ed3c141bbd5..097089a5e4d5 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -56,8 +56,6 @@ unsigned long highstart_pfn, highend_pfn; -static noinline int do_test_wp_bit(void); - bool __read_mostly __vmalloc_start_set = false; /* @@ -726,20 +724,21 @@ void __init paging_init(void) */ static void __init test_wp_bit(void) { + char z = 0; + printk(KERN_INFO "Checking if this processor honours the WP bit even in supervisor mode..."); - /* Any page-aligned address will do, the test is non-destructive */ - __set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_KERNEL_RO); - boot_cpu_data.wp_works_ok = do_test_wp_bit(); - clear_fixmap(FIX_WP_TEST); + __set_fixmap(FIX_WP_TEST, __pa_symbol(empty_zero_page), PAGE_KERNEL_RO); - if (!boot_cpu_data.wp_works_ok) { + if (probe_kernel_write((char *)fix_to_virt(FIX_WP_TEST), &z, 1) == 0) { printk(KERN_CONT "No.\n"); panic("Linux doesn't support CPUs with broken WP."); - } else { - printk(KERN_CONT "Ok.\n"); } + + clear_fixmap(FIX_WP_TEST); + + printk(KERN_CONT "Ok.\n"); } void __init mem_init(void) @@ -821,8 +820,7 @@ void __init mem_init(void) BUG_ON(VMALLOC_START >= VMALLOC_END); BUG_ON((unsigned long)high_memory > VMALLOC_START); - if (boot_cpu_data.wp_works_ok < 0) - test_wp_bit(); + test_wp_bit(); } #ifdef CONFIG_MEMORY_HOTPLUG @@ -850,30 +848,6 @@ int arch_remove_memory(u64 start, u64 size) #endif #endif -/* - * This function cannot be __init, since exceptions don't work in that - * section. Put this after the callers, so that it cannot be inlined. - */ -static noinline int do_test_wp_bit(void) -{ - char tmp_reg; - int flag; - - __asm__ __volatile__( - " movb %0, %1 \n" - "1: movb %1, %0 \n" - " xorl %2, %2 \n" - "2: \n" - _ASM_EXTABLE(1b,2b) - :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)), - "=q" (tmp_reg), - "=r" (flag) - :"2" (1) - :"memory"); - - return flag; -} - int kernel_set_to_readonly __read_mostly; void set_kernel_text_rw(void) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 4951fcf95143..6efa0cc425a2 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -1595,7 +1595,6 @@ asmlinkage __visible void __init xen_start_kernel(void) /* set up basic CPUID stuff */ cpu_detect(&new_cpu_data); set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU); - new_cpu_data.wp_works_ok = 1; new_cpu_data.x86_capability[CPUID_1_EDX] = cpuid_edx(1); #endif -- 2.9.3