From 6415813bae75feba10b8ca3ed6634a72c2a4d313 Mon Sep 17 00:00:00 2001 From: Mathias Krause Date: Sun, 12 Feb 2017 22:12:08 +0100 Subject: [PATCH] x86/cpu: Drop wp_works_ok member of struct cpuinfo_x86 Remove the wp_works_ok member of struct cpuinfo_x86. It's an optimization back from Linux v0.99 times where we had no fixup support yet and did the CR0.WP test via special code in the page fault handler. The < 0 test was an optimization to not do the special casing for each NULL ptr access violation but just for the first one doing the WP test. Today it serves no real purpose as the test no longer needs special code in the page fault handler and the only call side -- mem_init() -- calls it just once, anyway. However, Xen pre-initializes it to 1, to skip the test. Doing the test again for Xen should be no issue at all, as even the commit introducing skipping the test (commit d560bc61575e ("x86, xen: Suppress WP test on Xen")) mentioned it being ban aid only. And, in fact, testing the patch on Xen showed nothing breaks. The pre-fixup times are long gone and with the removal of the fallback handling code in commit a5c2a893dbd4 ("x86, 386 removal: Remove CONFIG_X86_WP_WORKS_OK") the kernel requires a working CR0.WP anyway. So just get rid of the "optimization" and do the test unconditionally. Signed-off-by: Mathias Krause Acked-by: Borislav Petkov Cc: Jesper Nilsson Cc: Jeremy Fitzhardinge Cc: Arnd Hannemann Cc: Mikael Starvik Cc: Geert Uytterhoeven Cc: Andrew Morton Cc: "David S. Miller" Link: http://lkml.kernel.org/r/1486933932-585-3-git-send-email-minipli@googlemail.com Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/processor.h | 4 +--- arch/x86/kernel/cpu/proc.c | 5 ++--- arch/x86/kernel/setup.c | 11 ++++------- arch/x86/mm/init_32.c | 9 +++++---- arch/x86/xen/enlighten.c | 1 - 5 files changed, 12 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 893f80e30bfb..4aa93b560a2b 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -89,9 +89,7 @@ struct cpuinfo_x86 { __u8 x86_vendor; /* CPU vendor */ __u8 x86_model; __u8 x86_mask; -#ifdef CONFIG_X86_32 - char wp_works_ok; /* It doesn't on 386's */ -#else +#ifdef CONFIG_X86_64 /* Number of 4K pages in DTLB/ITLB combined(in pages): */ int x86_tlbsize; #endif 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 4bf0c8926a1c..7cd7bbefd418 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -173,14 +173,11 @@ 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, -}; +/* cpu data as detected by the assembly code in head_32.S */ +struct cpuinfo_x86 new_cpu_data; + /* common cpu data for all cpus */ -struct cpuinfo_x86 boot_cpu_data __read_mostly = { - .wp_works_ok = -1, -}; +struct cpuinfo_x86 boot_cpu_data __read_mostly; EXPORT_SYMBOL(boot_cpu_data); unsigned int def_to_bigsmp; diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 2b4b53e6793f..4dddfaf6569a 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -716,15 +716,17 @@ void __init paging_init(void) */ static void __init test_wp_bit(void) { + int wp_works_ok; + 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(); + wp_works_ok = do_test_wp_bit(); clear_fixmap(FIX_WP_TEST); - if (!boot_cpu_data.wp_works_ok) { + if (!wp_works_ok) { printk(KERN_CONT "No.\n"); panic("Linux doesn't support CPUs with broken WP."); } else { @@ -811,8 +813,7 @@ 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 diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index ec1d5c46e58f..bc3dab5d47ca 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