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Message-Id: <79e844a7bb0da929fcf89f4b14d3552cf1ce672b.1490218061.git.luto@kernel.org>
Date: Wed, 22 Mar 2017 14:32:35 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Thomas Garnier <thgarnie@...gle.com>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 7/7] x86/boot/32: Rewrite test_wp_bit()
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 <luto@...nel.org>
---
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
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