e16d8a6cbb
This reverts commit 320d25b6a0.
This change was problematic for a couple of reasons:
1. It missed a some entry points (Xen things and 64-bit native).
2. The entry it changed can be executed more than once. This isn't
really a problem, but it conflated per-cpu state setup and global
state setup.
3. It broke 64-bit non-NX. 64-bit non-NX worked the other way around from
32-bit -- __supported_pte_mask had NX set initially and was *cleared*
in x86_configure_nx. With the patch applied, it never got cleared.
Reported-and-tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/59bd15f7f4b56b633a611b7f70876c6d2ad01a98.1461685884.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
62 lines
1.3 KiB
C
62 lines
1.3 KiB
C
#include <linux/spinlock.h>
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <asm/pgtable.h>
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#include <asm/proto.h>
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#include <asm/cpufeature.h>
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static int disable_nx;
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/*
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* noexec = on|off
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*
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* Control non-executable mappings for processes.
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*
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* on Enable
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* off Disable
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*/
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static int __init noexec_setup(char *str)
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{
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if (!str)
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return -EINVAL;
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if (!strncmp(str, "on", 2)) {
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disable_nx = 0;
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} else if (!strncmp(str, "off", 3)) {
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disable_nx = 1;
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}
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x86_configure_nx();
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return 0;
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}
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early_param("noexec", noexec_setup);
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void x86_configure_nx(void)
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{
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if (boot_cpu_has(X86_FEATURE_NX) && !disable_nx)
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__supported_pte_mask |= _PAGE_NX;
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else
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__supported_pte_mask &= ~_PAGE_NX;
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}
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void __init x86_report_nx(void)
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{
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if (!boot_cpu_has(X86_FEATURE_NX)) {
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printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
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"missing in CPU!\n");
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} else {
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#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
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if (disable_nx) {
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printk(KERN_INFO "NX (Execute Disable) protection: "
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"disabled by kernel command line option\n");
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} else {
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printk(KERN_INFO "NX (Execute Disable) protection: "
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"active\n");
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}
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#else
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/* 32bit non-PAE kernel, NX cannot be used */
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printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
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"cannot be enabled: non-PAE kernel!\n");
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#endif
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}
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}
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