linux/arch/x86/mm/setup_nx.c
Andy Lutomirski e16d8a6cbb Revert "x86/mm/32: Set NX in __supported_pte_mask before enabling paging"
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>
2016-04-26 19:52:57 +02:00

62 lines
1.3 KiB
C

#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <asm/pgtable.h>
#include <asm/proto.h>
#include <asm/cpufeature.h>
static int disable_nx;
/*
* noexec = on|off
*
* Control non-executable mappings for processes.
*
* on Enable
* off Disable
*/
static int __init noexec_setup(char *str)
{
if (!str)
return -EINVAL;
if (!strncmp(str, "on", 2)) {
disable_nx = 0;
} else if (!strncmp(str, "off", 3)) {
disable_nx = 1;
}
x86_configure_nx();
return 0;
}
early_param("noexec", noexec_setup);
void x86_configure_nx(void)
{
if (boot_cpu_has(X86_FEATURE_NX) && !disable_nx)
__supported_pte_mask |= _PAGE_NX;
else
__supported_pte_mask &= ~_PAGE_NX;
}
void __init x86_report_nx(void)
{
if (!boot_cpu_has(X86_FEATURE_NX)) {
printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
"missing in CPU!\n");
} else {
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
if (disable_nx) {
printk(KERN_INFO "NX (Execute Disable) protection: "
"disabled by kernel command line option\n");
} else {
printk(KERN_INFO "NX (Execute Disable) protection: "
"active\n");
}
#else
/* 32bit non-PAE kernel, NX cannot be used */
printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
"cannot be enabled: non-PAE kernel!\n");
#endif
}
}