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x86, mm: Clean up and simplify NX enablement

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The 32- and 64-bit code used very different mechanisms for enabling
NX, but even the 32-bit code was enabling NX in head_32.S if it is
available.  Furthermore, we had a bewildering collection of tests for
the available of NX.

This patch:

a) merges the 32-bit set_nx() and the 64-bit check_efer() function
   into a single x86_configure_nx() function.  EFER control is left
   to the head code.

b) eliminates the nx_enabled variable entirely.  Things that need to
   test for NX enablement can verify __supported_pte_mask directly,
   and cpu_has_nx gives the supported status of NX.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Vegard Nossum <vegardno@ifi.uio.no>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Chris Wright <chrisw@sous-sol.org>
LKML-Reference: <1258154897-6770-5-git-send-email-hpa@zytor.com>
Acked-by: Kees Cook <kees.cook@canonical.com>
This commit is contained in:
H. Peter Anvin
2009-11-13 15:28:16 -08:00
parent 583140afb9
commit 4763ed4d45
6 changed files with 13 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
arch/x86/mm/setup_nx.c
View File

@@ -3,10 +3,8 @@
#include <linux/init.h>
#include <asm/pgtable.h>
#include <asm/proto.h>
int nx_enabled;
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
static int disable_nx __cpuinitdata;
/*
@@ -22,48 +20,19 @@ static int __init noexec_setup(char *str)
if (!str)
return -EINVAL;
if (!strncmp(str, "on", 2)) {
__supported_pte_mask |= _PAGE_NX;
disable_nx = 0;
} else if (!strncmp(str, "off", 3)) {
disable_nx = 1;
__supported_pte_mask &= ~_PAGE_NX;
}
x86_configure_nx();
return 0;
}
early_param("noexec", noexec_setup);
#endif
#ifdef CONFIG_X86_PAE
void __init set_nx(void)
void __cpuinit x86_configure_nx(void)
{
unsigned int v[4], l, h;
if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
if ((v[3] & (1 << 20)) && !disable_nx) {
rdmsr(MSR_EFER, l, h);
l |= EFER_NX;
wrmsr(MSR_EFER, l, h);
nx_enabled = 1;
__supported_pte_mask |= _PAGE_NX;
}
}
}
#else
void set_nx(void)
{
}
#endif
#ifdef CONFIG_X86_64
void __cpuinit check_efer(void)
{
unsigned long efer;
rdmsrl(MSR_EFER, efer);
if (!(efer & EFER_NX) || disable_nx)
if (cpu_has_nx && !disable_nx)
__supported_pte_mask |= _PAGE_NX;
else
__supported_pte_mask &= ~_PAGE_NX;
}
#endif