[tip:x86/mm] x86, mm: Clean up and simplify NX enablement

tip-bot for H. Peter Anvin
2009-11-16T22:08:25Z

Commit-ID: 4763ed4d45522b876c97e1f7f4b659d211f75571
Gitweb: http://git.kernel.org/tip/4763ed4d45522b876c97e1f7f4b659d211f75571
Author: H. Peter Anvin <hpa@zytor.com>
AuthorDate: Fri, 13 Nov 2009 15:28:16 -0800
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Mon, 16 Nov 2009 13:44:59 -0800

x86, mm: Clean up and simplify NX enablement

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>
---
arch/x86/include/asm/proto.h | 2 +-
arch/x86/kernel/cpu/common.c | 2 +-
arch/x86/kernel/setup.c | 8 +-----
arch/x86/mm/init.c | 4 +-
arch/x86/mm/setup_nx.c | 43 +++++------------------------------------
arch/x86/xen/enlighten.c | 4 +--
6 files changed, 13 insertions(+), 50 deletions(-)

diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index 621f56d..add7f18 100644
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -16,7 +16,7 @@ extern void ia32_sysenter_target(void);

extern void syscall32_cpu_init(void);

-extern void check_efer(void);
+extern void x86_configure_nx(void);

extern int reboot_force;

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index cc25c2b..18346da 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1136,7 +1136,7 @@ void __cpuinit cpu_init(void)
wrmsrl(MSR_KERNEL_GS_BASE, 0);
barrier();

- check_efer();
+ x86_configure_nx();
if (cpu != 0)
enable_x2apic();

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0a6e94a..23b7f46 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -787,21 +787,17 @@ void __init setup_arch(char **cmdline_p)
strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
*cmdline_p = command_line;

-#ifdef CONFIG_X86_64
/*
* Must call this twice: Once just to detect whether hardware doesn't
* support NX (so that the early EHCI debug console setup can safely
* call set_fixmap(), and then again after parsing early parameters to
* honor the respective command line option.
*/
- check_efer();
-#endif
+ x86_configure_nx();

parse_early_param();

-#ifdef CONFIG_X86_64
- check_efer();
-#endif
+ x86_configure_nx();

/* Must be before kernel pagetables are setup */
vmi_activate();
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 73ffd55..27ec2c2 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -146,8 +146,8 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
use_gbpages = direct_gbpages;
#endif

- set_nx();
- if (nx_enabled)
+ /* XXX: replace this with Kees' improved messages */
+ if (__supported_pte_mask & _PAGE_NX)
printk(KERN_INFO "NX (Execute Disable) protection: active\n");

/* Enable PSE if available */
diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c
index 513d8ed..355818b 100644
--- a/arch/x86/mm/setup_nx.c
+++ b/arch/x86/mm/setup_nx.c
@@ -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)
-{
- 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)
+void __cpuinit x86_configure_nx(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
-
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 3439616..c5e805d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1082,10 +1082,8 @@ asmlinkage void __init xen_start_kernel(void)

__supported_pte_mask |= _PAGE_IOMAP;

-#ifdef CONFIG_X86_64
/* Work out if we support NX */
- check_efer();
-#endif
+ x86_configure_nx();

xen_setup_features();