x86: split NX setup into separate file to limit unstack-protected code

Move the NX setup into a separate file so that it can be compiled
without stack-protection while leaving the rest of the mm/init code
protected.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

4 files changed, 72 insertions, 65 deletions

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 54cb697f4900..e9918d99f83c 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -277,6 +277,7 @@ static inline pteval_t pte_flags(pte_t pte)
 typedef struct page *pgtable_t;
 
 extern pteval_t __supported_pte_mask;
+extern void set_nx(void);
 extern int nx_enabled;
 
 #define pgprot_writecombine     pgprot_writecombine
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index dd313d035de7..06630d26e56d 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -1,10 +1,10 @@
 obj-y   :=  init.o init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
-            pat.o pgtable.o physaddr.o gup.o
+            pat.o pgtable.o physaddr.o gup.o setup_nx.o
 
 # Make sure __phys_addr has no stackprotector
 nostackp := $(call cc-option, -fno-stack-protector)
 CFLAGS_physaddr.o               := $(nostackp)
-CFLAGS_init.o                   := $(nostackp)
+CFLAGS_setup_nx.o               := $(nostackp)
 
 obj-$(CONFIG_SMP)               += tlb.o
 
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 0607119cef94..73ffd5536f62 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -28,69 +28,6 @@ int direct_gbpages
 #endif
 ;
 
-int nx_enabled;
-
-#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
-static int disable_nx __cpuinitdata;
-
-/*
- * 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)) {
-                __supported_pte_mask |= _PAGE_NX;
-                disable_nx = 0;
-        } else if (!strncmp(str, "off", 3)) {
-                disable_nx = 1;
-                __supported_pte_mask &= ~_PAGE_NX;
-        }
-        return 0;
-}
-early_param("noexec", noexec_setup);
-#endif
-
-#ifdef CONFIG_X86_PAE
-static 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
-static inline 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)
-                __supported_pte_mask &= ~_PAGE_NX;
-}
-#endif
-
 static void __init find_early_table_space(unsigned long end, int use_pse,
                                           int use_gbpages)
 {
diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c
new file mode 100644
index 000000000000..513d8ed5d2ec
--- /dev/null
+++ b/arch/x86/mm/setup_nx.c
@@ -0,0 +1,69 @@
+#include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+
+#include <asm/pgtable.h>
+
+int nx_enabled;
+
+#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
+static int disable_nx __cpuinitdata;
+
+/*
+ * 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)) {
+                __supported_pte_mask |= _PAGE_NX;
+                disable_nx = 0;
+        } else if (!strncmp(str, "off", 3)) {
+                disable_nx = 1;
+                __supported_pte_mask &= ~_PAGE_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)
+{
+        unsigned long efer;
+
+        rdmsrl(MSR_EFER, efer);
+        if (!(efer & EFER_NX) || disable_nx)
+                __supported_pte_mask &= ~_PAGE_NX;
+}
+#endif
+