2 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index cc85a9278190..56fb8c16e20b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1664,6 +1664,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         noexec=on: enable non-executable mappings (default)
                         noexec=off: disable non-executable mappings
 
+        nosmep          [X86]
+                        Disable SMEP (Supervisor Mode Execution Protection)
+                        even if it is supported by processor.
+
         noexec32        [X86-64]
                         This affects only 32-bit executables.
                         noexec32=on: enable non-executable mappings (default)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 173f3a3fa1a6..cbc70a27430c 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -254,6 +254,25 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
 }
 #endif
 
+static int disable_smep __initdata;
+static __init int setup_disable_smep(char *arg)
+{
+        disable_smep = 1;
+        return 1;
+}
+__setup("nosmep", setup_disable_smep);
+
+static __init void setup_smep(struct cpuinfo_x86 *c)
+{
+        if (cpu_has(c, X86_FEATURE_SMEP)) {
+                if (unlikely(disable_smep)) {
+                        setup_clear_cpu_cap(X86_FEATURE_SMEP);
+                        clear_in_cr4(X86_CR4_SMEP);
+                } else
+                        set_in_cr4(X86_CR4_SMEP);
+        }
+}
+
 /*
  * Some CPU features depend on higher CPUID levels, which may not always
  * be available due to CPUID level capping or broken virtualization
@@ -667,6 +686,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
         c->cpu_index = 0;
 #endif
         filter_cpuid_features(c, false);
+
+        setup_smep(c);
 }
 
 void __init early_cpu_init(void)
@@ -752,6 +773,8 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
 #endif
         }
 
+        setup_smep(c);
+
         get_model_name(c); /* Default name */
 
         detect_nopl(c);