x86/arch_prctl: Add ARCH_[GET|SET]_CPUID

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / process.c

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index b12e95eceb83d76c2fb71cded930dc47be16fe3e..0bb88428cbf2697c89a60311051cc5351ea55fde 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -37,6 +37,7 @@
 #include <asm/vm86.h>
 #include <asm/switch_to.h>
 #include <asm/desc.h>
+#include <asm/prctl.h>
 
 /*
  * per-CPU TSS segments. Threads are completely 'soft' on Linux,
@@ -172,6 +173,73 @@ int set_tsc_mode(unsigned int val)
        return 0;
 }
 
+DEFINE_PER_CPU(u64, msr_misc_features_shadow);
+
+static void set_cpuid_faulting(bool on)
+{
+       u64 msrval;
+
+       msrval = this_cpu_read(msr_misc_features_shadow);
+       msrval &= ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
+       msrval |= (on << MSR_MISC_FEATURES_ENABLES_CPUID_FAULT_BIT);
+       this_cpu_write(msr_misc_features_shadow, msrval);
+       wrmsrl(MSR_MISC_FEATURES_ENABLES, msrval);
+}
+
+static void disable_cpuid(void)
+{
+       preempt_disable();
+       if (!test_and_set_thread_flag(TIF_NOCPUID)) {
+               /*
+                * Must flip the CPU state synchronously with
+                * TIF_NOCPUID in the current running context.
+                */
+               set_cpuid_faulting(true);
+       }
+       preempt_enable();
+}
+
+static void enable_cpuid(void)
+{
+       preempt_disable();
+       if (test_and_clear_thread_flag(TIF_NOCPUID)) {
+               /*
+                * Must flip the CPU state synchronously with
+                * TIF_NOCPUID in the current running context.
+                */
+               set_cpuid_faulting(false);
+       }
+       preempt_enable();
+}
+
+static int get_cpuid_mode(void)
+{
+       return !test_thread_flag(TIF_NOCPUID);
+}
+
+static int set_cpuid_mode(struct task_struct *task, unsigned long cpuid_enabled)
+{
+       if (!static_cpu_has(X86_FEATURE_CPUID_FAULT))
+               return -ENODEV;
+
+       if (cpuid_enabled)
+               enable_cpuid();
+       else
+               disable_cpuid();
+
+       return 0;
+}
+
+/*
+ * Called immediately after a successful exec.
+ */
+void arch_setup_new_exec(void)
+{
+       /* If cpuid was previously disabled for this task, re-enable it. */
+       if (test_thread_flag(TIF_NOCPUID))
+               enable_cpuid();
+}
+
 static inline void switch_to_bitmap(struct tss_struct *tss,
                                    struct thread_struct *prev,
                                    struct thread_struct *next,
@@ -225,6 +293,9 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 
        if ((tifp ^ tifn) & _TIF_NOTSC)
                cr4_toggle_bits(X86_CR4_TSD);
+
+       if ((tifp ^ tifn) & _TIF_NOCPUID)
+               set_cpuid_faulting(!!(tifn & _TIF_NOCPUID));
 }
 
 /*
@@ -549,5 +620,12 @@ out:
 long do_arch_prctl_common(struct task_struct *task, int option,
                          unsigned long cpuid_enabled)
 {
+       switch (option) {
+       case ARCH_GET_CPUID:
+               return get_cpuid_mode();
+       case ARCH_SET_CPUID:
+               return set_cpuid_mode(task, cpuid_enabled);
+       }
+
        return -EINVAL;
 }