powerpc: Add ppc_strict_facility_enable boot option
Add a boot option that strictly manages the MSR unavailable bits.
This catches kernel uses of FP/Altivec/SPE that would otherwise
corrupt user state.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 5cdd35c..1eafcee 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -87,7 +87,19 @@
static inline void check_if_tm_restore_required(struct task_struct *tsk) { }
#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
-static void msr_check_and_set(unsigned long bits)
+bool strict_msr_control;
+EXPORT_SYMBOL(strict_msr_control);
+
+static int __init enable_strict_msr_control(char *str)
+{
+ strict_msr_control = true;
+ pr_info("Enabling strict facility control\n");
+
+ return 0;
+}
+early_param("ppc_strict_facility_enable", enable_strict_msr_control);
+
+void msr_check_and_set(unsigned long bits)
{
unsigned long oldmsr = mfmsr();
unsigned long newmsr;
@@ -103,7 +115,7 @@
mtmsr_isync(newmsr);
}
-static void msr_check_and_clear(unsigned long bits)
+void __msr_check_and_clear(unsigned long bits)
{
unsigned long oldmsr = mfmsr();
unsigned long newmsr;
@@ -118,6 +130,7 @@
if (oldmsr != newmsr)
mtmsr_isync(newmsr);
}
+EXPORT_SYMBOL(__msr_check_and_clear);
#ifdef CONFIG_PPC_FPU
void giveup_fpu(struct task_struct *tsk)
