powerpc/kexec: Fix radix to hash kexec due to IAMR/AMOR

[sfrench/cifs-2.6.git] / arch / powerpc / kernel / process.c

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2ad725ef4368a3e525681b0ce4a56ef8e960bf48..9f3e2c932dccc1c3a1158fc174a8cf57e63dd75d 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -511,6 +511,10 @@ void restore_math(struct pt_regs *regs)
 {
        unsigned long msr;
 
+       /*
+        * Syscall exit makes a similar initial check before branching
+        * to restore_math. Keep them in synch.
+        */
        if (!msr_tm_active(regs->msr) &&
                !current->thread.load_fp && !loadvec(current->thread))
                return;
@@ -1133,6 +1137,11 @@ static inline void restore_sprs(struct thread_struct *old_thread,
 #endif
 }
 
+#ifdef CONFIG_PPC_BOOK3S_64
+#define CP_SIZE 128
+static const u8 dummy_copy_buffer[CP_SIZE] __attribute__((aligned(CP_SIZE)));
+#endif
+
 struct task_struct *__switch_to(struct task_struct *prev,
        struct task_struct *new)
 {
@@ -1195,12 +1204,14 @@ struct task_struct *__switch_to(struct task_struct *prev,
 
        __switch_to_tm(prev, new);
 
-       /*
-        * We can't take a PMU exception inside _switch() since there is a
-        * window where the kernel stack SLB and the kernel stack are out
-        * of sync. Hard disable here.
-        */
-       hard_irq_disable();
+       if (!radix_enabled()) {
+               /*
+                * We can't take a PMU exception inside _switch() since there
+                * is a window where the kernel stack SLB and the kernel stack
+                * are out of sync. Hard disable here.
+                */
+               hard_irq_disable();
+       }
 
        /*
         * Call restore_sprs() before calling _switch(). If we move it after
@@ -1220,8 +1231,28 @@ struct task_struct *__switch_to(struct task_struct *prev,
                batch->active = 1;
        }
 
-       if (current_thread_info()->task->thread.regs)
+       if (current_thread_info()->task->thread.regs) {
                restore_math(current_thread_info()->task->thread.regs);
+
+               /*
+                * The copy-paste buffer can only store into foreign real
+                * addresses, so unprivileged processes can not see the
+                * data or use it in any way unless they have foreign real
+                * mappings. We don't have a VAS driver that allocates those
+                * yet, so no cpabort is required.
+                */
+               if (cpu_has_feature(CPU_FTR_POWER9_DD1)) {
+                       /*
+                        * DD1 allows paste into normal system memory, so we
+                        * do an unpaired copy here to clear the buffer and
+                        * prevent a covert channel being set up.
+                        *
+                        * cpabort is not used because it is quite expensive.
+                        */
+                       asm volatile(PPC_COPY(%0, %1)
+                                       : : "r"(dummy_copy_buffer), "r"(0));
+               }
+       }
 #endif /* CONFIG_PPC_STD_MMU_64 */
 
        return last;