Merge tag 'powerpc-4.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc updates from Michael Ellerman:
 "Highlights include:

   - Support for STRICT_KERNEL_RWX on 64-bit server CPUs.

   - Platform support for FSP2 (476fpe) board

   - Enable ZONE_DEVICE on 64-bit server CPUs.

   - Generic & powerpc spin loop primitives to optimise busy waiting

   - Convert VDSO update function to use new update_vsyscall() interface

   - Optimisations to hypercall/syscall/context-switch paths

   - Improvements to the CPU idle code on Power8 and Power9.

  As well as many other fixes and improvements.

  Thanks to: Akshay Adiga, Andrew Donnellan, Andrew Jeffery, Anshuman
  Khandual, Anton Blanchard, Balbir Singh, Benjamin Herrenschmidt,
  Christophe Leroy, Christophe Lombard, Colin Ian King, Dan Carpenter,
  Gautham R. Shenoy, Hari Bathini, Ian Munsie, Ivan Mikhaylov, Javier
  Martinez Canillas, Madhavan Srinivasan, Masahiro Yamada, Matt Brown,
  Michael Neuling, Michal Suchanek, Murilo Opsfelder Araujo, Naveen N.
  Rao, Nicholas Piggin, Oliver O'Halloran, Paul Mackerras, Pavel Machek,
  Russell Currey, Santosh Sivaraj, Stephen Rothwell, Thiago Jung
  Bauermann, Yang Li"

* tag 'powerpc-4.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (158 commits)
  powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs
  powerpc/mm/radix: Implement STRICT_RWX/mark_rodata_ro() for Radix
  powerpc/mm/hash: Implement mark_rodata_ro() for hash
  powerpc/vmlinux.lds: Align __init_begin to 16M
  powerpc/lib/code-patching: Use alternate map for patch_instruction()
  powerpc/xmon: Add patch_instruction() support for xmon
  powerpc/kprobes/optprobes: Use patch_instruction()
  powerpc/kprobes: Move kprobes over to patch_instruction()
  powerpc/mm/radix: Fix execute permissions for interrupt_vectors
  powerpc/pseries: Fix passing of pp0 in updatepp() and updateboltedpp()
  powerpc/64s: Blacklist rtas entry/exit from kprobes
  powerpc/64s: Blacklist functions invoked on a trap
  powerpc/64s: Un-blacklist system_call() from kprobes
  powerpc/64s: Move system_call() symbol to just after setting MSR_EE
  powerpc/64s: Blacklist system_call() and system_call_common() from kprobes
  powerpc/64s: Convert .L__replay_interrupt_return to a local label
  powerpc64/elfv1: Only dereference function descriptor for non-text symbols
  cxl: Export library to support IBM XSL
  powerpc/dts: Use #include "..." to include local DT
  powerpc/perf/hv-24x7: Aggregate result elements on POWER9 SMT8
  ...

1 files changed, 38 insertions, 7 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2ad725ef4368..9f3e2c932dcc 100644
--- 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;