Merge tag 'powerpc-5.1-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc updates from Michael Ellerman:
 "Notable changes:

   - Enable THREAD_INFO_IN_TASK to move thread_info off the stack.

   - A big series from Christoph reworking our DMA code to use more of
     the generic infrastructure, as he said:
       "This series switches the powerpc port to use the generic swiotlb
        and noncoherent dma ops, and to use more generic code for the
        coherent direct mapping, as well as removing a lot of dead
        code."

   - Increase our vmalloc space to 512T with the Hash MMU on modern
     CPUs, allowing us to support machines with larger amounts of total
     RAM or distance between nodes.

   - Two series from Christophe, one to optimise TLB miss handlers on
     6xx, and another to optimise the way STRICT_KERNEL_RWX is
     implemented on some 32-bit CPUs.

   - Support for KCOV coverage instrumentation which means we can run
     syzkaller and discover even more bugs in our code.

  And as always many clean-ups, reworks and minor fixes etc.

  Thanks to: Alan Modra, Alexey Kardashevskiy, Alistair Popple, Andrea
  Arcangeli, Andrew Donnellan, Aneesh Kumar K.V, Aravinda Prasad, Balbir
  Singh, Brajeswar Ghosh, Breno Leitao, Christian Lamparter, Christian
  Zigotzky, Christophe Leroy, Christoph Hellwig, Corentin Labbe, Daniel
  Axtens, David Gibson, Diana Craciun, Firoz Khan, Gustavo A. R. Silva,
  Igor Stoppa, Joe Lawrence, Joel Stanley, Jonathan Neuschäfer, Jordan
  Niethe, Laurent Dufour, Madhavan Srinivasan, Mahesh Salgaonkar, Mark
  Cave-Ayland, Masahiro Yamada, Mathieu Malaterre, Matteo Croce, Meelis
  Roos, Michael W. Bringmann, Nathan Chancellor, Nathan Fontenot,
  Nicholas Piggin, Nick Desaulniers, Nicolai Stange, Oliver O'Halloran,
  Paul Mackerras, Peter Xu, PrasannaKumar Muralidharan, Qian Cai,
  Rashmica Gupta, Reza Arbab, Robert P. J. Day, Russell Currey,
  Sabyasachi Gupta, Sam Bobroff, Sandipan Das, Sergey Senozhatsky,
  Souptick Joarder, Stewart Smith, Tyrel Datwyler, Vaibhav Jain,
  YueHaibing"

* tag 'powerpc-5.1-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (200 commits)
  powerpc/32: Clear on-stack exception marker upon exception return
  powerpc: Remove export of save_stack_trace_tsk_reliable()
  powerpc/mm: fix "section_base" set but not used
  powerpc/mm: Fix "sz" set but not used warning
  powerpc/mm: Check secondary hash page table
  powerpc: remove nargs from __SYSCALL
  powerpc/64s: Fix unrelocated interrupt trampoline address test
  powerpc/powernv/ioda: Fix locked_vm counting for memory used by IOMMU tables
  powerpc/fsl: Fix the flush of branch predictor.
  powerpc/powernv: Make opal log only readable by root
  powerpc/xmon: Fix opcode being uninitialized in print_insn_powerpc
  powerpc/powernv: move OPAL call wrapper tracing and interrupt handling to C
  powerpc/64s: Fix data interrupts vs d-side MCE reentrancy
  powerpc/64s: Prepare to handle data interrupts vs d-side MCE reentrancy
  powerpc/64s: system reset interrupt preserve HSRRs
  powerpc/64s: Fix HV NMI vs HV interrupt recoverability test
  powerpc/mm/hash: Handle mmap_min_addr correctly in get_unmapped_area topdown search
  powerpc/hugetlb: Handle mmap_min_addr correctly in get_unmapped_area callback
  selftests/powerpc: Remove duplicate header
  powerpc sstep: Add support for modsd, modud instructions
  ...

1 files changed, 64 insertions, 38 deletions

diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
index e2c50b55138f..1e2276963f6d 100644
--- a/arch/powerpc/kernel/stacktrace.c
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -67,12 +67,17 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
 	unsigned long sp;
 
+	if (!try_get_task_stack(tsk))
+		return;
+
 	if (tsk == current)
 		sp = current_stack_pointer();
 	else
 		sp = tsk->thread.ksp;
 
 	save_context_stack(trace, sp, tsk, 0);
+
+	put_task_stack(tsk);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 
@@ -84,25 +89,21 @@ save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 EXPORT_SYMBOL_GPL(save_stack_trace_regs);
 
 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
-int
-save_stack_trace_tsk_reliable(struct task_struct *tsk,
-				struct stack_trace *trace)
+/*
+ * This function returns an error if it detects any unreliable features of the
+ * stack.  Otherwise it guarantees that the stack trace is reliable.
+ *
+ * If the task is not 'current', the caller *must* ensure the task is inactive.
+ */
+static int __save_stack_trace_tsk_reliable(struct task_struct *tsk,
+					   struct stack_trace *trace)
 {
 	unsigned long sp;
+	unsigned long newsp;
 	unsigned long stack_page = (unsigned long)task_stack_page(tsk);
 	unsigned long stack_end;
 	int graph_idx = 0;
-
-	/*
-	 * The last frame (unwinding first) may not yet have saved
-	 * its LR onto the stack.
-	 */
-	int firstframe = 1;
-
-	if (tsk == current)
-		sp = current_stack_pointer();
-	else
-		sp = tsk->thread.ksp;
+	bool firstframe;
 
 	stack_end = stack_page + THREAD_SIZE;
 	if (!is_idle_task(tsk)) {
@@ -129,40 +130,53 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk,
 		stack_end -= STACK_FRAME_OVERHEAD;
 	}
 
+	if (tsk == current)
+		sp = current_stack_pointer();
+	else
+		sp = tsk->thread.ksp;
+
 	if (sp < stack_page + sizeof(struct thread_struct) ||
 	    sp > stack_end - STACK_FRAME_MIN_SIZE) {
-		return 1;
+		return -EINVAL;
 	}
 
-	for (;;) {
+	for (firstframe = true; sp != stack_end;
+	     firstframe = false, sp = newsp) {
 		unsigned long *stack = (unsigned long *) sp;
-		unsigned long newsp, ip;
+		unsigned long ip;
 
 		/* sanity check: ABI requires SP to be aligned 16 bytes. */
 		if (sp & 0xF)
-			return 1;
-
-		/* Mark stacktraces with exception frames as unreliable. */
-		if (sp <= stack_end - STACK_INT_FRAME_SIZE &&
-		    stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
-			return 1;
-		}
+			return -EINVAL;
 
 		newsp = stack[0];
 		/* Stack grows downwards; unwinder may only go up. */
 		if (newsp <= sp)
-			return 1;
+			return -EINVAL;
 
 		if (newsp != stack_end &&
 		    newsp > stack_end - STACK_FRAME_MIN_SIZE) {
-			return 1; /* invalid backlink, too far up. */
+			return -EINVAL; /* invalid backlink, too far up. */
+		}
+
+		/*
+		 * We can only trust the bottom frame's backlink, the
+		 * rest of the frame may be uninitialized, continue to
+		 * the next.
+		 */
+		if (firstframe)
+			continue;
+
+		/* Mark stacktraces with exception frames as unreliable. */
+		if (sp <= stack_end - STACK_INT_FRAME_SIZE &&
+		    stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
+			return -EINVAL;
 		}
 
 		/* Examine the saved LR: it must point into kernel code. */
 		ip = stack[STACK_FRAME_LR_SAVE];
-		if (!firstframe && !__kernel_text_address(ip))
-			return 1;
-		firstframe = 0;
+		if (!__kernel_text_address(ip))
+			return -EINVAL;
 
 		/*
 		 * FIXME: IMHO these tests do not belong in
@@ -175,25 +189,37 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk,
 		 * as unreliable.
 		 */
 		if (ip == (unsigned long)kretprobe_trampoline)
-			return 1;
+			return -EINVAL;
 #endif
 
+		if (trace->nr_entries >= trace->max_entries)
+			return -E2BIG;
 		if (!trace->skip)
 			trace->entries[trace->nr_entries++] = ip;
 		else
 			trace->skip--;
+	}
+	return 0;
+}
 
-		if (newsp == stack_end)
-			break;
+int save_stack_trace_tsk_reliable(struct task_struct *tsk,
+				  struct stack_trace *trace)
+{
+	int ret;
 
-		if (trace->nr_entries >= trace->max_entries)
-			return -E2BIG;
+	/*
+	 * If the task doesn't have a stack (e.g., a zombie), the stack is
+	 * "reliably" empty.
+	 */
+	if (!try_get_task_stack(tsk))
+		return 0;
 
-		sp = newsp;
-	}
-	return 0;
+	ret = __save_stack_trace_tsk_reliable(tsk, trace);
+
+	put_task_stack(tsk);
+
+	return ret;
 }
-EXPORT_SYMBOL_GPL(save_stack_trace_tsk_reliable);
 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
 
 #if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI)