Merge branch 'core-stacktrace-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull stack trace updates from Ingo Molnar:
 "So Thomas looked at the stacktrace code recently and noticed a few
  weirdnesses, and we all know how such stories of crummy kernel code
  meeting German engineering perfection end: a 45-patch series to clean
  it all up! :-)

  Here's the changes in Thomas's words:

   'Struct stack_trace is a sinkhole for input and output parameters
    which is largely pointless for most usage sites. In fact if embedded
    into other data structures it creates indirections and extra storage
    overhead for no benefit.

    Looking at all usage sites makes it clear that they just require an
    interface which is based on a storage array. That array is either on
    stack, global or embedded into some other data structure.

    Some of the stack depot usage sites are outright wrong, but
    fortunately the wrongness just causes more stack being used for
    nothing and does not have functional impact.

    Another oddity is the inconsistent termination of the stack trace
    with ULONG_MAX. It's pointless as the number of entries is what
    determines the length of the stored trace. In fact quite some call
    sites remove the ULONG_MAX marker afterwards with or without nasty
    comments about it. Not all architectures do that and those which do,
    do it inconsistenly either conditional on nr_entries == 0 or
    unconditionally.

    The following series cleans that up by:

      1) Removing the ULONG_MAX termination in the architecture code

      2) Removing the ULONG_MAX fixups at the call sites

      3) Providing plain storage array based interfaces for stacktrace
         and stackdepot.

      4) Cleaning up the mess at the callsites including some related
         cleanups.

      5) Removing the struct stack_trace based interfaces

    This is not changing the struct stack_trace interfaces at the
    architecture level, but it removes the exposure to the generic
    code'"

* 'core-stacktrace-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits)
  x86/stacktrace: Use common infrastructure
  stacktrace: Provide common infrastructure
  lib/stackdepot: Remove obsolete functions
  stacktrace: Remove obsolete functions
  livepatch: Simplify stack trace retrieval
  tracing: Remove the last struct stack_trace usage
  tracing: Simplify stack trace retrieval
  tracing: Make ftrace_trace_userstack() static and conditional
  tracing: Use percpu stack trace buffer more intelligently
  tracing: Simplify stacktrace retrieval in histograms
  lockdep: Simplify stack trace handling
  lockdep: Remove save argument from check_prev_add()
  lockdep: Remove unused trace argument from print_circular_bug()
  drm: Simplify stacktrace handling
  dm persistent data: Simplify stack trace handling
  dm bufio: Simplify stack trace retrieval
  btrfs: ref-verify: Simplify stack trace retrieval
  dma/debug: Simplify stracktrace retrieval
  fault-inject: Simplify stacktrace retrieval
  mm/page_owner: Simplify stack trace handling
  ...

3 files changed, 40 insertions, 30 deletions

diff --git a/lib/Kconfig b/lib/Kconfig
index a9e56539bd11..e86975bfca6a 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -597,6 +597,10 @@ config ARCH_HAS_UACCESS_FLUSHCACHE
 config ARCH_HAS_UACCESS_MCSAFE
 	bool
 
+# Temporary. Goes away when all archs are cleaned up
+config ARCH_STACKWALK
+       bool
+
 config STACKDEPOT
 	bool
 	select STACKTRACE
diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index cf7b129b0b2b..e26aa4f65eb9 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -65,22 +65,16 @@ static bool fail_task(struct fault_attr *attr, struct task_struct *task)
 
 static bool fail_stacktrace(struct fault_attr *attr)
 {
-	struct stack_trace trace;
 	int depth = attr->stacktrace_depth;
 	unsigned long entries[MAX_STACK_TRACE_DEPTH];
-	int n;
+	int n, nr_entries;
 	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
 
 	if (depth == 0)
 		return found;
 
-	trace.nr_entries = 0;
-	trace.entries = entries;
-	trace.max_entries = depth;
-	trace.skip = 1;
-
-	save_stack_trace(&trace);
-	for (n = 0; n < trace.nr_entries; n++) {
+	nr_entries = stack_trace_save(entries, depth, 1);
+	for (n = 0; n < nr_entries; n++) {
 		if (attr->reject_start <= entries[n] &&
 			       entries[n] < attr->reject_end)
 			return false;
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index e513459a5601..605c61f65d94 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -194,40 +194,52 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
 	return NULL;
 }
 
-void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace)
+/**
+ * stack_depot_fetch - Fetch stack entries from a depot
+ *
+ * @handle:		Stack depot handle which was returned from
+ *			stack_depot_save().
+ * @entries:		Pointer to store the entries address
+ *
+ * Return: The number of trace entries for this depot.
+ */
+unsigned int stack_depot_fetch(depot_stack_handle_t handle,
+			       unsigned long **entries)
 {
 	union handle_parts parts = { .handle = handle };
 	void *slab = stack_slabs[parts.slabindex];
 	size_t offset = parts.offset << STACK_ALLOC_ALIGN;
 	struct stack_record *stack = slab + offset;
 
-	trace->nr_entries = trace->max_entries = stack->size;
-	trace->entries = stack->entries;
-	trace->skip = 0;
+	*entries = stack->entries;
+	return stack->size;
 }
-EXPORT_SYMBOL_GPL(depot_fetch_stack);
+EXPORT_SYMBOL_GPL(stack_depot_fetch);
 
 /**
- * depot_save_stack - save stack in a stack depot.
- * @trace - the stacktrace to save.
- * @alloc_flags - flags for allocating additional memory if required.
+ * stack_depot_save - Save a stack trace from an array
+ *
+ * @entries:		Pointer to storage array
+ * @nr_entries:		Size of the storage array
+ * @alloc_flags:	Allocation gfp flags
  *
- * Returns the handle of the stack struct stored in depot.
+ * Return: The handle of the stack struct stored in depot
  */
-depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
-				    gfp_t alloc_flags)
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+				      unsigned int nr_entries,
+				      gfp_t alloc_flags)
 {
-	u32 hash;
-	depot_stack_handle_t retval = 0;
 	struct stack_record *found = NULL, **bucket;
-	unsigned long flags;
+	depot_stack_handle_t retval = 0;
 	struct page *page = NULL;
 	void *prealloc = NULL;
+	unsigned long flags;
+	u32 hash;
 
-	if (unlikely(trace->nr_entries == 0))
+	if (unlikely(nr_entries == 0))
 		goto fast_exit;
 
-	hash = hash_stack(trace->entries, trace->nr_entries);
+	hash = hash_stack(entries, nr_entries);
 	bucket = &stack_table[hash & STACK_HASH_MASK];
 
 	/*
@@ -235,8 +247,8 @@ depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
 	 * The smp_load_acquire() here pairs with smp_store_release() to
 	 * |bucket| below.
 	 */
-	found = find_stack(smp_load_acquire(bucket), trace->entries,
-			   trace->nr_entries, hash);
+	found = find_stack(smp_load_acquire(bucket), entries,
+			   nr_entries, hash);
 	if (found)
 		goto exit;
 
@@ -264,10 +276,10 @@ depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
 
 	spin_lock_irqsave(&depot_lock, flags);
 
-	found = find_stack(*bucket, trace->entries, trace->nr_entries, hash);
+	found = find_stack(*bucket, entries, nr_entries, hash);
 	if (!found) {
 		struct stack_record *new =
-			depot_alloc_stack(trace->entries, trace->nr_entries,
+			depot_alloc_stack(entries, nr_entries,
 					  hash, &prealloc, alloc_flags);
 		if (new) {
 			new->next = *bucket;
@@ -297,4 +309,4 @@ exit:
 fast_exit:
 	return retval;
 }
-EXPORT_SYMBOL_GPL(depot_save_stack);
+EXPORT_SYMBOL_GPL(stack_depot_save);