1 files changed, 263 insertions, 35 deletions

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 81c69c08d1d1..79e894cf8406 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -11,7 +11,7 @@
  * Instead, stack depot maintains a hashtable of unique stacktraces. Since alloc
  * and free stacks repeat a lot, we save about 100x space.
  * Stacks are never removed from depot, so we store them contiguously one after
- * another in a contiguos memory allocation.
+ * another in a contiguous memory allocation.
  *
  * Author: Alexander Potapenko <glider@google.com>
  * Copyright (C) 2016 Google, Inc.
@@ -23,6 +23,7 @@
 #include <linux/jhash.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
@@ -30,6 +31,8 @@
 #include <linux/stackdepot.h>
 #include <linux/string.h>
 #include <linux/types.h>
+#include <linux/memblock.h>
+#include <linux/kasan-enabled.h>
 
 #define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8)
 
@@ -40,7 +43,8 @@
 #define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \
 					STACK_ALLOC_ALIGN)
 #define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \
-		STACK_ALLOC_NULL_PROTECTION_BITS - STACK_ALLOC_OFFSET_BITS)
+		STACK_ALLOC_NULL_PROTECTION_BITS - \
+		STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
 #define STACK_ALLOC_SLABS_CAP 8192
 #define STACK_ALLOC_MAX_SLABS \
 	(((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \
@@ -53,6 +57,7 @@ union handle_parts {
 		u32 slabindex : STACK_ALLOC_INDEX_BITS;
 		u32 offset : STACK_ALLOC_OFFSET_BITS;
 		u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS;
+		u32 extra : STACK_DEPOT_EXTRA_BITS;
 	};
 };
 
@@ -61,15 +66,26 @@ struct stack_record {
 	u32 hash;			/* Hash in the hastable */
 	u32 size;			/* Number of frames in the stack */
 	union handle_parts handle;
-	unsigned long entries[1];	/* Variable-sized array of entries. */
+	unsigned long entries[];	/* Variable-sized array of entries. */
 };
 
+static bool __stack_depot_want_early_init __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT);
+static bool __stack_depot_early_init_passed __initdata;
+
 static void *stack_slabs[STACK_ALLOC_MAX_SLABS];
 
 static int depot_index;
 static int next_slab_inited;
 static size_t depot_offset;
-static DEFINE_SPINLOCK(depot_lock);
+static DEFINE_RAW_SPINLOCK(depot_lock);
+
+unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
+{
+	union handle_parts parts = { .handle = handle };
+
+	return parts.extra;
+}
+EXPORT_SYMBOL(stack_depot_get_extra_bits);
 
 static bool init_stack_slab(void **prealloc)
 {
@@ -100,12 +116,11 @@ static bool init_stack_slab(void **prealloc)
 }
 
 /* Allocation of a new stack in raw storage */
-static struct stack_record *depot_alloc_stack(unsigned long *entries, int size,
-		u32 hash, void **prealloc, gfp_t alloc_flags)
+static struct stack_record *
+depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
 {
-	int required_size = offsetof(struct stack_record, entries) +
-		sizeof(unsigned long) * size;
 	struct stack_record *stack;
+	size_t required_size = struct_size(stack, entries, size);
 
 	required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);
 
@@ -135,27 +150,132 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int size,
 	stack->handle.slabindex = depot_index;
 	stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
 	stack->handle.valid = 1;
-	memcpy(stack->entries, entries, size * sizeof(unsigned long));
+	stack->handle.extra = 0;
+	memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
 	depot_offset += required_size;
 
 	return stack;
 }
 
-#define STACK_HASH_ORDER 20
-#define STACK_HASH_SIZE (1L << STACK_HASH_ORDER)
-#define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
+/* one hash table bucket entry per 16kB of memory */
+#define STACK_HASH_SCALE	14
+/* limited between 4k and 1M buckets */
+#define STACK_HASH_ORDER_MIN	12
+#define STACK_HASH_ORDER_MAX	20
 #define STACK_HASH_SEED 0x9747b28c
 
-static struct stack_record *stack_table[STACK_HASH_SIZE] = {
-	[0 ...	STACK_HASH_SIZE - 1] = NULL
-};
+static unsigned int stack_hash_order;
+static unsigned int stack_hash_mask;
+
+static bool stack_depot_disable;
+static struct stack_record **stack_table;
+
+static int __init is_stack_depot_disabled(char *str)
+{
+	int ret;
+
+	ret = kstrtobool(str, &stack_depot_disable);
+	if (!ret && stack_depot_disable) {
+		pr_info("Stack Depot is disabled\n");
+		stack_table = NULL;
+	}
+	return 0;
+}
+early_param("stack_depot_disable", is_stack_depot_disabled);
+
+void __init stack_depot_want_early_init(void)
+{
+	/* Too late to request early init now */
+	WARN_ON(__stack_depot_early_init_passed);
+
+	__stack_depot_want_early_init = true;
+}
+
+int __init stack_depot_early_init(void)
+{
+	unsigned long entries = 0;
+
+	/* This is supposed to be called only once, from mm_init() */
+	if (WARN_ON(__stack_depot_early_init_passed))
+		return 0;
+
+	__stack_depot_early_init_passed = true;
+
+	if (kasan_enabled() && !stack_hash_order)
+		stack_hash_order = STACK_HASH_ORDER_MAX;
+
+	if (!__stack_depot_want_early_init || stack_depot_disable)
+		return 0;
+
+	if (stack_hash_order)
+		entries = 1UL <<  stack_hash_order;
+	stack_table = alloc_large_system_hash("stackdepot",
+						sizeof(struct stack_record *),
+						entries,
+						STACK_HASH_SCALE,
+						HASH_EARLY | HASH_ZERO,
+						NULL,
+						&stack_hash_mask,
+						1UL << STACK_HASH_ORDER_MIN,
+						1UL << STACK_HASH_ORDER_MAX);
+
+	if (!stack_table) {
+		pr_err("Stack Depot hash table allocation failed, disabling\n");
+		stack_depot_disable = true;
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+int stack_depot_init(void)
+{
+	static DEFINE_MUTEX(stack_depot_init_mutex);
+	int ret = 0;
+
+	mutex_lock(&stack_depot_init_mutex);
+	if (!stack_depot_disable && !stack_table) {
+		unsigned long entries;
+		int scale = STACK_HASH_SCALE;
+
+		if (stack_hash_order) {
+			entries = 1UL << stack_hash_order;
+		} else {
+			entries = nr_free_buffer_pages();
+			entries = roundup_pow_of_two(entries);
+
+			if (scale > PAGE_SHIFT)
+				entries >>= (scale - PAGE_SHIFT);
+			else
+				entries <<= (PAGE_SHIFT - scale);
+		}
+
+		if (entries < 1UL << STACK_HASH_ORDER_MIN)
+			entries = 1UL << STACK_HASH_ORDER_MIN;
+		if (entries > 1UL << STACK_HASH_ORDER_MAX)
+			entries = 1UL << STACK_HASH_ORDER_MAX;
+
+		pr_info("Stack Depot allocating hash table of %lu entries with kvcalloc\n",
+				entries);
+		stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL);
+		if (!stack_table) {
+			pr_err("Stack Depot hash table allocation failed, disabling\n");
+			stack_depot_disable = true;
+			ret = -ENOMEM;
+		}
+		stack_hash_mask = entries - 1;
+	}
+	mutex_unlock(&stack_depot_init_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(stack_depot_init);
 
 /* Calculate hash for a stack */
 static inline u32 hash_stack(unsigned long *entries, unsigned int size)
 {
 	return jhash2((u32 *)entries,
-			       size * sizeof(unsigned long) / sizeof(u32),
-			       STACK_HASH_SEED);
+		      array_size(size,  sizeof(*entries)) / sizeof(u32),
+		      STACK_HASH_SEED);
 }
 
 /* Use our own, non-instrumented version of memcmp().
@@ -190,6 +310,49 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
 }
 
 /**
+ * stack_depot_snprint - print stack entries from a depot into a buffer
+ *
+ * @handle:	Stack depot handle which was returned from
+ *		stack_depot_save().
+ * @buf:	Pointer to the print buffer
+ *
+ * @size:	Size of the print buffer
+ *
+ * @spaces:	Number of leading spaces to print
+ *
+ * Return:	Number of bytes printed.
+ */
+int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
+		       int spaces)
+{
+	unsigned long *entries;
+	unsigned int nr_entries;
+
+	nr_entries = stack_depot_fetch(handle, &entries);
+	return nr_entries ? stack_trace_snprint(buf, size, entries, nr_entries,
+						spaces) : 0;
+}
+EXPORT_SYMBOL_GPL(stack_depot_snprint);
+
+/**
+ * stack_depot_print - print stack entries from a depot
+ *
+ * @stack:		Stack depot handle which was returned from
+ *			stack_depot_save().
+ *
+ */
+void stack_depot_print(depot_stack_handle_t stack)
+{
+	unsigned long *entries;
+	unsigned int nr_entries;
+
+	nr_entries = stack_depot_fetch(stack, &entries);
+	if (nr_entries > 0)
+		stack_trace_print(entries, nr_entries, 0);
+}
+EXPORT_SYMBOL_GPL(stack_depot_print);
+
+/**
  * stack_depot_fetch - Fetch stack entries from a depot
  *
  * @handle:		Stack depot handle which was returned from
@@ -202,9 +365,23 @@ 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];
+	void *slab;
 	size_t offset = parts.offset << STACK_ALLOC_ALIGN;
-	struct stack_record *stack = slab + offset;
+	struct stack_record *stack;
+
+	*entries = NULL;
+	if (!handle)
+		return 0;
+
+	if (parts.slabindex > depot_index) {
+		WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
+			parts.slabindex, depot_index, handle);
+		return 0;
+	}
+	slab = stack_slabs[parts.slabindex];
+	if (!slab)
+		return 0;
+	stack = slab + offset;
 
 	*entries = stack->entries;
 	return stack->size;
@@ -212,30 +389,60 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 EXPORT_SYMBOL_GPL(stack_depot_fetch);
 
 /**
- * stack_depot_save - Save a stack trace from an array
+ * __stack_depot_save - Save a stack trace from an array
  *
  * @entries:		Pointer to storage array
  * @nr_entries:		Size of the storage array
+ * @extra_bits:		Flags to store in unused bits of depot_stack_handle_t
  * @alloc_flags:	Allocation gfp flags
+ * @can_alloc:		Allocate stack slabs (increased chance of failure if false)
  *
- * Return: The handle of the stack struct stored in depot
+ * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
+ * %true, is allowed to replenish the stack slab pool in case no space is left
+ * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
+ * any allocations and will fail if no space is left to store the stack trace.
+ *
+ * If the stack trace in @entries is from an interrupt, only the portion up to
+ * interrupt entry is saved.
+ *
+ * Additional opaque flags can be passed in @extra_bits, stored in the unused
+ * bits of the stack handle, and retrieved using stack_depot_get_extra_bits()
+ * without calling stack_depot_fetch().
+ *
+ * Context: Any context, but setting @can_alloc to %false is required if
+ *          alloc_pages() cannot be used from the current context. Currently
+ *          this is the case from contexts where neither %GFP_ATOMIC nor
+ *          %GFP_NOWAIT can be used (NMI, raw_spin_lock).
+ *
+ * Return: The handle of the stack struct stored in depot, 0 on failure.
  */
-depot_stack_handle_t stack_depot_save(unsigned long *entries,
-				      unsigned int nr_entries,
-				      gfp_t alloc_flags)
+depot_stack_handle_t __stack_depot_save(unsigned long *entries,
+					unsigned int nr_entries,
+					unsigned int extra_bits,
+					gfp_t alloc_flags, bool can_alloc)
 {
 	struct stack_record *found = NULL, **bucket;
-	depot_stack_handle_t retval = 0;
+	union handle_parts retval = { .handle = 0 };
 	struct page *page = NULL;
 	void *prealloc = NULL;
 	unsigned long flags;
 	u32 hash;
 
-	if (unlikely(nr_entries == 0))
+	/*
+	 * If this stack trace is from an interrupt, including anything before
+	 * interrupt entry usually leads to unbounded stackdepot growth.
+	 *
+	 * Because use of filter_irq_stacks() is a requirement to ensure
+	 * stackdepot can efficiently deduplicate interrupt stacks, always
+	 * filter_irq_stacks() to simplify all callers' use of stackdepot.
+	 */
+	nr_entries = filter_irq_stacks(entries, nr_entries);
+
+	if (unlikely(nr_entries == 0) || stack_depot_disable)
 		goto fast_exit;
 
 	hash = hash_stack(entries, nr_entries);
-	bucket = &stack_table[hash & STACK_HASH_MASK];
+	bucket = &stack_table[hash & stack_hash_mask];
 
 	/*
 	 * Fast path: look the stack trace up without locking.
@@ -255,7 +462,7 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
 	 * The smp_load_acquire() here pairs with smp_store_release() to
 	 * |next_slab_inited| in depot_alloc_stack() and init_stack_slab().
 	 */
-	if (unlikely(!smp_load_acquire(&next_slab_inited))) {
+	if (unlikely(can_alloc && !smp_load_acquire(&next_slab_inited))) {
 		/*
 		 * Zero out zone modifiers, as we don't have specific zone
 		 * requirements. Keep the flags related to allocation in atomic
@@ -269,13 +476,12 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
 			prealloc = page_address(page);
 	}
 
-	spin_lock_irqsave(&depot_lock, flags);
+	raw_spin_lock_irqsave(&depot_lock, flags);
 
 	found = find_stack(*bucket, entries, nr_entries, hash);
 	if (!found) {
-		struct stack_record *new =
-			depot_alloc_stack(entries, nr_entries,
-					  hash, &prealloc, alloc_flags);
+		struct stack_record *new = depot_alloc_stack(entries, nr_entries, hash, &prealloc);
+
 		if (new) {
 			new->next = *bucket;
 			/*
@@ -293,15 +499,37 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
 		WARN_ON(!init_stack_slab(&prealloc));
 	}
 
-	spin_unlock_irqrestore(&depot_lock, flags);
+	raw_spin_unlock_irqrestore(&depot_lock, flags);
 exit:
 	if (prealloc) {
 		/* Nobody used this memory, ok to free it. */
 		free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
 	}
 	if (found)
-		retval = found->handle.handle;
+		retval.handle = found->handle.handle;
 fast_exit:
-	return retval;
+	retval.extra = extra_bits;
+
+	return retval.handle;
+}
+EXPORT_SYMBOL_GPL(__stack_depot_save);
+
+/**
+ * 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
+ *
+ * Context: Contexts where allocations via alloc_pages() are allowed.
+ *          See __stack_depot_save() for more details.
+ *
+ * Return: The handle of the stack struct stored in depot, 0 on failure.
+ */
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+				      unsigned int nr_entries,
+				      gfp_t alloc_flags)
+{
+	return __stack_depot_save(entries, nr_entries, 0, alloc_flags, true);
 }
 EXPORT_SYMBOL_GPL(stack_depot_save);