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-rw-r--r--lib/stackdepot.c535
1 files changed, 535 insertions, 0 deletions
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
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index 000000000..79e894cf8
--- /dev/null
+++ b/lib/stackdepot.c
@@ -0,0 +1,535 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic stack depot for storing stack traces.
+ *
+ * Some debugging tools need to save stack traces of certain events which can
+ * be later presented to the user. For example, KASAN needs to safe alloc and
+ * free stacks for each object, but storing two stack traces per object
+ * requires too much memory (e.g. SLUB_DEBUG needs 256 bytes per object for
+ * that).
+ *
+ * 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 contiguous memory allocation.
+ *
+ * Author: Alexander Potapenko <glider@google.com>
+ * Copyright (C) 2016 Google, Inc.
+ *
+ * Based on code by Dmitry Chernenkov.
+ */
+
+#include <linux/gfp.h>
+#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>
+#include <linux/stacktrace.h>
+#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)
+
+#define STACK_ALLOC_NULL_PROTECTION_BITS 1
+#define STACK_ALLOC_ORDER 2 /* 'Slab' size order for stack depot, 4 pages */
+#define STACK_ALLOC_SIZE (1LL << (PAGE_SHIFT + STACK_ALLOC_ORDER))
+#define STACK_ALLOC_ALIGN 4
+#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_DEPOT_EXTRA_BITS)
+#define STACK_ALLOC_SLABS_CAP 8192
+#define STACK_ALLOC_MAX_SLABS \
+ (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \
+ (1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_SLABS_CAP)
+
+/* The compact structure to store the reference to stacks. */
+union handle_parts {
+ depot_stack_handle_t handle;
+ struct {
+ 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;
+ };
+};
+
+struct stack_record {
+ struct stack_record *next; /* Link in the hashtable */
+ u32 hash; /* Hash in the hastable */
+ u32 size; /* Number of frames in the stack */
+ union handle_parts handle;
+ 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_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)
+{
+ if (!*prealloc)
+ return false;
+ /*
+ * This smp_load_acquire() pairs with smp_store_release() to
+ * |next_slab_inited| below and in depot_alloc_stack().
+ */
+ if (smp_load_acquire(&next_slab_inited))
+ return true;
+ if (stack_slabs[depot_index] == NULL) {
+ stack_slabs[depot_index] = *prealloc;
+ *prealloc = NULL;
+ } else {
+ /* If this is the last depot slab, do not touch the next one. */
+ if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) {
+ stack_slabs[depot_index + 1] = *prealloc;
+ *prealloc = NULL;
+ }
+ /*
+ * This smp_store_release pairs with smp_load_acquire() from
+ * |next_slab_inited| above and in stack_depot_save().
+ */
+ smp_store_release(&next_slab_inited, 1);
+ }
+ return true;
+}
+
+/* Allocation of a new stack in raw storage */
+static struct stack_record *
+depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
+{
+ struct stack_record *stack;
+ size_t required_size = struct_size(stack, entries, size);
+
+ required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);
+
+ if (unlikely(depot_offset + required_size > STACK_ALLOC_SIZE)) {
+ if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) {
+ WARN_ONCE(1, "Stack depot reached limit capacity");
+ return NULL;
+ }
+ depot_index++;
+ depot_offset = 0;
+ /*
+ * smp_store_release() here pairs with smp_load_acquire() from
+ * |next_slab_inited| in stack_depot_save() and
+ * init_stack_slab().
+ */
+ if (depot_index + 1 < STACK_ALLOC_MAX_SLABS)
+ smp_store_release(&next_slab_inited, 0);
+ }
+ init_stack_slab(prealloc);
+ if (stack_slabs[depot_index] == NULL)
+ return NULL;
+
+ stack = stack_slabs[depot_index] + depot_offset;
+
+ stack->hash = hash;
+ stack->size = size;
+ stack->handle.slabindex = depot_index;
+ stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
+ stack->handle.valid = 1;
+ stack->handle.extra = 0;
+ memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
+ depot_offset += required_size;
+
+ return stack;
+}
+
+/* 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 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,
+ array_size(size, sizeof(*entries)) / sizeof(u32),
+ STACK_HASH_SEED);
+}
+
+/* Use our own, non-instrumented version of memcmp().
+ *
+ * We actually don't care about the order, just the equality.
+ */
+static inline
+int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
+ unsigned int n)
+{
+ for ( ; n-- ; u1++, u2++) {
+ if (*u1 != *u2)
+ return 1;
+ }
+ return 0;
+}
+
+/* Find a stack that is equal to the one stored in entries in the hash */
+static inline struct stack_record *find_stack(struct stack_record *bucket,
+ unsigned long *entries, int size,
+ u32 hash)
+{
+ struct stack_record *found;
+
+ for (found = bucket; found; found = found->next) {
+ if (found->hash == hash &&
+ found->size == size &&
+ !stackdepot_memcmp(entries, found->entries, size))
+ return found;
+ }
+ return NULL;
+}
+
+/**
+ * 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
+ * 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;
+ size_t offset = parts.offset << STACK_ALLOC_ALIGN;
+ 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;
+}
+EXPORT_SYMBOL_GPL(stack_depot_fetch);
+
+/**
+ * __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)
+ *
+ * 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,
+ unsigned int extra_bits,
+ gfp_t alloc_flags, bool can_alloc)
+{
+ struct stack_record *found = NULL, **bucket;
+ union handle_parts retval = { .handle = 0 };
+ struct page *page = NULL;
+ void *prealloc = NULL;
+ unsigned long flags;
+ u32 hash;
+
+ /*
+ * 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];
+
+ /*
+ * Fast path: look the stack trace up without locking.
+ * The smp_load_acquire() here pairs with smp_store_release() to
+ * |bucket| below.
+ */
+ found = find_stack(smp_load_acquire(bucket), entries,
+ nr_entries, hash);
+ if (found)
+ goto exit;
+
+ /*
+ * Check if the current or the next stack slab need to be initialized.
+ * If so, allocate the memory - we won't be able to do that under the
+ * lock.
+ *
+ * The smp_load_acquire() here pairs with smp_store_release() to
+ * |next_slab_inited| in depot_alloc_stack() and init_stack_slab().
+ */
+ 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
+ * contexts and I/O.
+ */
+ alloc_flags &= ~GFP_ZONEMASK;
+ alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
+ alloc_flags |= __GFP_NOWARN;
+ page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
+ if (page)
+ prealloc = page_address(page);
+ }
+
+ 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);
+
+ if (new) {
+ new->next = *bucket;
+ /*
+ * This smp_store_release() pairs with
+ * smp_load_acquire() from |bucket| above.
+ */
+ smp_store_release(bucket, new);
+ found = new;
+ }
+ } else if (prealloc) {
+ /*
+ * We didn't need to store this stack trace, but let's keep
+ * the preallocated memory for the future.
+ */
+ WARN_ON(!init_stack_slab(&prealloc));
+ }
+
+ 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.handle = found->handle.handle;
+fast_exit:
+ 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);