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0621d160f1
Move all interface- and usage-related documentation comments to include/linux/stackdepot.h. It makes sense to have them in the header where they are available to the interface users. [akpm@linux-foundation.org: grammar fix, per Alexander] Link: https://lkml.kernel.org/r/fbfee41495b306dd8881f9b1c1b80999c885e82f.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
530 lines
15 KiB
C
530 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Stack depot - a stack trace storage that avoids duplication.
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*
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* Internally, stack depot maintains a hash table of unique stacktraces. The
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* stack traces themselves are stored contiguously one after another in a set
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* of separate page allocations.
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*
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* Author: Alexander Potapenko <glider@google.com>
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* Copyright (C) 2016 Google, Inc.
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*
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* Based on the code by Dmitry Chernenkov.
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*/
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#define pr_fmt(fmt) "stackdepot: " fmt
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#include <linux/gfp.h>
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#include <linux/jhash.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/mutex.h>
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#include <linux/percpu.h>
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#include <linux/printk.h>
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#include <linux/slab.h>
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#include <linux/stacktrace.h>
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#include <linux/stackdepot.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/memblock.h>
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#include <linux/kasan-enabled.h>
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#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8)
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#define DEPOT_VALID_BITS 1
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#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */
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#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER))
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#define DEPOT_STACK_ALIGN 4
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#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN)
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#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_VALID_BITS - \
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DEPOT_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
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#define DEPOT_POOLS_CAP 8192
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#define DEPOT_MAX_POOLS \
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(((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \
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(1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP)
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/* Compact structure that stores a reference to a stack. */
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union handle_parts {
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depot_stack_handle_t handle;
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struct {
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u32 pool_index : DEPOT_POOL_INDEX_BITS;
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u32 offset : DEPOT_OFFSET_BITS;
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u32 valid : DEPOT_VALID_BITS;
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u32 extra : STACK_DEPOT_EXTRA_BITS;
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};
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};
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struct stack_record {
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struct stack_record *next; /* Link in the hash table */
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u32 hash; /* Hash in the hash table */
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u32 size; /* Number of stored frames */
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union handle_parts handle;
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unsigned long entries[]; /* Variable-sized array of frames */
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};
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static bool stack_depot_disabled;
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static bool __stack_depot_early_init_requested __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT);
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static bool __stack_depot_early_init_passed __initdata;
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/* Use one hash table bucket per 16 KB of memory. */
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#define STACK_HASH_TABLE_SCALE 14
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/* Limit the number of buckets between 4K and 1M. */
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#define STACK_BUCKET_NUMBER_ORDER_MIN 12
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#define STACK_BUCKET_NUMBER_ORDER_MAX 20
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/* Initial seed for jhash2. */
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#define STACK_HASH_SEED 0x9747b28c
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/* Hash table of pointers to stored stack traces. */
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static struct stack_record **stack_table;
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/* Fixed order of the number of table buckets. Used when KASAN is enabled. */
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static unsigned int stack_bucket_number_order;
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/* Hash mask for indexing the table. */
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static unsigned int stack_hash_mask;
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/* Array of memory regions that store stack traces. */
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static void *stack_pools[DEPOT_MAX_POOLS];
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/* Currently used pool in stack_pools. */
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static int pool_index;
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/* Offset to the unused space in the currently used pool. */
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static size_t pool_offset;
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/* Lock that protects the variables above. */
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static DEFINE_RAW_SPINLOCK(pool_lock);
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/*
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* Stack depot tries to keep an extra pool allocated even before it runs out
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* of space in the currently used pool.
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* This flag marks that this next extra pool needs to be allocated and
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* initialized. It has the value 0 when either the next pool is not yet
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* initialized or the limit on the number of pools is reached.
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*/
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static int next_pool_required = 1;
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static int __init disable_stack_depot(char *str)
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{
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int ret;
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ret = kstrtobool(str, &stack_depot_disabled);
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if (!ret && stack_depot_disabled) {
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pr_info("disabled\n");
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stack_table = NULL;
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}
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return 0;
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}
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early_param("stack_depot_disable", disable_stack_depot);
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void __init stack_depot_request_early_init(void)
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{
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/* Too late to request early init now. */
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WARN_ON(__stack_depot_early_init_passed);
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__stack_depot_early_init_requested = true;
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}
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/* Allocates a hash table via memblock. Can only be used during early boot. */
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int __init stack_depot_early_init(void)
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{
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unsigned long entries = 0;
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/* This function must be called only once, from mm_init(). */
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if (WARN_ON(__stack_depot_early_init_passed))
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return 0;
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__stack_depot_early_init_passed = true;
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/*
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* If KASAN is enabled, use the maximum order: KASAN is frequently used
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* in fuzzing scenarios, which leads to a large number of different
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* stack traces being stored in stack depot.
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*/
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if (kasan_enabled() && !stack_bucket_number_order)
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stack_bucket_number_order = STACK_BUCKET_NUMBER_ORDER_MAX;
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if (!__stack_depot_early_init_requested || stack_depot_disabled)
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return 0;
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/*
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* If stack_bucket_number_order is not set, leave entries as 0 to rely
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* on the automatic calculations performed by alloc_large_system_hash.
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*/
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if (stack_bucket_number_order)
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entries = 1UL << stack_bucket_number_order;
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pr_info("allocating hash table via alloc_large_system_hash\n");
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stack_table = alloc_large_system_hash("stackdepot",
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sizeof(struct stack_record *),
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entries,
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STACK_HASH_TABLE_SCALE,
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HASH_EARLY | HASH_ZERO,
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NULL,
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&stack_hash_mask,
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1UL << STACK_BUCKET_NUMBER_ORDER_MIN,
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1UL << STACK_BUCKET_NUMBER_ORDER_MAX);
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if (!stack_table) {
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pr_err("hash table allocation failed, disabling\n");
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stack_depot_disabled = true;
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return -ENOMEM;
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}
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return 0;
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}
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/* Allocates a hash table via kvcalloc. Can be used after boot. */
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int stack_depot_init(void)
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{
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static DEFINE_MUTEX(stack_depot_init_mutex);
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unsigned long entries;
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int ret = 0;
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mutex_lock(&stack_depot_init_mutex);
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if (stack_depot_disabled || stack_table)
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goto out_unlock;
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/*
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* Similarly to stack_depot_early_init, use stack_bucket_number_order
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* if assigned, and rely on automatic scaling otherwise.
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*/
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if (stack_bucket_number_order) {
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entries = 1UL << stack_bucket_number_order;
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} else {
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int scale = STACK_HASH_TABLE_SCALE;
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entries = nr_free_buffer_pages();
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entries = roundup_pow_of_two(entries);
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if (scale > PAGE_SHIFT)
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entries >>= (scale - PAGE_SHIFT);
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else
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entries <<= (PAGE_SHIFT - scale);
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}
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if (entries < 1UL << STACK_BUCKET_NUMBER_ORDER_MIN)
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entries = 1UL << STACK_BUCKET_NUMBER_ORDER_MIN;
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if (entries > 1UL << STACK_BUCKET_NUMBER_ORDER_MAX)
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entries = 1UL << STACK_BUCKET_NUMBER_ORDER_MAX;
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pr_info("allocating hash table of %lu entries via kvcalloc\n", entries);
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stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL);
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if (!stack_table) {
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pr_err("hash table allocation failed, disabling\n");
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stack_depot_disabled = true;
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ret = -ENOMEM;
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goto out_unlock;
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}
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stack_hash_mask = entries - 1;
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out_unlock:
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mutex_unlock(&stack_depot_init_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(stack_depot_init);
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/* Uses preallocated memory to initialize a new stack depot pool. */
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static void depot_init_pool(void **prealloc)
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{
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/*
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* If the next pool is already initialized or the maximum number of
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* pools is reached, do not use the preallocated memory.
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* smp_load_acquire() here pairs with smp_store_release() below and
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* in depot_alloc_stack().
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*/
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if (!smp_load_acquire(&next_pool_required))
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return;
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/* Check if the current pool is not yet allocated. */
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if (stack_pools[pool_index] == NULL) {
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/* Use the preallocated memory for the current pool. */
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stack_pools[pool_index] = *prealloc;
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*prealloc = NULL;
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} else {
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/*
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* Otherwise, use the preallocated memory for the next pool
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* as long as we do not exceed the maximum number of pools.
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*/
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if (pool_index + 1 < DEPOT_MAX_POOLS) {
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stack_pools[pool_index + 1] = *prealloc;
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*prealloc = NULL;
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}
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/*
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* At this point, either the next pool is initialized or the
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* maximum number of pools is reached. In either case, take
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* note that initializing another pool is not required.
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* This smp_store_release pairs with smp_load_acquire() above
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* and in stack_depot_save().
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*/
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smp_store_release(&next_pool_required, 0);
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}
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}
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/* Allocates a new stack in a stack depot pool. */
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static struct stack_record *
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depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
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{
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struct stack_record *stack;
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size_t required_size = struct_size(stack, entries, size);
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required_size = ALIGN(required_size, 1 << DEPOT_STACK_ALIGN);
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/* Check if there is not enough space in the current pool. */
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if (unlikely(pool_offset + required_size > DEPOT_POOL_SIZE)) {
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/* Bail out if we reached the pool limit. */
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if (unlikely(pool_index + 1 >= DEPOT_MAX_POOLS)) {
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WARN_ONCE(1, "Stack depot reached limit capacity");
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return NULL;
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}
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/*
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* Move on to the next pool.
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* WRITE_ONCE pairs with potential concurrent read in
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* stack_depot_fetch().
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*/
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WRITE_ONCE(pool_index, pool_index + 1);
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pool_offset = 0;
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/*
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* If the maximum number of pools is not reached, take note
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* that the next pool needs to initialized.
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* smp_store_release() here pairs with smp_load_acquire() in
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* stack_depot_save() and depot_init_pool().
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*/
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if (pool_index + 1 < DEPOT_MAX_POOLS)
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smp_store_release(&next_pool_required, 1);
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}
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/* Assign the preallocated memory to a pool if required. */
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if (*prealloc)
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depot_init_pool(prealloc);
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/* Check if we have a pool to save the stack trace. */
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if (stack_pools[pool_index] == NULL)
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return NULL;
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/* Save the stack trace. */
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stack = stack_pools[pool_index] + pool_offset;
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stack->hash = hash;
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stack->size = size;
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stack->handle.pool_index = pool_index;
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stack->handle.offset = pool_offset >> DEPOT_STACK_ALIGN;
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stack->handle.valid = 1;
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stack->handle.extra = 0;
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memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
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pool_offset += required_size;
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return stack;
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}
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/* Calculates the hash for a stack. */
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static inline u32 hash_stack(unsigned long *entries, unsigned int size)
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{
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return jhash2((u32 *)entries,
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array_size(size, sizeof(*entries)) / sizeof(u32),
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STACK_HASH_SEED);
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}
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/*
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* Non-instrumented version of memcmp().
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* Does not check the lexicographical order, only the equality.
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*/
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static inline
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int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
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unsigned int n)
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{
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for ( ; n-- ; u1++, u2++) {
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if (*u1 != *u2)
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return 1;
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}
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return 0;
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}
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/* Finds a stack in a bucket of the hash table. */
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static inline struct stack_record *find_stack(struct stack_record *bucket,
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unsigned long *entries, int size,
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u32 hash)
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{
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struct stack_record *found;
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for (found = bucket; found; found = found->next) {
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if (found->hash == hash &&
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found->size == size &&
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!stackdepot_memcmp(entries, found->entries, size))
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return found;
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}
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return NULL;
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}
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depot_stack_handle_t __stack_depot_save(unsigned long *entries,
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unsigned int nr_entries,
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gfp_t alloc_flags, bool can_alloc)
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{
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struct stack_record *found = NULL, **bucket;
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union handle_parts retval = { .handle = 0 };
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struct page *page = NULL;
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void *prealloc = NULL;
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unsigned long flags;
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u32 hash;
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/*
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* If this stack trace is from an interrupt, including anything before
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* interrupt entry usually leads to unbounded stack depot growth.
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*
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* Since use of filter_irq_stacks() is a requirement to ensure stack
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* depot can efficiently deduplicate interrupt stacks, always
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* filter_irq_stacks() to simplify all callers' use of stack depot.
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*/
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nr_entries = filter_irq_stacks(entries, nr_entries);
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if (unlikely(nr_entries == 0) || stack_depot_disabled)
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goto fast_exit;
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hash = hash_stack(entries, nr_entries);
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bucket = &stack_table[hash & stack_hash_mask];
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/*
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* Fast path: look the stack trace up without locking.
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* The smp_load_acquire() here pairs with smp_store_release() to
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* |bucket| below.
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*/
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found = find_stack(smp_load_acquire(bucket), entries, nr_entries, hash);
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if (found)
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goto exit;
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/*
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* Check if another stack pool needs to be initialized. If so, allocate
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* the memory now - we won't be able to do that under the lock.
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*
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* The smp_load_acquire() here pairs with smp_store_release() to
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* |next_pool_inited| in depot_alloc_stack() and depot_init_pool().
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*/
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if (unlikely(can_alloc && smp_load_acquire(&next_pool_required))) {
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/*
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* Zero out zone modifiers, as we don't have specific zone
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* requirements. Keep the flags related to allocation in atomic
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* contexts and I/O.
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*/
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alloc_flags &= ~GFP_ZONEMASK;
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alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
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alloc_flags |= __GFP_NOWARN;
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page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
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if (page)
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prealloc = page_address(page);
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}
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raw_spin_lock_irqsave(&pool_lock, flags);
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found = find_stack(*bucket, entries, nr_entries, hash);
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if (!found) {
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struct stack_record *new =
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depot_alloc_stack(entries, nr_entries, hash, &prealloc);
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if (new) {
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new->next = *bucket;
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/*
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* This smp_store_release() pairs with
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* smp_load_acquire() from |bucket| above.
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*/
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smp_store_release(bucket, new);
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found = new;
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}
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} else if (prealloc) {
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/*
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* Stack depot already contains this stack trace, but let's
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* keep the preallocated memory for the future.
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*/
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depot_init_pool(&prealloc);
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}
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raw_spin_unlock_irqrestore(&pool_lock, flags);
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exit:
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if (prealloc) {
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/* Stack depot didn't use this memory, free it. */
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free_pages((unsigned long)prealloc, DEPOT_POOL_ORDER);
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}
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if (found)
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retval.handle = found->handle.handle;
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fast_exit:
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return retval.handle;
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}
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EXPORT_SYMBOL_GPL(__stack_depot_save);
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depot_stack_handle_t stack_depot_save(unsigned long *entries,
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unsigned int nr_entries,
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gfp_t alloc_flags)
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{
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return __stack_depot_save(entries, nr_entries, alloc_flags, true);
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}
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EXPORT_SYMBOL_GPL(stack_depot_save);
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unsigned int stack_depot_fetch(depot_stack_handle_t handle,
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unsigned long **entries)
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{
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union handle_parts parts = { .handle = handle };
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/*
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* READ_ONCE pairs with potential concurrent write in
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* depot_alloc_stack.
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*/
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int pool_index_cached = READ_ONCE(pool_index);
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void *pool;
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size_t offset = parts.offset << DEPOT_STACK_ALIGN;
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struct stack_record *stack;
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*entries = NULL;
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if (!handle)
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return 0;
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if (parts.pool_index > pool_index_cached) {
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WARN(1, "pool index %d out of bounds (%d) for stack id %08x\n",
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parts.pool_index, pool_index_cached, handle);
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return 0;
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}
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pool = stack_pools[parts.pool_index];
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if (!pool)
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return 0;
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stack = pool + offset;
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*entries = stack->entries;
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return stack->size;
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}
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EXPORT_SYMBOL_GPL(stack_depot_fetch);
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void stack_depot_print(depot_stack_handle_t stack)
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{
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unsigned long *entries;
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unsigned int nr_entries;
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|
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nr_entries = stack_depot_fetch(stack, &entries);
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if (nr_entries > 0)
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stack_trace_print(entries, nr_entries, 0);
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}
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EXPORT_SYMBOL_GPL(stack_depot_print);
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|
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int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
|
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int spaces)
|
|
{
|
|
unsigned long *entries;
|
|
unsigned int nr_entries;
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|
|
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nr_entries = stack_depot_fetch(handle, &entries);
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|
return nr_entries ? stack_trace_snprint(buf, size, entries, nr_entries,
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|
spaces) : 0;
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}
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|
EXPORT_SYMBOL_GPL(stack_depot_snprint);
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|
|
|
depot_stack_handle_t __must_check stack_depot_set_extra_bits(
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|
depot_stack_handle_t handle, unsigned int extra_bits)
|
|
{
|
|
union handle_parts parts = { .handle = handle };
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|
|
|
/* Don't set extra bits on empty handles. */
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|
if (!handle)
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|
return 0;
|
|
|
|
parts.extra = extra_bits;
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|
return parts.handle;
|
|
}
|
|
EXPORT_SYMBOL(stack_depot_set_extra_bits);
|
|
|
|
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);
|