linux-imx

// 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 contiguos 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/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>

​

#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)

#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;

    };

};

​

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;