linux/lib/stackdepot.c
Andrey Konovalov 735df3c3a3 lib/stackdepot: rename stack_depot_disable
Rename stack_depot_disable to stack_depot_disabled to make its name look
similar to the names of other stack depot flags.

Also put stack_depot_disabled's definition together with the other flags.

Also rename is_stack_depot_disabled to disable_stack_depot: this name
looks more conventional for a function that processes a boot parameter.

No functional changes.

Link: https://lkml.kernel.org/r/d78a07d222e689926e5ead229e4a2e3d87dc9aa7.1676063693.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>
2023-02-16 20:43:49 -08:00

538 lines
15 KiB
C

// 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.
*/
#define pr_fmt(fmt) "stackdepot: " fmt
#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_disabled;
static bool __stack_depot_early_init_requested __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);
/* 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 struct stack_record **stack_table;
static int __init disable_stack_depot(char *str)
{
int ret;
ret = kstrtobool(str, &stack_depot_disabled);
if (!ret && stack_depot_disabled) {
pr_info("disabled\n");
stack_table = NULL;
}
return 0;
}
early_param("stack_depot_disable", disable_stack_depot);
void __init stack_depot_request_early_init(void)
{
/* Too late to request early init now. */
WARN_ON(__stack_depot_early_init_passed);
__stack_depot_early_init_requested = 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_early_init_requested || stack_depot_disabled)
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("hash table allocation failed, disabling\n");
stack_depot_disabled = 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_disabled && !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("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("hash table allocation failed, disabling\n");
stack_depot_disabled = true;
ret = -ENOMEM;
}
stack_hash_mask = entries - 1;
}
mutex_unlock(&stack_depot_init_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(stack_depot_init);
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;
}
/* 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_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_disabled)
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);
/**
* 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_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_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);
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);