diff options
Diffstat (limited to 'lib/stackdepot.c')
| -rw-r--r-- | lib/stackdepot.c | 250 |
1 files changed, 127 insertions, 123 deletions
diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 5caa1f566553..4a7055a63d9f 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -22,6 +22,7 @@ #include <linux/list.h> #include <linux/mm.h> #include <linux/mutex.h> +#include <linux/poison.h> #include <linux/printk.h> #include <linux/rculist.h> #include <linux/rcupdate.h> @@ -43,17 +44,7 @@ #define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN) #define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \ STACK_DEPOT_EXTRA_BITS) -#if IS_ENABLED(CONFIG_KMSAN) && CONFIG_STACKDEPOT_MAX_FRAMES >= 32 -/* - * KMSAN is frequently used in fuzzing scenarios and thus saves a lot of stack - * traces. As KMSAN does not support evicting stack traces from the stack - * depot, the stack depot capacity might be reached quickly with large stack - * records. Adjust the maximum number of stack depot pools for this case. - */ -#define DEPOT_POOLS_CAP (8192 * (CONFIG_STACKDEPOT_MAX_FRAMES / 16)) -#else #define DEPOT_POOLS_CAP 8192 -#endif #define DEPOT_MAX_POOLS \ (((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \ (1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP) @@ -93,9 +84,6 @@ struct stack_record { }; }; -#define DEPOT_STACK_RECORD_SIZE \ - ALIGN(sizeof(struct stack_record), 1 << DEPOT_STACK_ALIGN) - 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; @@ -121,32 +109,31 @@ static void *stack_pools[DEPOT_MAX_POOLS]; static void *new_pool; /* Number of pools in stack_pools. */ static int pools_num; +/* Offset to the unused space in the currently used pool. */ +static size_t pool_offset = DEPOT_POOL_SIZE; /* Freelist of stack records within stack_pools. */ static LIST_HEAD(free_stacks); -/* - * Stack depot tries to keep an extra pool allocated even before it runs out - * of space in the currently used pool. This flag marks whether this extra pool - * needs to be allocated. It has the value 0 when either an extra pool is not - * yet allocated or if the limit on the number of pools is reached. - */ -static bool new_pool_required = true; /* The lock must be held when performing pool or freelist modifications. */ static DEFINE_RAW_SPINLOCK(pool_lock); /* Statistics counters for debugfs. */ enum depot_counter_id { - DEPOT_COUNTER_ALLOCS, - DEPOT_COUNTER_FREES, - DEPOT_COUNTER_INUSE, + DEPOT_COUNTER_REFD_ALLOCS, + DEPOT_COUNTER_REFD_FREES, + DEPOT_COUNTER_REFD_INUSE, DEPOT_COUNTER_FREELIST_SIZE, + DEPOT_COUNTER_PERSIST_COUNT, + DEPOT_COUNTER_PERSIST_BYTES, DEPOT_COUNTER_COUNT, }; static long counters[DEPOT_COUNTER_COUNT]; static const char *const counter_names[] = { - [DEPOT_COUNTER_ALLOCS] = "allocations", - [DEPOT_COUNTER_FREES] = "frees", - [DEPOT_COUNTER_INUSE] = "in_use", + [DEPOT_COUNTER_REFD_ALLOCS] = "refcounted_allocations", + [DEPOT_COUNTER_REFD_FREES] = "refcounted_frees", + [DEPOT_COUNTER_REFD_INUSE] = "refcounted_in_use", [DEPOT_COUNTER_FREELIST_SIZE] = "freelist_size", + [DEPOT_COUNTER_PERSIST_COUNT] = "persistent_count", + [DEPOT_COUNTER_PERSIST_BYTES] = "persistent_bytes", }; static_assert(ARRAY_SIZE(counter_names) == DEPOT_COUNTER_COUNT); @@ -294,48 +281,52 @@ out_unlock: EXPORT_SYMBOL_GPL(stack_depot_init); /* - * Initializes new stack depot @pool, release all its entries to the freelist, - * and update the list of pools. + * Initializes new stack pool, and updates the list of pools. */ -static void depot_init_pool(void *pool) +static bool depot_init_pool(void **prealloc) { - int offset; - lockdep_assert_held(&pool_lock); - /* Initialize handles and link stack records into the freelist. */ - for (offset = 0; offset <= DEPOT_POOL_SIZE - DEPOT_STACK_RECORD_SIZE; - offset += DEPOT_STACK_RECORD_SIZE) { - struct stack_record *stack = pool + offset; - - stack->handle.pool_index = pools_num; - stack->handle.offset = offset >> DEPOT_STACK_ALIGN; - stack->handle.extra = 0; - - /* - * Stack traces of size 0 are never saved, and we can simply use - * the size field as an indicator if this is a new unused stack - * record in the freelist. - */ - stack->size = 0; + if (unlikely(pools_num >= DEPOT_MAX_POOLS)) { + /* Bail out if we reached the pool limit. */ + WARN_ON_ONCE(pools_num > DEPOT_MAX_POOLS); /* should never happen */ + WARN_ON_ONCE(!new_pool); /* to avoid unnecessary pre-allocation */ + WARN_ONCE(1, "Stack depot reached limit capacity"); + return false; + } - INIT_LIST_HEAD(&stack->hash_list); - /* - * Add to the freelist front to prioritize never-used entries: - * required in case there are entries in the freelist, but their - * RCU cookie still belongs to the current RCU grace period - * (there can still be concurrent readers). - */ - list_add(&stack->free_list, &free_stacks); - counters[DEPOT_COUNTER_FREELIST_SIZE]++; + if (!new_pool && *prealloc) { + /* We have preallocated memory, use it. */ + WRITE_ONCE(new_pool, *prealloc); + *prealloc = NULL; } + if (!new_pool) + return false; /* new_pool and *prealloc are NULL */ + /* Save reference to the pool to be used by depot_fetch_stack(). */ - stack_pools[pools_num] = pool; + stack_pools[pools_num] = new_pool; + + /* + * Stack depot tries to keep an extra pool allocated even before it runs + * out of space in the currently used pool. + * + * To indicate that a new preallocation is needed new_pool is reset to + * NULL; do not reset to NULL if we have reached the maximum number of + * pools. + */ + if (pools_num < DEPOT_MAX_POOLS) + WRITE_ONCE(new_pool, NULL); + else + WRITE_ONCE(new_pool, STACK_DEPOT_POISON); /* Pairs with concurrent READ_ONCE() in depot_fetch_stack(). */ WRITE_ONCE(pools_num, pools_num + 1); ASSERT_EXCLUSIVE_WRITER(pools_num); + + pool_offset = 0; + + return true; } /* Keeps the preallocated memory to be used for a new stack depot pool. */ @@ -347,63 +338,51 @@ static void depot_keep_new_pool(void **prealloc) * If a new pool is already saved or the maximum number of * pools is reached, do not use the preallocated memory. */ - if (!new_pool_required) + if (new_pool) return; - /* - * Use the preallocated memory for the new pool - * as long as we do not exceed the maximum number of pools. - */ - if (pools_num < DEPOT_MAX_POOLS) { - new_pool = *prealloc; - *prealloc = NULL; - } - - /* - * At this point, either a new pool is kept or the maximum - * number of pools is reached. In either case, take note that - * keeping another pool is not required. - */ - WRITE_ONCE(new_pool_required, false); + WRITE_ONCE(new_pool, *prealloc); + *prealloc = NULL; } /* - * Try to initialize a new stack depot pool from either a previous or the - * current pre-allocation, and release all its entries to the freelist. + * Try to initialize a new stack record from the current pool, a cached pool, or + * the current pre-allocation. */ -static bool depot_try_init_pool(void **prealloc) +static struct stack_record *depot_pop_free_pool(void **prealloc, size_t size) { + struct stack_record *stack; + void *current_pool; + u32 pool_index; + lockdep_assert_held(&pool_lock); - /* Check if we have a new pool saved and use it. */ - if (new_pool) { - depot_init_pool(new_pool); - new_pool = NULL; + if (pool_offset + size > DEPOT_POOL_SIZE) { + if (!depot_init_pool(prealloc)) + return NULL; + } - /* Take note that we might need a new new_pool. */ - if (pools_num < DEPOT_MAX_POOLS) - WRITE_ONCE(new_pool_required, true); + if (WARN_ON_ONCE(pools_num < 1)) + return NULL; + pool_index = pools_num - 1; + current_pool = stack_pools[pool_index]; + if (WARN_ON_ONCE(!current_pool)) + return NULL; - return true; - } + stack = current_pool + pool_offset; - /* Bail out if we reached the pool limit. */ - if (unlikely(pools_num >= DEPOT_MAX_POOLS)) { - WARN_ONCE(1, "Stack depot reached limit capacity"); - return false; - } + /* Pre-initialize handle once. */ + stack->handle.pool_index = pool_index; + stack->handle.offset = pool_offset >> DEPOT_STACK_ALIGN; + stack->handle.extra = 0; + INIT_LIST_HEAD(&stack->hash_list); - /* Check if we have preallocated memory and use it. */ - if (*prealloc) { - depot_init_pool(*prealloc); - *prealloc = NULL; - return true; - } + pool_offset += size; - return false; + return stack; } -/* Try to find next free usable entry. */ +/* Try to find next free usable entry from the freelist. */ static struct stack_record *depot_pop_free(void) { struct stack_record *stack; @@ -420,7 +399,7 @@ static struct stack_record *depot_pop_free(void) * check the first entry. */ stack = list_first_entry(&free_stacks, struct stack_record, free_list); - if (stack->size && !poll_state_synchronize_rcu(stack->rcu_state)) + if (!poll_state_synchronize_rcu(stack->rcu_state)) return NULL; list_del(&stack->free_list); @@ -429,48 +408,73 @@ static struct stack_record *depot_pop_free(void) return stack; } +static inline size_t depot_stack_record_size(struct stack_record *s, unsigned int nr_entries) +{ + const size_t used = flex_array_size(s, entries, nr_entries); + const size_t unused = sizeof(s->entries) - used; + + WARN_ON_ONCE(sizeof(s->entries) < used); + + return ALIGN(sizeof(struct stack_record) - unused, 1 << DEPOT_STACK_ALIGN); +} + /* Allocates a new stack in a stack depot pool. */ static struct stack_record * -depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) +depot_alloc_stack(unsigned long *entries, unsigned int nr_entries, u32 hash, depot_flags_t flags, void **prealloc) { - struct stack_record *stack; + struct stack_record *stack = NULL; + size_t record_size; lockdep_assert_held(&pool_lock); /* This should already be checked by public API entry points. */ - if (WARN_ON_ONCE(!size)) + if (WARN_ON_ONCE(!nr_entries)) return NULL; - /* Check if we have a stack record to save the stack trace. */ - stack = depot_pop_free(); - if (!stack) { - /* No usable entries on the freelist - try to refill the freelist. */ - if (!depot_try_init_pool(prealloc)) - return NULL; + /* Limit number of saved frames to CONFIG_STACKDEPOT_MAX_FRAMES. */ + if (nr_entries > CONFIG_STACKDEPOT_MAX_FRAMES) + nr_entries = CONFIG_STACKDEPOT_MAX_FRAMES; + + if (flags & STACK_DEPOT_FLAG_GET) { + /* + * Evictable entries have to allocate the max. size so they may + * safely be re-used by differently sized allocations. + */ + record_size = depot_stack_record_size(stack, CONFIG_STACKDEPOT_MAX_FRAMES); stack = depot_pop_free(); - if (WARN_ON(!stack)) - return NULL; + } else { + record_size = depot_stack_record_size(stack, nr_entries); } - /* Limit number of saved frames to CONFIG_STACKDEPOT_MAX_FRAMES. */ - if (size > CONFIG_STACKDEPOT_MAX_FRAMES) - size = CONFIG_STACKDEPOT_MAX_FRAMES; + if (!stack) { + stack = depot_pop_free_pool(prealloc, record_size); + if (!stack) + return NULL; + } /* Save the stack trace. */ stack->hash = hash; - stack->size = size; - /* stack->handle is already filled in by depot_init_pool(). */ - refcount_set(&stack->count, 1); - memcpy(stack->entries, entries, flex_array_size(stack, entries, size)); + stack->size = nr_entries; + /* stack->handle is already filled in by depot_pop_free_pool(). */ + memcpy(stack->entries, entries, flex_array_size(stack, entries, nr_entries)); + + if (flags & STACK_DEPOT_FLAG_GET) { + refcount_set(&stack->count, 1); + counters[DEPOT_COUNTER_REFD_ALLOCS]++; + counters[DEPOT_COUNTER_REFD_INUSE]++; + } else { + /* Warn on attempts to switch to refcounting this entry. */ + refcount_set(&stack->count, REFCOUNT_SATURATED); + counters[DEPOT_COUNTER_PERSIST_COUNT]++; + counters[DEPOT_COUNTER_PERSIST_BYTES] += record_size; + } /* * Let KMSAN know the stored stack record is initialized. This shall * prevent false positive reports if instrumented code accesses it. */ - kmsan_unpoison_memory(stack, DEPOT_STACK_RECORD_SIZE); + kmsan_unpoison_memory(stack, record_size); - counters[DEPOT_COUNTER_ALLOCS]++; - counters[DEPOT_COUNTER_INUSE]++; return stack; } @@ -538,8 +542,8 @@ static void depot_free_stack(struct stack_record *stack) list_add_tail(&stack->free_list, &free_stacks); counters[DEPOT_COUNTER_FREELIST_SIZE]++; - counters[DEPOT_COUNTER_FREES]++; - counters[DEPOT_COUNTER_INUSE]--; + counters[DEPOT_COUNTER_REFD_FREES]++; + counters[DEPOT_COUNTER_REFD_INUSE]--; printk_deferred_exit(); raw_spin_unlock_irqrestore(&pool_lock, flags); @@ -660,7 +664,7 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries, * Allocate memory for a new pool if required now: * we won't be able to do that under the lock. */ - if (unlikely(can_alloc && READ_ONCE(new_pool_required))) { + if (unlikely(can_alloc && !READ_ONCE(new_pool))) { /* * Zero out zone modifiers, as we don't have specific zone * requirements. Keep the flags related to allocation in atomic @@ -681,7 +685,7 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries, found = find_stack(bucket, entries, nr_entries, hash, depot_flags); if (!found) { struct stack_record *new = - depot_alloc_stack(entries, nr_entries, hash, &prealloc); + depot_alloc_stack(entries, nr_entries, hash, depot_flags, &prealloc); if (new) { /* |