From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Add comments to stack_depot_early_init and stack_depot_init to explain certain parts of their implementation. Also add a pr_info message to stack_depot_early_init similar to the one in stack_depot_init. Also move the scale variable in stack_depot_init to the scope where it is being used. Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> --- lib/stackdepot.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 202e07c4f02d..9fab711e4826 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -115,24 +115,34 @@ void __init stack_depot_request_early_init(void) __stack_depot_early_init_requested = true; } +/* Allocates a hash table via memblock. Can only be used during early boot. */ int __init stack_depot_early_init(void) { unsigned long entries = 0; - /* This is supposed to be called only once, from mm_init() */ + /* This function must 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 is enabled, use the maximum order: KASAN is frequently used + * in fuzzing scenarios, which leads to a large number of different + * stack traces being stored in stack depot. + */ 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 is not set, leave entries as 0 to rely on the + * automatic calculations performed by alloc_large_system_hash. + */ if (stack_hash_order) - entries = 1UL << stack_hash_order; + entries = 1UL << stack_hash_order; + pr_info("allocating hash table via alloc_large_system_hash\n"); stack_table = alloc_large_system_hash("stackdepot", sizeof(struct stack_record *), entries, @@ -142,7 +152,6 @@ int __init stack_depot_early_init(void) &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; @@ -152,6 +161,7 @@ int __init stack_depot_early_init(void) return 0; } +/* Allocates a hash table via kvcalloc. Can be used after boot. */ int stack_depot_init(void) { static DEFINE_MUTEX(stack_depot_init_mutex); @@ -160,11 +170,16 @@ int stack_depot_init(void) mutex_lock(&stack_depot_init_mutex); if (!stack_depot_disabled && !stack_table) { unsigned long entries; - int scale = STACK_HASH_SCALE; + /* + * Similarly to stack_depot_early_init, use stack_hash_order + * if assigned, and rely on automatic scaling otherwise. + */ if (stack_hash_order) { entries = 1UL << stack_hash_order; } else { + int scale = STACK_HASH_SCALE; + entries = nr_free_buffer_pages(); entries = roundup_pow_of_two(entries); @@ -179,7 +194,7 @@ int stack_depot_init(void) if (entries > 1UL << STACK_HASH_ORDER_MAX) entries = 1UL << STACK_HASH_ORDER_MAX; - pr_info("allocating hash table of %lu entries with kvcalloc\n", + pr_info("allocating hash table of %lu entries via kvcalloc\n", entries); stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL); if (!stack_table) { -- 2.25.1