diff options
| -rw-r--r-- | Documentation/dev-tools/kfence.rst | 7 | ||||
| -rw-r--r-- | include/linux/kfence.h | 2 | ||||
| -rw-r--r-- | mm/kfence/core.c | 14 |
3 files changed, 18 insertions, 5 deletions
diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst index 936f6aaa75c8..541899353865 100644 --- a/Documentation/dev-tools/kfence.rst +++ b/Documentation/dev-tools/kfence.rst @@ -53,6 +53,13 @@ configurable via the Kconfig option ``CONFIG_KFENCE_DEFERRABLE``. The KUnit test suite is very likely to fail when using a deferrable timer since it currently causes very unpredictable sample intervals. +By default KFENCE will only sample 1 heap allocation within each sample +interval. *Burst mode* allows to sample successive heap allocations, where the +kernel boot parameter ``kfence.burst`` can be set to a non-zero value which +denotes the *additional* successive allocations within a sample interval; +setting ``kfence.burst=N`` means that ``1 + N`` successive allocations are +attempted through KFENCE for each sample interval. + The KFENCE memory pool is of fixed size, and if the pool is exhausted, no further KFENCE allocations occur. With ``CONFIG_KFENCE_NUM_OBJECTS`` (default 255), the number of available guarded objects can be controlled. Each object diff --git a/include/linux/kfence.h b/include/linux/kfence.h index 88100cc9caba..0ad1ddbb8b99 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -124,7 +124,7 @@ static __always_inline void *kfence_alloc(struct kmem_cache *s, size_t size, gfp if (!static_branch_likely(&kfence_allocation_key)) return NULL; #endif - if (likely(atomic_read(&kfence_allocation_gate))) + if (likely(atomic_read(&kfence_allocation_gate) > 0)) return NULL; return __kfence_alloc(s, size, flags); } diff --git a/mm/kfence/core.c b/mm/kfence/core.c index c5cb54fc696d..c3ef7eb8d4dc 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -99,6 +99,10 @@ module_param_cb(sample_interval, &sample_interval_param_ops, &kfence_sample_inte static unsigned long kfence_skip_covered_thresh __read_mostly = 75; module_param_named(skip_covered_thresh, kfence_skip_covered_thresh, ulong, 0644); +/* Allocation burst count: number of excess KFENCE allocations per sample. */ +static unsigned int kfence_burst __read_mostly; +module_param_named(burst, kfence_burst, uint, 0644); + /* If true, use a deferrable timer. */ static bool kfence_deferrable __read_mostly = IS_ENABLED(CONFIG_KFENCE_DEFERRABLE); module_param_named(deferrable, kfence_deferrable, bool, 0444); @@ -827,12 +831,12 @@ static void toggle_allocation_gate(struct work_struct *work) if (!READ_ONCE(kfence_enabled)) return; - atomic_set(&kfence_allocation_gate, 0); + atomic_set(&kfence_allocation_gate, -kfence_burst); #ifdef CONFIG_KFENCE_STATIC_KEYS /* Enable static key, and await allocation to happen. */ static_branch_enable(&kfence_allocation_key); - wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate)); + wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate) > 0); /* Disable static key and reset timer. */ static_branch_disable(&kfence_allocation_key); @@ -1052,6 +1056,7 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) unsigned long stack_entries[KFENCE_STACK_DEPTH]; size_t num_stack_entries; u32 alloc_stack_hash; + int allocation_gate; /* * Perform size check before switching kfence_allocation_gate, so that @@ -1080,14 +1085,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) if (s->flags & SLAB_SKIP_KFENCE) return NULL; - if (atomic_inc_return(&kfence_allocation_gate) > 1) + allocation_gate = atomic_inc_return(&kfence_allocation_gate); + if (allocation_gate > 1) return NULL; #ifdef CONFIG_KFENCE_STATIC_KEYS /* * waitqueue_active() is fully ordered after the update of * kfence_allocation_gate per atomic_inc_return(). */ - if (waitqueue_active(&allocation_wait)) { + if (allocation_gate == 1 && waitqueue_active(&allocation_wait)) { /* * Calling wake_up() here may deadlock when allocations happen * from within timer code. Use an irq_work to defer it. |