OSCL-LXR linux-6.0.1/​include/​linux/​kfence.h	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Kernel Electric-Fence (KFENCE). Public interface for allocator and fault
  * handler integration. For more info see Documentation/dev-tools/kfence.rst.
  *
  * Copyright (C) 2020, Google LLC.
  */
 
 #ifndef _LINUX_KFENCE_H
 #define _LINUX_KFENCE_H
 
 #include <linux/mm.h>
 #include <linux/types.h>
 
 #ifdef CONFIG_KFENCE
 
 #include <linux/atomic.h>
 #include <linux/static_key.h>
 
 extern unsigned long kfence_sample_interval;
 
 /*
  * We allocate an even number of pages, as it simplifies calculations to map
  * address to metadata indices; effectively, the very first page serves as an
  * extended guard page, but otherwise has no special purpose.
  */
 #define KFENCE_POOL_SIZE ((CONFIG_KFENCE_NUM_OBJECTS + 1) * 2 * PAGE_SIZE)
 extern char *__kfence_pool;
 
 DECLARE_STATIC_KEY_FALSE(kfence_allocation_key);
 extern atomic_t kfence_allocation_gate;
 
 /**
  * is_kfence_address() - check if an address belongs to KFENCE pool
  * @addr: address to check
  *
  * Return: true or false depending on whether the address is within the KFENCE
  * object range.
  *
  * KFENCE objects live in a separate page range and are not to be intermixed
  * with regular heap objects (e.g. KFENCE objects must never be added to the
  * allocator freelists). Failing to do so may and will result in heap
  * corruptions, therefore is_kfence_address() must be used to check whether
  * an object requires specific handling.
  *
  * Note: This function may be used in fast-paths, and is performance critical.
  * Future changes should take this into account; for instance, we want to avoid
  * introducing another load and therefore need to keep KFENCE_POOL_SIZE a
  * constant (until immediate patching support is added to the kernel).
  */
 static __always_inline bool is_kfence_address(const void *addr)
 {
     /*
      * The __kfence_pool != NULL check is required to deal with the case
      * where __kfence_pool == NULL && addr < KFENCE_POOL_SIZE. Keep it in
      * the slow-path after the range-check!
      */
     return unlikely((unsigned long)((char *)addr - __kfence_pool) < KFENCE_POOL_SIZE && __kfence_pool);
 }
 
 /**
  * kfence_alloc_pool() - allocate the KFENCE pool via memblock
  */
 void __init kfence_alloc_pool(void);
 
 /**
  * kfence_init() - perform KFENCE initialization at boot time
  *
  * Requires that kfence_alloc_pool() was called before. This sets up the
  * allocation gate timer, and requires that workqueues are available.
  */
 void __init kfence_init(void);
 
 /**
  * kfence_shutdown_cache() - handle shutdown_cache() for KFENCE objects
  * @s: cache being shut down
  *
  * Before shutting down a cache, one must ensure there are no remaining objects
  * allocated from it. Because KFENCE objects are not referenced from the cache
  * directly, we need to check them here.
  *
  * Note that shutdown_cache() is internal to SL*B, and kmem_cache_destroy() does
  * not return if allocated objects still exist: it prints an error message and
  * simply aborts destruction of a cache, leaking memory.
  *
  * If the only such objects are KFENCE objects, we will not leak the entire
  * cache, but instead try to provide more useful debug info by making allocated
  * objects "zombie allocations". Objects may then still be used or freed (which
  * is handled gracefully), but usage will result in showing KFENCE error reports
  * which include stack traces to the user of the object, the original allocation
  * site, and caller to shutdown_cache().
  */
 void kfence_shutdown_cache(struct kmem_cache *s);
 
 /*
  * Allocate a KFENCE object. Allocators must not call this function directly,
  * use kfence_alloc() instead.
  */
 void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags);
 
 /**
  * kfence_alloc() - allocate a KFENCE object with a low probability
  * @s:     struct kmem_cache with object requirements
  * @size:  exact size of the object to allocate (can be less than @s->size
  *         e.g. for kmalloc caches)
  * @flags: GFP flags
  *
  * Return:
  * * NULL     - must proceed with allocating as usual,
  * * non-NULL - pointer to a KFENCE object.
  *
  * kfence_alloc() should be inserted into the heap allocation fast path,
  * allowing it to transparently return KFENCE-allocated objects with a low
  * probability using a static branch (the probability is controlled by the
  * kfence.sample_interval boot parameter).
  */
 static __always_inline void *kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
 {
 #if defined(CONFIG_KFENCE_STATIC_KEYS) || CONFIG_KFENCE_SAMPLE_INTERVAL == 0
     if (!static_branch_unlikely(&kfence_allocation_key))
         return NULL;
 #else
     if (!static_branch_likely(&kfence_allocation_key))
         return NULL;
 #endif
     if (likely(atomic_read(&kfence_allocation_gate)))
         return NULL;
     return __kfence_alloc(s, size, flags);
 }
 
 /**
  * kfence_ksize() - get actual amount of memory allocated for a KFENCE object
  * @addr: pointer to a heap object
  *
  * Return:
  * * 0     - not a KFENCE object, must call __ksize() instead,
  * * non-0 - this many bytes can be accessed without causing a memory error.
  *
  * kfence_ksize() returns the number of bytes requested for a KFENCE object at
  * allocation time. This number may be less than the object size of the
  * corresponding struct kmem_cache.
  */
 size_t kfence_ksize(const void *addr);
 
 /**
  * kfence_object_start() - find the beginning of a KFENCE object
  * @addr: address within a KFENCE-allocated object
  *
  * Return: address of the beginning of the object.
  *
  * SL[AU]B-allocated objects are laid out within a page one by one, so it is
  * easy to calculate the beginning of an object given a pointer inside it and
  * the object size. The same is not true for KFENCE, which places a single
  * object at either end of the page. This helper function is used to find the
  * beginning of a KFENCE-allocated object.
  */
 void *kfence_object_start(const void *addr);
 
 /**
  * __kfence_free() - release a KFENCE heap object to KFENCE pool
  * @addr: object to be freed
  *
  * Requires: is_kfence_address(addr)
  *
  * Release a KFENCE object and mark it as freed.
  */
 void __kfence_free(void *addr);
 
 /**
  * kfence_free() - try to release an arbitrary heap object to KFENCE pool
  * @addr: object to be freed
  *
  * Return:
  * * false - object doesn't belong to KFENCE pool and was ignored,
  * * true  - object was released to KFENCE pool.
  *
  * Release a KFENCE object and mark it as freed. May be called on any object,
  * even non-KFENCE objects, to simplify integration of the hooks into the
  * allocator's free codepath. The allocator must check the return value to
  * determine if it was a KFENCE object or not.
  */
 static __always_inline __must_check bool kfence_free(void *addr)
 {
     if (!is_kfence_address(addr))
         return false;
     __kfence_free(addr);
     return true;
 }
 
 /**
  * kfence_handle_page_fault() - perform page fault handling for KFENCE pages
  * @addr: faulting address
  * @is_write: is access a write
  * @regs: current struct pt_regs (can be NULL, but shows full stack trace)
  *
  * Return:
  * * false - address outside KFENCE pool,
  * * true  - page fault handled by KFENCE, no additional handling required.
  *
  * A page fault inside KFENCE pool indicates a memory error, such as an
  * out-of-bounds access, a use-after-free or an invalid memory access. In these
  * cases KFENCE prints an error message and marks the offending page as
  * present, so that the kernel can proceed.
  */
 bool __must_check kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs);
 
 #ifdef CONFIG_PRINTK
 struct kmem_obj_info;
 /**
  * __kfence_obj_info() - fill kmem_obj_info struct
  * @kpp: kmem_obj_info to be filled
  * @object: the object
  *
  * Return:
  * * false - not a KFENCE object
  * * true - a KFENCE object, filled @kpp
  *
  * Copies information to @kpp for KFENCE objects.
  */
 bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab);
 #endif
 
 #else /* CONFIG_KFENCE */
 
 static inline bool is_kfence_address(const void *addr) { return false; }
 static inline void kfence_alloc_pool(void) { }
 static inline void kfence_init(void) { }
 static inline void kfence_shutdown_cache(struct kmem_cache *s) { }
 static inline void *kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) { return NULL; }
 static inline size_t kfence_ksize(const void *addr) { return 0; }
 static inline void *kfence_object_start(const void *addr) { return NULL; }
 static inline void __kfence_free(void *addr) { }
 static inline bool __must_check kfence_free(void *addr) { return false; }
 static inline bool __must_check kfence_handle_page_fault(unsigned long addr, bool is_write,
                              struct pt_regs *regs)
 {
     return false;
 }
 
 #ifdef CONFIG_PRINTK
 struct kmem_obj_info;
 static inline bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
 {
     return false;
 }
 #endif
 
 #endif
 
 #endif /* _LINUX_KFENCE_H */

This page was automatically generated by the 2.1.0 LXR engine. The LXR team