From fc0e5b91dfe4420a3f26bde36ee232aa8c6ded5d Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Thu, 12 May 2022 20:23:08 -0700 Subject: [PATCH] kasan: clean up comments in internal kasan.h Clean up comments in mm/kasan/kasan.h: clarify, unify styles, fix punctuation, etc. Link: https://lkml.kernel.org/r/a0680ff30035b56cb7bdd5f59fd400e71712ceb5.1652111464.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Alexander Potapenko Cc: Marco Elver Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Andrey Ryabinin Signed-off-by: Andrew Morton --- mm/kasan/kasan.h | 74 +++++++++++++++++++++--------------------------- 1 file changed, 33 insertions(+), 41 deletions(-) diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index b01b4bbe0409..fed4f7a00d33 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -42,6 +42,7 @@ static inline bool kasan_sync_fault_possible(void) { return kasan_mode == KASAN_MODE_SYNC || kasan_mode == KASAN_MODE_ASYMM; } + #else static inline bool kasan_stack_collection_enabled(void) @@ -73,47 +74,41 @@ static inline bool kasan_sync_fault_possible(void) #define KASAN_MEMORY_PER_SHADOW_PAGE (KASAN_GRANULE_SIZE << PAGE_SHIFT) #ifdef CONFIG_KASAN_GENERIC -#define KASAN_FREE_PAGE 0xFF /* page was freed */ -#define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocations */ -#define KASAN_KMALLOC_REDZONE 0xFC /* redzone inside slub object */ -#define KASAN_KMALLOC_FREE 0xFB /* object was freed (kmem_cache_free/kfree) */ -#define KASAN_VMALLOC_INVALID 0xF8 /* unallocated space in vmapped page */ +#define KASAN_FREE_PAGE 0xFF /* freed page */ +#define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocation */ +#define KASAN_KMALLOC_REDZONE 0xFC /* redzone for slab object */ +#define KASAN_KMALLOC_FREE 0xFB /* freed slab object */ +#define KASAN_VMALLOC_INVALID 0xF8 /* inaccessible space in vmap area */ #else #define KASAN_FREE_PAGE KASAN_TAG_INVALID #define KASAN_PAGE_REDZONE KASAN_TAG_INVALID #define KASAN_KMALLOC_REDZONE KASAN_TAG_INVALID #define KASAN_KMALLOC_FREE KASAN_TAG_INVALID -#define KASAN_VMALLOC_INVALID KASAN_TAG_INVALID /* only for SW_TAGS */ +#define KASAN_VMALLOC_INVALID KASAN_TAG_INVALID /* only used for SW_TAGS */ #endif #ifdef CONFIG_KASAN_GENERIC -#define KASAN_KMALLOC_FREETRACK 0xFA /* object was freed and has free track set */ +#define KASAN_KMALLOC_FREETRACK 0xFA /* freed slab object with free track */ #define KASAN_GLOBAL_REDZONE 0xF9 /* redzone for global variable */ -/* - * Stack redzone shadow values - * (Those are compiler's ABI, don't change them) - */ +/* Stack redzone shadow values. Compiler ABI, do not change. */ #define KASAN_STACK_LEFT 0xF1 #define KASAN_STACK_MID 0xF2 #define KASAN_STACK_RIGHT 0xF3 #define KASAN_STACK_PARTIAL 0xF4 -/* - * alloca redzone shadow values - */ +/* alloca redzone shadow values. */ #define KASAN_ALLOCA_LEFT 0xCA #define KASAN_ALLOCA_RIGHT 0xCB +/* alloca redzone size. Compiler ABI, do not change. */ #define KASAN_ALLOCA_REDZONE_SIZE 32 -/* - * Stack frame marker (compiler ABI). - */ +/* Stack frame marker. Compiler ABI, do not change. */ #define KASAN_CURRENT_STACK_FRAME_MAGIC 0x41B58AB3 -/* Don't break randconfig/all*config builds */ +/* Dummy value to avoid breaking randconfig/all*config builds. */ #ifndef KASAN_ABI_VERSION #define KASAN_ABI_VERSION 1 #endif @@ -141,21 +136,21 @@ struct kasan_report_info { unsigned long ip; }; -/* The layout of struct dictated by compiler */ +/* Do not change the struct layout: compiler ABI. */ struct kasan_source_location { const char *filename; int line_no; int column_no; }; -/* The layout of struct dictated by compiler */ +/* Do not change the struct layout: compiler ABI. */ struct kasan_global { const void *beg; /* Address of the beginning of the global variable. */ size_t size; /* Size of the global variable. */ - size_t size_with_redzone; /* Size of the variable + size of the red zone. 32 bytes aligned */ + size_t size_with_redzone; /* Size of the variable + size of the redzone. 32 bytes aligned. */ const void *name; const void *module_name; /* Name of the module where the global variable is declared. */ - unsigned long has_dynamic_init; /* This needed for C++ */ + unsigned long has_dynamic_init; /* This is needed for C++. */ #if KASAN_ABI_VERSION >= 4 struct kasan_source_location *location; #endif @@ -164,9 +159,7 @@ struct kasan_global { #endif }; -/** - * Structures to keep alloc and free tracks * - */ +/* Structures for keeping alloc and free tracks. */ #define KASAN_STACK_DEPTH 64 @@ -183,11 +176,8 @@ struct kasan_track { struct kasan_alloc_meta { struct kasan_track alloc_track; + /* Generic mode stores free track in kasan_free_meta. */ #ifdef CONFIG_KASAN_GENERIC - /* - * The auxiliary stack is stored into struct kasan_alloc_meta. - * The free stack is stored into struct kasan_free_meta. - */ depot_stack_handle_t aux_stack[2]; #else struct kasan_track free_track[KASAN_NR_FREE_STACKS]; @@ -203,18 +193,18 @@ struct qlist_node { }; /* - * Generic mode either stores free meta in the object itself or in the redzone - * after the object. In the former case free meta offset is 0, in the latter - * case it has some sane value smaller than INT_MAX. Use INT_MAX as free meta - * offset when free meta isn't present. + * Free meta is stored either in the object itself or in the redzone after the + * object. In the former case, free meta offset is 0. In the latter case, the + * offset is between 0 and INT_MAX. INT_MAX marks that free meta is not present. */ #define KASAN_NO_FREE_META INT_MAX +/* + * Free meta is only used by Generic mode while the object is in quarantine. + * After that, slab allocator stores the freelist pointer in the object. + */ struct kasan_free_meta { #ifdef CONFIG_KASAN_GENERIC - /* This field is used while the object is in the quarantine. - * Otherwise it might be used for the allocator freelist. - */ struct qlist_node quarantine_link; struct kasan_track free_track; #endif @@ -417,9 +407,10 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) return; /* * Explicitly initialize the memory with the precise object size to - * avoid overwriting the SLAB redzone. This disables initialization in - * the arch code and may thus lead to performance penalty. The penalty - * is accepted since SLAB redzones aren't enabled in production builds. + * avoid overwriting the slab redzone. This disables initialization in + * the arch code and may thus lead to performance penalty. This penalty + * does not affect production builds, as slab redzones are not enabled + * there. */ if (__slub_debug_enabled() && init && ((unsigned long)size & KASAN_GRANULE_MASK)) { @@ -503,8 +494,9 @@ void kasan_restore_multi_shot(bool enabled); /* * Exported functions for interfaces called from assembly or from generated - * code. Declarations here to avoid warning about missing declarations. + * code. Declared here to avoid warnings about missing declarations. */ + asmlinkage void kasan_unpoison_task_stack_below(const void *watermark); void __asan_register_globals(struct kasan_global *globals, size_t size); void __asan_unregister_globals(struct kasan_global *globals, size_t size); @@ -573,4 +565,4 @@ void __hwasan_storeN_noabort(unsigned long addr, size_t size); void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size); -#endif +#endif /* __MM_KASAN_KASAN_H */