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Message-Id: <a0680ff30035b56cb7bdd5f59fd400e71712ceb5.1652111464.git.andreyknvl@google.com>
Date: Mon, 9 May 2022 17:51:34 +0200
From: andrey.konovalov@...ux.dev
To: Marco Elver <elver@...gle.com>,
Alexander Potapenko <glider@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
kasan-dev@...glegroups.com,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v2 1/3] kasan: clean up comments in internal kasan.h
From: Andrey Konovalov <andreyknvl@...gle.com>
Clean up comments in mm/kasan/kasan.h: clarify, unify styles, fix
punctuation, etc.
Reviewed-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
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 */
--
2.25.1
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