[PATCH v2 14/19] lib/stackdepot, kasan: add flags to __stack_depot_save and rename

andrey.konovalov
2023-09-13T17:17:29Z

From: Andrey Konovalov <andreyknvl@google.com>

Change the bool can_alloc argument of __stack_depot_save to a
u32 argument that accepts a set of flags.

The following patch will add another flag to stack_depot_save_flags
besides the existing STACK_DEPOT_FLAG_CAN_ALLOC.

Also rename the function to stack_depot_save_flags, as __stack_depot_save
is a cryptic name,

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

---

Changes v1->v2:
- This is a new patch.
---
include/linux/stackdepot.h | 36 +++++++++++++++++++++++++-----------
lib/stackdepot.c | 16 +++++++++++-----
mm/kasan/common.c | 7 ++++---
mm/kasan/generic.c | 9 +++++----
mm/kasan/kasan.h | 2 +-
mm/kasan/tags.c | 3 ++-
6 files changed, 48 insertions(+), 25 deletions(-)

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index e58306783d8e..0b262e14144e 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -32,6 +32,17 @@ typedef u32 depot_stack_handle_t;
*/
#define STACK_DEPOT_EXTRA_BITS 5

+typedef u32 depot_flags_t;
+
+/*
+ * Flags that can be passed to stack_depot_save_flags(); see the comment next
+ * to its declaration for more details.
+ */
+#define STACK_DEPOT_FLAG_CAN_ALLOC ((depot_flags_t)0x0001)
+
+#define STACK_DEPOT_FLAGS_NUM 1
+#define STACK_DEPOT_FLAGS_MASK ((depot_flags_t)((1 << STACK_DEPOT_FLAGS_NUM) - 1))
+
/*
* Using stack depot requires its initialization, which can be done in 3 ways:
*
@@ -69,31 +80,34 @@ static inline int stack_depot_early_init(void) { return 0; }
#endif

/**
- * __stack_depot_save - Save a stack trace to stack depot
+ * stack_depot_save_flags - Save a stack trace to stack depot
*
* @entries: Pointer to the stack trace
* @nr_entries: Number of frames in the stack
* @alloc_flags: Allocation GFP flags
- * @can_alloc: Allocate stack pools (increased chance of failure if false)
+ * @depot_flags: Stack depot flags
+ *
+ * Saves a stack trace from @entries array of size @nr_entries.
*
- * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
- * %true, stack depot can replenish the stack pools in case no space is left
- * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
- * any allocations and fails if no space is left to store the stack trace.
+ * If STACK_DEPOT_FLAG_CAN_ALLOC is set in @depot_flags, stack depot can
+ * replenish the stack pools in case no space is left (allocates using GFP
+ * flags of @alloc_flags). Otherwise, stack depot avoids any allocations and
+ * fails if no space is left to store the stack trace.
*
* If the provided stack trace comes from the interrupt context, only the part
* up to the interrupt entry is saved.
*
- * Context: Any context, but setting @can_alloc to %false is required if
+ * Context: Any context, but setting STACK_DEPOT_FLAG_CAN_ALLOC is required if
* alloc_pages() cannot be used from the current context. Currently
* this is the case for contexts where neither %GFP_ATOMIC nor
* %GFP_NOWAIT can be used (NMI, raw_spin_lock).
*
* Return: Handle of the stack struct stored in depot, 0 on failure
*/
-depot_stack_handle_t __stack_depot_save(unsigned long *entries,
- unsigned int nr_entries,
- gfp_t gfp_flags, bool can_alloc);
+depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t gfp_flags,
+ depot_flags_t depot_flags);

/**
* stack_depot_save - Save a stack trace to stack depot
@@ -103,7 +117,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
* @alloc_flags: Allocation GFP flags
*
* Context: Contexts where allocations via alloc_pages() are allowed.
- * See __stack_depot_save() for more details.
+ * See stack_depot_save_flags() for more details.
*
* Return: Handle of the stack trace stored in depot, 0 on failure
*/
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 1b08897ebd2b..e5121225f124 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -438,19 +438,24 @@ static inline struct stack_record *find_stack(struct list_head *bucket,
return NULL;
}

-depot_stack_handle_t __stack_depot_save(unsigned long *entries,
- unsigned int nr_entries,
- gfp_t alloc_flags, bool can_alloc)
+depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t alloc_flags,
+ depot_flags_t depot_flags)
{
struct list_head *bucket;
struct stack_record *found = NULL;
depot_stack_handle_t handle = 0;
struct page *page = NULL;
void *prealloc = NULL;
+ bool can_alloc = depot_flags & STACK_DEPOT_FLAG_CAN_ALLOC;
bool need_alloc = false;
unsigned long flags;
u32 hash;

+ if (depot_flags & ~STACK_DEPOT_FLAGS_MASK)
+ return 0;
+
/*
* If this stack trace is from an interrupt, including anything before
* interrupt entry usually leads to unbounded stack depot growth.
@@ -529,13 +534,14 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
handle = found->handle.handle;
return handle;
}
-EXPORT_SYMBOL_GPL(__stack_depot_save);
+EXPORT_SYMBOL_GPL(stack_depot_save_flags);

depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
gfp_t alloc_flags)
{
- return __stack_depot_save(entries, nr_entries, alloc_flags, true);
+ return stack_depot_save_flags(entries, nr_entries, alloc_flags,
+ STACK_DEPOT_FLAG_CAN_ALLOC);
}
EXPORT_SYMBOL_GPL(stack_depot_save);

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 256930da578a..825a0240ec02 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -22,6 +22,7 @@
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
+#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
@@ -37,19 +38,19 @@ struct slab *kasan_addr_to_slab(const void *addr)
return NULL;
}

-depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc)
+depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags)
{
unsigned long entries[KASAN_STACK_DEPTH];
unsigned int nr_entries;

nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
- return __stack_depot_save(entries, nr_entries, flags, can_alloc);
+ return stack_depot_save_flags(entries, nr_entries, flags, depot_flags);
}

void kasan_set_track(struct kasan_track *track, gfp_t flags)
{
track->pid = current->pid;
- track->stack = kasan_save_stack(flags, true);
+ track->stack = kasan_save_stack(flags, STACK_DEPOT_FLAG_CAN_ALLOC);
}

#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 4d837ab83f08..5d168c9afb32 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -25,6 +25,7 @@
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
+#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
@@ -472,7 +473,7 @@ size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
sizeof(struct kasan_free_meta) : 0);
}

-static void __kasan_record_aux_stack(void *addr, bool can_alloc)
+static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
{
struct slab *slab = kasan_addr_to_slab(addr);
struct kmem_cache *cache;
@@ -489,17 +490,17 @@ static void __kasan_record_aux_stack(void *addr, bool can_alloc)
return;

alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
- alloc_meta->aux_stack[0] = kasan_save_stack(0, can_alloc);
+ alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);
}

void kasan_record_aux_stack(void *addr)
{
- return __kasan_record_aux_stack(addr, true);
+ return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC);
}

void kasan_record_aux_stack_noalloc(void *addr)
{
- return __kasan_record_aux_stack(addr, false);
+ return __kasan_record_aux_stack(addr, 0);
}

void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index f70e3d7a602e..de3206e11888 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -370,7 +370,7 @@ static inline void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int
static inline void kasan_init_object_meta(struct kmem_cache *cache, const void *object) { }
#endif

-depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc);
+depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags);
void kasan_set_track(struct kasan_track *track, gfp_t flags);
void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags);
void kasan_save_free_info(struct kmem_cache *cache, void *object);
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 7dcfe341d48e..4fd32121b0fd 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -13,6 +13,7 @@
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
+#include <linux/stackdepot.h>
#include <linux/static_key.h>
#include <linux/string.h>
#include <linux/types.h>
@@ -101,7 +102,7 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
struct kasan_stack_ring_entry *entry;
void *old_ptr;

- stack = kasan_save_stack(gfp_flags, true);
+ stack = kasan_save_stack(gfp_flags, STACK_DEPOT_FLAG_CAN_ALLOC);

/*
* Prevent save_stack_info() from modifying stack ring
--
2.25.1