On Mon, Feb 13, 2023 at 2:28 PM Alexander Potapenko <glider@google.com> wrote:
>
> On Fri, Feb 10, 2023 at 10:19 PM <andrey.konovalov@linux.dev> wrote:
> >
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Move all interface- and usage-related documentation comments to
> > include/linux/stackdepot.h.
> >
> > It makes sense to have them in the header where they are available to
> > the interface users.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Reviewed-by: Alexander Potapenko <glider@google.com>
>
> > + * For example, KASAN needs to save allocation and free stack traces for each
> > + * object. Storing two stack traces per object requires a lot of memory (e.g.
> > + * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
> > + * stack traces often repeat, using stack depot allows to save about 100x space.
> > + *
> > + * Stack traces are never removed from stack depot.
> ... from the stack depot?
I avoided using "the" for stack depot everywhere to make comments a
bit shorter, but I don't mind using it.
I see that Andrew already added a fix for this. There are other places
where "stack depot" is used without "the", but lets save this for
future clean-ups too.
Thanks!
@@ -2,6 +2,17 @@
/*
* Stack depot - a stack trace storage that avoids duplication.
*
+ * Stack depot is intended to be used by subsystems that need to store and
+ * later retrieve many potentially duplicated stack traces without wasting
+ * memory.
+ *
+ * For example, KASAN needs to save allocation and free stack traces for each
+ * object. Storing two stack traces per object requires a lot of memory (e.g.
+ * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
+ * stack traces often repeat, using stack depot allows to save about 100x space.
+ *
+ * Stack traces are never removed from stack depot.
+ *
* Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc.
*
@@ -57,24 +68,100 @@ static inline void stack_depot_request_early_init(void) { }
static inline int stack_depot_early_init(void) { return 0; }
#endif
+/**
+ * __stack_depot_save - 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)
+ *
+ * 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 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
+ * 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);
+/**
+ * stack_depot_save - 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
+ *
+ * Context: Contexts where allocations via alloc_pages() are allowed.
+ * See __stack_depot_save() for more details.
+ *
+ * Return: Handle of the stack trace stored in depot, 0 on failure
+ */
depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries, gfp_t gfp_flags);
+/**
+ * stack_depot_fetch - Fetch a stack trace from stack depot
+ *
+ * @handle: Stack depot handle returned from stack_depot_save()
+ * @entries: Pointer to store the address of the stack trace
+ *
+ * Return: Number of frames for the fetched stack
+ */
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries);
+/**
+ * stack_depot_print - Print a stack trace from stack depot
+ *
+ * @stack: Stack depot handle returned from stack_depot_save()
+ */
void stack_depot_print(depot_stack_handle_t stack);
+/**
+ * stack_depot_snprint - Print a stack trace from stack depot into a buffer
+ *
+ * @handle: Stack depot handle returned from stack_depot_save()
+ * @buf: Pointer to the print buffer
+ * @size: Size of the print buffer
+ * @spaces: Number of leading spaces to print
+ *
+ * Return: Number of bytes printed
+ */
int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
int spaces);
+/**
+ * stack_depot_set_extra_bits - Set extra bits in a stack depot handle
+ *
+ * @handle: Stack depot handle returned from stack_depot_save()
+ * @extra_bits: Value to set the extra bits
+ *
+ * Return: Stack depot handle with extra bits set
+ *
+ * Stack depot handles have a few unused bits, which can be used for storing
+ * user-specific information. These bits are transparent to the stack depot.
+ */
depot_stack_handle_t __must_check stack_depot_set_extra_bits(
depot_stack_handle_t handle, unsigned int extra_bits);
+/**
+ * stack_depot_get_extra_bits - Retrieve extra bits from a stack depot handle
+ *
+ * @handle: Stack depot handle with extra bits saved
+ *
+ * Return: Extra bits retrieved from the stack depot handle
+ */
unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle);
#endif
@@ -2,21 +2,10 @@
/*
* Stack depot - a stack trace storage that avoids duplication.
*
- * Stack depot is intended to be used by subsystems that need to store and
- * later retrieve many potentially duplicated stack traces without wasting
- * memory.
- *
- * For example, KASAN needs to save allocation and free stack traces for each
- * object. Storing two stack traces per object requires a lot of memory (e.g.
- * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
- * stack traces often repeat, using stack depot allows to save about 100x space.
- *
* Internally, stack depot maintains a hash table of unique stacktraces. The
* stack traces themselves are stored contiguously one after another in a set
* of separate page allocations.
*
- * Stack traces are never removed from stack depot.
- *
* Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc.
*
@@ -360,29 +349,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
return NULL;
}
-/**
- * __stack_depot_save - 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)
- *
- * 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 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
- * 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 alloc_flags, bool can_alloc)
@@ -477,18 +443,6 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
}
EXPORT_SYMBOL_GPL(__stack_depot_save);
-/**
- * stack_depot_save - 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
- *
- * Context: Contexts where allocations via alloc_pages() are allowed.
- * See __stack_depot_save() for more details.
- *
- * Return: Handle of the stack trace stored in depot, 0 on failure
- */
depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
gfp_t alloc_flags)
@@ -497,14 +451,6 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
}
EXPORT_SYMBOL_GPL(stack_depot_save);
-/**
- * stack_depot_fetch - Fetch a stack trace from stack depot
- *
- * @handle: Stack depot handle returned from stack_depot_save()
- * @entries: Pointer to store the address of the stack trace
- *
- * Return: Number of frames for the fetched stack
- */
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries)
{
@@ -537,11 +483,6 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
}
EXPORT_SYMBOL_GPL(stack_depot_fetch);
-/**
- * stack_depot_print - Print a stack trace from stack depot
- *
- * @stack: Stack depot handle returned from stack_depot_save()
- */
void stack_depot_print(depot_stack_handle_t stack)
{
unsigned long *entries;
@@ -553,16 +494,6 @@ void stack_depot_print(depot_stack_handle_t stack)
}
EXPORT_SYMBOL_GPL(stack_depot_print);
-/**
- * stack_depot_snprint - Print a stack trace from stack depot into a buffer
- *
- * @handle: Stack depot handle returned from stack_depot_save()
- * @buf: Pointer to the print buffer
- * @size: Size of the print buffer
- * @spaces: Number of leading spaces to print
- *
- * Return: Number of bytes printed
- */
int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
int spaces)
{
@@ -575,17 +506,6 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
}
EXPORT_SYMBOL_GPL(stack_depot_snprint);
-/**
- * stack_depot_set_extra_bits - Set extra bits in a stack depot handle
- *
- * @handle: Stack depot handle returned from stack_depot_save()
- * @extra_bits: Value to set the extra bits
- *
- * Return: Stack depot handle with extra bits set
- *
- * Stack depot handles have a few unused bits, which can be used for storing
- * user-specific information. These bits are transparent to the stack depot.
- */
depot_stack_handle_t __must_check stack_depot_set_extra_bits(
depot_stack_handle_t handle, unsigned int extra_bits)
{
@@ -600,13 +520,6 @@ depot_stack_handle_t __must_check stack_depot_set_extra_bits(
}
EXPORT_SYMBOL(stack_depot_set_extra_bits);
-/**
- * stack_depot_get_extra_bits - Retrieve extra bits from a stack depot handle
- *
- * @handle: Stack depot handle with extra bits saved
- *
- * Return: Extra bits retrieved from the stack depot handle
- */
unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
{
union handle_parts parts = { .handle = handle };