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lib/stacktrace, kasan, kmsan: rework extra_bits interface

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The current implementation of the extra_bits interface is confusing:
passing extra_bits to __stack_depot_save makes it seem that the extra
bits are somehow stored in stack depot. In reality, they are only
embedded into a stack depot handle and are not used within stack depot.

Drop the extra_bits argument from __stack_depot_save and instead provide
a new stack_depot_set_extra_bits function (similar to the exsiting
stack_depot_get_extra_bits) that saves extra bits into a stack depot
handle.

Update the callers of __stack_depot_save to use the new interace.

This change also fixes a minor issue in the old code: __stack_depot_save
does not return NULL if saving stack trace fails and extra_bits is used.

Link: https://lkml.kernel.org/r/317123b5c05e2f82854fc55d8b285e0869d3cb77.1676063693.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov
2023-02-10 22:16:03 +01:00
committed by Andrew Morton
parent d11a5621f3
commit 36aa1e6779
4 changed files with 44 additions and 14 deletions
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42
lib/stackdepot.c
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@@ -357,7 +357,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
*
* @entries: Pointer to storage array
* @nr_entries: Size of the storage array
* @extra_bits: Flags to store in unused bits of depot_stack_handle_t
* @alloc_flags: Allocation gfp flags
* @can_alloc: Allocate stack pools (increased chance of failure if false)
*
@@ -369,10 +368,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
* If the stack trace in @entries is from an interrupt, only the portion up to
* interrupt entry is saved.
*
* Additional opaque flags can be passed in @extra_bits, stored in the unused
* bits of the stack handle, and retrieved using stack_depot_get_extra_bits()
* without calling stack_depot_fetch().
*
* 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 from contexts where neither %GFP_ATOMIC nor
@@ -382,7 +377,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
*/
depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
unsigned int extra_bits,
gfp_t alloc_flags, bool can_alloc)
{
struct stack_record *found = NULL, **bucket;
@@ -471,8 +465,6 @@ exit:
if (found)
retval.handle = found->handle.handle;
fast_exit:
retval.extra = extra_bits;
return retval.handle;
}
EXPORT_SYMBOL_GPL(__stack_depot_save);
@@ -493,7 +485,7 @@ 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, 0, alloc_flags, true);
return __stack_depot_save(entries, nr_entries, alloc_flags, true);
}
EXPORT_SYMBOL_GPL(stack_depot_save);
@@ -576,6 +568,38 @@ 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)
{
union handle_parts parts = { .handle = handle };
/* Don't set extra bits on empty handles. */
if (!handle)
return 0;
parts.extra = extra_bits;
return parts.handle;
}
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 };