Some users (currently only KMSAN) may want to use spare bits in depot_stack_handle_t. Let them do so by adding @extra_bits to __stack_depot_save() to store arbitrary flags, and providing stack_depot_get_extra_bits() to retrieve those flags. Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> --- Link: https://linux-review.googlesource.com/id/I0587f6c777667864768daf07821d594bce6d8ff9 --- include/linux/stackdepot.h | 8 ++++++++ lib/stackdepot.c | 29 ++++++++++++++++++++++++----- 2 files changed, 32 insertions(+), 5 deletions(-) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index 17f992fe6355b..fd641d266bead 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -14,9 +14,15 @@ #include <linux/gfp.h> typedef u32 depot_stack_handle_t; +/* + * Number of bits in the handle that stack depot doesn't use. Users may store + * information in them. + */ +#define STACK_DEPOT_EXTRA_BITS 5 depot_stack_handle_t __stack_depot_save(unsigned long *entries, unsigned int nr_entries, + unsigned int extra_bits, gfp_t gfp_flags, bool can_alloc); /* @@ -41,6 +47,8 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int stack_depot_fetch(depot_stack_handle_t handle, unsigned long **entries); +unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle); + int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, int spaces); diff --git a/lib/stackdepot.c b/lib/stackdepot.c index bf5ba9af05009..6dc11a3b7b88e 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -42,7 +42,8 @@ #define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \ STACK_ALLOC_ALIGN) #define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \ - STACK_ALLOC_NULL_PROTECTION_BITS - STACK_ALLOC_OFFSET_BITS) + STACK_ALLOC_NULL_PROTECTION_BITS - \ + STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS) #define STACK_ALLOC_SLABS_CAP 8192 #define STACK_ALLOC_MAX_SLABS \ (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \ @@ -55,6 +56,7 @@ union handle_parts { u32 slabindex : STACK_ALLOC_INDEX_BITS; u32 offset : STACK_ALLOC_OFFSET_BITS; u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS; + u32 extra : STACK_DEPOT_EXTRA_BITS; }; }; @@ -73,6 +75,14 @@ static int next_slab_inited; static size_t depot_offset; static DEFINE_RAW_SPINLOCK(depot_lock); +unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle) +{ + union handle_parts parts = { .handle = handle }; + + return parts.extra; +} +EXPORT_SYMBOL(stack_depot_get_extra_bits); + static bool init_stack_slab(void **prealloc) { if (!*prealloc) @@ -136,6 +146,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) stack->handle.slabindex = depot_index; stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN; stack->handle.valid = 1; + stack->handle.extra = 0; memcpy(stack->entries, entries, flex_array_size(stack, entries, size)); depot_offset += required_size; @@ -320,6 +331,7 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); * * @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 slabs (increased chance of failure if false) * @@ -331,6 +343,10 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); * 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 @@ -340,10 +356,11 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); */ 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; - depot_stack_handle_t retval = 0; + union handle_parts retval = { .handle = 0 }; struct page *page = NULL; void *prealloc = NULL; unsigned long flags; @@ -427,9 +444,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER); } if (found) - retval = found->handle.handle; + retval.handle = found->handle.handle; fast_exit: - return retval; + retval.extra = extra_bits; + + return retval.handle; } EXPORT_SYMBOL_GPL(__stack_depot_save); @@ -449,6 +468,6 @@ 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(entries, nr_entries, 0, alloc_flags, true); } EXPORT_SYMBOL_GPL(stack_depot_save); -- 2.35.1.1021.g381101b075-goog
