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Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Also adapt KASAN to the new prototype by passing extra_bits=0, as KASAN does not intend to store additional information in the stack handle. Signed-off-by: Alexander Potapenko --- v4: -- per Marco Elver's request, fold "kasan: common: adapt to the new prototype of __stack_depot_save()" into this patch to prevent bisection breakages. Link: https://linux-review.googlesource.com/id/I0587f6c777667864768daf07821d594bce6d8ff9 --- include/linux/stackdepot.h | 8 ++++++++ lib/stackdepot.c | 29 ++++++++++++++++++++++++----- mm/kasan/common.c | 2 +- 3 files changed, 33 insertions(+), 6 deletions(-) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index bc2797955de90..9ca7798d7a318 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -14,9 +14,15 @@ #include 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); /* @@ -59,6 +65,8 @@ 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 5ca0d086ef4a3..3d1dbdd5a87f6 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; }; }; @@ -76,6 +78,14 @@ 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) @@ -139,6 +149,7 @@ 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; @@ -343,6 +354,7 @@ 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) * @@ -354,6 +366,10 @@ 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 @@ -363,10 +379,11 @@ 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; @@ -450,9 +467,11 @@ 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); @@ -472,6 +491,6 @@ 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); diff --git a/mm/kasan/common.c b/mm/kasan/common.c index c40c0e7b3b5f1..ba4fceeec173c 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -36,7 +36,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) 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(entries, nr_entries, 0, flags, can_alloc); } void kasan_set_track(struct kasan_track *track, gfp_t flags) -- 2.37.0.rc0.161.g10f37bed90-goog