From 02754e0a484a50a92d44c38879f2cb2792ebc572 Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Thu, 27 Oct 2016 17:46:44 -0700 Subject: lib/stackdepot.c: bump stackdepot capacity from 16MB to 128MB KASAN uses stackdepot to memorize stacks for all kmalloc/kfree calls. Current stackdepot capacity is 16MB (1024 top level entries x 4 pages on second level). Size of each stack is (num_frames + 3) * sizeof(long). Which gives us ~84K stacks. This capacity was chosen empirically and it is enough to run kernel normally. However, when lots of configs are enabled and a fuzzer tries to maximize code coverage, it easily hits the limit within tens of minutes. I've tested for long a time with number of top level entries bumped 4x (4096). And I think I've seen overflow only once. But I don't have all configs enabled and code coverage has not reached maximum yet. So bump it 8x to 8192. Since we have two-level table, memory cost of this is very moderate -- currently the top-level table is 8KB, with this patch it is 64KB, which is negligible under KASAN. Here is some approx math. 128MB allows us to memorize ~670K stacks (assuming stack is ~200b). I've grepped kernel for kmalloc|kfree|kmem_cache_alloc|kmem_cache_free| kzalloc|kstrdup|kstrndup|kmemdup and it gives ~60K matches. Most of alloc/free call sites are reachable with only one stack. But some utility functions can have large fanout. Assuming average fanout is 5x, total number of alloc/free stacks is ~300K. Link: http://lkml.kernel.org/r/1476458416-122131-1-git-send-email-dvyukov@google.com Signed-off-by: Dmitry Vyukov Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Joonsoo Kim Cc: Baozeng Ding Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/stackdepot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib/stackdepot.c') diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 60f77f1d470a..4d830e299989 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -50,7 +50,7 @@ STACK_ALLOC_ALIGN) #define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \ STACK_ALLOC_NULL_PROTECTION_BITS - STACK_ALLOC_OFFSET_BITS) -#define STACK_ALLOC_SLABS_CAP 1024 +#define STACK_ALLOC_SLABS_CAP 8192 #define STACK_ALLOC_MAX_SLABS \ (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \ (1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_SLABS_CAP) -- cgit v1.2.1 From ae65a21fb851f09bf6341761d884fb86b644b75a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 10 Nov 2016 10:46:47 -0800 Subject: lib/stackdepot: export save/fetch stack for drivers Some drivers would like to record stacktraces in order to aide leak tracing. As stackdepot already provides a facility for only storing the unique traces, thereby reducing the memory required, export that functionality for use by drivers. The code was originally created for KASAN and moved under lib in commit cd11016e5f521 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB") so that it could be shared with mm/. In turn, we want to share it now with drivers. Link: http://lkml.kernel.org/r/20161108133209.22704-1-chris@chris-wilson.co.uk Signed-off-by: Chris Wilson Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Joonsoo Kim Cc: "Kirill A. Shutemov" Cc: Daniel Vetter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/stackdepot.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'lib/stackdepot.c') diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 4d830e299989..f87d138e9672 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -192,6 +192,7 @@ void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace) trace->entries = stack->entries; trace->skip = 0; } +EXPORT_SYMBOL_GPL(depot_fetch_stack); /** * depot_save_stack - save stack in a stack depot. @@ -283,3 +284,4 @@ exit: fast_exit: return retval; } +EXPORT_SYMBOL_GPL(depot_save_stack); -- cgit v1.2.1