From 7c31190bcfdbff225950902a9f226e4eb79ca94f Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Thu, 5 May 2016 16:22:35 -0700 Subject: [PATCH] lib/stackdepot: avoid to return 0 handle Recently, we allow to save the stacktrace whose hashed value is 0. It causes the problem that stackdepot could return 0 even if in success. User of stackdepot cannot distinguish whether it is success or not so we need to solve this problem. In this patch, 1 bit are added to handle and make valid handle none 0 by setting this bit. After that, valid handle will not be 0 and 0 handle will represent failure correctly. Fixes: 33334e25769c ("lib/stackdepot.c: allow the stack trace hash to be zero") Link: http://lkml.kernel.org/r/1462252403-1106-1-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim Cc: Alexander Potapenko Cc: Andrey Ryabinin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/stackdepot.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 9e0b0315a724..53ad6c0831ae 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -42,12 +42,14 @@ #define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8) +#define STACK_ALLOC_NULL_PROTECTION_BITS 1 #define STACK_ALLOC_ORDER 2 /* 'Slab' size order for stack depot, 4 pages */ #define STACK_ALLOC_SIZE (1LL << (PAGE_SHIFT + STACK_ALLOC_ORDER)) #define STACK_ALLOC_ALIGN 4 #define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \ STACK_ALLOC_ALIGN) -#define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - STACK_ALLOC_OFFSET_BITS) +#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_MAX_SLABS \ (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \ @@ -59,6 +61,7 @@ union handle_parts { struct { u32 slabindex : STACK_ALLOC_INDEX_BITS; u32 offset : STACK_ALLOC_OFFSET_BITS; + u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS; }; }; @@ -136,6 +139,7 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int size, stack->size = size; stack->handle.slabindex = depot_index; stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN; + stack->handle.valid = 1; memcpy(stack->entries, entries, size * sizeof(unsigned long)); depot_offset += required_size; -- 2.34.1