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| author | Joonsoo Kim <iamjoonsoo.kim@lge.com> | 2016-05-05 16:22:35 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-05 17:38:53 -0700 |
| commit | 7c31190bcfdbff225950902a9f226e4eb79ca94f (patch) | |
| tree | 3d9c55c6df3e04a3c0a87106d4d424e8db1bcdb9 /lib | |
| parent | 172400c69cb0d0d684b7cd75ac75872b3d7c61a1 (diff) | |
| download | lwn-7c31190bcfdbff225950902a9f226e4eb79ca94f.tar.gz lwn-7c31190bcfdbff225950902a9f226e4eb79ca94f.zip | |
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 <iamjoonsoo.kim@lge.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/stackdepot.c | 6 |
1 files changed, 5 insertions, 1 deletions
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; |