lib/stackdepot: avoid to return 0 handle (7c31190b) · Commits · 戴 / test

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: ("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>

lib/stackdepot.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -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;

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