lib/stackdepot: avoid to return 0 handle

[deliverable/linux.git] / lib / stackdepot.c

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 9e0b0315a724caf24ea195e275ed431639a262b4..53ad6c0831aebe6d3c9ec7cfc1387fa34ca7ea72 100644 (file)
--- 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;