From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/stackdepot.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff -puN lib/stackdepot.c~lib-stackdepot-avoid-to-return-0-handle lib/stackdepot.c
--- a/lib/stackdepot.c~lib-stackdepot-avoid-to-return-0-handle
+++ a/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->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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