lib/stackdepot.c: use a non-instrumented version of memcpy()
Subsystems (2)
PATCH 1/1 lib/stackdepot.c: use a non-instrumented version of memcpy()
stackdepot used to call memcpy(), which compiler tools normally instrument, therefore every lookup used to unnecessarily call instrumented code. This is somewhat ok in the case of KASAN, but under KMSAN a lot of time was spent in the instrumentation.
(A similar change has been previously committed for memcmp())
--- lib/stackdepot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
lib/stackdepot.c +1 -1
@@ -140,7 +140,7 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int 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 )); +__memcpy (stack->entries, entries, size *sizeof (unsigned long )); depot_offset += required_size;return stack;
Signature · 1 line
2.17.0.441.gb46fe60e1d-goog
Quoted 19 lines · Alexander Potapenko
stackdepot used to call
memcpy(), which compiler tools normally instrument, therefore every lookup used to unnecessarily call instrumented code. This is somewhat ok in the case of KASAN, but under KMSAN a lot of time was spent in the instrumentation.(A similar change has been previously committed for
memcmp())Signed-off-by Alexander Potapenko <[email protected]>Cc Andrey Ryabinin <[email protected]>Cc Dmitry Vyukov <[email protected]>--- lib/stackdepot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)lib/stackdepot.c +0
-0
lib/stackdepot.c static struct stack_record *depot_alloc_stack(unsigned long *entries, int size, · line 143
Quoted 5 lines
lib/stackdepot.c +1
-1@@ -140,7 +140,7 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int 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 )); +__memcpy (stack->entries, entries, size *sizeof (unsigned long ));
This has no effect. Since the whole file is not instrumented memcpy automagically replaced with __memcpy.
Quoted 3 lines · Andrey Ryabinin
Quoted 2 lines · Alexander Potapenko
stackdepot used to call
memcpy(), which compiler tools normally instrument, therefore every lookup used to unnecessarily call
instrumented
Quoted 1 line
Quoted 1 line
code. This is somewhat ok in the case of KASAN, but under KMSAN a lot
of
Quoted 11 lines
Quoted 11 lines
time was spent in the instrumentation.
(A similar change has been previously committed for
memcmp())Signed-off-by Alexander Potapenko <[email protected]>Cc Andrey Ryabinin <[email protected]>Cc Dmitry Vyukov <[email protected]>--- lib/stackdepot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Quoted 5 lines
lib/stackdepot.c static struct stack_record
Quoted 5 lines
lib/stackdepot.c +0
-0@@ -140,7 +140,7 @@ static struct stack_record
*depot_alloc_stack(unsigned long *entries, int size,
Quoted 7 lines
lib/stackdepot.c static struct stack_record *depot_alloc_stack(unsigned long *entries, int size, · line 143
Quoted 5 lines
lib/stackdepot.c +1
-1stack->handle.slabindex = depot_index; stack->handle.offset = depot_offset >>STACK_ALLOC_ALIGN ; stack->handle.valid =1 ; -memcpy (stack->entries, entries, size *sizeof (unsigned long )); +__memcpy (stack->entries, entries, size *sizeof (unsigned long ));This has no effect. Since the whole file is not instrumented memcpy
automagically replaced with __memcpy.
You're right, we just didn't have the code defining memcpy() to __memcpy() in KMSAN. I'll fix that instead.
Signature · 10 lines
Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
kbuild test robot
build botI love your patch! Yet something to improve:
Hi Alexander,
I love your patch! Yet something to improve:
[auto build test ERROR on linus/master]
[also build test ERROR on v4.17-rc5 next-20180517]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Alexander-Potapenko/lib-stackdepot-c-use-a-non-instrumented-version-of-memcpy/20180518-015328
config: sh-allmodconfig (attached as .config)
compiler: sh4-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=sh
All errors (new ones prefixed by >>):
lib/stackdepot.c: In function 'depot_alloc_stack':
>> lib/stackdepot.c:143:2: error: implicit declaration of function '__memcpy'; did you mean 'memcpy'? [-Werror=implicit-function-declaration]
__memcpy(stack->entries, entries, size * sizeof(unsigned long));
^~~~~~~~
memcpycc1: some warnings being treated as errors
vim +143 lib/stackdepot.c
106
107 /* Allocation of a new stack in raw storage */
108 static struct stack_record *depot_alloc_stack(unsigned long *entries, int size,
109 u32 hash, void **prealloc, gfp_t alloc_flags)
110 {
111 int required_size = offsetof(struct stack_record, entries) +
112 sizeof(unsigned long) * size;
113 struct stack_record *stack;
114
115 required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);
116
117 if (unlikely(depot_offset + required_size > STACK_ALLOC_SIZE)) {
118 if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) {
119 WARN_ONCE(1, "Stack depot reached limit capacity");
120 return NULL;
121 }
122 depot_index++;
123 depot_offset = 0;
124 /*
125 * smp_store_release() here pairs with smp_load_acquire() from
126 * |next_slab_inited| in depot_save_stack() and
127 * init_stack_slab().
128 */
129 if (depot_index + 1 < STACK_ALLOC_MAX_SLABS)
130 smp_store_release(&next_slab_inited, 0);
131 }
132 init_stack_slab(prealloc);
133 if (stack_slabs[depot_index] == NULL)
134 return NULL;
135
136 stack = stack_slabs[depot_index] + depot_offset;
137
138 stack->hash = hash;
139 stack->size = size;
140 stack->handle.slabindex = depot_index;
141 stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
142 stack->handle.valid = 1;
> 143 __memcpy(stack->entries, entries, size * sizeof(unsigned long));
144 depot_offset += required_size;
145
146 return stack;
147 }
148
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