Messages in this thread | | | From | Arnd Bergmann <> | Date | Fri, 3 Mar 2017 15:30:37 +0100 | Subject | Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation |
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On Fri, Mar 3, 2017 at 2:55 PM, Alexander Potapenko <glider@google.com> wrote: > On Fri, Mar 3, 2017 at 2:50 PM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>>> @@ -416,6 +416,17 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s >>> */ >>> #define noinline_for_stack noinline >>> >>> +/* >>> + * CONFIG_KASAN can lead to extreme stack usage with certain patterns when >>> + * one function gets inlined many times and each instance requires a stack >>> + * ckeck. >>> + */ >>> +#ifdef CONFIG_KASAN >>> +#define noinline_for_kasan noinline __maybe_unused >> >> >> noinline_iff_kasan might be a better name. noinline_for_kasan gives the impression >> that we always noinline function for the sake of kasan, while noinline_iff_kasan >> clearly indicates that function is noinline only if kasan is used.
Fine with me. I actually tried to come up with a name that implies that the symbol is actually "inline" (or even __always_inline_ without KASAN, but couldn't think of any good name for it.
> FWIW we may be facing the same problem with other compiler-based > tools, e.g. KMSAN (which isn't there yet). > So it might be better to choose a macro name that doesn't use the name "KASAN". > E.g. noinline_iff_memtool (or noinline_iff_memory_tool if that's not too long). > WDYT?
Would KMSAN also force local variables to be non-overlapping the way that asan-stack=1 and -fsanitize-address-use-after-scope do? As I understood it, KMSAN would add extra code for maintaining the uninit bits, but in an example like this
int f(int *); static inline __attribute__((always_inline)) int g(void) { int i; f(&i); return i; } int f(void) { return g()+g()+g()+g(); }
each of the four copies of 'i' could have the same location on the stack and get marked uninitialized again before calling f(). We only need noinline_for_kasan (whatever we end up calling that) for compiler features that force each instance of 'i' to have its own stack redzone.
Arnd
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