Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation

Arnd Bergmann
2017-03-03T14:52:11Z

On Fri, Mar 3, 2017 at 3:33 PM, Alexander Potapenko <glider@google.com> wrote:
> On Fri, Mar 3, 2017 at 3:30 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>> On Fri, Mar 3, 2017 at 2:55 PM, Alexander Potapenko <glider@google.com> wrote:
>>
>> 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
> The thing is that KMSAN (and other tools that insert heavyweight
> instrumentation) may cause heavy register spilling which will also
> blow up the stack frames.

In that case, I would expect a mostly distinct set of functions to have large
stack frames with KMSAN, compared to the ones that need
noinline_for_kasan. In most cases I patched, the called inline function is
actually trivial, but invoked many times from the same caller.

Arnd