Re: [PATCH net-next v5 02/20] zinc: introduce minimal cryptography library

[Andy Lutomirski]

> On Sep 20, 2018, at 8:41 AM, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> 
> (+ Arnd, Eric)
> 
> On 18 September 2018 at 09:16, Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
> ...
> 
>> diff --git a/lib/zinc/Makefile b/lib/zinc/Makefile
>> new file mode 100644
>> index 000000000000..83dfd63988c0
>> --- /dev/null
>> +++ b/lib/zinc/Makefile
>> @@ -0,0 +1,4 @@
> 
> Apologies for not spotting these before:
> 
>> +ccflags-y := -O3
> 
> -O3 optimization has been problematic in the past, at least on x86 but
> I think on other architectures as well. Please stick with -O2.
> 
>> +ccflags-y += -Wframe-larger-than=$(if (CONFIG_KASAN),16384,8192)
> 
> There is no way we can support code in the kernel with that kind of
> stack space requirements. I will let Arnd comment on what we typically
> allow, since he deals with such issues on a regular basis.

To make matters worse, KASAN is incompatible with VMAP_STACK right now, and KASAN is not so good at detecting stack overflow.

> 
>> +ccflags-y += -D'pr_fmt(fmt)="zinc: " fmt'
>> +ccflags-$(CONFIG_ZINC_DEBUG) += -DDEBUG
>> --
>> 2.19.0
>>