On Thu, Feb 28, 2019 at 04:22:04PM +0100, Dmitry Vyukov wrote: > On Thu, Feb 28, 2019 at 4:05 PM Peter Zijlstra <pet...@infradead.org> wrote: > > > > Because __asan_{load,store}{N,1,2,4,8,16}_noabort() get called from > > UACCESS context, and kasan_report() is most definitely _NOT_ safe to > > be called from there, move it into an exception much like BUG/WARN. > > > > *compile tested only* > > > Please test it by booting KASAN kernel and then loading module > produced by CONFIG_TEST_KASAN=y. There are too many subtle aspects to > rely on "compile tested only", reviewers can't catch all of them > either.
Sure, I'll do that. I just wanted to share the rest of the patches. A quick test shows it dies _REAAAAAAAALY_ early, as in: "Booting the kernel." is the first and very last thing it says... I wonder how I did that :-) > > +static __always_inline void > > +kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long > > ip) > > +{ > > + unsigned long rdi = addr, rsi = size, rdx = is_write, rcx = ip; > > + > > + _BUG_FLAGS(ASM_UD2, BUGFLAG_KASAN, > > + "D" (rdi), "S" (rsi), "d" (rdx), "c" (rcx)); > > Can BUG return? Yes. Also see the annotate_reachable(). > This should be able to return. > We also have other tools coming (KMSAN/KTSAN) where distinction > between fast path that does nothing and slower-paths are very blurred > and there are dozens of them, I don't think this BUG thunk will be > sustainable. What does BUG do what a normal call can't do? It keeps the SMAP validation rules nice and tight. If we were to add (and allow) things like pushf;clac;call ponies;popf or similar things, it all becomes complicated real quick. How would KMSAN/KTSAN interact with SMAP ? > > + annotate_reachable(); > > +} > > @@ -228,7 +228,7 @@ void __asan_unregister_globals(struct ka > > EXPORT_SYMBOL(__asan_unregister_globals); > > > > #define DEFINE_ASAN_LOAD_STORE(size) \ > > - void __asan_load##size(unsigned long addr) \ > > + notrace void __asan_load##size(unsigned long addr) \ > > > We already have: > CFLAGS_REMOVE_generic.o = -pg > Doesn't it imply notrace for all functions? Indeed so, I'll make these hunks go away.