Re: [Xen-devel] [PATCH VERY RFC 3/5] tools/fuzz: introduce x86 instruction emulator target

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Dec 09, 2016 at 01:09:45AM -0700, Jan Beulich wrote:
> >>> On 08.12.16 at 18:57, <wei.liu2@xxxxxxxxxx> wrote:
> > On Thu, Dec 08, 2016 at 08:03:04AM -0700, Jan Beulich wrote:
> >> >>> On 08.12.16 at 14:54, <wei.liu2@xxxxxxxxxx> wrote:
> >> > Instruction emulator fuzzing code is from code previous written by
> >> > Andrew and George. Adapted to llvm fuzzer and hook up the build system.
> >> 
> >> With this, how much of the new code could be shared between
> >> Google's fuzzer and AFL, for which George had put this together
> >> originally afaik? Or are we now no longer planning on having an
> >> AFL target?
> >> 
> >> > --- /dev/null
> >> > +++ b/tools/fuzz/x86_instruction_emulator/Makefile
> >> > @@ -0,0 +1,33 @@
> >> > +XEN_ROOT=$(CURDIR)/../../..
> >> > +include $(XEN_ROOT)/tools/Rules.mk
> >> > +
> >> > +x86-instruction-emulator-fuzzer-all: x86-insn-emulator.a 
> >> > x86-insn-emulator-fuzzer.o
> >> > +
> >> > +x86_emulate/x86_emulate.c x86_emulate/x86_emulate.h:
> >> > +        [ -L x86_emulate ] || ln -sf 
> >> > $(XEN_ROOT)/xen/arch/x86/x86_emulate .
> >> > +
> >> > +x86_emulate.c:
> >> > +        [ -L x86_emulate.c ] || ln -sf 
> >> > $(XEN_ROOT)/tools/tests/x86_emulator/x86_emulate.c
> >> > +
> >> > +x86_emulate.h:
> >> > +        [ -L x86_emulate.h ] || ln -sf 
> >> > $(XEN_ROOT)/tools/tests/x86_emulator/x86_emulate.h
> >> 
> >> I think these two could easily be a single (pattern) rule, with (slightly
> >> unusually) the file extension being the stem.
> > 
> > I think it is better to have them explicitly spelled out, because using
> > something like
> > 
> > x86_emulate.%:
> >     [ -L x86_emulate.$* ] || ln -sf 
> > $(XEN_ROOT)/tools/tests/x86_emulator/x86_emulate.$*
> > 
> > would cause the x86_emulate.o compiled in tools/tests/x86_emulator be
> > linked here, too, due to another rule we have:
> > 
> > x86_emulate.o: x86_emulate.c x86_emulate.h x86_emulate/x86_emulate.c 
> > x86_emulate/x86_emulate.h 
> 
> Good point.
> 
> > Please let me know if you have some other ideas to deal with this.
> 
> A static pattern rule may then still be better than repeating the
> same thing twice (and later perhaps even more often, i.e. once
> we gain shared helper routine source/header files):
> 
> x86_emulate.c x86_emulate.h: %:
>       [ -L $* ] || ln -sf $(XEN_ROOT)/tools/tests/x86_emulator/$*
> 

This is a good idea. I've made the change to my code.

Wei.

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