Re: [Xen-devel] [PATCH 1/3] fuzz/x86emul: avoid race in link farm rune

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Feb 16, 2017 at 07:10:41PM +0000, Andrew Cooper wrote:
> On 16/02/17 18:56, Wei Liu wrote:
> > Several `ln -sf` can race with each other and cause error like:
> >
> > 14:43:56 00:07:06 O: ln: cannot remove 'asm': No such file or directory
> >
> > Provide dedicated targets for soft-linking directories.
> >
> > Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> >  tools/fuzz/x86_instruction_emulator/Makefile | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/fuzz/x86_instruction_emulator/Makefile 
> > b/tools/fuzz/x86_instruction_emulator/Makefile
> > index fede7e9afd..0cd49753cf 100644
> > --- a/tools/fuzz/x86_instruction_emulator/Makefile
> > +++ b/tools/fuzz/x86_instruction_emulator/Makefile
> > @@ -8,12 +8,16 @@ else
> >  x86-instruction-emulator-fuzzer-all:
> >  endif
> >  
> > -x86_emulate/x86_emulate.c x86_emulate/x86_emulate.h:
> > +x86_emulate:
> >     [ -L x86_emulate ] || ln -sf $(XEN_ROOT)/xen/arch/x86/x86_emulate .
> >  
> > -asm/x86-vendors.h asm/x86-defns.h asm/msr-index.h:
> > +x86_emulate/x86_emulate.c x86_emulate/x86_emulate.h: x86_emulate
> 
> You should be able to do this:
> 
> x86_emulate/%: x86_emulate
> 

Using % won't work. Jan made a similar comment during the first
iteration of the fuzzer series. It turned out that we needed to list
explicitly every file because of the other rules explicitly listed
those files.


> > +
> > +asm:
> >     [ -L asm ] || ln -sf $(XEN_ROOT)/xen/include/asm-x86 asm
> >  
> > +asm/x86-vendors.h asm/x86-defns.h asm/msr-index.h: asm
> 
> And this:
> 
> asm/%: asm
> 

This can be made work by eliminating the explicit listing of individual
files because we're linking asm-x86 wholesale.

Wei.

> Otherwise, Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> > +
> >  x86_emulate.c x86_emulate.h: %:
> >     [ -L $* ] || ln -sf $(XEN_ROOT)/tools/tests/x86_emulator/$*
> >  
> 

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