Re: [PATCH v5 13/28] xsplice, symbols: Implement symbol name resolution on address.

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>,
	andrew.cooper3@citrix.com, mpohlack@amazon.de,
	ross.lagerwall@citrix.com, sasha.levin@oracle.com,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v5 13/28] xsplice, symbols: Implement symbol name resolution on address.
Date: Wed, 6 Apr 2016 23:14:34 -0400	[thread overview]
Message-ID: <20160407031434.GE24604@char.us.oracle.com> (raw)
In-Reply-To: <56FEABCC02000078000E232F@prv-mh.provo.novell.com>

On Fri, Apr 01, 2016 at 09:11:40AM -0600, Jan Beulich wrote:
> >>> On 24.03.16 at 21:00, <konrad.wilk@oracle.com> wrote:
> > --- a/xen/arch/x86/Makefile
> > +++ b/xen/arch/x86/Makefile
> > @@ -113,12 +113,14 @@ $(TARGET)-syms: prelink.o xen.lds $(BASEDIR)/common/symbols-dummy.o
> >  	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
> >  	    $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
> >  	$(NM) -pa --format=sysv $(@D)/.$(@F).0 \
> > -		| $(BASEDIR)/tools/symbols --sysv --sort >$(@D)/.$(@F).0.S
> > +		| $(BASEDIR)/tools/symbols --all-symbols --sysv --sort \
> > +		>$(@D)/.$(@F).0.S
> >  	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
> >  	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
> >  	    $(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
> >  	$(NM) -pa --format=sysv $(@D)/.$(@F).1 \
> > -		| $(BASEDIR)/tools/symbols --sysv --sort --warn-dup >$(@D)/.$(@F).1.S
> > +		| $(BASEDIR)/tools/symbols --all-symbols --sysv --sort --warn-dup \
> > +		>$(@D)/.$(@F).1.S
> 
> This addition should be dependent on CONFIG_XSPLICE, not the
> least because I expect it to bloat the symbol table quite a bit. And
> then - how come this is needed here, but not in the xen.efi rule?

I added it to xen.efi rule and got:

home/konrad/xen/xen/.xen.efi.0s.S: Assembler messages:
/home/konrad/xen/xen/.xen.efi.0s.S:21: Warning: value 0x7d2f80000543 truncated to 0x80000543
/home/konrad/xen/xen/.xen.efi.0s.S:22: Warning: value 0x7d2f800008b2 truncated to 0x800008b2
/home/konrad/xen/xen/.xen.efi.0s.S:23: Warning: value 0x7d2f800008b4 truncated to 0x800008b4
/home/konrad/xen/xen/.xen.efi.0s.S:24: Warning: value 0x7d2f800008b9 truncated to 0x800008b9
/home/konrad/xen/xen/.xen.efi.0s.S:25: Warning: value 0x7d2f8000103f truncated to 0x8000103f
/home/konrad/xen/xen/.xen.efi.0s.S:26: Warning: value 0x7d2f80001043 truncated to 0x80001043
/home/konrad/xen/xen/.xen.efi.0s.S:27: Warning: value 0x7d2f80001047 truncated to 0x80001047
/home/konrad/xen/xen/.xen.efi.0s.S:6746: Warning: value 0x100650000 truncated to 0x650000

and so on.. Not sure why. The xen.efi file boots thought?
> > +        rc = xensyms_read(&symnum, &type, &addr, name);

> > +        if ( rc )
> > +            break;
> > +
> > +        if ( !strcmp(name, symname) )
> > +        {
> > +            outaddr = addr;
> > +            break;
> > +        }
> > +    } while ( name[0] != '\0' );
> > +
> > +    return outaddr;
> > +}
> 
> Huh - a brute force linear lookup. We've got some 7,000 symbols
> right now, and I think we can't expect that to go down.

I left it as such. I will need to redo this as the xensyms_read is not
the best for this and this will need to be redone to be much faster.

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