Re: [microblaze-uclinux] microblaze-uclinux-elf2flt mistranslation

["Steven J. Magnani" <steve@xxxxxxxxxxxxxxx>]

On Wed, 2009-05-27 at 11:04 -0400, Rod Campbell wrote:
> Hi Steve,
> 
> I ran into the same problem a year or so ago.  I posted this issue to 
> the group in June of 2008:
> http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/archive/2008/06/msg00108.html
> 
> I came to the same conclusions that you did.  Instead of spending a lot 
> of time trying to fix elf2flt, I developed a work-around:
> 
> * Take the same elf file that was used by elf2flt to generate the flat 
> executable and create a binary file with mb-objcopy.
> * Replace the .data section of the flat executable with the binary 
> file's version. 
> 
> I created a utility to do compare the 2 data sections and do the 
> replacement.  I often see a couple mismatches between the binary file's 
> data section and the flat file's.  I have this as part of every 
> microblaze compile.

OK, I tried something similar. I found that 'fixing' the flat data
section can actually break a program. Specifically, it looks like
'agetty' has a table of days of the week. In my build, the pointer to
"Fri" mistranslates as a pointer to "\r\n". A brute-force copy of the
ELF .data section to the FLT file fixes the corruption, but agetty then
fails to display a login prompt.

> 
> Here is a run of tail end of my compile script:
> mb-flthdr -p la5600
> la5600
>     Magic:        bFLT
>     Rev:          4
>     Build Date:   Tue May 26 18:07:37 2009
>     Entry:        0x50
>     Data Start:   0x2eb40
>     Data End:     0x41ec0
>     BSS End:      0x55dc0
>     Stack Size:   0x8000
>     Reloc Start:  0x41ec0
>     Reloc Count:  0x12e7
>     Flags:        0x1 ( Load-to-Ram )
> ==============================================================
> * Compare flat file Data Sect with bin file & fix flat file  *
> ==============================================================
> mb-objcopy -O binary la5600.gdb la5600.bin
> ./la_fltfix -v -f la5600 -b la5600.bin -o la5600
> ./la_fltfix INFO: Flat File Flags=0x00000001
> ./la_fltfix INFO: DataSect Len=0x13380,78720 Ofst:Flt=0x2eb40 Bin=0x2eb00
> ./la_fltfix INFO: DIFF @DataSect+0xf29e Flt=0xec Bin=0xed
> ./la_fltfix INFO: DIFF @DataSect+0xf29f Flt=0x6c Bin=0xd8
> ./la_fltfix INFO: DIFF @DataSect+0xf31e Flt=0xec Bin=0xed
> ./la_fltfix INFO: DIFF @DataSect+0xf31f Flt=0x6c Bin=0xd8
> ./la_fltfix INFO: 4 DIFFs found
> ./la_fltfix INFO: Created Output flat file "la5600"
> ./la_fltfix INFO: Return code=0
> 
> I hope this helps.
> 
> Rod Campbell
> 
> Steven J. Magnani wrote:
> > Hi,
> >
> > Has anyone run into problems with microblaze-uclinux-elf2flt?
> >
> > We have a program that contains a constant global array something like
> > this:
> >
> > const struct
> > {
> >    const char*          source;
> >    const char*          target;
> >    unsigned long        flags;
> >    const char*          options;
> >    unsigned int         channel;
> >    unsigned long        devnum;
> > } myGlobalStruct[9] = { blah blah blah };
> >
> > What we are seeing is for certain sequences of executable code, one of
> > the .target fields in the array gets mis-translated, so instead of
> > pointing to the constant string associated with array element [3], it
> > points to the constant string associated with array element [0]. It's
> > definitely a translation problem because I can use
> > microblaze-uclinux-objcopy to extract the .data segment from the .gdb
> > file and the structure is correct there.
> >
> > Depending on how we change the program flow, the problem can come and
> > go. If we add a printf to one module the problem goes away.
> >
> > Any suggestions? Is there a more recent version of microblaze-uclinux
> > tools available anywhere, or in the works? Tool problems like this make
> > us very nervous because there's no telling what else is being corrupted.
> >
> > Thanks.
> > ------------------------------------------------------------------------
> >  Steven J. Magnani               "I claim this network for MARS!
> >  www.digidescorp.com              Earthling, return my space modulator!"
> >
> >  #include <standard.disclaimer>
> >
> >
> > ___________________________
> > microblaze-uclinux mailing list
> > microblaze-uclinux@xxxxxxxxxxxxxx
> > Project Home Page : http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux
> > Mailing List Archive : http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/
> >
> >
> >   
> 
> 


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