I think there were cases where the ELF loader was used to load to actual
physical addresses in FS mode. I don't remember the specifics.
Gabe
On Tue, Nov 18, 2014 at 8:21 AM, Nilay Vaish via gem5-dev <gem5-dev@gem5.org
> wrote:
> I checked the elf-64 draft and I think you right. But I am not able to
> understand why do we use p_paddr at all. Should we not be using p_vaddr
> everywhere?
>
> --
> Nilay
>
>
>
> On Tue, 18 Nov 2014, Romana, Alexandre via gem5-dev wrote:
>
> Hi everybody,
>>
>> Looks to me like there is a bug/typo in elf_loader.cc:
>>
>>
>> 318 // Check to see if this segment contains the bss section.
>>
>> 319 if (phdr.p_paddr <= bssSecStart &&
>>
>> 320 phdr.p_paddr + phdr.p_memsz > bssSecStart &&
>>
>> 321 phdr.p_memsz - phdr.p_filesz > 0) {
>>
>> 322 bss.baseAddr = phdr.p_paddr + phdr.p_filesz;
>>
>> 323 bss.size = phdr.p_memsz - phdr.p_filesz;
>>
>> 324 bss.fileImage = NULL;
>>
>> 325 }
>>
>> 326
>>
>> 327 // Check to see if this is the text or data segment
>>
>> 328 if (phdr.p_vaddr <= textSecStart &&
>>
>> 329 phdr.p_vaddr + phdr.p_filesz > textSecStart) {
>>
>> 330 text.baseAddr = phdr.p_paddr;
>>
>> 331 text.size = phdr.p_filesz;
>>
>> 332 text.fileImage = fileData + phdr.p_offset;
>>
>> 333 } else if (phdr.p_vaddr <= dataSecStart &&
>>
>> 334 phdr.p_vaddr + phdr.p_filesz > dataSecStart) {
>>
>> 335 data.baseAddr = phdr.p_paddr;
>>
>> 336 data.size = phdr.p_filesz;
>>
>> 337 data.fileImage = fileData + phdr.p_offset;
>>
>> 338 } else {
>>
>> 339 // If it's none of the above but is loadable,
>>
>> 340 // load the filesize worth of data
>>
>> 341 Segment extra;
>>
>> 342 extra.baseAddr = phdr.p_paddr;
>>
>> 343 extra.size = phdr.p_filesz;
>>
>> 344 extra.fileImage = fileData + phdr.p_offset;
>>
>> 345 extraSegments.push_back(extra);
>>
>>
>> I guess nobody used so far the loader with the bss section mapped onto a
>> segment with different virtual and physical addresses…
>> To double check you can look at the bssSecStart definition:
>> bssSecStart = shdr.sh_addr;
>> sh_addr being the virtual address, I think we can safely assume there’s
>> a typo line 319-320, and I can submit a patch (changing 2 characters in the
>> code),
>> or could anybody please explain why we are comparing virtual with
>> physical addresses here?
>>
>> Thanks,
>> Alexandre
>>
>> Texas Instruments France SAS, Immeuble Le Khapa, 65 Quai Georges Gorse,
>> ZAC Seguin Rives de Seine, 92100 Boulogne Billancourt. 036 420 040 R.C.S
>> Nanterre. Capital de EUR 12.654.784
>>
>>
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>>
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