[Bug ld/2809] ld incorrect applies LTOFF22X/LDXMOV relocations

[cgray at cse dot unsw dot edu dot au]

------- Additional Comments From cgray at cse dot unsw dot edu dot au  
2006-06-22 06:59 -------
I'm confused. You don't believe that ld doing these relocations creates a fixed
fixed address relationship between segments? Or you don't believe that this is
what the IA64 ABI is saying you can't do?

If I compile some simple code, say,

        printf( "string" );

ld applies relocations to get:

        addl r14=-99976,r1 ;;
        ...
        ld8 r32=[r14]

However, the -99976 is *much* bigger than the size of the read/write data
section the gp is in, as shown here: (leading zeros removed for formatting)

  LOAD off    0x0005cb50 vaddr 0x0006cb50 paddr 0x00006cb50 align 2**16
        filesz 0x00002428 memsz 0x000049d0 flags rw-

So the relocated code assumes a fixed address relationship between sections. If
I load the read-only data at a modified offset, things crash.

You claim "offset from GP is fixed in executable or shared library", however
this is only true at linktime for read/write data. Only the dynamic linker can
extend this to read-only data. The ABI says so. 

This only seems to work for the current VM system in the current version of
Linux. I'd like to supply you with a small test case, however that would require
also supplying you with a whole new VM system, or in my case, OS.

I think it's very clear from the emitted code that ld does *not* obey what is
specified in the ABI, so I don't think sample code is really that necessary. Any
code which uses static read-only data can be used for testing.

If ld is fine with being by default non-ABI compliant, is it not possible to
have command line flags to disable these relocations? Alternatively, do they
already exist and are just undocumented?

Thanks,
     Chuck

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=2809

------- You are receiving this mail because: -------
You are on the CC list for the bug, or are watching someone who is.