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Altera_Forum
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17 years ago

Linux with MMU on NEEK

Hi, all. I'm testing Linux MMU version, on my NEEK. http://www.nioswiki.com/linux It works fine and I can use "bash" shell. This is the evident proof that we are using the true 'fo...
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Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Hi,

Now, I'm trying to implement the relocating codes to the Nios's dynamic linker. At first, I must make the 'static' linker ' nios2-wrs-linux-gnu-ld' or 'ld' put relocating information. So I added some codes for two functions 'nios2_elf32_relocate_section' and 'nios2_elf32_check_relocs' in the file '/nios2gcc4/src/binutils-2.17.50/bfd/elf32-nios2.c'. About the details, please refer the attached file.

With these 'static' linkers, we can compile the 'Samples', main.c, a.c and b.c as follows 


nios2-wrs-linux-gnu-gcc -g -shared -Wl,-Bsymbolic -G0 a.c -o a.so
nios2-wrs-linux-gnu-gcc -g -shared -Wl,-Bsymbolic -G0 b.c -o b.so
nios2-wrs-linux-gnu-gcc -g  main.c a.so b.so -o main
The relocation information of shared libraries are as follows.

In 'a.readelf' 


Relocation section '.rela.dyn' at offset 0x308 contains 18 entries:
 Offset     Info    Type            Sym.Value  Sym. Name + Addend
00001834  00000027 R_NIOS2_RELATIVE                             00001748
00001838  00000027 R_NIOS2_RELATIVE                             00001864
0000183c  00000027 R_NIOS2_RELATIVE                             00001860
00001840  00000027 R_NIOS2_RELATIVE                             000004b0
00001844  00000027 R_NIOS2_RELATIVE                             0000056c
00001848  00000027 R_NIOS2_RELATIVE                             0000173c
0000184c  00000027 R_NIOS2_RELATIVE                             0000062c
00001854  00000027 R_NIOS2_RELATIVE                             0000185c
0000185c  00000027 R_NIOS2_RELATIVE                             0000185c
00001860  00000027 R_NIOS2_RELATIVE                             00001744
000005f4  00001104 R_NIOS2_CALL26    00000000   func_b + 0
00000614  00001104 R_NIOS2_CALL26    00000000   func_b + 0
000005fc  0000100b R_NIOS2_HIADJ16   00000000   j + 0
00000600  0000100a R_NIOS2_LO16      00000000   j + 0
00000608  0000100b R_NIOS2_HIADJ16   00000000   j + 0
0000060c  0000100a R_NIOS2_LO16      00000000   j + 0
00001850  00000b25 R_NIOS2_GLOB_DAT  00000000   _Jv_RegisterClasses + 0
00001858  00000f25 R_NIOS2_GLOB_DAT  00000000   __cxa_finalize + 0
Relocation section '.rela.plt' at offset 0x3e0 contains 2 entries:
 Offset     Info    Type            Sym.Value  Sym. Name + Addend
0000182c  00000f26 R_NIOS2_JUMP_SLOT 00000000   __cxa_finalize + 0
00001830  00001126 R_NIOS2_JUMP_SLOT 00000000   func_b + 0
There are no unwind sections in this file.
Symbol table '.dynsym' contains 21 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 000003f8     0 SECTION LOCAL  DEFAULT    8 
     2: 000004b0     0 SECTION LOCAL  DEFAULT   10 
     3: 000006bc     0 SECTION LOCAL  DEFAULT   11 
     4: 00000734     0 SECTION LOCAL  DEFAULT   12 
     5: 00001738     0 SECTION LOCAL  DEFAULT   13 
     6: 00001740     0 SECTION LOCAL  DEFAULT   14 
     7: 00001748     0 SECTION LOCAL  DEFAULT   15 
     8: 0000185c     0 SECTION LOCAL  DEFAULT   18 
     9: 00001864     0 SECTION LOCAL  DEFAULT   19 
    10: 000005dc    80 FUNC    GLOBAL DEFAULT   10 func_a
    11: 00000000     0 NOTYPE  WEAK   DEFAULT  UND _Jv_RegisterClasses
    12: 000006bc     0 NOTYPE  GLOBAL DEFAULT   11 _fini
    13: 00009810     0 NOTYPE  GLOBAL DEFAULT  ABS _gp
    14: 00001864     0 NOTYPE  GLOBAL DEFAULT  ABS __bss_start
    15: 00000000   356 FUNC    WEAK   DEFAULT  UND __cxa_finalize@GLIBC_2.10 (2)
    16: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND j
    17: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND func_b
    18: 00001868     0 NOTYPE  GLOBAL DEFAULT  ABS _end
    19: 00001864     0 NOTYPE  GLOBAL DEFAULT  ABS _edata
    20: 000003f8     0 NOTYPE  GLOBAL DEFAULT    8 _init
.

In 'b.readelf' 


Relocation section '.rela.dyn' at offset 0x300 contains 17 entries:
 Offset     Info    Type            Sym.Value  Sym. Name + Addend
00001850  00000027 R_NIOS2_RELATIVE                             0000175c
00001854  00000027 R_NIOS2_RELATIVE                             00001880
00001858  00000027 R_NIOS2_RELATIVE                             0000187c
0000185c  00000027 R_NIOS2_RELATIVE                             00000484
00001860  00000027 R_NIOS2_RELATIVE                             00000540
00001864  00000027 R_NIOS2_RELATIVE                             00001750
00001868  00000027 R_NIOS2_RELATIVE                             00000640
00001870  00000027 R_NIOS2_RELATIVE                             00001878
00001878  00000027 R_NIOS2_RELATIVE                             00001878
0000187c  00000027 R_NIOS2_RELATIVE                             00001758
000005f8  00000004 R_NIOS2_CALL26                               000005b0
00000600  0000000b R_NIOS2_HIADJ16                              00001830
00000604  0000000a R_NIOS2_LO16                                 00001830
00000618  0000000b R_NIOS2_HIADJ16                              00001830
0000061c  0000000a R_NIOS2_LO16                                 00001830
0000186c  00000b25 R_NIOS2_GLOB_DAT  00000000   _Jv_RegisterClasses + 0
00001874  00000f25 R_NIOS2_GLOB_DAT  00000000   __cxa_finalize + 0
Relocation section '.rela.plt' at offset 0x3cc contains 1 entries:
 Offset     Info    Type            Sym.Value  Sym. Name + Addend
0000184c  00000f26 R_NIOS2_JUMP_SLOT 00000000   __cxa_finalize + 0
There are no unwind sections in this file.
Symbol table '.dynsym' contains 21 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 000003d8     0 SECTION LOCAL  DEFAULT    8 
     2: 00000484     0 SECTION LOCAL  DEFAULT   10 
     3: 000006d0     0 SECTION LOCAL  DEFAULT   11 
     4: 00000748     0 SECTION LOCAL  DEFAULT   12 
     5: 0000174c     0 SECTION LOCAL  DEFAULT   13 
     6: 00001754     0 SECTION LOCAL  DEFAULT   14 
     7: 0000175c     0 SECTION LOCAL  DEFAULT   15 
     8: 00001830     0 SECTION LOCAL  DEFAULT   17 
     9: 00001878     0 SECTION LOCAL  DEFAULT   19 
    10: 00001880     0 SECTION LOCAL  DEFAULT   20 
    11: 00000000     0 NOTYPE  WEAK   DEFAULT  UND _Jv_RegisterClasses
    12: 000006d0     0 NOTYPE  GLOBAL DEFAULT   11 _fini
    13: 00009830     0 NOTYPE  GLOBAL DEFAULT  ABS _gp
    14: 00001880     0 NOTYPE  GLOBAL DEFAULT  ABS __bss_start
    15: 00000000   356 FUNC    WEAK   DEFAULT  UND __cxa_finalize@GLIBC_2.10 (2)
    16: 00001830     4 OBJECT  GLOBAL DEFAULT   17 j
    17: 000005e0    96 FUNC    GLOBAL DEFAULT   10 func_b
    18: 00001884     0 NOTYPE  GLOBAL DEFAULT  ABS _end
    19: 00001880     0 NOTYPE  GLOBAL DEFAULT  ABS _edata
    20: 000003d8     0 NOTYPE  GLOBAL DEFAULT    8 _init
.

And for the 'dynamic' linker, I put some relocating codes to the machine dependent function 'elf_machine_rela' of '/nios2gcc4/src/glibc-ports-2.5/sysdeps/nios2/dl-machine.h'.

Unfortunately this relocation rewrites the 'text' section, so we must set the flag of elf's 'Program Headers' like 


Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x000000 0x00000000 0x00000000 0x00738 0x00738 RWE 0x1000 <-- Flg must be RWE instead of R E.
  LOAD           0x000738 0x00001738 0x00001738 0x0012c 0x0012d RW  0x1000
  DYNAMIC        0x00074c 0x0000174c 0x0000174c 0x000c8 0x000c8 RW  0x4
.

Now I can't do this through the linker, so now I used a 'binary editor' and rewrote it.

Anyway, we can make the position dependent codes to shared libraries, but we need switches '-Bsymbolic' and '-G0' (this is needed to avoid the use of gp register for optimization), instead of '-fPIC'. I'm not sure that this direction is right or not.

Kazu