[Cbe-oss-dev] MARS and SPU-GCC 4.6

[Paul Keir]

> Can you look at the output of "spu-readelf -l" on the
> output of new vs. old compilers?

It looks like the new compiler adds a new, first program
header segment: .interrupt. I've put the full spu-readelf
output at the end.

I wired in task_map_elf from MARS into their hello example
to see exactly what's happening. There's a for loop within
task_map_elf which iterates the program segments. In
the new elf file, the Elf32_Phdr pointer fails a test at
line 84 of task.c:

phdr->p_vaddr != MARS_TASK_BASE_ADDR

MARS_TASK_BASE_ADDR is #defined to 0x4000. This
hex address is also seen in the 3rd of 5 commands called by
the "hello" example's makefile:

spu-gcc -Wall -O3 -funroll-loops -o mpu_task.task mpu_task.task_o -lmars_task -Wl,--section-start,.init=0x4000 -lmars_base -Wl,-gc-sections

Perhaps the new spu-gcc isn't correctly forwarding
the linker switches? Does spu-gcc actually invoke a
separate spu-ld executable?

I'm still not sure how to get round this, but it seems that this
spu-gcc command is only useful in that it invokes the linker. I'm
unsure of the spu-ld syntax (e.g. Should it be a comma that
follows --section-start?), but I'm working to replace that
call to spu-gcc with one to spu-ld. Or am I barking up the
wrong tree...?

Many thanks,
Paul

-bash-3.2# spu-readelf -l mpu_task.task.good

Elf file type is EXEC (Executable file)
Entry point 0x4028
There are 3 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x000100 0x00004000 0x00004000 0x00ad0 0x00ad0 R E 0x80
  LOAD           0x000c00 0x00004b00 0x00004b00 0x00350 0x00380 RW  0x80
  NOTE           0x007c20 0x00000000 0x00000000 0x00024 0x00024 R   0x10

 Section to Segment mapping:
  Segment Sections...
   00     .init .text .fini .rodata
   01     .ctors .dtors .jcr .data .bss
   02     .note.spu_name

-bash-3.2# spu-readelf -l mpu_task.task.bad

Elf file type is EXEC (Executable file)
Entry point 0x4020
There are 4 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x000100 0x00000000 0x00000000 0x00010 0x00010 R E 0x80
  LOAD           0x000180 0x00004000 0x00004000 0x009f0 0x009f0 R E 0x80
  LOAD           0x000b80 0x00004a00 0x00004a00 0x00320 0x00360 RW  0x80
  NOTE           0x008410 0x00000000 0x00000000 0x00024 0x00000 R   0x10

 Section to Segment mapping:
  Segment Sections...
   00     .interrupt
   01     .init .text .fini .rodata
   02     .ctors .dtors .jcr .data .bss
   03     .note.spu_name

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