RE: VMA section overlap warnings for overlays

["David Stubbs" <stubbs at IceraSemi dot com>]

> On Fri, May 07, 2010 at 05:14:06PM +0100, David Stubbs wrote:
> > Does the following patch look like the correct fix?
> 
> No, it doesn't look correct.  I think your problem is more likely
> due
> to a ldlang.c bug in setting lma.  Do you have a testcase handy?

Thanks for the response. I didn't realize / think that you needed to
allocate filespace for bss sections when they're followed by non BSS
sections in the same segment. 

I wasn't able to reproduce the problem, but that turned out to be
because I'd somehow lost the bit of code that calls write_zeros in our
copy of the source.

I have however found another potential problem with strip. Here's the
test:

---
brsbs01 0>cat start.s
  	.section	.text,"ax",@progbits
        .globl  _start
        .type   _start, @function
_start:
        nop
       
        .section .dmem.bss,"aw",@nobits
        .zero 0x10
brsbs01 0>cat over.S
        .section SEC_NAME,"ax",@progbits
        .zero 0x10

        .section SEC_NAME.bss,"aw",@nobits
        .zero 0x10
brsbs01 0>cat ldscript.x
OUTPUT_FORMAT("elf32-i386")
OUTPUT_ARCH(i386)

ENTRY(_start)

PHDRS
{
  mem PT_LOAD;
  imem PT_LOAD;
}

SECTIONS
{
  .text 0x1000:
  {
    *(.text)
  } :mem

  .dmem.bss 0x2000
    : AT (LOADADDR (.text) + SIZEOF (.text))
  {
    *(.dmem.bss)
  } :imem

  .overlay1 ADDR (.dmem.bss) + SIZEOF (.dmem.bss)
    : AT (LOADADDR (.dmem.bss) + SIZEOF (.dmem.bss))
  {
    *(.overlay1)
  } :imem
      
  .overlay2 ADDR (.dmem.bss) + SIZEOF (.dmem.bss)
    : AT (LOADADDR (.overlay1) + SIZEOF (.overlay1))
  {
    *(.overlay2)
  } :imem

  .overlay1.bss ADDR (.overlay1) + SIZEOF (.overlay1)
    : AT (LOADADDR (.overlay2) + SIZEOF (.overlay2))
  {
    *(.overlay1.bss)
  } :imem

  .overlay2.bss ADDR (.overlay2) + SIZEOF (.overlay2)
    : AT (LOADADDR (.overlay1.bss) + SIZEOF (.overlay1.bss))
  {
    *(.overlay1.bss)
  } :imem

}
brsbs01 0>gcc over.S -DSEC_NAME=.overlay1 -c -o over1.o
brsbs01 0>gcc over.S -DSEC_NAME=.overlay2 -c -o over2.o
brsbs01 0>gcc start.s -c -o start.o
brsbs01 0>ld over1.o over2.o start.o -T ldscript.x -o test.exe 
brsbs01 1>strip test.exe
BFD: stHVOxcK: section .overlay1.bss lma 0x1021 overlaps previous
sections
BFD: stHVOxcK: section .overlay2.bss lma 0x1021 overlaps previous
sections
---

The overlap warning is being emitted because 'adjust' is being
calculated as a negative number. I don't yet know why.

Thanks again,
Dave.