[Bug gold/11997] Different behevior of MEMORY regions

[nickc at redhat dot com]

------- Additional Comments From nickc at redhat dot com  2010-09-27 15:41 
-------
There is a discrepancy between the behaviour of LD and GOLD with regard to
unspecified VMA and LMA values for sections mentioned in linker scripts that use
memory regions.  LD will place any section which does not have an explicit VMA
address or an explicit output region into the first region in the MEMORY list
that has compatible attributes.  (In the testcase being used in the LD and GOLD
testsuites this means that sec0 is placed into region2).  This is contrary to
the documentation which says:

  Output Section Address

  The "address" is an expression for the VMA (the virtual memory
  address) of the output section.  If you do not provide "address",
  the linker will set it based on "region" if present, or otherwise
  based on the current value of the location counter.

If the section has an VMA address but does not have an LMA address then LD will
again base the LMA on the first compatible memory region, whereas GOLD will just
set the LMA to be the same as the VMA. The manual states that:

  If neither AT nor AT> is specified for an allocatable
  section, the linker will set the LMA such that the difference between
  VMA and LMA for the section is the same as the preceding output
  section in the same region.  If there is no preceding output section
  or the section is not allocatable, the linker will set the LMA equal
  to the VMA.

It does not specify what happens if the section does not have a memory region
specified for it.  

In the testcase sec3 is given an LMA of 0x5000 by GOLD (the same as its VMA) but
it is given an LMA of 0x412c by LD.  (0x412c comes from subtracting 0xed4 from
0x5000, so that VMA - LMA of sec3 == VMA - LMA of sec1.  sec1 is in region2
which is the first viable memory region).

I am now working on a patch to:

  a) update the linker documentation.  (On the assumption that LD's behaviour is
correct).

  b) update GOLD to behave in the same way as LD.


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=11997

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