Peng Fan wrote:
hi,
Now I have a idea about how to include local symbols in the RAP file,
and try to not increase the size of the RAP file.
1. About the relocations.
The current layout for the relocations is:
| header | reloc entries|
the first bit of header indicates whether it is rela or not. the
remaining 30 bits indicates the number of reloc entries.
But now I want to include elf object index for reloc entries and symbols
to resolve conflicting local symbols. For example two objects both
contains the ".LC0" symbols, how to figure out which ".LC0" symbol is
needed for the reloc entry.
I want to use the following layout for reloc part of RAP file .
| header | counts(object 1) | reloc entries | counts(object 2) | reloc
entries .....
It looks fine if we finally decide we need locals in a RAP file.
Please note if the RAP format changes we need to change the RAP version
number. The RAP header has a version number and currently it is hard
coded in rtems-ld. I think this should be added as a const to the 'rap'
namespace and formatted into the header. The target side needs to check
which version it can support, ie up to a specific version and not
higher. The version is an incrementing number. I will look at adding
this soon.
The header still contains the total number of reloc entries just like
the current implementation.
2. About the local symbols.
Now there is a 'symtab_size' variable to indicates how many global
symbols are in the rap file.
Because I want to include local symbols, I want to add a local symbol
table after the global symbol table.
| global_symtab_size | local_symtab_size | .......
| global symbol table
| object1 local_symtab_size | object1 local symbol table
| object2 local_symtab_size| object2 local symbol table | ....
My current implementation is each reloc entry contains an object index
and each symbol contains an object index. But this may consume more
space, I prepare to rewrite this using 1 and 2.
However I am not sure whether this is ok.
I am still wondering if we need locals in the RAP file. Could some form
of incremental linking pass in rtems-ld remove them ?
Do you have a simple C piece of code with a compile command line that
results in an ELF file with these local symbols ? I would like to
understand why they are present.
Chris
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