overlapping ELF symbols and disassembly output

overlapping ELF symbols and disassembly output

[Mike Frysinger]

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it is valid in ELF to have overlapping ELF symbols right ?  so if i have a 
symbol "foo" which starts at say 0x10 and has a size of 0x100, i can have 
another symbol "moo" which starts at say 0x20 and has a size of 0x10 ?

what i'm trying to do is embed some data into a function and have objdump do 
the right thing ... so for example:
.type foo,%function
foo:
	R0 = 0;
	... some more assembly ...
.type moo,%object
moo:
	.asciz "a data string";
.size moo, . - moo
	... some more assembly ...
.size foo, . - foo

objdump on this shows proper disassembly from the start of "foo" up to the 
start of "moo", and then shows that the "moo" symbol is data, but after the 
end of "moo" to the end of "foo", the information is continued to be 
interpreted as data rather than disassembled as object code.  i imagine this 
is not normal, but can it be expected to work ? :)
-mike

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Re: overlapping ELF symbols and disassembly output

[Daniel Jacobowitz]

On Sat, Oct 27, 2007 at 04:30:05PM -0400, Mike Frysinger wrote:
> objdump on this shows proper disassembly from the start of "foo" up to the 
> start of "moo", and then shows that the "moo" symbol is data, but after the 
> end of "moo" to the end of "foo", the information is continued to be 
> interpreted as data rather than disassembled as object code.  i imagine this 
> is not normal, but can it be expected to work ? :)

Not really.  Most tools don't support overlapping symbols.  GDB "sort
of" does.

ARM solved this problem with a separate set of mapping symbols; you
may want to look at that.  Other tools have solved it with annotations
in DWARF .debug_line data.

-- 
Daniel Jacobowitz
CodeSourcery