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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
There is a part of the documentation that says this
2.4.4 Executable and Linkable Format wrote:
To create executable file, follow the format choice directive with the executable keyword. It allows to use entry directive followed by the value to set as entry point of program. On the other hand it makes extrn and public directives unavailable, and instead of section there should be the segment directive used, followed only by one or more segment permission flags. The origin of segment is aligned to page (4096 bytes), and available flags for are: readable, writeable and executable.


I think that a reader with non deep knowledge of ELF specification could think that the origin is of the form [mem_offset mod 4096 = 0] when actually is [mem_offset mod 4096 = file_offset mod 4096]. If the user really needs a page aligned address he will need to use "align 4096" even if the previous line was the segment declaration. What is true, however, is that the first accessible byte within the segment is aligned to page size and the segment virtual space size is multiple of 4096 too, but, those first and last bytes may be overlapped with either elf metadata or another segment (still, you're allowed to access it at the permissions you specified without any trouble).

Code:
format ELF executable

segment readable
origin:
label firstByte at origin mod 4096

;origin <> firstByte
.
.
.
end:
label lastByte at ($ + 4095) mod 4096
;end <> lastByte    
Post 08 Jul 2007, 21:49
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