# FreeBSD ABI Specs



## David John (Oct 27, 2017)

Can somebody guide me in the right direction and point out the ABI Specs used in FreeBSD? Is it the same as System V ABI (https://software.intel.com/sites/default/files/article/402129/mpx-linux64-abi.pdf)?

Thank you.


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## Phishfry (Oct 27, 2017)

I have read the term ABI over and over but I have never really seen a spec.
It seems the System V ABI is indeed used with different versions for 32 bit and 64 bit Intel plus Itanium has its own.
https://people.freebsd.org/~obrien/amd64-elf-abi.pdf

Here they note that there are small differences between Mac, Linux and FreeBSD
https://stackoverflow.com/questions/2171177/what-is-an-application-binary-interface-abi/2456882

More practically FreeBSD documents much in the source.
/usr/src/kern/syscalls.master

There does appear to be a dead link in the handbook for the DRAFT AMD64 ABI pdf
https://www.freebsd.org/platforms/amd64.html


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## David John (Oct 27, 2017)

Phishfry said:


> https://people.freebsd.org/~obrien/amd64-elf-abi.pdf


I have looked at this doc but it's not an official document (a draft version that's shared by a developer). 

This stackoverflow question made me believe that the FreeBSD ABI is not exactly the same as Unix System V ABI.



Phishfry said:


> /usr/src/kern/syscalls.master


 Not sure how the syscall lookup is useful here?

Thank you Phishfry for your time and help.


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