Re: [Crackerjack-devel] [TESTING] [POWERPC] Add fast little-endian switch() system call

[Michael K. <mtk...@go...>]

Paul Mackerras wrote:
> Subrata Modak writes:
> 
>> You have added the new system call switch() for the POWERPC architecture
>> in the recent 2.6.26 kernel. Could you please share with us the ways you
>> tested it. Did you develop/write an automated test case for this. In
>> such a case, would you be willing to contribute the same test case(s) to
>> LTP (http://ltp.cvs.sourceforge.net/ltp/ltp/testcases/kernel/syscalls/)
>> under GPLv2 ?
> 
> This can only be tested on a POWER6 machine.  A program to test it is
> attached.

Paul,

In the interests of perhaps documenting this (I don't know Power assembler),
can you provide some more info on this interface, like:

* What are the settings to enable little/big endian mode?  (Or is it
just a toggle, with successive identical calls just switching the mode?)

* Does the call return any information about the previous endianess state?
(It appears not, but I better check.)  If not then how does one determine
the current state?  (I realize that a userspace program could just test
where the bytes of a (say) long are placed in relation to one another,
and so determine the information in that way, but I'm wondering if there
is another way, e.g., inspecting some processor status flag.)

* Is any wrapper support for this interface going into glibc, do you know?

Cheers,

Michael


-- 
Michael Kerrisk
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