RE: A question about S/390 port

[John Baldwin <jhb@xxxxxxxxxxx>]

On 10-Jul-2002 Serguei Tzukanov wrote:
> Some working notes.
> 
> I've written the libc/csu part, kernel successfully starts init and init 
> forks off for the execve of -sh,
> (http://tzukanov.narod.ru/freebsd390/bootlog.txt)
> but there is problem with printing from userland, e.g. output from 
> userland are not visible. Write syscall to descs 1,2 in init returns 
> with success.
> I'm sure it's something very stupid, so maybe someone have a clue?
> 
> And another problem (well-known?):
> __syscall returns 64-bit value but mmap returns 4-byte word in the 
> td->td_retval[0]. Wrapper for mmap in libc casts 64 rv to 32 and alays 
> gets zero. This leads to truncating to zero due to cast on 32-bit 
> big-endian architectures.
> The solution is obvious - using constructs like
> td->td_retval[_QUAD_LOWWORD] = xxx in MI code.
> 
> For now I just avoid it with hack in syscall handler.

td_retval[0] is the low word, and td_retval[1] is the high word, you just
need to make sure the values from those two words get returned properly
to userland.

-- 

John Baldwin <jhb@xxxxxxxxxxx>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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