Thanks for the info Paul, but unfortunately I didn't specify my question
adequately. I'm writing *IBM* assembler, where a move is spelled MVC. My
third-hand doc says to write IBM opcodes but use Unix syntax. Whatever that
means. Here's a simplified example that would get 2 errors, for 2 label
references:
__asm__ __volatile__(
" CHI %3,20\n"
" BH LABEL1\n"
" LA 2,1\n"
" B LABEL2
"LABEL1 LA 2,0\n"
"LABEL2 BR 14\n"
: "=a" (retValue)
: "d" (pProc), "d" (pStack), "d" (cbStack)
);
I have already displayed that certain simple register manipulation works in
context, so I am confident that this language works, and that I am on the
right track.
On the other hand, it's news to me that AT&T/Unix assembler can work on an
IBM S/390 box. I was only brought in on this project cuz I know IBM
assembler. If Unix assembler can be used just as well, maybe I will try to
dump this thing back on our Unix guy...
CXC
-----Original Message-----
From: Paul L. Rogers [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, April 24, 2002 11:59 AM
To: Condit, Christopher
Subject: Re: Addressing problems using asm embedded in C
It's been many years since I did any assembly programing, but I seem
to recall that different assemblers would use a different syntax to
denote if the address or the contents of the address should be used.
Any chance that this explanation would apply?
From: http://www.cis.ohio-state.edu/~parent/classes/360/faq.html
Relocation Truncated to Fit
The problem is that if you have declared a label, say something like:
X: .word 20
Then in your code, suppose you say something like:
mov X, %r3
What you are trying to do is to copy the value in the word corresponding
to X into %r3; except the right way to do it is first get the address of X
into another register etc.
The reason why the assembler assembles this without complaint is thatthe
(unrelocated) address of X is typically small enough to fit in 13 bits
available in the mov instruction; so it assembles using that address. Then
the loader relocates the stuff and now the relocated address won't fit in
the 13 bits, so it `truncates the relocation to fit'.
Paul
On Wed, 24 Apr 2002, Condit, Christopher wrote:
> Date: Wed, 24 Apr 2002 14:13:17 -0400
> From: "Condit, Christopher" <[EMAIL PROTECTED]>
> Reply-To: Linux on 390 Port <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: Addressing problems using asm embedded in C
>
> I'm trying to write some assembler embedded in C via __asm__
__volatile__().
> A couple hundred lines or so. Compiler doesn't complain, but linker
gives
> "relocation truncated to fit" errors on any instruction that refers to a
> label (B's and EX's). I know that message usually (in C) means you are
> calling an unknown function or else are branching too far. Neither of
these
> conditions is the case, since I am only branching down a few bytes, and
I'm
> not calling any functions by name. Total dll length is under 32K.
>
> Fooling around, I note that by recoding to avoid using any labels (lots of
> relative branching), I can eliminate the link time errors. So my linker
is
> choking basically on all labels. Anybody know what's up, or what I can do
> about it? Writing labelless code is not an appealing prospect.
>
> TIA,
> Christopher
>
Paul L. Rogers [EMAIL PROTECTED]
Are you prepared for NetDay? http://www.netday.org/
Linux: It works for me. http://www.linuxdoc.org/
