Writing MIPS assembler instructions in C

[M. Warner Losh]

In message: <201002251525.o1PFPgOD028776 at ns.mahan.org>
            Patrick Mahan <mahan at mahan.org> writes:
: > On Thu, Feb 25, 2010 at 11:56 AM, Patrick Mahan <mahan at mahan.org> wrote:
: > >
: > >>> Now my problem is I still need to force the value pointed to "addr" into
: > >>> a specific register because there is a jalr to a function else where
: > >>> that I only have binary access too and it expects it's a value in
: > >>> that register.  Can I coerce this?
: > >>
: > >>I may be missing something here,  but have you tried :
: > >>
: > >>__asm__ __volatile__(
: > >>           "ld     $8, 0(%0)\n\t"
: > >>           "jalr   $8\n"
: > >>           : : "r"(addr) : "$8");
: > >>}
: > >>
: > >>Or is there a reason this will not work?
: > >>
: > >
: > > This is the equivalent of "ld t0, 0(a0)", yes?
: > 
: > Yes that should be equivalent, but assemblers don't know about 't0' only '$8'
: > 
: > > No I tried that method as well, but without success.  (or so it
: > > seemed to me).
: > 
: > I was trying to see what the issue with this method is. Do you get a
: > compiler error, or is it incorrect code? Usually you can figure out
: > what is going wrong by looking at the objdump or the output of 'cc -S'
: > to see if the requested register was used.
: >
: 
: No compiler error but the code does not seem to execute, and I am getting
: no 'illegal instruction' error.  My concern is coming from the issue that
: using binutils built by the manufacturer of the chip (cavium) which only
: run on a linux platform, I tried to disassemble the .o containing the 
: asm statement, but it does not decode to the expected instruction.  So I
: am leary that I have correctly generated the asm (inline asm's not my
: strong suit...)

I've used those binutils on FreeBSD with the linuxulator...

Warner