Date: Thu, 25 Feb 2010 09:39:05 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: mahan@mahan.org Cc: freebsd-mips@FreeBSD.org Subject: Re: Writing MIPS assembler instructions in C Message-ID: <20100225.093905.864843819598471490.imp@bsdimp.com> In-Reply-To: <201002251525.o1PFPgOD028776@ns.mahan.org> References: <19077.1267079184@mahan.org> <98a59be81002242231mc491517sa5d752cb870c1f9@mail.gmail.com> <201002251525.o1PFPgOD028776@ns.mahan.org>
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In message: <201002251525.o1PFPgOD028776@ns.mahan.org>
Patrick Mahan <mahan@mahan.org> writes:
: > On Thu, Feb 25, 2010 at 11:56 AM, Patrick Mahan <mahan@mahan.org> w=
rote:
: > >
: > >>> Now my problem is I still need to force the value pointed to "a=
ddr" 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. =A0Can I coerce this?
: > >>
: > >>I may be missing something here, =A0but have you tried :
: > >>
: > >>__asm__ __volatile__(
: > >> =A0 =A0 =A0 =A0 =A0 "ld =A0 =A0 $8, 0(%0)\n\t"
: > >> =A0 =A0 =A0 =A0 =A0 "jalr =A0 $8\n"
: > >> =A0 =A0 =A0 =A0 =A0 : : "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. =A0(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 get=
ting
: no 'illegal instruction' error. My concern is coming from the issue =
that
: using binutils built by the manufacturer of the chip (cavium) which o=
nly
: run on a linux platform, I tried to disassemble the .o containing the=
=
: asm statement, but it does not decode to the expected instruction. S=
o 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
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