Date: Fri, 8 Dec 2000 10:19:34 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Julian Elischer <julian@elischer.org> Cc: current@FreeBSD.ORG Subject: Re: __asm help.. Message-ID: <200012081819.eB8IJYH20561@earth.backplane.com> References: <3A31236B.23501A47@elischer.org>
next in thread | previous in thread | raw e-mail | index | archive | help
:I'm trying to write some experimental mutex operations similar to those
:in -current, but to do differnt things (e.g. a read/write lock)
:however, I am having some problems with the __asm stuff.
:
:What I want to do is to define some operations that will
:assemble down to:
: pushfl
: cli
: [stuff]
: popfl
:
:I can generate the code, but it seems to me that there should be
:a way of telling gcc that you have just pushed an item onto the stack,
:so that if you were to have some C code between the push and po
:(of the flags reg) the compiler has a correct idea of where the
:SP is. I can imagine that it doesn't matter so it may be that there
:is no constaint for that purpose (I read the gcc asm info pages)
:but I wanted to make sure that that is the case because if it does turn
:out to be important, it may manifest itself as a wierd bug sometime
:in 2002.
:
:The current pushfl code in the kernel has the following:
: __asm __volatile("pushfl; popl %0" : "=r" (ef));
:which has no long term effect on the stack pointer so I cannot
:use it as a guide.
:
:--
: __--_|\ Julian Elischer
I think all you can do is move the addresses and data used
by 'stuff' into registers prior to the push, then manipulate
the registers between the push and the pop.
-Matt
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200012081819.eB8IJYH20561>