From owner-cvs-all  Sat Feb 24 23:36:49 2001
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To: Bruce Evans <bde@zeta.org.au>
Cc: Jake Burkholder <jake@FreeBSD.org>, cvs-committers@FreeBSD.org,
	cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/i386/i386 db_trace.c exception.s machdep.c trap.c src/sys/i386/include asnames.h 
In-Reply-To: <Pine.BSF.4.21.0102251745170.5881-100000@besplex.bde.org> 
Date: Sat, 24 Feb 2001 23:36:31 -0800
From: Peter Wemm <peter@netplex.com.au>
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Bruce Evans wrote:
> On Sat, 24 Feb 2001, Jake Burkholder wrote:
> 
> > jake        2001/02/24 18:53:06 PST
> > 
> >   Modified files:
> >     sys/i386/i386        db_trace.c exception.s machdep.c trap.c 
> >     sys/i386/include     asnames.h 
> >   Log:
> >   - Rename the lcall system call handler from Xsyscall to Xlcall_syscall
> >     to be more like Xint0x80_syscall and less like c function syscall().
> 
> This is sort of backwards.  Xsyscall is supposed to be named like the C
> function syscall(), but it should be used for normal int 0x80 syscalls.

Well, given that we have two, "Xsyscall" was wrong as it implies that it
was the "normal" one (it is not).  Would you rather that Xint0x80syscall
be renamed to Xsyscall instead?

> >   - Reduce code duplication between the int0x80 and lcall handlers by
> >     shuffling the elfags into the right place, saving the sizeof the
> >     instruction in tf_err and jumping into the common int0x80 code.
> 
> This breaks profiling and pessimizes Xsyscall a little.  Please back this
> out.

Are you sure? The X*syscall stubs dont seem to be profiled..

#define IDTVEC(name)    ALIGN_TEXT; .globl __CONCAT(X,name); \
                        .type __CONCAT(X,name),@function; __CONCAT(X,name):

        SUPERALIGN_TEXT
IDTVEC(int0x80_syscall)
        pushl   $2                      /* sizeof "int 0x80" */
syscall_with_err_pushed:
        subl    $4,%esp                 /* skip over tf_trapno */
        pushal
        pushl   %ds
        pushl   %es
        pushl   %fs
        mov     $KDSEL,%ax              /* switch to kernel segments */
        mov     %ax,%ds
        mov     %ax,%es
        mov     $KPSEL,%ax
        mov     %ax,%fs
        FAKE_MCOUNT(13*4(%esp))
        call    syscall
        MEXITCOUNT
        jmp     doreti

Obviously I could easily be misunderstanding things, but the FAKE_MCOUNT
pulls the caller off the stack, right?  How does this all tie in?
Would this change imply that the cpu time of the lcall version would be
applied to the int0x80 version?

> Bruce

Cheers,
-Peter
--
Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au
"All of this is for nothing if we don't go to the stars" - JMS/B5


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