Re: Experimental fix for my memcpy_{to,from}fs problem

[Eduardo Pereira Habkost <ehabkost@conectiva.com.br>]

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Interesting:

The diff between dev86-0.16.0 and 0.16.15 shows:

@@ -664,8 +693,34 @@
        if( main_flag > 2 )
           globl("environ");
     }
+#ifdef I8088
+    regfuse = 0;
+#endif
     lbrace();
     compound();
+#ifdef I8088
+    if (regfuse & callee1mask) {
+        outstr("! Register");
+        if (regfuse & INDREG0 & callee1mask) outstr(" BX");
+        if (regfuse & INDREG1 & callee1mask) outstr(" SI");
+       if (regfuse & INDREG2 & callee1mask) outstr(" DI");
+       outstr(" used in function ");
+       outnstr(funcname);
+       if (optimise && !callersaves) {
+           outstr(funcname);
+           outnstr(".off = 0");
+       }
+    } else
+       if (optimise && !callersaves) {
+           outstr(funcname);
+           outstr(".off = ");
+#ifndef I80386
+           outnhex(4);
+#else
+           outnhex(i386_32?12:4);
+#endif
+       }
+#endif
     clearfunclabels();
 }

This register-saving optmization was added after 0.16.0. The fix is valid,
but probably it will break systems using dev86 <= 0.16.0.

On Tue, Jun 01, 2004 at 07:02:35PM -0300, Eduardo Pereira Habkost wrote:
> 
> The following patch fixes the problem on my system. Probably
> with some versions of bcc the patch will break something.
> 
> I've added code to save the contents of SI and DI, I don't know if the
> callers of these functions assume that SI and DI are touched, but just
> in case.
> 
> Now the system booted and ran flawlessly.
> 
> --- elks/arch/i86/mm/user.c	3 Jun 2002 22:22:58 -0000	1.15
> +++ elks/arch/i86/mm/user.c	1 Jun 2004 20:44:51 -0000
> @@ -34,10 +34,12 @@
>  
>  #ifndef S_SPLINT_S
>  #asm
> +	push	si
> +	push	di
>  	mov	dx,es
>  	mov	bx,ds
>  	mov	es,bx
> -	mov	ax,[bp-6]	! source segment (local variable)
> +	mov	ax,[bp-2]	! source segment (local variable)
>  	mov	ds,ax
>  	mov	di,[bp+4]	! destination address
>  	mov	si,[bp+6]	! source address
> @@ -47,8 +49,11 @@
>  	movsb
>  	mov	ds,bx
>  	mov	es,dx
> +	pop	di
> +	pop	si
>  #endasm
>  #endif
> +
>  }
>  
>  int verified_memcpy_fromfs(void *daddr, void *saddr, size_t len)
> @@ -69,8 +74,10 @@
>  
>  #ifndef S_SPLINT_S
>  #asm
> +	push	si
> +	push	di
>  	mov	dx,es
> -	mov	ax,[bp-6]	! source segment (local variable)
> +	mov	ax,[bp-2]	! source segment (local variable)
>  	mov	es,ax
>  	mov	di,[bp+4]	! destination address
>  	mov	si,[bp+6]	! source address
> @@ -79,6 +86,8 @@
>  	rep
>  	movsb
>  	mov	es,dx
> +	pop	di
> +	pop	si
>  #endasm
>  #endif
>  }
> 
> -- 
> Eduardo



-- 
Eduardo

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