[OpenBIOS] r800 - dev/geode

[svn at openbios.org]

Author: wmb
Date: 2008-01-31 18:27:36 +0100 (Thu, 31 Jan 2008)
New Revision: 800

Modified:
   dev/geode/smi.fth
Log:
Geode SMI handler - cleaned up the return from 32-bit to 16-bit mode.


Modified: dev/geode/smi.fth
===================================================================
--- dev/geode/smi.fth	2008-01-31 10:15:58 UTC (rev 799)
+++ dev/geode/smi.fth	2008-01-31 17:27:36 UTC (rev 800)
@@ -13,7 +13,7 @@
 h#      1000 constant smm-size  \ We use about 3K of this, 2K for stacks
 : +smm  ( offset -- adr )  smm-base +  ;
 
-h# 28 constant /smm-gdt
+h# 30 constant /smm-gdt
 
 \ The handler code takes about h# 140 bytes
 
@@ -43,10 +43,10 @@
 
 : set-smm-descs  ( -- )
 \   smm-base -1 code32 format-descriptor  smm-gdt 8 + +smm d!  \ Boosted code32
-   smm-base smm-size 1- code16 h# 08 set-descr
-   smm-base smm-size 1- data16 h# 10 set-descr
-   0 -1 code32 h# 18 set-descr
-   0 -1 data32 h# 20 set-descr
+   smm-base smm-size 1- code16 h# 10 set-descr
+   smm-base smm-size 1- data16 h# 18 set-descr
+   0 -1 code32 h# 20 set-descr
+   0 -1 data32 h# 28 set-descr
    /smm-gdt 1-   smm-gdtp +smm      w!  \ GDT limit
    smm-gdt +smm  smm-gdtp +smm wa1+ l!  \ GDT base
 ;
@@ -58,14 +58,15 @@
    16-bit
 
    cs: ds  smm-save-seg d# 00 +  #)  svdc
-   cs: smm-gdt h# 10 + #)  ds  rsdc   \ Now we have a data segment
+   cs: smm-gdt h# 18 + #)  ds  rsdc   \ GDT reference
+   \ Now we can use the data segment
    es  smm-save-seg d# 10 +  #)  svdc
    fs  smm-save-seg d# 20 +  #)  svdc
    gs  smm-save-seg d# 30 +  #)  svdc
    ss  smm-save-seg d# 40 +  #)  svdc
    cs  smm-save-seg d# 50 +  #)  svdc       \ So we can get back to the boost segment
 
-   smm-gdt h# 10 + #)  ss  rsdc
+   smm-gdt h# 18 + #)  ss  rsdc  \ GDT reference
 
    op: sp  smm-save-esp #)  mov
    smm-stack #  sp  mov      \ Now we have a stack
@@ -85,11 +86,11 @@
    op: smm-gdtp     #) lgdt
 
    cr0 ax mov  1 # al or  ax cr0 mov   \ Enter protected mode
-   op: here 7 + smm-handler - +smm  h# 18 #)  far jmp
+   op: here 7 + smm-handler - +smm  h# 20 #)  far jmp  \ GDT reference
    32-bit
 
    \ Reload segment registers with protected mode bits
-   op: h# 20 # ax mov
+   op: h# 28 # ax mov   \ GDT reference
    ax ds mov  ax es mov  ax fs mov  ax gs mov  ax ss mov
 
    \ Turn on paging
@@ -131,16 +132,14 @@
    \ Turn off paging
    cr0 ax mov  h# 8000.0000 invert # ax and  ax cr0 mov	 \ Turn off Paging Enable bit
 
-   cr0 ax mov  1 invert # al and  ax cr0 mov   \ Enter real mode
-
-   \ Return to the boosted code-16 address space
-   smm-save-seg d# 50 + +smm #)  cs  rsdc
+   here 7 +  smm-handler -  h# 08 #)  far jmp     \ Get into the boosted segment
    16-bit
-   op:  here 5 +  smm-base - #) jmp  \ Decrease IP while increasing the segment register
 
+   cr0 ax mov  1 invert # al and  ax cr0 mov   \ Exit protected mode
+
    \ Reload data segment registers
-   cs: smm-gdt h# 10 + #)  ss  rsdc
-   cs: smm-gdt h# 10 + #)  ds  rsdc
+   cs: smm-gdt h# 18 + #)  ss  rsdc   \ GDT reference
+   cs: smm-gdt h# 18 + #)  ds  rsdc   \ GDT reference
 
    op: smm-save-gdt #) lgdt
 
@@ -186,11 +185,7 @@
    h# 000ff.0.00.000ff.1.01. h# 180e msr!
 
    \  Base     Limit
-\   smm-base  smm-size 1-  h# 133b msr!
-   \ The limit here must be large enough to cover the code address
-   \ between the time that we reenter real mode and the time we
-   \ reestablish the boosted descriptor.
-   smm-base  -1  h# 133b msr!   \ Big limit
+   smm-base  smm-size 1-  h# 133b msr!
 
    smm-base smm-header + 0   h# 132b msr!  \ Offset of SMM Header