Changeset 67785 in vbox for trunk/src/VBox/Devices/PC/BIOS

Timestamp:

Jul 5, 2017 8:46:04 AM (8 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

116703

Message:

BIOS: Preserve most flags on INT 16h/01h, 11h. Some software depends on enabling interrupts and/or preserving TF, DF.

Location:

trunk/src/VBox/Devices/PC/BIOS

Files:

• biosint.h (modified) (1 diff)
• keyboard.c (modified) (3 diffs)
• notes.txt (modified) (1 diff)
• orgs.asm (modified) (3 diffs)

trunk/src/VBox/Devices/PC/BIOS/biosint.h

@@ -170 +170 @@
     uint16_t        es;
     uint16_t        ds;
+    uint16_t        ifl;
     iret_addr_t     ra;
 } kbd_regs_t;

trunk/src/VBox/Devices/PC/BIOS/keyboard.c

@@ -645 +645 @@
 #define SP      r.gr.u.r16.sp
 #define FLAGS   r.ra.flags.u.r16.flags
+#define IFLGS   r.ifl
 
 /* Interrupt 16h service implementation. */
@@ -686 +687 @@
 
     case 0x01: /* check keyboard status */
-        SET_IF();   /* Enable interrupts. Some callers depend on that! */
+        /* Enable interrupts, preserve most flags. Some callers depend on that! */
+        FLAGS = IFLGS;
         if ( !dequeue_key(&scan_code, &ascii_code, 0) ) {
             SET_ZF();
@@ -763 +765 @@
 
     case 0x11: /* check MF-II keyboard status */
-        SET_IF();
+        /* Enable interrupts, preserve most flags. Some callers depend on that! */
+        FLAGS = IFLGS;
         if ( !dequeue_key(&scan_code, &ascii_code, 0) ) {
             SET_ZF();

trunk/src/VBox/Devices/PC/BIOS/notes.txt

@@ -12 +12 @@
   emulation.
 
-- Keystroke check (INT 16h, fn 01h/10h) always enables interrupts on return.
+- Keystroke check (INT 16h, fn 01h/11h) always enables interrupts on return.
   DOS POWER.EXE depends on that in some situations.
+
+- IBM DOS J5.00/V is even worse and does a far jump into INT 16h/11h after
+  pushing garbage on the stack. Using IRET directly may change IOPL, set
+  TF, change direction flag, etc. We have to use or simulate RETF 2 instead.
 
 - MS-DOS 5.0/V setup assumes that INT 13h always returns with interrupts

trunk/src/VBox/Devices/PC/BIOS/orgs.asm

@@ -873 +873 @@
 int16_handler:
                 sti
+                ;; Flags are saved *after* enabling interrupts, and with
+                ;; implicitly cleared TF. Software may depend on that.
+                pushf
                 push    es
                 push    ds
@@ -888 +891 @@
                 pop     ds
                 pop     es
+                add     sp, 2           ; Skip saved flags
                 iret
 
@@ -915 +919 @@
                 pop     ds
                 pop     es
+                add     sp, 2           ; Skip saved flags
 ; TODO: review/enable? If so, flags should be restored here?
 if 0