--- //depot/vendor/freebsd/src/sys/boot/i386/btx/btx/btx.S	2008/03/10 21:45:25
+++ //depot/user/jhb/boot/sys/boot/i386/btx/btx/btx.S	2008/05/23 19:58:47
@@ -34,6 +34,12 @@
 		.set PAG_SIZ,0x1000		# Page size
 		.set PAG_CNT,0x1000		# Pages to map
 /*
+ * Fields in %eflags.
+ */
+		.set PSL_T,0x00000100		# Trap flag
+		.set PSL_I,0x00000200		# Interrupt enable flag
+		.set PSL_VM,0x00020000		# Virtual 8086 mode flag
+/*
  * Segment selectors.
  */
 		.set SEL_SCODE,0x8		# Supervisor code
@@ -54,6 +60,7 @@
  */
 		.set SYS_EXIT,0x0		# Exit
 		.set SYS_EXEC,0x1		# Exec
+		.set SYS_PANIC,0x1		# Panic
 /*
  * Fields in V86 interface structure.
  */
@@ -369,7 +376,7 @@
 		je except.3			# Yes
 		cmpb $0x1,(%esp,1)		# Debug?
 		jne except.2a			# No
-		testl $0x100,0x10(%esp,1)	# Trap flag set?
+		testl $PSL_T,0x10(%esp,1)	# Trap flag set?
 		jnz except.3			# Yes
 except.2a:	jmp exit			# Exit
 except.3:	leal 0x8(%esp,1),%esp		# Discard err, int no
@@ -460,7 +467,17 @@
 		pushl %ds			#  address
 		popl %es			#  data
 		leal 0x44(%esp,1),%esi		# Base of frame
-		movl -0x14(%esi),%eax		# Get Int no
+		testl $PSL_I,-0x08(%esi)	# Are interrupts enabled?
+		jnz intusr.1			# Yes
+		movl $clivm86,%esi		# Display bad
+		call putstr			#  VM86 call
+		popl %es			# Restore
+		popl %ds			#  seg
+		popl %fs			#  regs
+		popl %gs
+		popal				# Restore gp regs
+		jmp ex_noc			# Panic
+intusr.1:	movl -0x14(%esi),%eax		# Get Int no
 		cmpl $-1,%eax			# Hardware interrupt?
 		jne intusr.2			# Yes
 /*
@@ -491,7 +508,7 @@
 		movl %edx,-0x40(%esi)		# Real mode %ds of 0
 		movl %edx,-0x44(%esi)		# Real mode %es of 0
 		movl -0x08(%esi),%ebx		# Pass user flags with
-		andl $~0x200,%ebx		#  interrupts disabled
+		andl $~PSL_I,%ebx		#  interrupts disabled
 		movw %bx,MEM_ESPR-0x12		#  to real mode target
 /*
  * %eax now holds either the interrupt number or segment:offset of function.
@@ -667,8 +684,12 @@
 		leal 0x4(%eax),%esp		#  stack
 		popl %eax			# Call
 		call *%eax			#  program
-intx30.1:	orb $0x1,%ss:btx_hdr+0x7	# Flag reboot
+intx30.1:	cmpl $SYS_EXIT,%eax		# Exit system call?
+		jne intx30.2			# No
+		orb $0x1,%ss:btx_hdr+0x7	# Flag reboot
 		jmp exit			# Exit
+intx30.2:	pushl $0x30			# Interrupt Number
+		jmp ex_noc			# Panic
 /*
  * Dump structure [EBX] to [EDI], using format string [ESI].
  */
@@ -696,7 +717,7 @@
 dump.2: 	testb $DMP_MEM,%ch		# Dump memory?
 		jz dump.8			# No
 		pushl %ds			# Save
-		testb $0x2,0x52(%ebx)		# V86 mode?
+		testl $PSL_VM,0x50(%ebx)	# V86 mode?
 		jnz dump.3			# Yes
 		verr 0x4(%esi)	 		# Readable selector?
 		jnz dump.3			# No
@@ -1028,6 +1049,7 @@
  * Bad VM86 call panic
  */
 badvm86:	.asciz "Invalid VM86 Request\n"
+clivm86:	.asciz "VM86 Request with interrupts disabled\n"
 
 /*
  * End of BTX memory.
--- //depot/vendor/freebsd/src/sys/boot/i386/btx/lib/btxsys.s	2001/07/17 07:17:28
+++ //depot/user/jhb/boot/sys/boot/i386/btx/lib/btxsys.s	2008/05/23 19:58:47
@@ -24,6 +24,7 @@
 #
 		.global __exit
 		.global __exec
+		.global __panic
 #
 # Constants.
 #
@@ -38,3 +39,8 @@
 #
 __exec: 	movl $0x1,%eax			# BTX system
 		int $INT_SYS			#  call 0x1
+#
+# System call: panic
+#
+__panic:	movl $0x2,%eax			# BTX system
+		int $INT_SYS			#  call 0x2
--- //depot/vendor/freebsd/src/sys/boot/i386/btx/lib/btxv86.s	2001/07/17 07:17:28
+++ //depot/user/jhb/boot/sys/boot/i386/btx/lib/btxv86.s	2008/05/23 19:58:47
@@ -55,6 +55,11 @@
 		call __v86_swap			# Load user registers
 		addl $0x4,%esp			# Discard pointer
 		pushl __v86ret			# Restore return address
+		pushfl				# Push flags
+		testl $0x200,(%esp,1)		# Interrupts enabled?
+		jnz 1f				# Yes
+		call __panic			# Panic otherwise
+1:		popfl				# Restore flags
 		ret 				# To user
 #
 # Swap V86 and user registers.