[syslinux:master] core: Make cfarcall IF-preserving

[syslinux-bot for H. Peter Anvin]

Commit-ID:  8659757a388ad9071156f2e3d6b04813960dcfed
Gitweb:     http://syslinux.zytor.com/commit/8659757a388ad9071156f2e3d6b04813960dcfed
Author:     H. Peter Anvin <hpa at linux.intel.com>
AuthorDate: Mon, 21 Jun 2010 15:59:40 -0700
Committer:  H. Peter Anvin <hpa at linux.intel.com>
CommitDate: Mon, 21 Jun 2010 15:59:40 -0700

core: Make cfarcall IF-preserving

cfarcall does not take a register image on input, so we need to
explicitly preserve IF in the code flow.

Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>


---
 core/callback.inc |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/core/callback.inc b/core/callback.inc
index 6a35132..d98d800 100644
--- a/core/callback.inc
+++ b/core/callback.inc
@@ -84,13 +84,15 @@ core_syscall:
 		bits 16
 		section .text16
 .rm:
+		mov ax,sp
+		add ax,9*4+4*2
+		mov [CallbackSP],ax
 		pop gs
 		pop fs
 		pop es
 		pop ds
 		popad
 		popfd
-		mov [cs:CallbackSP],sp
 		retf				; Invoke routine
 
 .rm_return:
@@ -138,6 +140,7 @@ core_syscall:
 ;
 ; Cfarcall invocation.  We copy the stack frame to the real-mode stack,
 ; followed by the return CS:IP and the CS:IP of the target function.
+; The value of IF is copied from the calling routine.
 ;
 		global core_cfarcall
 core_cfarcall:
@@ -156,11 +159,14 @@ core_cfarcall:
 		mov [word CallbackSP],di
 		sub edi,ecx		; Allocate space for stack frame
 		and edi,~3		; Round
-		sub edi,4*2		; Return pointer, return value
+		sub edi,4*3		; Return pointer, return value, EFLAGS
 		mov [word RealModeSSSP],di
 		shl ebx,4
 		add edi,ebx		; Create linear address
 
+		mov eax,[esp+5*4]	; EFLAGS from entry
+		and eax,0x202		; IF only
+		stosd
 		mov eax,[esp+7*4]	; CS:IP
 		stosd			; Save to stack frame
 		mov eax,.rm_return	; Return seg:off
@@ -179,6 +185,7 @@ core_cfarcall:
 		bits 16
 		section .text16
 .rm:
+		popfd
 		retf
 .rm_return:
 		mov sp,[cs:CallbackSP]