isolinux: handle systems which disables interrupts in El Torito

At least one system has been identified which disables interrupts when
El Torito INT 13h is executed.  Thus, save/restore IF around INT 13h.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/core/isolinux.asm b/core/isolinux.asm
index 090999d..fd18bd3 100644 (file)
--- a/core/isolinux.asm
+++ b/core/isolinux.asm
@@ -703,20 +703,26 @@ writechr_simple:
                ret
 
 ;
-; int13: save all the segment registers and call INT 13h
-;       Some CD-ROM BIOSes have been found to corrupt segment registers.
+; int13: save all the segment registers and call INT 13h.
+;       Some CD-ROM BIOSes have been found to corrupt segment registers
+;       and/or disable interrupts.
 ;
 int13:
-
+               pushf
+               push bp
                push ds
                push es
                push fs
                push gs
                int 13h
+               mov bp,sp
+               setc [bp+10]            ; Propagate CF to the caller
                pop gs
                pop fs
                pop es
                pop ds
+               pop bp
+               popf
                ret
 
 ;
@@ -778,8 +784,8 @@ getlinsec_ebios:
                push ds
                push ss
                pop ds                          ; DS <- SS
-                mov ah,42h                      ; Extended Read
-               int 13h
+               mov ah,42h                      ; Extended Read
+               call int13
                pop ds
                popad
                lea sp,[si+16]                  ; Remove DAPA
@@ -804,7 +810,7 @@ getlinsec_ebios:
                pushad                          ; Try resetting the device
                xor ax,ax
                mov dl,[DriveNumber]
-               int 13h
+               call int13
                popad
                loop .retry                     ; CX-- and jump if not zero
 
@@ -880,7 +886,7 @@ getlinsec_cbios:
                mov bp,retry_count
 .retry:
                pushad
-               int 13h
+               call int13
                popad
                jc .error
 .resume: