diskstart: don't let the function number clobber the LBA

The LBA for getonesec and getlinsec is in EDX:EAX, but both DL and AX
are function inputs to INT 13h (drive number and function number).  We
need to preserve the LBA across *both* those, otherwise retries will
not function.

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

diff --git a/core/diskstart.inc b/core/diskstart.inc
index 01439b8..c0ba52a 100644 (file)
--- a/core/diskstart.inc
+++ b/core/diskstart.inc
@@ -294,8 +294,10 @@ getonesec_ebios:
                push word 1
                push word 16
                mov si,sp
+               pushad
                 mov ah,42h                      ; Extended Read
                call xint13
+               popad
                lea sp,[si+16]                  ; Remove DAPA
                jc .error
                 ret
@@ -308,7 +310,7 @@ getonesec_ebios:
 
                pushad                          ; Try resetting the device
                xor ax,ax
-               int 13h
+               call xint13
                popad
                loop .retry                     ; CX-- and jump if not zero
 
@@ -407,9 +409,7 @@ writestr_early:
 ;
 xint13:
                 mov dl,[DriveNumber]
-               pushad
                int 13h
-               popad
                ret
 
 ;
@@ -641,12 +641,14 @@ getlinsec_ebios:
                push di
                push word 16
                mov si,sp
+               pushad
                 mov ah,42h                      ; Extended Read
                push ds
                push ss
                pop ds
                call xint13
                pop ds
+               popad
                lea sp,[si+16]                  ; Remove DAPA
                jc .error
                pop bp
@@ -738,7 +740,9 @@ getlinsec_cbios:
                mov ah,02h              ; Read sectors
                mov bp,retry_count
 .retry:
+               pushad
                call xint13
+               popad
                jc .error
 .resume:
                movzx ecx,al            ; ECX <- sectors transferred