PXELINUX: when chaining an NBP, restore *all* registers

On at least ASUS A8N-E, unless *all* registers are restored to pre-PXE
status, localboot doesn't work.  We were clobbering DS, ESI and EDX
when chainloading an NBP, which meant that localboot wouldn't work in
the chainloaded NBP.  Fix this.

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

diff --git a/core/bootsect.inc b/core/bootsect.inc
index 3ea36bf..200f00a 100644 (file)
--- a/core/bootsect.inc
+++ b/core/bootsect.inc
@@ -74,13 +74,19 @@ load_bootsec:
                xor ax,ax
                rep movsw
                pop si                  ; DS:SI points to partition info
+               xor bx,bx
 %elif IS_ISOLINUX
                mov dl,[DriveNumber]
+               xor bx,bx
 %elif IS_PXELINUX
                mov byte [KeepPXE],03h  ; Chainloading + keep PXE
                call reset_pxe
+               lfs si,[InitStack]
+               ; Put restore DS, EDX and ESI to the true initial values
+               mov bx,[fs:si+6]
+               mov edx,[fs:si+28]
+               mov esi,[fs:si+12]
 %endif
-               xor bx,bx
 
 ;
 ; replace_bootstrap for the special case where we have exactly one
@@ -91,12 +97,12 @@ load_bootsec:
 replace_bootstrap_one:
                mov eax,[trackbuf]              ; Base address
                add eax,[trackbuf+8]            ; Length
-               movzx edx,word [BIOS_fbm]
-               shl edx,10                      ; Free Base Memory
-               sub edx,eax
+               movzx ecx,word [BIOS_fbm]
+               shl ecx,10                      ; Free Base Memory
+               sub ecx,eax
                mov [trackbuf+12],eax
                or dword [trackbuf+16],-1       ; Zero memory
-               mov [trackbuf+20],edx
+               mov [trackbuf+20],ecx
                push word 2                     ; Length of descriptor list
                ; Fall through