Try falling back to CBIOS if EBIOS totally fails.

diff --git a/ldlinux.asm b/ldlinux.asm
index 02521e9..20d86d8 100644 (file)
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -327,8 +327,7 @@ eddcheck:
                ;
                ; We have EDD support...
                ;
-               ; 0xEB = short jump
-               mov word [getlinsec_cbios],((getlinsec_ebios-(getlinsec_cbios+2)) << 8) + 0xeb
+               mov byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
 .noedd:
 
 ;
@@ -374,7 +373,73 @@ getlinsec:
                add eax,[bsHidden]              ; Add partition offset
                xor edx,edx                     ; Zero-extend LBA (eventually allow 64 bits)
 
-               ; Fall through.  In the case of EBIOS, we patch over the first instruction.
+.jmp:          jmp strict short getlinsec_cbios
+
+;
+; getlinsec_ebios:
+;
+; getlinsec implementation for EBIOS (EDD)
+;
+getlinsec_ebios:
+.loop:
+                push bp                         ; Sectors left
+.retry2:
+               call maxtrans                   ; Enforce maximum transfer size
+               movzx edi,bp                    ; Sectors we are about to read
+               mov cx,retry_count
+.retry:
+
+               ; Form DAPA on stack
+               push edx
+               push eax
+               push es
+               push bx
+               push di
+               push word 16
+               mov si,sp
+                mov dl,[DriveNumber]
+                mov ah,42h                      ; Extended Read
+               push ds
+               push ss
+               pop ds                          ; DS <- SS
+               pushad
+               int 13h
+               popad
+               pop ds
+               lea sp,[si+16]                  ; Remove DAPA
+               jc .error
+               pop bp
+               add eax,edi                     ; Advance sector pointer
+               sub bp,di                       ; Sectors left
+                shl di,SECTOR_SHIFT            ; 512-byte sectors
+                add bx,di                      ; Advance buffer pointer
+                and bp,bp
+                jnz .loop
+
+                ret
+
+.error:
+               ; Some systems seem to get "stuck" in an error state when
+               ; using EBIOS.  Doesn't happen when using CBIOS, which is
+               ; good, since some other systems get timeout failures
+               ; waiting for the floppy disk to spin up.
+
+               pushad                          ; Try resetting the device
+               xor ax,ax
+               int 13h
+               popad
+               loop .retry                     ; CX-- and jump if not zero
+
+               shr word [MaxTransfer],1        ; Reduce the transfer size
+               jnz .retry2
+
+               ; Total failure.  Try falling back to CBIOS.
+               mov byte [getlinsec.jmp+1],(getlinsec_cbios-(getlinsec.jmp+2))
+               mov byte [MaxTransfer],63       ; Max possibe CBIOS transfer
+
+               pop bp
+               ; ... fall through ...
+
 ;
 ; getlinsec_cbios:
 ;
@@ -452,73 +517,11 @@ getlinsec_cbios:
                dec bp
                jnz .retry
 
-               xor ax,ax               ; Sectors transferred <- 0
+               xchg ax,bp              ; Sectors transferred <- 0
                shr word [MaxTransfer],1
-               jnz .error
-               jmp disk_error
-
-;
-; getlinsec_ebios:
-;
-; getlinsec implementation for EBIOS (EDD)
-;
-getlinsec_ebios:
-.loop:
-                push bp                         ; Sectors left
-.retry2:
-               call maxtrans                   ; Enforce maximum transfer size
-               movzx edi,bp                    ; Sectors we are about to read
-               mov cx,retry_count
-.retry:
-
-               ; Form DAPA on stack
-               push edx
-               push eax
-               push es
-               push bx
-               push di
-               push word 16
-               mov si,sp
-                mov dl,[DriveNumber]
-                mov ah,42h                      ; Extended Read
-               push ds
-               push ss
-               pop ds                          ; DS <- SS
-               pushad
-               int 13h
-               popad
-               pop ds
-               lea sp,[si+16]                  ; Remove DAPA
-               jc .error
-               pop bp
-               add eax,edi                     ; Advance sector pointer
-               sub bp,di                       ; Sectors left
-                shl di,SECTOR_SHIFT            ; 512-byte sectors
-                add bx,di                      ; Advance buffer pointer
-                and bp,bp
-                jnz .loop
-
-                ret
-
-.error:
-               ; Some systems seem to get "stuck" in an error state when
-               ; using EBIOS.  Doesn't happen when using CBIOS, which is
-               ; good, since some other systems get timeout failures
-               ; waiting for the floppy disk to spin up.
-
-               pushad                          ; Try resetting the device
-               xor ax,ax
-               int 13h
-               popad
-               loop .retry                     ; CX-- and jump if not zero
-
-               shr word [MaxTransfer],1        ; Reduce the transfer size
-               jnz .retry2
-
-               ; Fall back to CBIOS here?
-
+               jnz .resume
                ; Fall through to disk_error
-
+       
 ;
 ; kaboom: write a message and bail out.
 ;
@@ -555,22 +558,14 @@ maxtrans:
                mov bp,[MaxTransfer]
 .ok:           ret
 
-
 ;
 ; Error message on failure
 ;
-bailmsg:       db 'Boot failed', 0Dh, 0Ah, 0
-
-%if 1
-bs_checkpt_off equ ($-$$)
-%ifndef DEPEND
-%if bs_checkpt_off > 1F8h
-%error "Boot sector overflow"
-%endif
-%endif
+bailmsg:       db 'Boot error', 0Dh, 0Ah, 0
 
+               ; This fails if the boot sector overflows
                zb 1F8h-($-$$)
-%endif
+
 FirstSector    dd 0xDEADBEEF                   ; Location of sector 1
 MaxTransfer    dw 0x007F                       ; Max transfer size
 bootsignature  dw 0AA55h
@@ -628,6 +623,17 @@ ldlinux_ent:
                call writestr
 
 ;
+; Tell the user if we're using EBIOS or CBIOS
+;
+print_bios:
+               mov si,bios_name
+               cmp byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
+               jne .cbios
+               mov byte [si],'E'
+.cbios:
+               call writestr
+
+;
 ; Now we read the rest of LDLINUX.SYS. Don't bother loading the first
 ; sector again, though.
 ;
@@ -720,6 +726,11 @@ getlinsecsr:       pushad
 checksumerr_msg        db 'Load error - ', 0   ; Boot failed appended
 
 ;
+; BIOS type string
+;
+bios_name      db 'CBIOS', 0
+
+;
 ; Debug routine
 ;
 %ifdef debug