Fix COMBOOT return; support DOS system calls 00 and 4C (both are EXIT.)

diff --git a/NEWS b/NEWS
index 7675b95..7edf945 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -19,6 +19,12 @@ Changes in 1.75:
        * ISOLINUX: Add a few more workarounds for various broken El
          Torito BIOSes.
        * Make sure .depend files aren't accidentally packed...
+       * ALL: Fix bugs in the extension-detect code; this caused
+         files like COMBOOT images and CD boot sectors to be
+         mis-identified as Linux kernels and rejected.
+       * ALL: Fix the return from COMBOOT.
+       * ALL: Do some of the early groundwork for supporting DOS
+         system calls in COMBOOT.
 
 Changes in 1.74:
        * SYSLINUX: fix bug that would cause valid kernel images to be

diff --git a/comboot.inc b/comboot.inc
index fbda097..5d7019e 100644 (file)
--- a/comboot.inc
+++ b/comboot.inc
@@ -37,12 +37,15 @@ is_comboot_image:
                ;
                ; Set up the DOS vectors in the IVT (INT 20h-3fh)
                ;
-               mov dword [4*0x20],comboot_return       ; INT 20h vector
-               mov eax,comboot_bogus
-               mov di,4*0x21
-               mov cx,31               ; All remaining DOS vectors
+               mov di,4*0x20           ; DOS interrupt vectors
+               mov eax,comboot_return
+               stosd
+               mov ax,comboot_int21
+               stosd
+               mov ax,comboot_bogus
+               mov cx,30               ; All remaining DOS vectors
                rep stosd
-       
+
                mov cx,comboot_seg
                mov es,cx
 
@@ -79,8 +82,7 @@ comboot_end_cmd: mov al,0Dh           ; CR after last character
                mov [es:80h], al        ; Store command line length
 
                mov [SavedSSSP],sp
-               mov ax,ss               ; Save away SS:SP
-               mov [SavedSSSP+2],ax
+               mov [SavedSSSP+2],ss    ; Save away SS:SP
 
                call vgaclearmode       ; Reset video
 
@@ -94,23 +96,36 @@ comboot_end_cmd: mov al,0Dh         ; CR after last character
 
 ; Proper return vector
 comboot_return:        cli                     ; Don't trust anyone
-               lss sp,[cs:SavedSSSP]
-               mov ds,ax
-               mov es,ax
-               sti
-               cld
-               jmp cb_enter
+               xor ax,ax
+               jmp comboot_exit
+
+; INT 21h: generic DOS system call
+comboot_int21: and ah,ah               ; 00 = return
+               je comboot_return
+               cmp ah,4Ch              ; 4C = return with status
+               je comboot_return
 
-; Attempted to execute DOS system call
+               ; Otherwise fall through to comboot_bogus
+
+; Attempted to execute non-21h DOS system call
 comboot_bogus: cli                     ; Don't trust anyone
+               mov ax,err_notdos
+
+;
+; Generic COMBOOT return to command line code
+;
+comboot_exit:
                lss sp,[cs:SavedSSSP]
-               mov ds,ax
-               mov es,ax
+               xor dx,dx
+               mov ds,dx
+               mov es,dx
                sti
                cld
+               and ax,ax
+               je .nomsg
                mov si,KernelCName
                call cwritestr
-               mov si,err_notdos
+               xchg si,ax
                call cwritestr
-               jmp cb_enter
+.nomsg:                jmp cb_enter
 

diff --git a/isolinux.asm b/isolinux.asm
index bfa6b91..3373f59 100644 (file)
--- a/isolinux.asm
+++ b/isolinux.asm
@@ -646,7 +646,8 @@ checkerr_msg:       db 'Image checksum error, sorry...', CR, LF, 0
 
 err_bootfailed db CR, LF, 'Boot failed: press a key to retry...'
 bailmsg                equ err_bootfailed
-crlf_msg       db CR, LF, 0
+crlf_msg       db CR, LF
+null_msg       db 0
 
 ;
 ; El Torito spec packet

diff --git a/ldlinux.asm b/ldlinux.asm
index 008a82f..955665a 100644 (file)
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -1685,7 +1685,8 @@ loading_msg     db 'Loading ', 0
 dotdot_msg      db '.'
 dot_msg         db '.', 0
 aborted_msg    db ' aborted.'                  ; Fall through to crlf_msg!
-crlf_msg       db CR, LF, 0
+crlf_msg       db CR, LF
+null_msg       db 0
 crff_msg       db CR, FF, 0
 syslinux_cfg   db 'SYSLINUXCFG'
 ;

diff --git a/pxelinux.asm b/pxelinux.asm
index a549432..9615b45 100644 (file)
--- a/pxelinux.asm
+++ b/pxelinux.asm
@@ -2297,7 +2297,8 @@ dotdot_msg      db '.'
 dot_msg         db '.', 0
 fourbs_msg     db BS, BS, BS, BS, 0
 aborted_msg    db ' aborted.'                  ; Fall through to crlf_msg!
-crlf_msg       db CR, LF, 0
+crlf_msg       db CR, LF
+null_msg       db 0
 crff_msg       db CR, FF, 0
 default_str    db 'default', 0
 default_len    equ ($-default_str)