Add "onerror" configuration directivesyslinux-2.08-pre6

9 files changed, 80 insertions, 10 deletions

diff --git a/NEWS b/NEWS
index 7c76e874..ec26f7d2 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,8 @@ them.
 Changes in 2.08:
 	* Add new configuration command "ontimeout" to allow timeout
 	  to have a different action than just pressing Enter.
+	* Add new configuration command "onerror" to allow a custom
+	  command to be executed in case the kernel image is not found.
 	* Fix bugs in the COMBOOT/COM32 command-line parsing.  APPEND
 	  now works with COMBOOT/COM32 images.
 	* PXELINUX: Poll for ARP requests while sitting at the
@@ -15,7 +17,8 @@ Changes in 2.08:
 	* MEMDISK: Add an API to query for the existence of MEMDISK.
 	* SYSLINUX: Fix loading boot sectors (.bs/.bss) from floppy
 	  disk.
-	* .c32 is now one of the extensions searched for automatically.
+	* .c32 is now one of the extensions searched for
+	  automatically.
 
 Changes in 2.07:
 	* MEMDISK: Workaround for BIOSes which go into a snit when
diff --git a/isolinux.asm b/isolinux.asm
index 57488cb7..fd67d2e4 100644
--- a/isolinux.asm
+++ b/isolinux.asm
@@ -134,6 +134,7 @@ VKernelBuf:	resb vk_size		; "Current" vkernel
 		alignb 4
 AppendBuf       resb max_cmd_len+1	; append=
 Ontimeout	resb max_cmd_len+1	; ontimeout
+Onerror		resb max_cmd_len+1	; onerror
 KbdMap		resb 256		; Keyboard map
 FKeyName	resb 10*FILENAME_MAX	; File names for F-key help
 NumBuf		resb 15			; Buffer to load number
@@ -1614,6 +1615,7 @@ img_table:
 ;
 AppendLen       dw 0                    ; Bytes in append= command
 OntimeoutLen	dw 0			; Bytes in ontimeout command
+OnerrorLen	dw 0			; Bytes in onerror command
 KbdTimeOut      dw 0                    ; Keyboard timeout (if any)
 CmdLinePtr	dw cmd_line_here	; Command line advancing pointer
 initrd_flag	equ $
diff --git a/keywords b/keywords
index 4e55f152..28efdbcd 100644
--- a/keywords
+++ b/keywords
@@ -14,6 +14,7 @@ say
 serial
 timeout
 ontimeout
+onerror
 f0
 f1
 f2
diff --git a/keywords.inc b/keywords.inc
index 2fcae3b6..7496dabf 100644
--- a/keywords.inc
+++ b/keywords.inc
@@ -58,6 +58,7 @@ keywd_table:
 		keyword serial,    pc_serial
 		keyword timeout,   pc_timeout
 		keyword ontimeout, pc_ontimeout
+		keyword onerror,   pc_onerror
 		keyword f1,        pc_fkey,     FKeyName+(0<<FILENAME_MAX_LG2)
 		keyword f2,        pc_fkey,     FKeyName+(1<<FILENAME_MAX_LG2)
 		keyword f3,        pc_fkey,     FKeyName+(2<<FILENAME_MAX_LG2)
diff --git a/ldlinux.asm b/ldlinux.asm
index 13b9b36d..745aec2f 100644
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -124,6 +124,7 @@ VKernelBuf:	resb vk_size		; "Current" vkernel
 		alignb 4
 AppendBuf       resb max_cmd_len+1	; append=
 Ontimeout	resb max_cmd_len+1	; ontimeout
+Onerror		resb max_cmd_len+1	; onerror
 KbdMap		resb 256		; Keyboard map
 FKeyName	resb 10*16		; File names for F-key help
 NumBuf		resb 15			; Buffer to load number
@@ -1434,6 +1435,7 @@ debug_magic	dw 0D00Dh		; Debug code sentinel
 %endif
 AppendLen       dw 0                    ; Bytes in append= command
 OntimeoutLen	dw 0			; Bytes in ontimeout command
+OnerrorLen	dw 0			; Bytes in onerror command
 KbdTimeOut      dw 0                    ; Keyboard timeout (if any)
 CmdLinePtr	dw cmd_line_here	; Command line advancing pointer
 initrd_flag	equ $
diff --git a/parseconfig.inc b/parseconfig.inc
index 34842d85..ebb74de1 100644
--- a/parseconfig.inc
+++ b/parseconfig.inc
@@ -22,8 +22,7 @@
 ; 
 pc_default:	mov di,default_cmd
 		call getline
-		xor al,al
-		stosb				; null-terminate
+		mov byte [di-1],0		; null-terminate
 		ret
 
 ;
@@ -31,11 +30,20 @@ pc_default:	mov di,default_cmd
 ;
 pc_ontimeout:	mov di,Ontimeout
 		call getline
-		sub di,Ontimeout
+		sub di,Ontimeout+1		; Don't need final space
 		mov [OntimeoutLen],di
 		ret
 
 ;
+; "onerror" command
+;
+pc_onerror:	mov di,Onerror
+		call getline
+		sub di,Onerror
+		mov [OnerrorLen],di
+		ret
+
+;
 ; "append" command
 ;
 pc_append:      cmp word [VKernelCtr],byte 0
diff --git a/pxelinux.asm b/pxelinux.asm
index d53924bb..0822992e 100644
--- a/pxelinux.asm
+++ b/pxelinux.asm
@@ -206,6 +206,7 @@ VKernelBuf:	resb vk_size		; "Current" vkernel
 		alignb 4
 AppendBuf       resb max_cmd_len+1	; append=
 Ontimeout	resb max_cmd_len+1	; ontimeout
+Onerror		resb max_cmd_len+1	; onerror
 KbdMap		resb 256		; Keyboard map
 BootFile	resb 256		; Boot file from DHCP packet
 PathPrefix	resb 256		; Path prefix derived from the above
@@ -2509,6 +2510,7 @@ BaseStack	dd StackBuf		; SS:ESP of base stack
 		dw 0
 AppendLen       dw 0                    ; Bytes in append= command
 OntimeoutLen	dw 0			; Bytes in ontimeout command
+OnerrorLen	dw 0			; Bytes in onerror command
 KbdTimeOut      dw 0                    ; Keyboard timeout (if any)
 CmdLinePtr	dw cmd_line_here	; Command line advancing pointer
 initrd_flag	equ $
diff --git a/syslinux.doc b/syslinux.doc
index 2cf01013..e621b50b 100644
--- a/syslinux.doc
+++ b/syslinux.doc
@@ -228,6 +228,23 @@ ONTIMEOUT kernel options...
 	then "DEFAULT" is used only if the user presses <Enter> to
 	boot.
 
+ONERROR kernel options...
+	If a kernel image is not found (either due to it not existing,
+	or because IMPLICIT is set), run the specified command.  The
+	faulty command line is appended to the specified options, so
+	if the ONERROR directive reads as:
+
+		ONERROR xyzzy plugh
+
+	... and the command line as entered by the user is:
+
+		foo bar baz
+
+	... SYSLINUX will execute the following as if entered by the
+	user:
+	
+		xyzzy plugh foo bar baz
+
 SERIAL port [[baudrate] flowcontrol]
 	Enables a serial port to act as the console.  "port" is a
 	number (0 = /dev/ttyS0 = COM1, etc.) or an I/O port address
diff --git a/ui.inc b/ui.inc
index 8688c323..c11c088d 100644
--- a/ui.inc
+++ b/ui.inc
@@ -276,7 +276,17 @@ get_kernel:     mov byte [KernelName+FILENAME_MAX],0	; Zero-terminate filename/e
 		add bx,byte 4
 		cmp bx,exten_table_end
 		jna .search_loop		; allow == case (final case)
-bad_kernel:     
+		; Fall into bad_kernel
+;
+; bad_kernel: Kernel image not found
+; bad_implicit: The user entered a nonvirtual kernel name, with "implicit 0"
+;
+bad_implicit:
+bad_kernel:
+		mov cx,[OnerrorLen]
+		and cx,cx
+		jnz on_error
+.really:
 		mov si,KernelName
                 mov di,KernelCName
 		push di
@@ -287,13 +297,37 @@ bad_kernel:
                 call cwritestr
                 mov si,crlf_msg
                 jmp abort_load                  ; Ask user for clue
+
 ;
-; bad_implicit: The user entered a nonvirtual kernel name, with "implicit 0"
+; on_error: bad kernel, but we have onerror set
 ;
-bad_implicit:   mov si,KernelName		; For the error message
-                mov di,KernelCName
-                call unmangle_name
-                jmp short bad_kernel
+on_error:
+		mov si,Onerror
+		mov di,command_line
+		push si				; <A>
+		push di				; <B>
+		push cx				; <C>
+		push cx				; <D>
+		push di				; <E>
+		repe cmpsb
+		pop di				; <E> di == command_line
+		pop bx				; <D> bx == [OnerrorLen]
+		je bad_kernel.really		; Onerror matches command_line already
+		neg bx				; bx == -[OnerrorLen]
+		lea cx,[max_cmd_len+bx]
+		; CX == max_cmd_len-[OnerrorLen]
+		mov di,command_line+max_cmd_len-1
+		mov byte [di+1],0		; Enforce null-termination
+		lea si,[di+bx]
+		std
+		rep movsb			; Make space in command_line
+		cld
+		pop cx				; <C> cx == [OnerrorLen]
+		pop di				; <B> di == command_line
+		pop si				; <A> si  == Onerror
+		rep movsb
+		jmp load_kernel
+
 ;
 ; vk_found: We *are* using a "virtual kernel"
 ;