Syslinux - Nov 2008 - [PATCH 1/1] COMBOOT: add get config file full name

From: Gene Cumm <gene.cumm at gmail.com>

COMBOOT API: Add get config full file name to SYSLINUX

Signed-off-by: Gene Cumm <gene.cumm at gmail.com>

---

Returns the full configuration file name.  Int 22h AX 001Eh for now as
it appears that the COMBOOT API is designed to be strictly sequential.
 The API gets extended but only implemented (for now) for SYSLINUX in
ldlinux.asm.  Implementation and documentation are derived from Int
22h AX 000Eh.

There may be a way to be more efficient (with the push/pop on either
side of the call to open in order to preserve the current di value)
however I'm not sure what registers are available and utilizing the
stack would require changes in all variants.

diff --git a/core/comboot.inc b/core/comboot.inc
index 810d825..22757e7 100644
--- a/core/comboot.inc
+++ b/core/comboot.inc
@@ -1033,6 +1033,18 @@ comapi_getadv:
 ;
 comapi_writeadv        equ adv_write

+;
+; INT 22h AX=001Eh     Get full name of config file
+;
+%if IS_SYSLINUX
+comapi_configfilefull  mov P_ES,cs
+               mov P_BX,ConfigNameFull
+               clc
+               ret
+%else
+comapi_configfilefull  equ comapi_err
+%endif
+
                section .data

 %macro         int21 2
@@ -1085,6 +1097,7 @@ int22_table:
                dw comapi_shufflerm     ; 001B cleanup, shuffle and boot to rm
                dw comapi_getadv        ; 001C get pointer to ADV
                dw comapi_writeadv      ; 001D write ADV to disk
+               dw comapi_configfilefull        ; 001E get full name of config f
 int22_count    equ ($-int22_table)/2

 APIKeyWait     db 0
@@ -1109,3 +1122,4 @@ err_comlarge      db 'COMBOOT image too large.',
CR, LF, 0
                alignb 4
 DOSErrTramp    resd    33              ; Error trampolines
 ConfigName     resb    FILENAME_MAX
+ConfigNameFull resb    FILENAME_MAX    ; Can't find a better length
definition
diff --git a/core/ldlinux.asm b/core/ldlinux.asm
index c7f6577..859a52e 100644
--- a/core/ldlinux.asm
+++ b/core/ldlinux.asm
@@ -904,15 +904,26 @@ getfattype:
                mov eax,[RootDir]       ; Make the root directory ...
                mov [CurrentDir],eax    ; ... the current directory
                mov di,syslinux_cfg1
+               push di
                call open
+               pop di
                jnz .config_open
                mov di,syslinux_cfg2
+               push di
                call open
+               pop di
                jnz .config_open
                mov di,syslinux_cfg3
+               push di
                call open
+               pop di
                jz no_config_file
 .config_open:
+               push si
+               mov si,di
+               mov di,ConfigNameFull
+               call strcpy
+               pop si
                mov eax,[PrevDir]       ; Make the directory with syslinux.cfg .
                mov [CurrentDir],eax    ; ... the current directory

diff --git a/doc/comboot.txt b/doc/comboot.txt
index ceee93a..ed63e60 100644
--- a/doc/comboot.txt
+++ b/doc/comboot.txt
@@ -908,3 +908,11 @@ AX=001Dh [3.60]    Write auxilliary data vector

        In a future version, PXELINUX may end up attempting to save
        the ADV on the server via TFTP write.
+
+
+AX=001Eh [BETA]        Get configuration file full name
+       Input:  AX      0000Eh
+       Output: ES:BX   null-terminated file name string
+
+       Returns the full name of the configuration file.  Note that it is
+       possible that the configuration file doesn't actually exist.

Gene Cumm wrote:
> 
> Returns the full configuration file name.  Int 22h AX 001Eh for now as
> it appears that the COMBOOT API is designed to be strictly sequential.
>  The API gets extended but only implemented (for now) for SYSLINUX in
> ldlinux.asm.  Implementation and documentation are derived from Int
> 22h AX 000Eh.
> 
> There may be a way to be more efficient (with the push/pop on either
> side of the call to open in order to preserve the current di value)
> however I'm not sure what registers are available and utilizing the
> stack would require changes in all variants.
I think we can just have 000Eh return the full configuration file name.
 The important thing, of course, is that the filename is valid.

As far as registers, it's probably easier to simply push/pop di around
the call to searchdir in getc.inc.  I have been trying to clean up the
register conventions more in the core.

	-hpa