2 COMBOOT and COM32 files
5 Syslinux supports simple standalone programs, using a file format
6 similar to DOS ".com" files. A 32-bit version, called COM32, is also
7 provided. A simple API provides access to a limited set of filesystem
11 ++++ COMBOOT file format ++++
13 A COMBOOT file is a raw binary file containing 16-bit code. It should
14 be linked to run at offset 0x100, and contain no absolute segment
15 references. It is run in 16-bit real mode.
17 A COMBOOT image can be written to be compatible with MS-DOS. Such a
18 file will usually have extension ".com". A COMBOOT file which is not
19 compatible with MS-DOS will usually have extension ".cbt".
21 Before running the program, Syslinux sets up the following fields in
22 the Program Segment Prefix (PSP), a structure at offset 0 in the
26 0 word Contains an INT 20h instruction
27 2 word Contains the paragraph (16-byte "segment" address) at
28 the end of memory available to the program.
29 128 byte Length of the command line arguments, including the leading
30 space but not including the final CR character.
31 129 127b Command line arguments, starting with a space and ending
32 with a CR character (ASCII 13).
34 The program is allowed to use memory between the PSP paragraph (which
35 all the CS, DS, ES and SS registers point to at program start) and the
36 paragraph value given at offset 2.
38 On startup, SP is set up to point to the end of the 64K segment, at
39 0xfffe. Under DOS it is possible for SP to contain a smaller
40 value if memory is very tight; this is never the case under Syslinux.
42 The program should make no assumptions about what segment address it
43 will be loaded at; instead it should look at the segment registers on
44 program startup. Both DOS and Syslinux will guarantee CS == DS == ES
45 == SS on program start; the program should not assume anything about
46 the values of FS or GS.
48 To exit, a program can either execute a near RET (which will jump to
49 offset 0 which contains an INT 20h instruction, terminating the
50 program), or execute INT 20h or INT 21h AH=00h or INT 21h AH=4Ch.
51 If compatiblity with Syslinux 1.xx is desired, use INT 20h.
54 ++++ COM32R file format ++++
56 A COM32R file is a raw binary file containing 32-bit code. It should
57 be self-relocating, as it will be loaded by the Syslinux core at any
58 4K aligned address. It will be run in flat-memory 32-bit protected
59 mode. Under Syslinux, it will be run in CPL 0, however, since it may
60 be possible to create a COM32 execution engine that would run under
61 something like Linux DOSEMU, it is recommended that the code does not
62 assume CPL 0 unless absolutely necessary.
64 A COM32R program must start with the byte sequence B8 FE 4C CD 21 (mov
65 eax,21cd4cfeh) as a magic number.
67 The COM32R format replaces the earlier COM32 format, which was linked
68 to a fixed address (0x101000).
70 A COM32R file should have extension ".c32".
72 On startup, CS will be set up as a flat 32-bit code segment, and DS ==
73 ES == SS will be set up as the equivalent flat 32-bit data segment.
74 FS and GS are reserved for future use and are currently initialized to
75 zero. A COM32R image should not assume any particular values of
78 ESP is set up at the end of available memory and also serves as
79 notification to the program how much memory is available.
81 The following arguments are passed to the program on the stack:
84 [ESP] dword Return (termination) address
85 [ESP+4] dword Number of additional arguments (currently 8)
86 [ESP+8] dword Pointer to the command line arguments (null-terminated string)
87 [ESP+12] dword Pointer to INT call helper function
88 [ESP+16] dword Pointer to low memory bounce buffer
89 [ESP+20] dword Size of low memory bounce buffer
90 [ESP+24] dword Pointer to FAR call helper function (new in 2.05)
91 [ESP+28] dword Pointer to CDECL helper function (new in 3.54)
92 [ESP+32] dword Amount of memory controlled by the Syslinux core (new in 3.74)
93 [ESP+36] dword Pointer to the filename of the com32 module (new in 3.86)
94 [ESP+40] dword Pointer to protected-mode functions (new in 4.00)
96 The libcom32 startup code loads this into a structure named __com32,
99 extern struct com32_sys_args {
102 void __cdecl(*cs_intcall)(uint8_t, const com32sys_t *, com32sys_t *);
104 uint32_t cs_bounce_size;
105 void __cdecl(*cs_farcall)(uint32_t, const com32sys_t *, com32sys_t *);
106 int __cdecl(*cs_cfarcall)(uint32_t, const void *, uint32_t);
109 const struct com32_pmapi *cs_pm;
112 The intcall helper function can be used to issue BIOS or Syslinux API
113 calls, and takes the interrupt number as first argument. The second
114 argument is a pointer to the input register definition, an instance of
115 the following structure (available in <com32.h>):
124 uint16_t gs; /* Offset 0 */
125 uint16_t fs; /* Offset 2 */
126 uint16_t es; /* Offset 4 */
127 uint16_t ds; /* Offset 6 */
129 reg32_t edi; /* Offset 8 */
130 reg32_t esi; /* Offset 12 */
131 reg32_t ebp; /* Offset 16 */
132 reg32_t _unused_esp; /* Offset 20 */
133 reg32_t ebx; /* Offset 24 */
134 reg32_t edx; /* Offset 28 */
135 reg32_t ecx; /* Offset 32 */
136 reg32_t eax; /* Offset 36 */
138 reg32_t eflags; /* Offset 40 */
141 The third argument is a pointer to the output register definition, an
142 instance of the same structure. The third argument can also be zero
145 Since BIOS or Syslinux API calls can generally only manipulate data
146 below address 0x100000, a "bounce buffer" in low memory, at least 64K
147 in size, is available, to copy data in and out.
149 The farcall helper function behaves similarly, but takes as its first
150 argument the CS:IP (in the form (CS << 16) + IP) of procedure to be
151 invoked via a FAR CALL.
153 The cfarcall helper function takes (CS << 16)+IP, a pointer to a stack
154 frame, a size of that stack frame, and returns the return value of EAX
155 (which may need to be appropriate truncated by the user.)
157 Starting in version 4.00, some of these API calls are available as
158 protected-mode function calls, using the regparm(3) calling convention
159 (the first three argumetns in EAX, EDX, ECX; the rest on the stack.)
160 Those functions are defined in struct com32_pmapi, defined in
164 ++++ SYSLINUX API CALLS +++
166 Syslinux provides the following API calls. Syslinux 1.xx only
167 supported INT 20h - terminate program. [] indicates the first version
168 of Syslinux which supported this feature (correctly.)
170 NOTE: Most of the API functionality is still experimental. Expect to
174 ++++ DOS-COMPATIBLE API CALLS ++++
176 INT 20h [1.48] Terminate program
177 INT 21h AH=00h [2.00] Terminate program
178 INT 21h AH=4Ch [2.00] Terminate program
180 All of these terminate the program.
183 INT 21h AH=01h [2.01] Get Key with Echo
185 Reads a key from the console input, with echo to the console
186 output. The read character is returned in AL. Extended
187 characters received from the keyboard are returned as NUL (00h)
188 + the extended character code.
191 INT 21h AH=02h [2.01] Write Character
193 Writes a character in DL to the console (video and serial)
197 INT 21h AH=04h [2.01] Write Character to Serial Port
199 Writes a character in DL to the serial console output
200 (if enabled.) If no serial port is configured, this routine
204 INT 21h AH=08h [2.09] Get Key without Echo
206 Reads a key fron the console input, without echoing it to the
207 console output. The read character is returned in AL.
210 INT 21h AH=09h [2.01] Write DOS String to Console
212 Writes a DOS $-terminated string in DS:DX to the console.
215 INT 21h AH=0Bh [2.00] Check Keyboard
217 Returns AL=FFh if there is a keystroke waiting (which can then
218 be read with INT 21h, AH=01h or AH=08h), otherwise AL=00h.
221 INT 21h AH=30h [2.00] Check DOS Version
223 This function returns AX=BX=CX=DX=0, corresponding to a
224 hypothetical "DOS 0.0", but the high parts of EAX-EBX-ECX-EDX
227 EAX=59530000h EBX=4C530000h ECX=4E490000h EDX=58550000h
229 This function can thus be used to distinguish running on
230 Syslinux from running on DOS.
233 ++++ SYSLINUX-SPECIFIC API CALLS ++++
235 Syslinux-specific API calls are executed using INT 22h, with a
236 function number in AX. INT 22h is used by DOS for internal purposes;
237 do not execute INT 22h under DOS.
239 DOS-compatible function INT 21h, AH=30h can be used to detect if the
240 Syslinux API calls are available.
242 Any register not specifically listed as modified is preserved;
243 however, future versions of Syslinux may add additional output
244 registers to existing calls.
246 All calls return CF=0 on success, CF=1 on failure. The noted outputs
247 apply if CF=0 only unless otherwise noted. All calls clobber the
248 arithmetric flags (CF, PF, AF, ZF, SF and OF) but leave all other
249 flags unchanged unless otherwise noted.
252 AX=0001h [2.00] Get Version
255 Output: AX number of INT 22h API functions available
256 CH Syslinux major version number
257 CL Syslinux minor version number
258 DL Syslinux derivative ID (e.g. 32h = PXELINUX)
259 ES:SI Syslinux version string
260 ES:DI Syslinux copyright string
262 This API call returns the Syslinux version and API
265 Note: before version 3.86, the version string had a leading CR LF
266 and the copyright string had a leading space. The strings might
267 still contain trailing CR and/or LF.
270 AX=0002h [2.01] Write String
273 ES:BX null-terminated string
276 Writes a null-terminated string on the console.
279 AX=0003h [2.01] Run command
282 ES:BX null-terminated command string
283 Output: Does not return
285 This API call terminates the program and executes the command
286 string as if the user had entered it at the Syslinux command
287 line. This API call does not return.
290 AX=0004h [2.01] Run default command
293 Output: Does not return
295 This API call terminates the program and executes the default
296 command string as if the user had pressed Enter alone on the
297 Syslinux command line. This API call does not return.
300 AX=0005h [2.00] Force text mode
305 If the screen was in graphics mode (due to displaying a splash
306 screen using the <Ctrl-X> command in a message file, or
307 similar), return to text mode.
310 AX=0006h [2.08] Open file
313 ES:SI null-terminated filename
314 Output: SI file handle
315 EAX length of file in bytes, or -1
318 Open a file for reading. The exact syntax of the filenames
319 allowed depends on the particular Syslinux derivative.
321 The Syslinux file system is block-oriented. The size of a
322 block will always be a power of two and no greater than 16K.
324 Note: Syslinux considers a zero-length file to be nonexistent.
326 In 3.70 or later, EAX can contain -1 indicating that the file
331 int cs_pm->open_file(const char *filename, struct com32_filedata *data)
333 filename - null-terminated filename
334 data - pointer to a file data buffer
336 Returns the file handle, or -1 on failure.
337 The file data buffer contains block size and file size.
340 AX=0007h [2.08] Read file
345 CX number of blocks to read
346 Output: SI file handle, or 0 if EOF was reached
347 ECX number of bytes read [3.70]
349 Read blocks from a file. Note that the file handle that is
350 returned in SI may not be the same value that was passed in.
352 If end of file was reached (SI=0), the file was automatically
355 In 3.70 or later, ECX returns the number of bytes read. This
356 will always be a multiple of the block size unless EOF is
359 The address of the buffer (ES:BX) should be at least 512-byte
360 aligned. Syslinux guarantees at least this alignment for the
361 COMBOOT load segment or the COM32 bounce buffer.
363 Keep in mind that a "file" may be a TFTP connection, and that
364 leaving a file open for an extended period of time may result
367 WARNING: Calling this function with an invalid file handle
368 will probably crash the system.
372 size_t cs_pm->read_file(uint16_t *handle, void *buf, size_t blocks)
374 handle - file handle (input and output, set to zero on end of file)
375 buf - buffer to write to
376 blocks - number of blocks to read
378 Returns number of bytes read, or 0 on failure.
381 AX=0008h [2.08] Close file
387 Close a file before reaching the end of file.
389 WARNING: Calling this function with an invalid file handle
390 will probably crash the system.
394 void cs_pm->close_file(uint16_t handle)
396 handle - file handle to close
399 AX=0009h [2.00] Call PXE Stack [PXELINUX ONLY]
402 BX PXE function number
403 ES:DI PXE parameter structure buffer
404 Output: AX PXE return status code
406 Invoke an arbitrary PXE stack function. On SYSLINUX/ISOLINUX,
407 this function returns with an error (CF=1) and no action is
408 taken. On PXELINUX, this function always returns with CF=0
409 indicating that the PXE stack was successfully invoked; check
410 the status code in AX and in the first word of the data buffer
411 to determine if the PXE call succeeded or not.
413 The PXE stack will have the UDP stack OPEN; if you change that
414 you cannot call any of the file-related API functions, and
415 must restore UDP OPEN before returning to PXELINUX.
417 PXELINUX reserves UDP port numbers from 49152 to 65535 for its
418 own use; port numbers below that range is available.
421 AX=000Ah [2.00] Get Derivative-Specific Information
425 CL 9 (to get a valid return in CL for all versions)
426 Output: AL 31h (SYSLINUX), 34h (EXTLINUX)
428 CL sector size as a power of 2 (9 = 512 bytes) [3.35]
432 ES:BX pointer to partition table entry (if DL >= 80h)
433 FS:SI pointer to initial ES:DI value [3.53]
434 GS:DI pointer to partition offset (QWORD) [4.00]
436 Note: This function was broken in EXTLINUX 3.00-3.02.
438 On boot, ES:DI is supposed to point to the BIOS $PnP
439 structure, although in practice most operating systems
440 will search for it in memory. However, preserving
441 this while chainloading is probably a good idea.
443 Note that FS:SI is a pointer to a memory location
444 containing the original ES:DI value, not the value
450 Output: AL 32h (PXELINUX)
451 DX PXE API version detected (DH=major, DL=minor)
452 ECX Local IP number (network byte order) [3.85]
453 ES:BX pointer to PXENV+ or !PXE structure
454 FS:SI pointer to original stack with invocation record
455 GS:DI pointer to network information [4.00]
457 Note: DX notes the API version detected by PXELINUX,
458 which may be more conservative than the actual version
459 available. For exact information examine the API
460 version entry in the PXENV+ structure, or the API
461 version entries in the ROMID structures pointed from
464 PXELINUX will use, and provide, the !PXE structure
465 over the PXENV+ structure. Examine the structure
466 signature to determine which particular structure was
469 The FS:SI pointer points to the top of the original stack
470 provided by the PXE stack, with the following values
471 pushed at the time PXELINUX is started:
473 [fs:si+0] GS <- top of stack
486 [fs:si+44] PXE return IP <- t.o.s. when PXELINUX invoked
487 [fs:si+46] PXE return CS
489 GS:DI points to a structure of the following form:
493 [gs:di+8] Boot server IP
494 [gs:di+12] Gateway IP
499 Output: AL 33h (ISOLINUX)
501 CL 11 (sector size as a power of 2) [3.35]
504 1 = Hybrid (hard disk), CBIOS mode
505 2 = Hybrid (hard disk), EBIOS mode
506 ES:BX pointer to El Torito spec packet
507 FS:SI pointer to initial ES:DI value [3.53]
508 GS:DI pointer to partition offset (QWORD) [4.00]
510 Note: Some very broken El Torito implementations do
511 not provide the spec packet information. If so, ES:BX
512 may point to all zeroes or to garbage. Call INT 13h,
513 AX=4B01h to obtain the spec packet directly from the
517 AX=000Bh [2.00] Get Serial Console Configuration
520 Output: DX serial port I/O base (e.g. 3F8h = COM1...)
521 CX baud rate divisor (1 = 115200 bps, 2 = 57600 bps...)
522 BX flow control configuration bits (see syslinux.txt)
523 -> bit 15 is set if the video console is disabled
525 If no serial port is configured, DX will be set to 0 and the
526 other registers are undefined.
529 AX=000Ch [2.00] Perform final cleanup
531 DX derivative-specific flags (0000h = clean up all)
534 This routine performs any "final cleanup" the boot loader
535 would normally perform before loading a kernel, such as
536 unloading the PXE stack in the case of PXELINUX. AFTER
537 INVOKING THIS CALL, NO OTHER API CALLS MAY BE INVOKED, NOR MAY
538 THE PROGRAM TERMINATE AND RETURN TO THE BOOT LOADER. This
539 call basically tells the boot loader "get out of the way, I'll
540 handle it from here."
542 For COM32 images, the boot loader will continue to provide
543 interrupt and BIOS call thunking services as long its memory
544 areas (0x0800-0xffff, 0x100000-0x100fff) are not overwritten.
545 MAKE SURE TO DISABLE INTERRUPTS, AND INSTALL NEW GDT AND IDTS
546 BEFORE OVERWRITING THESE MEMORY AREAS.
548 The permissible values for DX is an OR of these values:
550 SYSLINUX: 0000h Normal cleanup
552 PXELINUX: 0000h Normal cleanup
553 0003h Keep UNDI and PXE stacks loaded
555 ISOLINUX: 0000h Normal cleanup
557 EXTLINUX: 0000h Normal cleanup
559 All other values are undefined, and may have different
560 meanings in future versions of Syslinux.
563 AX=000Dh [2.08] Obsoleted in 3.80
566 AX=000Eh [2.11] Get configuration file name
568 Output: ES:BX null-terminated file name string
570 Returns the name of the configuration file. Note that it is
571 possible that the configuration file doesn't actually exist.
574 AX=000Fh [3.00] Get IPAPPEND strings [PXELINUX]
576 Output: CX number of strings (currently 2)
577 ES:BX pointer to an array of NEAR pointers in
578 the same segment, one for each of the above
581 Returns the same strings that the "ipappend" option would have
582 added to the command line, one for each bit of the "ipappend"
583 flag value, so entry 0 is the "ip=" string and entry 1 is the
587 AX=0010h [3.00] Resolve hostname [PXELINUX]
589 ES:BX pointer to null-terminated hostname
590 Output: EAX IP address of hostname (zero if not found)
592 Queries the DNS server(s) for a specific hostname. If the
593 hostname does not contain a dot (.), the local domain name
594 is automatically appended.
596 This function only return CF=1 if the function is not
597 supported. If the function is supported, but the hostname did
598 not resolve, it returns with CF=0, EAX=0.
600 The IP address is returned in network byte order, i.e. if the
601 IP address is 1.2.3.4, EAX will contain 0x04030201. Note that
602 all uses of IP addresses in PXE are also in network byte order.
605 AX=0011h [3.05] Obsoleted in 3.80
608 AX=0012h [3.50] Obsoleted in 3.80
611 AX=0013h [3.08] Idle loop call
615 Call this routine while sitting in an idle loop. It performs
616 any periodic activities required by the filesystem code. At
617 the moment, this is a no-op on all derivatives except
618 PXELINUX, where it executes PXE calls to answer ARP queries.
620 Starting with version 3.10, this API call harmlessly returns
621 failure (CF=1) if invoked on a platform which does not need
622 idle calls. Additionally, it's safe to call this API call on
623 previous Syslinux versions (2.00 or later); it will just
624 harmlessly fail. Thus, if this call returns failure (CF=1),
625 it means that there is no technical reason to call this
626 function again, although doing so is of course safe.
629 AX=0014h [3.10] Local boot [PXELINUX, ISOLINUX]
631 DX Local boot parameter
632 Output: Does not return
634 This function invokes the equivalent of the "localboot"
635 configuration file option. The parameter in DX is the same
636 parameter as would be entered after "localboot" in the
637 configuration file; this parameter is derivative-specific --
638 see syslinux.txt for the definition.
641 AX=0015h [3.10] Get feature flags
643 Output: ES:BX pointer to flags in memory
644 CX number of flag bytes
646 This function reports whether or not this Syslinux version and
647 derivative supports specific features. Keep in mind that
648 future versions might have more bits; remember to treat any
649 bits beyond the end of the array (as defined by the value in
652 Currently the following feature flag is defined:
655 ----------------------------------------------------
656 0 0 Local boot (AX=0014h) supported
657 1 Idle loop call (AX=0013h) is a no-op
659 All other flags are reserved.
662 AX=0016h [3.10] Run kernel image
664 DS:SI Filename of kernel image (zero-terminated string)
665 ES:BX Command line (zero-terminated string)
666 ECX IPAPPEND flags [PXELINUX]
667 EDX Type of file (since 3.50)
668 Output: Does not return if successful; returns with CF=1 if
669 the kernel image is not found.
671 This function is similiar to AX=0003h Run command, except that
672 the filename and command line are treated as if specified in a
673 KERNEL and APPEND statement of a LABEL statement, which means:
675 - The filename has to be exact; no variants are tried;
676 - No global APPEND statement is applied;
677 - ALLOWOPTIONS and IMPLICIT statements in the configuration
678 file do not apply. It is therefore important that the
679 COMBOOT module doesn't allow the end user to violate the
680 intent of the administrator.
682 Additionally, this function returns with a failure if the file
683 doesn't exist, instead of returning to the command line. (It
684 may still return to the command line if the image is somehow
687 The file types are defined as follows:
690 EDX Config Extensions Type of file
691 0 KERNEL Determined by filename extension
692 1 LINUX none Linux kernel image
693 2 BOOT .bs .bin Bootstrap program
694 3 BSS .bss Boot sector with patch [SYSLINUX]
695 4 PXE .0 PXE Network Bootstrap Prog [PXELINUX]
696 5 FDIMAGE .img Floppy disk image [ISOLINUX]
697 6 COMBOOT .com .cbt 16-bit COMBOOT program
698 7 COM32 .c32 COM32 program
699 8 CONFIG Configuration file
702 AX=0017h [3.30] Report video mode change
706 Bit 1: non-default mode
708 Bit 3: text functions not supported
709 CX For graphics modes, pixel columns
710 DX For graphics modes, pixel rows
713 This function is used to report video mode changes to
714 Syslinux. It does NOT actually change the video mode, but
715 rather, allows Syslinux to take appropriate action in response
716 to a video mode change. Modes that cannot be exited either
717 with the conventional BIOS mode set command (INT 10h, AH=00h)
718 or the VESA VBE mode set command (INT 10h, AX=4F02h) should
721 This function returns with a failure if BX contains any bits
722 which are undefined in the current version of Syslinux.
724 The following bits in BX are currently defined:
728 Indicates that the mode is a graphics mode, as opposed
731 Bit 1: non-standard mode
733 A non-standard mode is any mode except text mode and
734 graphics mode 0012h (VGA 640x480, 16 color.)
738 This mode is a VESA mode, and has to be exited with
739 the VESA VBE API (INT 10h, AX=4F02h) as opposed to the
740 conventional BIOS API (INT 10h, AH=00h).
742 Bit 3: Text functions not supported
744 This indicates that the BIOS text output functions
745 (INT 10h, AH=02h, 03h, 06h, 09h, 0Eh, 11h) don't work.
746 If this bit is set, Syslinux will reset the mode
747 before printing any characters on the screen.
749 This is common for VESA modes.
752 AX=0018h [3.30] Query custom font
754 Output: AL Height of custom font in scan lines, or zero
755 ES:BX Pointer to custom font in memory
757 This call queries if a custom display font has been loaded via
758 the "font" configuration file command. If no custom font has
759 been loaded, AL contains zero.
762 AX=0019h [3.50] Read disk [SYSLINUX, ISOLINUX, EXTLINUX]
764 EDX Sector number (LSW)
765 ESI Sector number (MSW) [4.00]
766 EDI Reserved - MUST BE ZERO
771 Read disk blocks from the active filesystem (partition); for
772 disks, sector number zero is the boot sector. For ISOLINUX,
773 this call reads the CD-ROM.
775 For compatiblity with all systems, the buffer should
776 *neither* cross 64K boundaries, *nor* wrap around the segment.
778 This routine reports "boot failed" (and does not return) on
781 Note: for ISOLINUX in hybrid mode, this call uses simulated
782 2048-byte CD-ROM sector numbers.
785 AX=001Ah [3.50] Obsoleted in 3.80
788 AX=001Bh [3.50] Obsoleted in 3.80
791 AX=001Ch [3.60] Get pointer to auxilliary data vector
793 Output: ES:BX Auxilliary data vector
794 CX Size of the ADV (currently 500 bytes)
796 The auxillary data vector is a tagged data structure used
797 to carry a small amount of information (up to 500 bytes) from
801 AX=001Dh [3.60] Write auxilliary data vector
805 Write the auxilliary data vector back to disk. Returns
806 failure for non-disk-based derivatives unless the "auxdata"
807 configuration command is used to specify a disk location
808 (not yet implemented.)
810 In a future version, PXELINUX may end up attempting to save
811 the ADV on the server via TFTP write.
814 AX=001Eh [3.74] Keyboard remapping table
816 DX 0000h - all other values reserved
817 Output: AX format version (1)
818 CX length in bytes (256)
819 ES:BX pointer to keyboard table
821 This call queries the keyboard remapping table. For the current
822 version, the format code is always 1 and the length is always
823 256. This version can be updated simply by overwriting the version
824 in memory; this may not be true in the future.
827 AX=001Fh [3.74] Get current working directory
829 Output: ES:BX null-terminated directory name string
831 Returns the current working directory.
834 AX=0020h [3.74] Obsoleted in 4.00
835 AX=0021h [3.74] Obsoleted in 4.00
836 AX=0022h [3.74] Obsoleted in 4.00
838 These three functions provided opendir/readdir/closedir
839 functionality in the late 3.xx series. They have been
840 replaced by the protected-mode interface.
843 AX=0023h [3.80] Get shuffler parameters
845 Output: CX size of shuffler "safe area" in bytes
846 Other registers reserved for future use
848 This call gives the size of the required shuffler "safe area",
849 in bytes; for call 0024h. In the future, it may provide
850 additional parameters.
853 AX=0024h [3.80] Cleanup, shuffle and boot, raw version
855 DX derivative-specific flags (see function 000Ch)
856 EDI shuffle descriptor list safe area
857 ESI shuffle descriptor list source
858 ECX byte count of shuffle descriptor list
859 Output: Does not return
861 This routine performs final cleanup, then performs a sequence
862 of copies, and jumps to a specified real mode entry point.
863 This is a more general version of function 000Dh, which can
864 also be used to load other types of programs.
866 Unlike previous obsolete versions of this function, there are
867 no restrictions that copies must not touch memory below
868 address 7C00h. Either the shuffle descriptor list or the safe
869 area (or both) may be located in high memory.
871 ESI points to a list of descriptors each of the form:
874 0 dword destination address
875 4 dword source address (-1 = zero)
876 8 dword length in bytes (0 = end of list)
878 The copies are overlap-safe, like memmove().
880 Before actually executing the move list, the list is moved to
881 the address specified in EDI. The caller is responsibe to
882 ensure that the moved descriptor list plus a "safe area"
883 immediately afterwards (the size of which is specified by
884 function 0023h) is not disturbed by the copy sequence. It is,
885 however, safe to overwrite descriptors already consumed.
887 If the source address is -1 (FFFFFFFFh) then the block
888 specified by the destination address and the length is set to
891 The list is terminated by an entry with length 0. For that
892 entry, the destination is used as an entry point, and the
893 source represents the type of entry point:
895 0 16-bit protected mode (dst is CS.base)
896 1 Flat 32-bit protected mode (dst is EIP)
898 This routine does not set up any GPR register state
899 whatsoever, including stack. It is the responsibility of the
900 caller to make sure the entry point provided sets up any
903 For mode 0 (16-bit real mode), EAX will contain CR0 with bit 0
904 masked out, suitable for loading into CR0 to immediately enter
905 real mode. Note: if real-mode entry is planned,
906 (CS.base & 0xfff0000f) should == 0 for compatibility with KVM,
907 and possibly other virtualization solutions.
909 In both mode 0 and mode 1, the data segments will be loaded
910 with read/write data segments, matching the respective code
911 segment. For mode 0, B=0 and the limits will be 64K, for mode
912 1, B=1 and the limits will be 4 GB.
915 ++++ 32-BIT ONLY API CALLS ++++
917 void *cs_pm->lmalloc(size_t bytes)
919 Allocate a buffer in low memory (below 1 MB).
922 void cs_pm->lfree(void *ptr)
924 Free a buffer allocated with cs_pm->lmalloc().
927 DIR *cs_pm->opendir(const char *pathname)
932 struct dirent *cs_pm->readdir(DIR *dir)
934 Read an entry from a directory. The entry is returned in a
938 int cs_pm->closedir(DIR *dir)