1 ;; $Id: com32.inc,v 1.9 2005/01/06 22:34:06 hpa Exp $
2 ;; -----------------------------------------------------------------------
4 ;; Copyright 1994-2003 H. Peter Anvin - All Rights Reserved
6 ;; This program is free software; you can redistribute it and/or modify
7 ;; it under the terms of the GNU General Public License as published by
8 ;; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
9 ;; Boston MA 02111-1307, USA; either version 2 of the License, or
10 ;; (at your option) any later version; incorporated herein by reference.
12 ;; -----------------------------------------------------------------------
17 ;; Common code for running a COM32 image
21 ; Load a COM32 image. A COM32 image is the 32-bit analogue to a DOS
22 ; .com file. A COM32 image is loaded at address 0x101000, with %esp
23 ; set to the high end of usable memory.
25 ; A COM32 image should begin with the magic bytes:
26 ; B8 FF 4C CD 21, which is "mov eax,0x21cd4cff" in 32-bit mode and
27 ; "mov ax,0x4cff; int 0x21" in 16-bit mode. This will abort the
28 ; program with an error if run in 16-bit mode.
31 pm_entry: equ 0x101000
46 push si ; Save file handle
47 push dx ; File length held in DX:AX
50 call make_plain_cmdline
51 ; Copy the command line into the low cmdline buffer
57 inc cx ; Include final null
61 call highmemsize ; We need the high memory size...
62 call comboot_setup_api ; Set up the COMBOOT-style API
64 mov edi,pm_entry ; Load address
67 xor dx,dx ; No padding
72 mov ebx,com32_call_start ; Where to go in PM
86 lgdt [bcopy_gdt] ; We can use the same GDT just fine
87 lidt [com32_pmidt] ; Set up the IDT
90 mov cr0,eax ; Enter protected mode
95 xor eax,eax ; Available for future use...
99 mov al,28h ; Set up data segments
104 mov esp,[PMESP] ; Load protmode %esp if available
105 jmp ebx ; Go to where we need to go
108 ; This is invoked right before the actually starting the COM32
109 ; progam, in 32-bit mode...
113 ; Point the stack to the end of high memory
115 mov esp,[word HighMemSize]
118 ; Set up the protmode IDT and the interrupt jump buffers
119 ; We set these up in the system area at 0x100000,
120 ; but we could also put them beyond the stack.
124 ; Form an interrupt gate descriptor
125 mov eax,0x00200000+((pm_idt+8*256)&0x0000ffff)
126 mov ebx,0x0000ee00+((pm_idt+8*256)&0xffff0000)
141 ; Each entry in the interrupt jump buffer contains
142 ; the following instructions:
145 ; 00000001 B0xx mov al,<interrupt#>
146 ; 00000003 E9xxxxxxxx jmp com32_handle_interrupt
149 mov ebx,com32_handle_interrupt-(pm_idt+8*256+8)
153 sub [edi-2],cl ; Interrupt #
160 ; Now everything is set up for interrupts...
162 push dword com32_farcall ; Farcall entry point
163 push dword (1 << 16) ; 64K bounce buffer
164 push dword (comboot_seg << 4) ; Bounce buffer address
165 push dword com32_intcall ; Intcall entry point
166 push dword command_line ; Command line pointer
167 push dword 5 ; Argument count
168 sti ; Interrupts OK now
169 call pm_entry ; Run the program...
170 ; ... on return, fall through to com32_exit ...
173 mov bx,com32_done ; Return to command loop
178 mov [PMESP],esp ; Save exit %esp
179 xor esp,esp ; Make sure the high bits are zero
180 jmp 08h:.in_pm16 ; Return to 16-bit mode first
184 mov ax,18h ; Real-mode-like segment
191 lidt [com32_rmidt] ; Real-mode IDT (rm needs no GDT)
197 .in_rm: ; Back in real mode
198 mov ax,cs ; Set up sane segments
203 lss sp,[SavedSSSP] ; Restore stack
204 jmp bx ; Go to whereever we need to go...
212 ; 16-bit support code
217 ; 16-bit interrupt-handling code
220 pushf ; Flags on stack
221 push cs ; Return segment
222 push word .cont ; Return address
223 push dword edx ; Segment:offset of IVT entry
224 retf ; Invoke IVT routine
225 .cont: ; ... on resume ...
226 mov ebx,com32_int_resume
227 jmp com32_enter_pm ; Go back to PM
230 ; 16-bit system call handling code
239 mov [cs:Com32SysSP],sp
240 retf ; Invoke routine
242 ; We clean up SP here because we don't know if the
243 ; routine returned with RET, RETF or IRET
244 mov sp,[cs:Com32SysSP]
251 mov ebx,com32_sys_resume
255 ; 32-bit support code
260 ; This is invoked on getting an interrupt in protected mode. At
261 ; this point, we need to context-switch to real mode and invoke
262 ; the interrupt routine.
264 ; When this gets invoked, the registers are saved on the stack and
265 ; AL contains the register number.
267 com32_handle_interrupt:
269 xor ebx,ebx ; Actually makes the code smaller
270 mov edx,[ebx+eax*4] ; Get the segment:offset of the routine
272 jmp com32_enter_rm ; Go to real mode
279 ; Intcall/farcall invocation. We manifest a structure on the real-mode stack,
280 ; containing the com32sys_t structure from <com32.h> as well as
281 ; the following entries (from low to high address):
285 ; - Return segment (== real mode cs == 0)
289 pushfd ; Save IF among other things...
290 pushad ; We only need to save some, but...
292 mov eax,[esp+10*4] ; CS:IP
297 pushfd ; Save IF among other things...
298 pushad ; We only need to save some, but...
300 movzx eax,byte [esp+10*4] ; INT number
301 mov eax,[eax*4] ; Get CS:IP from low memory
306 movzx edi,word [word SavedSSSP]
307 movzx ebx,word [word SavedSSSP+2]
308 sub edi,54 ; Allocate 54 bytes
309 mov [word SavedSSSP],di
311 add edi,ebx ; Create linear address
313 mov esi,[esp+11*4] ; Source regs
315 mov cl,11 ; 44 bytes to copy
318 ; EAX is already set up to be CS:IP
319 stosd ; Save in stack frame
320 mov eax,com32_sys_rm.return ; Return seg:offs
321 stosd ; Save in stack frame
322 mov eax,[edi-12] ; Return flags
323 and eax,0x200cd7 ; Mask (potentially) unsafe flags
324 mov [edi-12],eax ; Primary flags entry
328 jmp com32_enter_rm ; Go to real mode
330 ; On return, the 44-byte return structure is on the
331 ; real-mode stack, plus the 10 additional bytes used
332 ; by the target address (see above.)
334 movzx esi,word [word SavedSSSP]
335 movzx eax,word [word SavedSSSP+2]
336 mov edi,[esp+12*4] ; Dest regs
338 add esi,eax ; Create linear address
339 and edi,edi ; NULL pointer?
341 .no_copy: mov edi,esi ; Do a dummy copy-to-self
342 .do_copy: xor ecx,ecx
344 rep movsd ; Copy register block
346 add dword [word SavedSSSP],54 ; Remove from stack
350 ret ; Return to 32-bit program
356 PMESP resd 1 ; Protected-mode ESP
357 Com32SysSP resw 1 ; SP saved during COM32 syscall