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/*
2 
 * Protected-mode bootstrap, to be jumped to by a Primary Bootstrap Sector.
3 
 * Load with -H3 -R4 -T0xNNNNNNNN to get a binary image with no header.
4 
 * Note that the processor is in 'real' mode on entry, so care must be taken
5 
 * as the assembler assumes protected mode, hence the sometimes weird-looking
6 
 * code to assure 16-bit instructions are issued.
7 
 */
8 
#include "mem.h"
9 
#include "/sys/src/boot/pc/x16.h"
10 
 
11 
#undef BIOSCALL		/* we don't know what evil the bios gets up to */
12 
#define BIOSCALL(b)	INT $(b); CLI
13 
 
14 
#define CMPL(r0, r1)	BYTE $0x66; CMP(r0, r1)
15 
#define LLI(i, rX)	BYTE $0x66;		/* i -> rX */		\
16 
			BYTE $(0xB8+rX);				\
17 
			LONG $i;
18 
 
19 
/*
20 
 * Start:
21 
 *	disable interrupts;
22 
 *	set all segments;
23 
 *	create temporary stack.
24 
 */
25 
TEXT _start16r(SB), $0
26 
	CLI				/* interrupts off */
27 
 
28 
	MFSR(rCS, rAX)
29 
	MTSR(rAX, rDS)			/* set the data segment */
30 
 
31 
	LWI(0, rAX)			/* always put stack in first 64k */
32 
	MTSR(rAX, rSS)
33 
	LWI(PXEBASE, rSP)		/* set the stack */
34 
 
35 
	LWI(0x2401, rAX)		/* enable a20 line */
36 
	BIOSCALL(0x15)
37 
 
38 
/*
39 
 * Do any real-mode BIOS calls before going to protected mode.
40 
 * Data will be stored at BIOSTABLES, not ROUND(end, BY2PG) as before.
41 
 */
42 
 
43 
/*
44 
 * Check for CGA mode.
45 
 */
46 
_cgastart:
47 
	LWI(0x0F00, rAX)		/* get current video mode in AL */
48 
	BIOSCALL(0x10)
49 
	ANDI(0x007F, rAX)
50 
	SUBI(0x0003, rAX)		/* is it mode 3? */
51 
	JEQ	_cgaputs
52 
 
53 
	LWI(0x0003, rAX)		/* turn on text mode 3 */
54 
	BIOSCALL(0x10)
55 
 
56 
_cgaputs:				/* output a cheery wee message */
57 
	LWI(_hello(SB), rSI)
58 
	CLR(rBX)
59 
_cgaputsloop:
60 
	LODSB
61 
	ORB(rAL, rAL)
62 
	JEQ	_cgaend
63 
 
64 
	LBI(0x0E,rAH)
65 
	BIOSCALL(0x10)
66 
	JMP	_cgaputsloop
67 
_cgaend:
68 
 
69 
/*
70 
 * Reset floppy disc system.
71 
 * If successful, make sure the motor is off.
72 
 */
73 
_floppystart:
74 
	CLR(rAX)
75 
	CLR(rDX)
76 
	BIOSCALL(0x13)
77 
	ORB(rAL, rAL)
78 
	JNE	_floppyend
79 
	OUTPORTB(0x3F2, 0x00)		/* turn off motor */
80 
_floppyend:
81 
 
82 
	LLI(BIOSTABLES, rAX)	/* tables in low memory, not after end */
83 
	OPSIZE; ANDL $~(BY2PG-1), AX
84 
	OPSIZE; SHRL $4, AX
85 
	SW(rAX, _ES(SB))
86 
	CLR(rDI)
87 
	SW(rDI, _DI(SB))
88 
 
89 
	MTSR(rAX, rES)
90 
 
91 
/*
92 
 * Check for APM1.2 BIOS support.
93 
 */
94 
	LWI(0x5304, rAX)		/* disconnect anyone else */
95 
	CLR(rBX)
96 
	BIOSCALL(0x15)
97 
	JCS	_apmfail
98 
 
99 
	LWI(0x5303, rAX)		/* connect */
100 
	CLR(rBX)
101 
	CLC
102 
	BIOSCALL(0x15)
103 
	JCC	_apmpush
104 
_apmfail:
105 
	LW(_ES(SB), rAX)		/* no support */
106 
	MTSR(rAX, rES)
107 
	LW(_DI(SB), rDI)
108 
	JCS	_apmend
109 
 
110 
_apmpush:
111 
	OPSIZE; PUSHR(rSI)		/* save returned APM data on stack */
112 
	OPSIZE; PUSHR(rBX)
113 
	PUSHR(rDI)
114 
	PUSHR(rDX)
115 
	PUSHR(rCX)
116 
	PUSHR(rAX)
117 
 
118 
	LW(_ES(SB), rAX)
119 
	MTSR(rAX, rES)
120 
	LW(_DI(SB), rDI)
121 
 
122 
	LWI(0x5041, rAX)		/* first 4 bytes are APM\0 */
123 
	STOSW
124 
	LWI(0x004D, rAX)
125 
	STOSW
126 
 
127 
	LWI(8, rCX)			/* pop the saved APM data */
128 
_apmpop:
129 
	POPR(rAX)
130 
	STOSW
131 
	LOOP	_apmpop
132 
_apmend:
133 
 
134 
/*
135 
 * Try to retrieve the 0xE820 memory map.
136 
 * This is weird because some BIOS do not seem to preserve
137 
 * ES/DI on failure. Consequently they may not be valid
138 
 * at _e820end:.
139 
 */
140 
	SW(rDI, _DI(SB))		/* save DI */
141 
	CLR(rAX)			/* write terminator */
142 
	STOSW
143 
	STOSW
144 
 
145 
	CLR(rBX)
146 
	PUSHR(rBX)			/* keep loop count on stack */
147 
					/* BX is the continuation value */
148 
_e820loop:
149 
	POPR(rAX)
150 
	INC(rAX)
151 
	PUSHR(rAX)			/* doesn't affect FLAGS */
152 
	CMPI(32, rAX)			/* mmap[32+1] in C code */
153 
	JGT	_e820pop
154 
 
155 
	LLI(20, rCX)			/* buffer size */
156 
	LLI(0x534D4150, rDX)		/* signature - ASCII "SMAP" */
157 
	LLI(0x0000E820, rAX)		/* function code */
158 
 
159 
	BIOSCALL(0x15)			/* writes 20 bytes at (es,di) */
160 
 
161 
	JCS	_e820pop		/* some kind of error */
162 
	LLI(0x534D4150, rDX)
163 
	CMPL(rDX, rAX)			/* verify correct BIOS version */
164 
	JNE	_e820pop
165 
	LLI(20, rDX)
166 
	CMPL(rDX, rCX)			/* verify correct count */
167 
	JNE	_e820pop
168 
 
169 
	SUBI(4, rDI)			/* overwrite terminator */
170 
	LWI(0x414D, rAX)		/* first 4 bytes are "MAP\0" */
171 
	STOSW
172 
	LWI(0x0050, rAX)
173 
	STOSW
174 
 
175 
	ADDI(20, rDI)			/* bump to next entry */
176 
 
177 
	SW(rDI, _DI(SB))		/* save DI */
178 
	CLR(rAX)			/* write terminator */
179 
	STOSW
180 
	STOSW
181 
 
182 
	OR(rBX, rBX)			/* zero if last entry */
183 
	JNE	_e820loop
184 
 
185 
_e820pop:
186 
	POPR(rAX)			/* loop count */
187 
	LW(_DI(SB), rDI)
188 
	CLR(rAX)
189 
	MTSR(rAX, rES)
190 
_e820end:
191 
 
192 
/*
193 
 * Done with BIOS calls for now.  realmode calls may use the BIOS later.
194 
 */
195 
 
196 
/*
197 
 * Load a basic GDT to map 4GB, turn on the protected mode bit in CR0,
198 
 * set all the segments to point to the new GDT then jump to the 32-bit code.
199 
 */
200 
_real:
201 
	LGDT(_gdtptr16r(SB))		/* load a basic gdt */
202 
 
203 
	MFCR(rCR0, rAX)
204 
	ORI(1, rAX)
205 
	MTCR(rAX, rCR0)			/* turn on protected mode */
206 
	DELAY				/* JMP .+2 */
207 
 
208 
	LWI(SELECTOR(1, SELGDT, 0), rAX)/* set all segments */
209 
	MTSR(rAX, rDS)
210 
	MTSR(rAX, rES)
211 
	MTSR(rAX, rFS)
212 
	MTSR(rAX, rGS)
213 
	MTSR(rAX, rSS)
214 
 
215 
	FARJUMP32(SELECTOR(2, SELGDT, 0), _start32p-KZERO(SB))
216 
 
217 
TEXT _hello(SB), $0
218 
	BYTE $'\r';
219 
	BYTE $'\n';
220 
	BYTE $'P'; BYTE $'l'; BYTE $'a'; BYTE $'n';
221 
	BYTE $' '; BYTE $'9'; BYTE $' '; BYTE $'f';
222 
	BYTE $'r'; BYTE $'o'; BYTE $'m'; BYTE $' ';
223 
	BYTE $'B'; BYTE $'e'; BYTE $'l'; BYTE $'l';
224 
	BYTE $' '; BYTE $'L'; BYTE $'a'; BYTE $'b';
225 
	BYTE $'s';
226 
	BYTE $'\z';
227 
 
228 
TEXT _DI(SB), $0
229 
	LONG $0
230 
 
231 
TEXT _ES(SB), $0
232 
	LONG $0