[comboot] Reset console before starting COMBOOT executable
[ipxe.git] / src / arch / i386 / image / comboot.c
1 /*
2 * Copyright (C) 2008 Daniel Verkamp <daniel@drv.nu>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17 * 02110-1301, USA.
18 */
19
20 /**
21 * @file
22 *
23 * SYSLINUX COMBOOT (16-bit) image format
24 *
25 */
26
27 FILE_LICENCE ( GPL2_OR_LATER );
28
29 #include <stdint.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <strings.h>
33 #include <errno.h>
34 #include <assert.h>
35 #include <realmode.h>
36 #include <basemem.h>
37 #include <comboot.h>
38 #include <ipxe/uaccess.h>
39 #include <ipxe/image.h>
40 #include <ipxe/segment.h>
41 #include <ipxe/init.h>
42 #include <ipxe/features.h>
43 #include <ipxe/console.h>
44
45 FEATURE ( FEATURE_IMAGE, "COMBOOT", DHCP_EB_FEATURE_COMBOOT, 1 );
46
47 /**
48 * COMBOOT PSP, copied to offset 0 of code segment
49 */
50 struct comboot_psp {
51 /** INT 20 instruction, executed if COMBOOT image returns with RET */
52 uint16_t int20;
53 /** Segment of first non-free paragraph of memory */
54 uint16_t first_non_free_para;
55 };
56
57 /** Offset in PSP of command line */
58 #define COMBOOT_PSP_CMDLINE_OFFSET 0x81
59
60 /** Maximum length of command line in PSP
61 * (127 bytes minus space and CR) */
62 #define COMBOOT_MAX_CMDLINE_LEN 125
63
64
65 /**
66 * Copy command line to PSP
67 *
68 * @v image COMBOOT image
69 */
70 static void comboot_copy_cmdline ( struct image * image, userptr_t seg_userptr ) {
71 const char *cmdline = ( image->cmdline ? image->cmdline : "" );
72 int cmdline_len = strlen ( cmdline );
73 if( cmdline_len > COMBOOT_MAX_CMDLINE_LEN )
74 cmdline_len = COMBOOT_MAX_CMDLINE_LEN;
75 uint8_t len_byte = cmdline_len;
76 char spc = ' ', cr = '\r';
77
78 /* Copy length to byte before command line */
79 copy_to_user ( seg_userptr, COMBOOT_PSP_CMDLINE_OFFSET - 1,
80 &len_byte, 1 );
81
82 /* Command line starts with space */
83 copy_to_user ( seg_userptr,
84 COMBOOT_PSP_CMDLINE_OFFSET,
85 &spc, 1 );
86
87 /* Copy command line */
88 copy_to_user ( seg_userptr,
89 COMBOOT_PSP_CMDLINE_OFFSET + 1,
90 cmdline, cmdline_len );
91
92 /* Command line ends with CR */
93 copy_to_user ( seg_userptr,
94 COMBOOT_PSP_CMDLINE_OFFSET + cmdline_len + 1,
95 &cr, 1 );
96 }
97
98 /**
99 * Initialize PSP
100 *
101 * @v image COMBOOT image
102 * @v seg_userptr segment to initialize
103 */
104 static void comboot_init_psp ( struct image * image, userptr_t seg_userptr ) {
105 struct comboot_psp psp;
106
107 /* Fill PSP */
108
109 /* INT 20h instruction, byte order reversed */
110 psp.int20 = 0x20CD;
111
112 /* get_fbms() returns BIOS free base memory counter, which is in
113 * kilobytes; x * 1024 / 16 == x * 64 == x << 6 */
114 psp.first_non_free_para = get_fbms() << 6;
115
116 DBGC ( image, "COMBOOT %p: first non-free paragraph = 0x%x\n",
117 image, psp.first_non_free_para );
118
119 /* Copy the PSP to offset 0 of segment.
120 * The rest of the PSP was already zeroed by
121 * comboot_prepare_segment. */
122 copy_to_user ( seg_userptr, 0, &psp, sizeof( psp ) );
123
124 /* Copy the command line to the PSP */
125 comboot_copy_cmdline ( image, seg_userptr );
126 }
127
128 /**
129 * Execute COMBOOT image
130 *
131 * @v image COMBOOT image
132 * @ret rc Return status code
133 */
134 static int comboot_exec_loop ( struct image *image ) {
135 userptr_t seg_userptr = real_to_user ( COMBOOT_PSP_SEG, 0 );
136 int state;
137
138 state = rmsetjmp ( comboot_return );
139
140 switch ( state ) {
141 case 0: /* First time through; invoke COMBOOT program */
142
143 /* Initialize PSP */
144 comboot_init_psp ( image, seg_userptr );
145
146 /* Hook COMBOOT API interrupts */
147 hook_comboot_interrupts();
148
149 DBGC ( image, "executing 16-bit COMBOOT image at %4x:0100\n",
150 COMBOOT_PSP_SEG );
151
152 /* Unregister image, so that a "boot" command doesn't
153 * throw us into an execution loop. We never
154 * reregister ourselves; COMBOOT images expect to be
155 * removed on exit.
156 */
157 unregister_image ( image );
158
159 /* Store stack segment at 0x38 and stack pointer at 0x3A
160 * in the PSP and jump to the image */
161 __asm__ __volatile__ (
162 REAL_CODE ( /* Save return address with segment on old stack */
163 "popw %%ax\n\t"
164 "pushw %%cs\n\t"
165 "pushw %%ax\n\t"
166 /* Set DS=ES=segment with image */
167 "movw %w0, %%ds\n\t"
168 "movw %w0, %%es\n\t"
169 /* Set SS:SP to new stack (end of image segment) */
170 "movw %w0, %%ss\n\t"
171 "xor %%sp, %%sp\n\t"
172 "pushw $0\n\t"
173 "pushw %w0\n\t"
174 "pushw $0x100\n\t"
175 /* Zero registers (some COM files assume GP regs are 0) */
176 "xorw %%ax, %%ax\n\t"
177 "xorw %%bx, %%bx\n\t"
178 "xorw %%cx, %%cx\n\t"
179 "xorw %%dx, %%dx\n\t"
180 "xorw %%si, %%si\n\t"
181 "xorw %%di, %%di\n\t"
182 "xorw %%bp, %%bp\n\t"
183 "lret\n\t" )
184 : : "r" ( COMBOOT_PSP_SEG ) : "eax" );
185 DBGC ( image, "COMBOOT %p: returned\n", image );
186 break;
187
188 case COMBOOT_EXIT:
189 DBGC ( image, "COMBOOT %p: exited\n", image );
190 break;
191
192 case COMBOOT_EXIT_RUN_KERNEL:
193 assert ( image->replacement );
194 DBGC ( image, "COMBOOT %p: exited to run kernel %s\n",
195 image, image->replacement->name );
196 break;
197
198 case COMBOOT_EXIT_COMMAND:
199 DBGC ( image, "COMBOOT %p: exited after executing command\n",
200 image );
201 break;
202
203 default:
204 assert ( 0 );
205 break;
206 }
207
208 unhook_comboot_interrupts();
209 comboot_force_text_mode();
210
211 return 0;
212 }
213
214 /**
215 * Check image name extension
216 *
217 * @v image COMBOOT image
218 * @ret rc Return status code
219 */
220 static int comboot_identify ( struct image *image ) {
221 const char *ext;
222
223 ext = strrchr( image->name, '.' );
224
225 if ( ! ext ) {
226 DBGC ( image, "COMBOOT %p: no extension\n",
227 image );
228 return -ENOEXEC;
229 }
230
231 ++ext;
232
233 if ( strcasecmp( ext, "cbt" ) ) {
234 DBGC ( image, "COMBOOT %p: unrecognized extension %s\n",
235 image, ext );
236 return -ENOEXEC;
237 }
238
239 return 0;
240 }
241
242 /**
243 * Load COMBOOT image into memory, preparing a segment and returning it
244 * @v image COMBOOT image
245 * @ret rc Return status code
246 */
247 static int comboot_prepare_segment ( struct image *image )
248 {
249 userptr_t seg_userptr;
250 size_t filesz, memsz;
251 int rc;
252
253 /* Load image in segment */
254 seg_userptr = real_to_user ( COMBOOT_PSP_SEG, 0 );
255
256 /* Allow etra 0x100 bytes before image for PSP */
257 filesz = image->len + 0x100;
258
259 /* Ensure the entire 64k segment is free */
260 memsz = 0xFFFF;
261
262 /* Prepare, verify, and load the real-mode segment */
263 if ( ( rc = prep_segment ( seg_userptr, filesz, memsz ) ) != 0 ) {
264 DBGC ( image, "COMBOOT %p: could not prepare segment: %s\n",
265 image, strerror ( rc ) );
266 return rc;
267 }
268
269 /* Zero PSP */
270 memset_user ( seg_userptr, 0, 0, 0x100 );
271
272 /* Copy image to segment:0100 */
273 memcpy_user ( seg_userptr, 0x100, image->data, 0, image->len );
274
275 return 0;
276 }
277
278 /**
279 * Probe COMBOOT image
280 *
281 * @v image COMBOOT image
282 * @ret rc Return status code
283 */
284 static int comboot_probe ( struct image *image ) {
285 int rc;
286
287 DBGC ( image, "COMBOOT %p: name '%s'\n",
288 image, image->name );
289
290 /* Check if this is a COMBOOT image */
291 if ( ( rc = comboot_identify ( image ) ) != 0 ) {
292
293 return rc;
294 }
295
296 return 0;
297 }
298
299 /**
300 * Execute COMBOOT image
301 *
302 * @v image COMBOOT image
303 * @ret rc Return status code
304 */
305 static int comboot_exec ( struct image *image ) {
306 int rc;
307
308 /* Sanity check for filesize */
309 if( image->len >= 0xFF00 ) {
310 DBGC( image, "COMBOOT %p: image too large\n",
311 image );
312 return -ENOEXEC;
313 }
314
315 /* Prepare segment and load image */
316 if ( ( rc = comboot_prepare_segment ( image ) ) != 0 ) {
317 return rc;
318 }
319
320 /* Reset console */
321 console_reset();
322
323 return comboot_exec_loop ( image );
324 }
325
326 /** SYSLINUX COMBOOT (16-bit) image type */
327 struct image_type comboot_image_type __image_type ( PROBE_NORMAL ) = {
328 .name = "COMBOOT",
329 .probe = comboot_probe,
330 .exec = comboot_exec,
331 };