1/* ----------------------------------------------------------------------- *
2 *
3 *   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
4 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
5 *
6 *   Permission is hereby granted, free of charge, to any person
7 *   obtaining a copy of this software and associated documentation
8 *   files (the "Software"), to deal in the Software without
9 *   restriction, including without limitation the rights to use,
10 *   copy, modify, merge, publish, distribute, sublicense, and/or
11 *   sell copies of the Software, and to permit persons to whom
12 *   the Software is furnished to do so, subject to the following
13 *   conditions:
14 *
15 *   The above copyright notice and this permission notice shall
16 *   be included in all copies or substantial portions of the Software.
17 *
18 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
20 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
22 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
23 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
24 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
25 *   OTHER DEALINGS IN THE SOFTWARE.
26 *
27 * ----------------------------------------------------------------------- */
28
29/*
30 * shuffle_rm.c
31 *
32 * Shuffle and boot to protected mode code
33 */
34
35#include <stdlib.h>
36#include <inttypes.h>
37#include <com32.h>
38#include <string.h>
39#include <syslinux/movebits.h>
40#include <syslinux/bootrm.h>
41
42enum gpr_index { R_AX, R_CX, R_DX, R_BX, R_SP, R_BP, R_SI, R_DI };
43enum seg_index { R_ES, R_CS, R_SS, R_DS, R_FS, R_GS };
44
45#define ST8(P,V)						\
46  do {								\
47    uint8_t *_p = (void *)(P);					\
48    *_p++ = (V);						\
49    (P) = (void *)_p;						\
50  } while (0);
51#define ST16(P,V)						\
52  do {								\
53    uint16_t *_p = (void *)(P);					\
54    *_p++ = (V);						\
55    (P) = (void *)_p;						\
56  } while (0)
57#define ST32(P,V)						\
58  do {								\
59    uint32_t *_p = (void *)(P);					\
60    *_p++ = (V);						\
61    (P) = (void *)_p;						\
62  } while (0)
63
64#define MOV_TO_SEG(P,S,R)					\
65    ST16(P, 0xc08e + ((R) << 8) + ((S) << 11))
66#define MOV_TO_R16(P,R,V)					\
67  do {								\
68    ST8(P, 0xb8 + (R));						\
69    ST16(P, V);							\
70  }  while (0)
71#define MOV_TO_R32(P,R,V)					\
72  do {								\
73    ST16(P, 0xb866 + ((R) << 8));				\
74    ST32(P, V);							\
75  } while (0)
76
77int syslinux_shuffle_boot_rm(struct syslinux_movelist *fraglist,
78			     struct syslinux_memmap *memmap,
79			     uint16_t bootflags, struct syslinux_rm_regs *regs)
80{
81    const struct syslinux_rm_regs_alt {
82	uint16_t seg[6];
83	uint32_t gpr[8];
84	uint32_t csip;
85	bool sti;
86    } *rp;
87    int i, rv;
88    uint8_t handoff_code[8 + 5 * 5 + 8 * 6 + 1 + 5], *p;
89    uint16_t off;
90    struct syslinux_memmap *tmap;
91    addr_t regstub, stublen;
92    /* Assign GPRs for each sreg, don't use AX and SP */
93    static const uint8_t gpr_for_seg[6] =
94	{ R_CX, R_DX, R_BX, R_BP, R_SI, R_DI };
95
96    tmap = syslinux_target_memmap(fraglist, memmap);
97    if (!tmap)
98	return -1;
99
100    /*
101     * Search for a good place to put the real-mode register stub.
102     * We prefer it as low as possible above 0x800.  KVM barfs horribly
103     * if we're not aligned to a paragraph boundary, so set the alignment
104     * appropriately.
105     */
106    regstub = 0x800;
107    stublen = sizeof handoff_code;
108    rv = syslinux_memmap_find_type(tmap, SMT_FREE, &regstub, &stublen, 16);
109
110    if (rv || (regstub > 0x100000 - sizeof handoff_code)) {
111	/*
112	 * Uh-oh.  This isn't real-mode accessible memory.
113	 * It might be possible to do something insane here like
114	 * putting the stub in the IRQ vectors, or in the 0x5xx segment.
115	 * This code tries the 0x510-0x7ff range and hopes for the best.
116	 */
117	regstub = 0x510;	/* Try the 0x5xx segment... */
118	stublen = sizeof handoff_code;
119	rv = syslinux_memmap_find_type(tmap, SMT_FREE, &regstub, &stublen, 16);
120
121	if (!rv && (regstub > 0x100000 - sizeof handoff_code))
122	    rv = -1;		/* No acceptable memory found */
123    }
124
125    syslinux_free_memmap(tmap);
126    if (rv)
127	return -1;
128
129    /* Build register-setting stub */
130    p = handoff_code;
131    rp = (const struct syslinux_rm_regs_alt *)regs;
132
133    /* Set up GPRs with segment registers - don't use AX */
134    for (i = 0; i < 6; i++) {
135	if (i != R_CS)
136	    MOV_TO_R16(p, gpr_for_seg[i], rp->seg[i]);
137    }
138
139    /* Actual transition to real mode */
140    ST32(p, 0xeac0220f);	/* MOV CR0,EAX; JMP FAR */
141    off = (p - handoff_code) + 4;
142    ST16(p, off);		/* Offset */
143    ST16(p, regstub >> 4);	/* Segment */
144
145    /* Load SS and ESP immediately */
146    MOV_TO_SEG(p, R_SS, R_BX);
147    MOV_TO_R32(p, R_SP, rp->gpr[R_SP]);
148
149    /* Load the other segments */
150    MOV_TO_SEG(p, R_ES, R_CX);
151    MOV_TO_SEG(p, R_DS, R_BP);
152    MOV_TO_SEG(p, R_FS, R_SI);
153    MOV_TO_SEG(p, R_GS, R_DI);
154
155    for (i = 0; i < 8; i++) {
156	if (i != R_SP)
157	    MOV_TO_R32(p, i, rp->gpr[i]);
158    }
159
160    ST8(p, rp->sti ? 0xfb : 0xfa);	/* STI/CLI */
161
162    ST8(p, 0xea);		/* JMP FAR */
163    ST32(p, rp->csip);
164
165    /* Add register-setting stub to shuffle list */
166    if (syslinux_add_movelist(&fraglist, regstub, (addr_t) handoff_code,
167			      sizeof handoff_code))
168	return -1;
169
170    return syslinux_do_shuffle(fraglist, memmap, regstub, 0, bootflags);
171}
172