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 42 enum gpr_index { R_AX, R_CX, R_DX, R_BX, R_SP, R_BP, R_SI, R_DI }; 43 enum 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 77 int 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, ®stub, &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, ®stub, &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
