/* MN10300 Misalignment fixup handler * * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if 0 #define kdebug(FMT, ...) printk(KERN_DEBUG FMT, ##__VA_ARGS__) #else #define kdebug(FMT, ...) do {} while (0) #endif static int misalignment_addr(unsigned long *registers, unsigned params, unsigned opcode, unsigned disp, void **_address, unsigned long **_postinc); static int misalignment_reg(unsigned long *registers, unsigned params, unsigned opcode, unsigned disp, unsigned long **_register); static inline unsigned int_log2(unsigned x) { unsigned y; asm("bsch %1,%0" : "=r"(y) : "r"(x), "0"(0)); return y; } #define log2(x) int_log2(x) static const unsigned Dreg_index[] = { REG_D0 >> 2, REG_D1 >> 2, REG_D2 >> 2, REG_D3 >> 2 }; static const unsigned Areg_index[] = { REG_A0 >> 2, REG_A1 >> 2, REG_A2 >> 2, REG_A3 >> 2 }; static const unsigned Rreg_index[] = { REG_E0 >> 2, REG_E1 >> 2, REG_E2 >> 2, REG_E3 >> 2, REG_E4 >> 2, REG_E5 >> 2, REG_E6 >> 2, REG_E7 >> 2, REG_A0 >> 2, REG_A1 >> 2, REG_A2 >> 2, REG_A3 >> 2, REG_D0 >> 2, REG_D1 >> 2, REG_D2 >> 2, REG_D3 >> 2 }; enum format_id { FMT_S0, FMT_S1, FMT_S2, FMT_S4, FMT_D0, FMT_D1, FMT_D2, FMT_D4, FMT_D6, FMT_D7, FMT_D8, FMT_D9, }; struct { u_int8_t opsz, dispsz; } format_tbl[16] = { [FMT_S0] = { 8, 0 }, [FMT_S1] = { 8, 8 }, [FMT_S2] = { 8, 16 }, [FMT_S4] = { 8, 32 }, [FMT_D0] = { 16, 0 }, [FMT_D1] = { 16, 8 }, [FMT_D2] = { 16, 16 }, [FMT_D4] = { 16, 32 }, [FMT_D6] = { 24, 0 }, [FMT_D7] = { 24, 8 }, [FMT_D8] = { 24, 24 }, [FMT_D9] = { 24, 32 }, }; enum value_id { DM0, /* data reg in opcode in bits 0-1 */ DM1, /* data reg in opcode in bits 2-3 */ DM2, /* data reg in opcode in bits 4-5 */ AM0, /* addr reg in opcode in bits 0-1 */ AM1, /* addr reg in opcode in bits 2-3 */ AM2, /* addr reg in opcode in bits 4-5 */ RM0, /* reg in opcode in bits 0-3 */ RM1, /* reg in opcode in bits 2-5 */ RM2, /* reg in opcode in bits 4-7 */ RM4, /* reg in opcode in bits 8-11 */ RM6, /* reg in opcode in bits 12-15 */ RD0, /* reg in displacement in bits 0-3 */ RD2, /* reg in displacement in bits 4-7 */ SP, /* stack pointer */ SD8, /* 8-bit signed displacement */ SD16, /* 16-bit signed displacement */ SD24, /* 24-bit signed displacement */ SIMM4_2, /* 4-bit signed displacement in opcode bits 4-7 */ SIMM8, /* 8-bit signed immediate */ IMM24, /* 24-bit unsigned immediate */ IMM32, /* 32-bit unsigned immediate */ IMM32_HIGH8, /* 32-bit unsigned immediate, high 8-bits in opcode */ DN0 = DM0, DN1 = DM1, DN2 = DM2, AN0 = AM0, AN1 = AM1, AN2 = AM2, RN0 = RM0, RN1 = RM1, RN2 = RM2, RN4 = RM4, RN6 = RM6, DI = DM1, RI = RM2, }; struct mn10300_opcode { const char *name; u_int32_t opcode; u_int32_t opmask; unsigned exclusion; enum format_id format; unsigned cpu_mask; #define AM33 330 unsigned params[2]; #define MEM(ADDR) (0x80000000 | (ADDR)) #define MEM2(ADDR1, ADDR2) (0x80000000 | (ADDR1) << 8 | (ADDR2)) #define MEMINC(ADDR) (0x81000000 | (ADDR)) #define MEMINC2(ADDR, INC) (0x81000000 | (ADDR) << 8 | (INC)) }; /* LIBOPCODES EXCERPT Assemble Matsushita MN10300 instructions. Copyright 1996, 1997, 1998, 1999, 2000 Free Software Foundation, Inc. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public Licence as published by the Free Software Foundation; either version 2 of the Licence, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public Licence for more details. You should have received a copy of the GNU General Public Licence along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ static const struct mn10300_opcode mn10300_opcodes[] = { { "mov", 0x60, 0xf0, 0, FMT_S0, 0, {DM1, MEM(AN0)}}, { "mov", 0x70, 0xf0, 0, FMT_S0, 0, {MEM(AM0), DN1}}, { "mov", 0xf000, 0xfff0, 0, FMT_D0, 0, {MEM(AM0), AN1}}, { "mov", 0xf010, 0xfff0, 0, FMT_D0, 0, {AM1, MEM(AN0)}}, { "mov", 0xf300, 0xffc0, 0, FMT_D0, 0, {MEM2(DI, AM0), DN2}}, { "mov", 0xf340, 0xffc0, 0, FMT_D0, 0, {DM2, MEM2(DI, AN0)}}, { "mov", 0xf380, 0xffc0, 0, FMT_D0, 0, {MEM2(DI, AM0), AN2}}, { "mov", 0xf3c0, 0xffc0, 0, FMT_D0, 0, {AM2, MEM2(DI, AN0)}}, { "mov", 0xf80000, 0xfff000, 0, FMT_D1, 0, {MEM2(SD8, AM0), DN1}}, { "mov", 0xf81000, 0xfff000, 0, FMT_D1, 0, {DM1, MEM2(SD8, AN0)}}, { "mov", 0xf82000, 0xfff000, 0, FMT_D1, 0, {MEM2(SD8,AM0), AN1}}, { "mov", 0xf83000, 0xfff000, 0, FMT_D1, 0, {AM1, MEM2(SD8, AN0)}}, { "mov", 0xf8f000, 0xfffc00, 0, FMT_D1, AM33, {MEM2(SD8, AM0), SP}}, { "mov", 0xf8f400, 0xfffc00, 0, FMT_D1, AM33, {SP, MEM2(SD8, AN0)}}, { "mov", 0xf90a00, 0xffff00, 0, FMT_D6, AM33, {MEM(RM0), RN2}}, { "mov", 0xf91a00, 0xffff00, 0, FMT_D6, AM33, {RM2, MEM(RN0)}}, { "mov", 0xf96a00, 0xffff00, 0x12, FMT_D6, AM33, {MEMINC(RM0), RN2}}, { "mov", 0xf97a00, 0xffff00, 0, FMT_D6, AM33, {RM2, MEMINC(RN0)}}, { "mov", 0xfa000000, 0xfff00000, 0, FMT_D2, 0, {MEM2(SD16, AM0), DN1}}, { "mov", 0xfa100000, 0xfff00000, 0, FMT_D2, 0, {DM1, MEM2(SD16, AN0)}}, { "mov", 0xfa200000, 0xfff00000, 0, FMT_D2, 0, {MEM2(SD16, AM0), AN1}}, { "mov", 0xfa300000, 0xfff00000, 0, FMT_D2, 0, {AM1, MEM2(SD16, AN0)}}, { "mov", 0xfb0a0000, 0xffff0000, 0, FMT_D7, AM33, {MEM2(SD8, RM0), RN2}}, { "mov", 0xfb1a0000, 0xffff0000, 0, FMT_D7, AM33, {RM2, MEM2(SD8, RN0)}}, { "mov", 0xfb6a0000, 0xffff0000, 0x22, FMT_D7, AM33, {MEMINC2 (RM0, SIMM8), RN2}}, { "mov", 0xfb7a0000, 0xffff0000, 0, FMT_D7, AM33, {RM2, MEMINC2 (RN0, SIMM8)}}, { "mov", 0xfb8e0000, 0xffff000f, 0, FMT_D7, AM33, {MEM2(RI, RM0), RD2}}, { "mov", 0xfb9e0000, 0xffff000f, 0, FMT_D7, AM33, {RD2, MEM2(RI, RN0)}}, { "mov", 0xfc000000, 0xfff00000, 0, FMT_D4, 0, {MEM2(IMM32,AM0), DN1}}, { "mov", 0xfc100000, 0xfff00000, 0, FMT_D4, 0, {DM1, MEM2(IMM32,AN0)}}, { "mov", 0xfc200000, 0xfff00000, 0, FMT_D4, 0, {MEM2(IMM32,AM0), AN1}}, { "mov", 0xfc300000, 0xfff00000, 0, FMT_D4, 0, {AM1, MEM2(IMM32,AN0)}}, { "mov", 0xfd0a0000, 0xffff0000, 0, FMT_D8, AM33, {MEM2(SD24, RM0), RN2}}, { "mov", 0xfd1a0000, 0xffff0000, 0, FMT_D8, AM33, {RM2, MEM2(SD24, RN0)}}, { "mov", 0xfd6a0000, 0xffff0000, 0x22, FMT_D8, AM33, {MEMINC2 (RM0, IMM24), RN2}}, { "mov", 0xfd7a0000, 0xffff0000, 0, FMT_D8, AM33, {RM2, MEMINC2 (RN0, IMM24)}}, { "mov", 0xfe0a0000, 0xffff0000, 0, FMT_D9, AM33, {MEM2(IMM32_HIGH8,RM0), RN2}}, { "mov", 0xfe1a0000, 0xffff0000, 0, FMT_D9, AM33, {RM2, MEM2(IMM32_HIGH8, RN0)}}, { "mov", 0xfe6a0000, 0xffff0000, 0x22, FMT_D9, AM33, {MEMINC2 (RM0, IMM32_HIGH8), RN2}}, { "mov", 0xfe7a0000, 0xffff0000, 0, FMT_D9, AM33, {RN2, MEMINC2 (RM0, IMM32_HIGH8)}}, { "movhu", 0xf060, 0xfff0, 0, FMT_D0, 0, {MEM(AM0), DN1}}, { "movhu", 0xf070, 0xfff0, 0, FMT_D0, 0, {DM1, MEM(AN0)}}, { "movhu", 0xf480, 0xffc0, 0, FMT_D0, 0, {MEM2(DI, AM0), DN2}}, { "movhu", 0xf4c0, 0xffc0, 0, FMT_D0, 0, {DM2, MEM2(DI, AN0)}}, { "movhu", 0xf86000, 0xfff000, 0, FMT_D1, 0, {MEM2(SD8, AM0), DN1}}, { "movhu", 0xf87000, 0xfff000, 0, FMT_D1, 0, {DM1, MEM2(SD8, AN0)}}, { "movhu", 0xf94a00, 0xffff00, 0, FMT_D6, AM33, {MEM(RM0), RN2}}, { "movhu", 0xf95a00, 0xffff00, 0, FMT_D6, AM33, {RM2, MEM(RN0)}}, { "movhu", 0xf9ea00, 0xffff00, 0x12, FMT_D6, AM33, {MEMINC(RM0), RN2}}, { "movhu", 0xf9fa00, 0xffff00, 0, FMT_D6, AM33, {RM2, MEMINC(RN0)}}, { "movhu", 0xfa600000, 0xfff00000, 0, FMT_D2, 0, {MEM2(SD16, AM0), DN1}}, { "movhu", 0xfa700000, 0xfff00000, 0, FMT_D2, 0, {DM1, MEM2(SD16, AN0)}}, { "movhu", 0xfb4a0000, 0xffff0000, 0, FMT_D7, AM33, {MEM2(SD8, RM0), RN2}}, { "movhu", 0xfb5a0000, 0xffff0000, 0, FMT_D7, AM33, {RM2, MEM2(SD8, RN0)}}, { "movhu", 0xfbce0000, 0xffff000f, 0, FMT_D7, AM33, {MEM2(RI, RM0), RD2}}, { "movhu", 0xfbde0000, 0xffff000f, 0, FMT_D7, AM33, {RD2, MEM2(RI, RN0)}}, { "movhu", 0xfbea0000, 0xffff0000, 0x22, FMT_D7, AM33, {MEMINC2 (RM0, SIMM8), RN2}}, { "movhu", 0xfbfa0000, 0xffff0000, 0, FMT_D7, AM33, {RM2, MEMINC2 (RN0, SIMM8)}}, { "movhu", 0xfc600000, 0xfff00000, 0, FMT_D4, 0, {MEM2(IMM32,AM0), DN1}}, { "movhu", 0xfc700000, 0xfff00000, 0, FMT_D4, 0, {DM1, MEM2(IMM32,AN0)}}, { "movhu", 0xfd4a0000, 0xffff0000, 0, FMT_D8, AM33, {MEM2(SD24, RM0), RN2}}, { "movhu", 0xfd5a0000, 0xffff0000, 0, FMT_D8, AM33, {RM2, MEM2(SD24, RN0)}}, { "movhu", 0xfdea0000, 0xffff0000, 0x22, FMT_D8, AM33, {MEMINC2 (RM0, IMM24), RN2}}, { "movhu", 0xfdfa0000, 0xffff0000, 0, FMT_D8, AM33, {RM2, MEMINC2 (RN0, IMM24)}}, { "movhu", 0xfe4a0000, 0xffff0000, 0, FMT_D9, AM33, {MEM2(IMM32_HIGH8,RM0), RN2}}, { "movhu", 0xfe5a0000, 0xffff0000, 0, FMT_D9, AM33, {RM2, MEM2(IMM32_HIGH8, RN0)}}, { "movhu", 0xfeea0000, 0xffff0000, 0x22, FMT_D9, AM33, {MEMINC2 (RM0, IMM32_HIGH8), RN2}}, { "movhu", 0xfefa0000, 0xffff0000, 0, FMT_D9, AM33, {RN2, MEMINC2 (RM0, IMM32_HIGH8)}}, { 0, 0, 0, 0, 0, 0, {0}}, }; /* * fix up misalignment problems where possible */ asmlinkage void misalignment(struct pt_regs *regs, enum exception_code code) { const struct exception_table_entry *fixup; const struct mn10300_opcode *pop; unsigned long *registers = (unsigned long *) regs; unsigned long data, *store, *postinc; mm_segment_t seg; siginfo_t info; uint32_t opcode, disp, noc, xo, xm; uint8_t *pc, byte; void *address; unsigned tmp, npop; kdebug("MISALIGN at %lx\n", regs->pc); if (in_interrupt()) die("Misalignment trap in interrupt context", regs, code); if (regs->epsw & EPSW_IE) asm volatile("or %0,epsw" : : "i"(EPSW_IE)); seg = get_fs(); set_fs(KERNEL_DS); fixup = search_exception_tables(regs->pc); /* first thing to do is to match the opcode */ pc = (u_int8_t *) regs->pc; if (__get_user(byte, pc) != 0) goto fetch_error; opcode = byte; noc = 8; for (pop = mn10300_opcodes; pop->name; pop++) { npop = log2(pop->opcode | pop->opmask); if (npop <= 0 || npop > 31) continue; npop = (npop + 8) & ~7; got_more_bits: if (npop == noc) { if ((opcode & pop->opmask) == pop->opcode) goto found_opcode; } else if (npop > noc) { xo = pop->opcode >> (npop - noc); xm = pop->opmask >> (npop - noc); if ((opcode & xm) != xo) continue; /* we've got a partial match (an exact match on the * first N bytes), so we need to get some more data */ pc++; if (__get_user(byte, pc) != 0) goto fetch_error; opcode = opcode << 8 | byte; noc += 8; goto got_more_bits; } else { /* there's already been a partial match as long as the * complete match we're now considering, so this one * should't match */ continue; } } /* didn't manage to find a fixup */ if (!user_mode(regs)) printk(KERN_CRIT "MISALIGN: %lx: unsupported instruction %x\n", regs->pc, opcode); failed: set_fs(seg); if (die_if_no_fixup("misalignment error", regs, code)) return; info.si_signo = SIGBUS; info.si_errno = 0; info.si_code = BUS_ADRALN; info.si_addr = (void *) regs->pc; force_sig_info(SIGBUS, &info, current); return; /* error reading opcodes */ fetch_error: if (!user_mode(regs)) printk(KERN_CRIT "MISALIGN: %p: fault whilst reading instruction data\n", pc); goto failed; bad_addr_mode: if (!user_mode(regs)) printk(KERN_CRIT "MISALIGN: %lx: unsupported addressing mode %x\n", regs->pc, opcode); goto failed; bad_reg_mode: if (!user_mode(regs)) printk(KERN_CRIT "MISALIGN: %lx: unsupported register mode %x\n", regs->pc, opcode); goto failed; unsupported_instruction: if (!user_mode(regs)) printk(KERN_CRIT "MISALIGN: %lx: unsupported instruction %x (%s)\n", regs->pc, opcode, pop->name); goto failed; transfer_failed: set_fs(seg); if (fixup) { regs->pc = fixup->fixup; return; } if (die_if_no_fixup("misalignment fixup", regs, code)) return; info.si_signo = SIGSEGV; info.si_errno = 0; info.si_code = 0; info.si_addr = (void *) regs->pc; force_sig_info(SIGSEGV, &info, current); return; /* we matched the opcode */ found_opcode: kdebug("MISALIGN: %lx: %x==%x { %x, %x }\n", regs->pc, opcode, pop->opcode, pop->params[0], pop->params[1]); tmp = format_tbl[pop->format].opsz; if (tmp > noc) BUG(); /* match was less complete than it ought to have been */ if (tmp < noc) { tmp = noc - tmp; opcode >>= tmp; pc -= tmp >> 3; } /* grab the extra displacement (note it's LSB first) */ disp = 0; tmp = format_tbl[pop->format].dispsz >> 3; while (tmp > 0) { tmp--; disp <<= 8; pc++; if (__get_user(byte, pc) != 0) goto fetch_error; disp |= byte; } set_fs(KERNEL_XDS); if (fixup || regs->epsw & EPSW_nSL) set_fs(seg); tmp = (pop->params[0] ^ pop->params[1]) & 0x80000000; if (!tmp) { if (!user_mode(regs)) printk(KERN_CRIT "MISALIGN: %lx:" " insn not move to/from memory %x\n", regs->pc, opcode); goto failed; } if (pop->params[0] & 0x80000000) { /* move memory to register */ if (!misalignment_addr(registers, pop->params[0], opcode, disp, &address, &postinc)) goto bad_addr_mode; if (!misalignment_reg(registers, pop->params[1], opcode, disp, &store)) goto bad_reg_mode; if (strcmp(pop->name, "mov") == 0) { kdebug("FIXUP: mov (%p),DARn\n", address); if (copy_from_user(&data, (void *) address, 4) != 0) goto transfer_failed; if (pop->params[0] & 0x1000000) *postinc += 4; } else if (strcmp(pop->name, "movhu") == 0) { kdebug("FIXUP: movhu (%p),DARn\n", address); data = 0; if (copy_from_user(&data, (void *) address, 2) != 0) goto transfer_failed; if (pop->params[0] & 0x1000000) *postinc += 2; } else { goto unsupported_instruction; } *store = data; } else { /* move register to memory */ if (!misalignment_reg(registers, pop->params[0], opcode, disp, &store)) goto bad_reg_mode; if (!misalignment_addr(registers, pop->params[1], opcode, disp, &address, &postinc)) goto bad_addr_mode; data = *store; if (strcmp(pop->name, "mov") == 0) { kdebug("FIXUP: mov %lx,(%p)\n", data, address); if (copy_to_user((void *) address, &data, 4) != 0) goto transfer_failed; if (pop->params[1] & 0x1000000) *postinc += 4; } else if (strcmp(pop->name, "movhu") == 0) { kdebug("FIXUP: movhu %hx,(%p)\n", (uint16_t) data, address); if (copy_to_user((void *) address, &data, 2) != 0) goto transfer_failed; if (pop->params[1] & 0x1000000) *postinc += 2; } else { goto unsupported_instruction; } } tmp = format_tbl[pop->format].opsz + format_tbl[pop->format].dispsz; regs->pc += tmp >> 3; set_fs(seg); return; } /* * determine the address that was being accessed */ static int misalignment_addr(unsigned long *registers, unsigned params, unsigned opcode, unsigned disp, void **_address, unsigned long **_postinc) { unsigned long *postinc = NULL, address = 0, tmp; params &= 0x7fffffff; do { switch (params & 0xff) { case DM0: postinc = ®isters[Dreg_index[opcode & 0x03]]; address += *postinc; break; case DM1: postinc = ®isters[Dreg_index[opcode >> 2 & 0x0c]]; address += *postinc; break; case DM2: postinc = ®isters[Dreg_index[opcode >> 4 & 0x30]]; address += *postinc; break; case AM0: postinc = ®isters[Areg_index[opcode & 0x03]]; address += *postinc; break; case AM1: postinc = ®isters[Areg_index[opcode >> 2 & 0x0c]]; address += *postinc; break; case AM2: postinc = ®isters[Areg_index[opcode >> 4 & 0x30]]; address += *postinc; break; case RM0: postinc = ®isters[Rreg_index[opcode & 0x0f]]; address += *postinc; break; case RM1: postinc = ®isters[Rreg_index[opcode >> 2 & 0x0f]]; address += *postinc; break; case RM2: postinc = ®isters[Rreg_index[opcode >> 4 & 0x0f]]; address += *postinc; break; case RM4: postinc = ®isters[Rreg_index[opcode >> 8 & 0x0f]]; address += *postinc; break; case RM6: postinc = ®isters[Rreg_index[opcode >> 12 & 0x0f]]; address += *postinc; break; case RD0: postinc = ®isters[Rreg_index[disp & 0x0f]]; address += *postinc; break; case RD2: postinc = ®isters[Rreg_index[disp >> 4 & 0x0f]]; address += *postinc; break; case SD8: case SIMM8: address += (int32_t) (int8_t) (disp & 0xff); break; case SD16: address += (int32_t) (int16_t) (disp & 0xffff); break; case SD24: tmp = disp << 8; asm("asr 8,%0" : "=r"(tmp) : "0"(tmp)); address += tmp; break; case SIMM4_2: tmp = opcode >> 4 & 0x0f; tmp <<= 28; asm("asr 28,%0" : "=r"(tmp) : "0"(tmp)); address += tmp; break; case IMM24: address += disp & 0x00ffffff; break; case IMM32: case IMM32_HIGH8: address += disp; break; default: return 0; } } while ((params >>= 8)); *_address = (void *) address; *_postinc = postinc; return 1; } /* * determine the register that is acting as source/dest */ static int misalignment_reg(unsigned long *registers, unsigned params, unsigned opcode, unsigned disp, unsigned long **_register) { params &= 0x7fffffff; if (params & 0xffffff00) return 0; switch (params & 0xff) { case DM0: *_register = ®isters[Dreg_index[opcode & 0x03]]; break; case DM1: *_register = ®isters[Dreg_index[opcode >> 2 & 0x03]]; break; case DM2: *_register = ®isters[Dreg_index[opcode >> 4 & 0x03]]; break; case AM0: *_register = ®isters[Areg_index[opcode & 0x03]]; break; case AM1: *_register = ®isters[Areg_index[opcode >> 2 & 0x03]]; break; case AM2: *_register = ®isters[Areg_index[opcode >> 4 & 0x03]]; break; case RM0: *_register = ®isters[Rreg_index[opcode & 0x0f]]; break; case RM1: *_register = ®isters[Rreg_index[opcode >> 2 & 0x0f]]; break; case RM2: *_register = ®isters[Rreg_index[opcode >> 4 & 0x0f]]; break; case RM4: *_register = ®isters[Rreg_index[opcode >> 8 & 0x0f]]; break; case RM6: *_register = ®isters[Rreg_index[opcode >> 12 & 0x0f]]; break; case RD0: *_register = ®isters[Rreg_index[disp & 0x0f]]; break; case RD2: *_register = ®isters[Rreg_index[disp >> 4 & 0x0f]]; break; case SP: *_register = ®isters[REG_SP >> 2]; break; default: return 0; } return 1; }