/* $Id: unaligned.c,v 1.23 2001/04/09 04:29:03 davem Exp $ * unaligned.c: Unaligned load/store trap handling with special * cases for the kernel to do them more quickly. * * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu) * Copyright (C) 1996,1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz) */ #include #include #include #include #include #include #include #include #include #include #include #include #include /* #define DEBUG_MNA */ enum direction { load, /* ld, ldd, ldh, ldsh */ store, /* st, std, sth, stsh */ both, /* Swap, ldstub, cas, ... */ fpld, fpst, invalid, }; #ifdef DEBUG_MNA static char *dirstrings[] = { "load", "store", "both", "fpload", "fpstore", "invalid" }; #endif static inline enum direction decode_direction(unsigned int insn) { unsigned long tmp = (insn >> 21) & 1; if(!tmp) return load; else { switch ((insn>>19)&0xf) { case 15: /* swap* */ return both; default: return store; } } } /* 16 = double-word, 8 = extra-word, 4 = word, 2 = half-word */ static inline int decode_access_size(unsigned int insn) { unsigned int tmp; tmp = ((insn >> 19) & 0xf); if (tmp == 11 || tmp == 14) /* ldx/stx */ return 8; tmp &= 3; if(!tmp) return 4; else if(tmp == 3) return 16; /* ldd/std - Although it is actually 8 */ else if(tmp == 2) return 2; else { printk("Impossible unaligned trap. insn=%08x\n", insn); die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs); } } static inline int decode_asi(unsigned int insn, struct pt_regs *regs) { if (insn & 0x800000) { if (insn & 0x2000) return (unsigned char)(regs->tstate >> 24); /* %asi */ else return (unsigned char)(insn >> 5); /* imm_asi */ } else return ASI_P; } /* 0x400000 = signed, 0 = unsigned */ static inline int decode_signedness(unsigned int insn) { return (insn & 0x400000); } static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2, unsigned int rd, int from_kernel) { if(rs2 >= 16 || rs1 >= 16 || rd >= 16) { if(from_kernel != 0) __asm__ __volatile__("flushw"); else flushw_user(); } } static inline long sign_extend_imm13(long imm) { return imm << 51 >> 51; } static unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs) { unsigned long value; if(reg < 16) return (!reg ? 0 : regs->u_regs[reg]); if (regs->tstate & TSTATE_PRIV) { struct reg_window *win; win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS); value = win->locals[reg - 16]; } else if (current->thread.flags & SPARC_FLAG_32BIT) { struct reg_window32 *win32; win32 = (struct reg_window32 *)((unsigned long)((u32)regs->u_regs[UREG_FP])); get_user(value, &win32->locals[reg - 16]); } else { struct reg_window *win; win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS); get_user(value, &win->locals[reg - 16]); } return value; } static unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs) { if(reg < 16) return ®s->u_regs[reg]; if (regs->tstate & TSTATE_PRIV) { struct reg_window *win; win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS); return &win->locals[reg - 16]; } else if (current->thread.flags & SPARC_FLAG_32BIT) { struct reg_window32 *win32; win32 = (struct reg_window32 *)((unsigned long)((u32)regs->u_regs[UREG_FP])); return (unsigned long *)&win32->locals[reg - 16]; } else { struct reg_window *win; win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS); return &win->locals[reg - 16]; } } unsigned long compute_effective_address(struct pt_regs *regs, unsigned int insn, unsigned int rd) { unsigned int rs1 = (insn >> 14) & 0x1f; unsigned int rs2 = insn & 0x1f; int from_kernel = (regs->tstate & TSTATE_PRIV) != 0; if(insn & 0x2000) { maybe_flush_windows(rs1, 0, rd, from_kernel); return (fetch_reg(rs1, regs) + sign_extend_imm13(insn)); } else { maybe_flush_windows(rs1, rs2, rd, from_kernel); return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs)); } } /* This is just to make gcc think die_if_kernel does return... */ static void __attribute_used__ unaligned_panic(char *str, struct pt_regs *regs) { die_if_kernel(str, regs); } #define do_integer_load(dest_reg, size, saddr, is_signed, asi, errh) ({ \ __asm__ __volatile__ ( \ "wr %4, 0, %%asi\n\t" \ "cmp %1, 8\n\t" \ "bge,pn %%icc, 9f\n\t" \ " cmp %1, 4\n\t" \ "be,pt %%icc, 6f\n" \ "4:\t" " lduba [%2] %%asi, %%l1\n" \ "5:\t" "lduba [%2 + 1] %%asi, %%l2\n\t" \ "sll %%l1, 8, %%l1\n\t" \ "brz,pt %3, 3f\n\t" \ " add %%l1, %%l2, %%l1\n\t" \ "sllx %%l1, 48, %%l1\n\t" \ "srax %%l1, 48, %%l1\n" \ "3:\t" "ba,pt %%xcc, 0f\n\t" \ " stx %%l1, [%0]\n" \ "6:\t" "lduba [%2 + 1] %%asi, %%l2\n\t" \ "sll %%l1, 24, %%l1\n" \ "7:\t" "lduba [%2 + 2] %%asi, %%g7\n\t" \ "sll %%l2, 16, %%l2\n" \ "8:\t" "lduba [%2 + 3] %%asi, %%g1\n\t" \ "sll %%g7, 8, %%g7\n\t" \ "or %%l1, %%l2, %%l1\n\t" \ "or %%g7, %%g1, %%g7\n\t" \ "or %%l1, %%g7, %%l1\n\t" \ "brnz,a,pt %3, 3f\n\t" \ " sra %%l1, 0, %%l1\n" \ "3:\t" "ba,pt %%xcc, 0f\n\t" \ " stx %%l1, [%0]\n" \ "9:\t" "lduba [%2] %%asi, %%l1\n" \ "10:\t" "lduba [%2 + 1] %%asi, %%l2\n\t" \ "sllx %%l1, 56, %%l1\n" \ "11:\t" "lduba [%2 + 2] %%asi, %%g7\n\t" \ "sllx %%l2, 48, %%l2\n" \ "12:\t" "lduba [%2 + 3] %%asi, %%g1\n\t" \ "sllx %%g7, 40, %%g7\n\t" \ "sllx %%g1, 32, %%g1\n\t" \ "or %%l1, %%l2, %%l1\n\t" \ "or %%g7, %%g1, %%g7\n" \ "13:\t" "lduba [%2 + 4] %%asi, %%l2\n\t" \ "or %%l1, %%g7, %%g7\n" \ "14:\t" "lduba [%2 + 5] %%asi, %%g1\n\t" \ "sllx %%l2, 24, %%l2\n" \ "15:\t" "lduba [%2 + 6] %%asi, %%l1\n\t" \ "sllx %%g1, 16, %%g1\n\t" \ "or %%g7, %%l2, %%g7\n" \ "16:\t" "lduba [%2 + 7] %%asi, %%l2\n\t" \ "sllx %%l1, 8, %%l1\n\t" \ "or %%g7, %%g1, %%g7\n\t" \ "or %%l1, %%l2, %%l1\n\t" \ "or %%g7, %%l1, %%g7\n\t" \ "cmp %1, 8\n\t" \ "be,a,pt %%icc, 0f\n\t" \ " stx %%g7, [%0]\n\t" \ "srlx %%g7, 32, %%l1\n\t" \ "sra %%g7, 0, %%g7\n\t" \ "stx %%l1, [%0]\n\t" \ "stx %%g7, [%0 + 8]\n" \ "0:\n\t" \ "wr %%g0, %5, %%asi\n\n\t" \ ".section __ex_table\n\t" \ ".word 4b, " #errh "\n\t" \ ".word 5b, " #errh "\n\t" \ ".word 6b, " #errh "\n\t" \ ".word 7b, " #errh "\n\t" \ ".word 8b, " #errh "\n\t" \ ".word 9b, " #errh "\n\t" \ ".word 10b, " #errh "\n\t" \ ".word 11b, " #errh "\n\t" \ ".word 12b, " #errh "\n\t" \ ".word 13b, " #errh "\n\t" \ ".word 14b, " #errh "\n\t" \ ".word 15b, " #errh "\n\t" \ ".word 16b, " #errh "\n\n\t" \ ".previous\n\t" \ : : "r" (dest_reg), "r" (size), "r" (saddr), "r" (is_signed), \ "r" (asi), "i" (ASI_AIUS) \ : "l1", "l2", "g7", "g1", "cc"); \ }) #define store_common(dst_addr, size, src_val, asi, errh) ({ \ __asm__ __volatile__ ( \ "wr %3, 0, %%asi\n\t" \ "ldx [%2], %%l1\n" \ "cmp %1, 2\n\t" \ "be,pn %%icc, 2f\n\t" \ " cmp %1, 4\n\t" \ "be,pt %%icc, 1f\n\t" \ " srlx %%l1, 24, %%l2\n\t" \ "srlx %%l1, 56, %%g1\n\t" \ "srlx %%l1, 48, %%g7\n" \ "4:\t" "stba %%g1, [%0] %%asi\n\t" \ "srlx %%l1, 40, %%g1\n" \ "5:\t" "stba %%g7, [%0 + 1] %%asi\n\t" \ "srlx %%l1, 32, %%g7\n" \ "6:\t" "stba %%g1, [%0 + 2] %%asi\n" \ "7:\t" "stba %%g7, [%0 + 3] %%asi\n\t" \ "srlx %%l1, 16, %%g1\n" \ "8:\t" "stba %%l2, [%0 + 4] %%asi\n\t" \ "srlx %%l1, 8, %%g7\n" \ "9:\t" "stba %%g1, [%0 + 5] %%asi\n" \ "10:\t" "stba %%g7, [%0 + 6] %%asi\n\t" \ "ba,pt %%xcc, 0f\n" \ "11:\t" " stba %%l1, [%0 + 7] %%asi\n" \ "1:\t" "srl %%l1, 16, %%g7\n" \ "12:\t" "stba %%l2, [%0] %%asi\n\t" \ "srl %%l1, 8, %%l2\n" \ "13:\t" "stba %%g7, [%0 + 1] %%asi\n" \ "14:\t" "stba %%l2, [%0 + 2] %%asi\n\t" \ "ba,pt %%xcc, 0f\n" \ "15:\t" " stba %%l1, [%0 + 3] %%asi\n" \ "2:\t" "srl %%l1, 8, %%l2\n" \ "16:\t" "stba %%l2, [%0] %%asi\n" \ "17:\t" "stba %%l1, [%0 + 1] %%asi\n" \ "0:\n\t" \ "wr %%g0, %4, %%asi\n\n\t" \ ".section __ex_table\n\t" \ ".word 4b, " #errh "\n\t" \ ".word 5b, " #errh "\n\t" \ ".word 6b, " #errh "\n\t" \ ".word 7b, " #errh "\n\t" \ ".word 8b, " #errh "\n\t" \ ".word 9b, " #errh "\n\t" \ ".word 10b, " #errh "\n\t" \ ".word 11b, " #errh "\n\t" \ ".word 12b, " #errh "\n\t" \ ".word 13b, " #errh "\n\t" \ ".word 14b, " #errh "\n\t" \ ".word 15b, " #errh "\n\t" \ ".word 16b, " #errh "\n\t" \ ".word 17b, " #errh "\n\n\t" \ ".previous\n\t" \ : : "r" (dst_addr), "r" (size), "r" (src_val), "r" (asi), "i" (ASI_AIUS)\ : "l1", "l2", "g7", "g1", "cc"); \ }) #define do_integer_store(reg_num, size, dst_addr, regs, asi, errh) ({ \ unsigned long zero = 0; \ unsigned long *src_val = &zero; \ \ if (size == 16) { \ size = 8; \ zero = (((long)(reg_num ? \ (unsigned)fetch_reg(reg_num, regs) : 0)) << 32) | \ (unsigned)fetch_reg(reg_num + 1, regs); \ } else if (reg_num) src_val = fetch_reg_addr(reg_num, regs); \ store_common(dst_addr, size, src_val, asi, errh); \ }) /* XXX Need to capture/release other cpu's for SMP around this. */ #define do_atomic(srcdest_reg, mem, errh) ({ \ unsigned long flags, tmp; \ \ save_and_cli(flags); \ tmp = *srcdest_reg; \ do_integer_load(srcdest_reg, 4, mem, 0, errh); \ store_common(mem, 4, &tmp, errh); \ restore_flags(flags); \ }) static inline void advance(struct pt_regs *regs) { regs->tpc = regs->tnpc; regs->tnpc += 4; if ((current->thread.flags & SPARC_FLAG_32BIT) != 0) { regs->tpc &= 0xffffffff; regs->tnpc &= 0xffffffff; } } static inline int floating_point_load_or_store_p(unsigned int insn) { return (insn >> 24) & 1; } static inline int ok_for_kernel(unsigned int insn) { return !floating_point_load_or_store_p(insn); } void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn) __asm__ ("kernel_mna_trap_fault"); void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn) { unsigned long g2 = regs->u_regs [UREG_G2]; unsigned long fixup = search_exception_table (regs->tpc, &g2); if (!fixup) { unsigned long address = compute_effective_address(regs, insn, ((insn >> 25) & 0x1f)); if(address < PAGE_SIZE) { printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler"); } else printk(KERN_ALERT "Unable to handle kernel paging request in mna handler"); printk(KERN_ALERT " at virtual address %016lx\n",address); printk(KERN_ALERT "current->{mm,active_mm}->context = %016lx\n", (current->mm ? current->mm->context : current->active_mm->context)); printk(KERN_ALERT "current->{mm,active_mm}->pgd = %016lx\n", (current->mm ? (unsigned long) current->mm->pgd : (unsigned long) current->active_mm->pgd)); die_if_kernel("Oops", regs); /* Not reached */ } regs->tpc = fixup; regs->tnpc = regs->tpc + 4; regs->u_regs [UREG_G2] = g2; regs->tstate &= ~TSTATE_ASI; regs->tstate |= (ASI_AIUS << 24UL); } asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn, unsigned long sfar, unsigned long sfsr) { enum direction dir = decode_direction(insn); int size = decode_access_size(insn); if(!ok_for_kernel(insn) || dir == both) { printk("Unsupported unaligned load/store trap for kernel at <%016lx>.\n", regs->tpc); unaligned_panic("Kernel does fpu/atomic unaligned load/store.", regs); __asm__ __volatile__ ("\n" "kernel_unaligned_trap_fault:\n\t" "mov %0, %%o0\n\t" "call kernel_mna_trap_fault\n\t" " mov %1, %%o1\n\t" : : "r" (regs), "r" (insn) : "o0", "o1", "o2", "o3", "o4", "o5", "o7", "g1", "g2", "g3", "g4", "g5", "g7", "cc"); } else { unsigned long addr = compute_effective_address(regs, insn, ((insn >> 25) & 0x1f)); #ifdef DEBUG_MNA printk("KMNA: pc=%016lx [dir=%s addr=%016lx size=%d] retpc[%016lx]\n", regs->tpc, dirstrings[dir], addr, size, regs->u_regs[UREG_RETPC]); #endif switch(dir) { case load: do_integer_load(fetch_reg_addr(((insn>>25)&0x1f), regs), size, (unsigned long *) addr, decode_signedness(insn), decode_asi(insn, regs), kernel_unaligned_trap_fault); break; case store: do_integer_store(((insn>>25)&0x1f), size, (unsigned long *) addr, regs, decode_asi(insn, regs), kernel_unaligned_trap_fault); break; #if 0 /* unsupported */ case both: do_atomic(fetch_reg_addr(((insn>>25)&0x1f), regs), (unsigned long *) addr, kernel_unaligned_trap_fault); break; #endif default: panic("Impossible kernel unaligned trap."); /* Not reached... */ } advance(regs); } } static char popc_helper[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, }; int handle_popc(u32 insn, struct pt_regs *regs) { u64 value; int ret, i, rd = ((insn >> 25) & 0x1f); int from_kernel = (regs->tstate & TSTATE_PRIV) != 0; if (insn & 0x2000) { maybe_flush_windows(0, 0, rd, from_kernel); value = sign_extend_imm13(insn); } else { maybe_flush_windows(0, insn & 0x1f, rd, from_kernel); value = fetch_reg(insn & 0x1f, regs); } for (ret = 0, i = 0; i < 16; i++) { ret += popc_helper[value & 0xf]; value >>= 4; } if(rd < 16) { if (rd) regs->u_regs[rd] = ret; } else { if (current->thread.flags & SPARC_FLAG_32BIT) { struct reg_window32 *win32; win32 = (struct reg_window32 *)((unsigned long)((u32)regs->u_regs[UREG_FP])); put_user(ret, &win32->locals[rd - 16]); } else { struct reg_window *win; win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS); put_user(ret, &win->locals[rd - 16]); } } advance(regs); return 1; } extern void do_fpother(struct pt_regs *regs); extern void do_privact(struct pt_regs *regs); extern void spitfire_data_access_exception(struct pt_regs *regs, unsigned long sfsr, unsigned long sfar); int handle_ldf_stq(u32 insn, struct pt_regs *regs) { unsigned long addr = compute_effective_address(regs, insn, 0); int freg = ((insn >> 25) & 0x1e) | ((insn >> 20) & 0x20); struct fpustate *f = FPUSTATE; int asi = decode_asi(insn, regs); int flag = (freg < 32) ? FPRS_DL : FPRS_DU; save_and_clear_fpu(); current->thread.xfsr[0] &= ~0x1c000; if (freg & 3) { current->thread.xfsr[0] |= (6 << 14) /* invalid_fp_register */; do_fpother(regs); return 0; } if (insn & 0x200000) { /* STQ */ u64 first = 0, second = 0; if (current->thread.fpsaved[0] & flag) { first = *(u64 *)&f->regs[freg]; second = *(u64 *)&f->regs[freg+2]; } if (asi < 0x80) { do_privact(regs); return 1; } switch (asi) { case ASI_P: case ASI_S: break; case ASI_PL: case ASI_SL: { /* Need to convert endians */ u64 tmp = __swab64p(&first); first = __swab64p(&second); second = tmp; break; } default: spitfire_data_access_exception(regs, 0, addr); return 1; } if (put_user (first >> 32, (u32 *)addr) || __put_user ((u32)first, (u32 *)(addr + 4)) || __put_user (second >> 32, (u32 *)(addr + 8)) || __put_user ((u32)second, (u32 *)(addr + 12))) { spitfire_data_access_exception(regs, 0, addr); return 1; } } else { /* LDF, LDDF, LDQF */ u32 data[4] __attribute__ ((aligned(8))); int size, i; int err; if (asi < 0x80) { do_privact(regs); return 1; } else if (asi > ASI_SNFL) { spitfire_data_access_exception(regs, 0, addr); return 1; } switch (insn & 0x180000) { case 0x000000: size = 1; break; case 0x100000: size = 4; break; default: size = 2; break; } for (i = 0; i < size; i++) data[i] = 0; err = get_user (data[0], (u32 *)addr); if (!err) { for (i = 1; i < size; i++) err |= __get_user (data[i], (u32 *)(addr + 4*i)); } if (err && !(asi & 0x2 /* NF */)) { spitfire_data_access_exception(regs, 0, addr); return 1; } if (asi & 0x8) /* Little */ { u64 tmp; switch (size) { case 1: data[0] = le32_to_cpup(data + 0); break; default:*(u64 *)(data + 0) = le64_to_cpup((u64 *)(data + 0)); break; case 4: tmp = le64_to_cpup((u64 *)(data + 0)); *(u64 *)(data + 0) = le64_to_cpup((u64 *)(data + 2)); *(u64 *)(data + 2) = tmp; break; } } if (!(current->thread.fpsaved[0] & FPRS_FEF)) { current->thread.fpsaved[0] = FPRS_FEF; current->thread.gsr[0] = 0; } if (!(current->thread.fpsaved[0] & flag)) { if (freg < 32) memset(f->regs, 0, 32*sizeof(u32)); else memset(f->regs+32, 0, 32*sizeof(u32)); } memcpy(f->regs + freg, data, size * 4); current->thread.fpsaved[0] |= flag; } advance(regs); return 1; } void handle_ld_nf(u32 insn, struct pt_regs *regs) { int rd = ((insn >> 25) & 0x1f); int from_kernel = (regs->tstate & TSTATE_PRIV) != 0; unsigned long *reg; maybe_flush_windows(0, 0, rd, from_kernel); reg = fetch_reg_addr(rd, regs); if (from_kernel || rd < 16) { reg[0] = 0; if ((insn & 0x780000) == 0x180000) reg[1] = 0; } else if (current->thread.flags & SPARC_FLAG_32BIT) { put_user(0, (int *)reg); if ((insn & 0x780000) == 0x180000) put_user(0, ((int *)reg) + 1); } else { put_user(0, reg); if ((insn & 0x780000) == 0x180000) put_user(0, reg + 1); } advance(regs); } void handle_lddfmna(struct pt_regs *regs, unsigned long sfar, unsigned long sfsr) { unsigned long pc = regs->tpc; unsigned long tstate = regs->tstate; u32 insn; u32 first, second; u64 value; u8 asi, freg; int flag; struct fpustate *f = FPUSTATE; if(tstate & TSTATE_PRIV) die_if_kernel("lddfmna from kernel", regs); if(current->thread.flags & SPARC_FLAG_32BIT) pc = (u32)pc; if (get_user(insn, (u32 *)pc) != -EFAULT) { asi = sfsr >> 16; if ((asi > ASI_SNFL) || (asi < ASI_P)) goto daex; if (get_user(first, (u32 *)sfar) || get_user(second, (u32 *)(sfar + 4))) { if (asi & 0x2) /* NF */ { first = 0; second = 0; } else goto daex; } save_and_clear_fpu(); freg = ((insn >> 25) & 0x1e) | ((insn >> 20) & 0x20); value = (((u64)first) << 32) | second; if (asi & 0x8) /* Little */ value = __swab64p(&value); flag = (freg < 32) ? FPRS_DL : FPRS_DU; if (!(current->thread.fpsaved[0] & FPRS_FEF)) { current->thread.fpsaved[0] = FPRS_FEF; current->thread.gsr[0] = 0; } if (!(current->thread.fpsaved[0] & flag)) { if (freg < 32) memset(f->regs, 0, 32*sizeof(u32)); else memset(f->regs+32, 0, 32*sizeof(u32)); } *(u64 *)(f->regs + freg) = value; current->thread.fpsaved[0] |= flag; } else { daex: spitfire_data_access_exception(regs, sfsr, sfar); return; } advance(regs); return; } void handle_stdfmna(struct pt_regs *regs, unsigned long sfar, unsigned long sfsr) { unsigned long pc = regs->tpc; unsigned long tstate = regs->tstate; u32 insn; u64 value; u8 asi, freg; int flag; struct fpustate *f = FPUSTATE; if(tstate & TSTATE_PRIV) die_if_kernel("stdfmna from kernel", regs); if(current->thread.flags & SPARC_FLAG_32BIT) pc = (u32)pc; if (get_user(insn, (u32 *)pc) != -EFAULT) { freg = ((insn >> 25) & 0x1e) | ((insn >> 20) & 0x20); asi = sfsr >> 16; value = 0; flag = (freg < 32) ? FPRS_DL : FPRS_DU; if ((asi > ASI_SNFL) || (asi < ASI_P)) goto daex; save_and_clear_fpu(); if (current->thread.fpsaved[0] & flag) value = *(u64 *)&f->regs[freg]; switch (asi) { case ASI_P: case ASI_S: break; case ASI_PL: case ASI_SL: value = __swab64p(&value); break; default: goto daex; } if (put_user (value >> 32, (u32 *)sfar) || __put_user ((u32)value, (u32 *)(sfar + 4))) goto daex; } else { daex: spitfire_data_access_exception(regs, sfsr, sfar); return; } advance(regs); return; }