/* * Handle unaligned accesses by emulation. * * This file is subject to the terms and conditions of the GNU General Public * License. See the file "COPYING" in the main directory of this archive * for more details. * * Copyright (C) 1996, 1998, 1999, 2002 by Ralf Baechle * Copyright (C) 1999 Silicon Graphics, Inc. * * This file contains exception handler for address error exception with the * special capability to execute faulting instructions in software. The * handler does not try to handle the case when the program counter points * to an address not aligned to a word boundary. * * Putting data to unaligned addresses is a bad practice even on Intel where * only the performance is affected. Much worse is that such code is non- * portable. Due to several programs that die on MIPS due to alignment * problems I decided to implement this handler anyway though I originally * didn't intend to do this at all for user code. * * For now I enable fixing of address errors by default to make life easier. * I however intend to disable this somewhen in the future when the alignment * problems with user programs have been fixed. For programmers this is the * right way to go. * * Fixing address errors is a per process option. The option is inherited * across fork(2) and execve(2) calls. If you really want to use the * option in your user programs - I discourage the use of the software * emulation strongly - use the following code in your userland stuff: * * #include * * ... * sysmips(MIPS_FIXADE, x); * ... * * The argument x is 0 for disabling software emulation, enabled otherwise. * * Below a little program to play around with this feature. * * #include * #include * * struct foo { * unsigned char bar[8]; * }; * * main(int argc, char *argv[]) * { * struct foo x = {0, 1, 2, 3, 4, 5, 6, 7}; * unsigned int *p = (unsigned int *) (x.bar + 3); * int i; * * if (argc > 1) * sysmips(MIPS_FIXADE, atoi(argv[1])); * * printf("*p = %08lx\n", *p); * * *p = 0xdeadface; * * for(i = 0; i <= 7; i++) * printf("%02x ", x.bar[i]); * printf("\n"); * } * * Coprocessor loads are not supported; I think this case is unimportant * in the practice. * * TODO: Handle ndc (attempted store to doubleword in uncached memory) * exception for the R6000. * A store crossing a page boundary might be executed only partially. * Undo the partial store in this case. */ #include #include #include #include #include #include #include #include #include #include #include #include #define STR(x) __STR(x) #define __STR(x) #x #ifdef CONFIG_PROC_FS unsigned long unaligned_instructions; #endif static inline int emulate_load_store_insn(struct pt_regs *regs, void __user *addr, unsigned int __user *pc, unsigned long **regptr, unsigned long *newvalue) { union mips_instruction insn; unsigned long value; unsigned int res; regs->regs[0] = 0; *regptr=NULL; /* * This load never faults. */ __get_user(insn.word, pc); switch (insn.i_format.opcode) { /* * These are instructions that a compiler doesn't generate. We * can assume therefore that the code is MIPS-aware and * really buggy. Emulating these instructions would break the * semantics anyway. */ case ll_op: case lld_op: case sc_op: case scd_op: /* * For these instructions the only way to create an address * error is an attempted access to kernel/supervisor address * space. */ case ldl_op: case ldr_op: case lwl_op: case lwr_op: case sdl_op: case sdr_op: case swl_op: case swr_op: case lb_op: case lbu_op: case sb_op: goto sigbus; /* * The remaining opcodes are the ones that are really of interest. */ case lh_op: if (!access_ok(VERIFY_READ, addr, 2)) goto sigbus; __asm__ __volatile__ (".set\tnoat\n" #ifdef __BIG_ENDIAN "1:\tlb\t%0, 0(%2)\n" "2:\tlbu\t$1, 1(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tlb\t%0, 1(%2)\n" "2:\tlbu\t$1, 0(%2)\n\t" #endif "sll\t%0, 0x8\n\t" "or\t%0, $1\n\t" "li\t%1, 0\n" "3:\t.set\tat\n\t" ".section\t.fixup,\"ax\"\n\t" "4:\tli\t%1, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=&r" (value), "=r" (res) : "r" (addr), "i" (-EFAULT)); if (res) goto fault; *newvalue = value; *regptr = ®s->regs[insn.i_format.rt]; break; case lw_op: if (!access_ok(VERIFY_READ, addr, 4)) goto sigbus; __asm__ __volatile__ ( #ifdef __BIG_ENDIAN "1:\tlwl\t%0, (%2)\n" "2:\tlwr\t%0, 3(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tlwl\t%0, 3(%2)\n" "2:\tlwr\t%0, (%2)\n\t" #endif "li\t%1, 0\n" "3:\t.section\t.fixup,\"ax\"\n\t" "4:\tli\t%1, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=&r" (value), "=r" (res) : "r" (addr), "i" (-EFAULT)); if (res) goto fault; *newvalue = value; *regptr = ®s->regs[insn.i_format.rt]; break; case lhu_op: if (!access_ok(VERIFY_READ, addr, 2)) goto sigbus; __asm__ __volatile__ ( ".set\tnoat\n" #ifdef __BIG_ENDIAN "1:\tlbu\t%0, 0(%2)\n" "2:\tlbu\t$1, 1(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tlbu\t%0, 1(%2)\n" "2:\tlbu\t$1, 0(%2)\n\t" #endif "sll\t%0, 0x8\n\t" "or\t%0, $1\n\t" "li\t%1, 0\n" "3:\t.set\tat\n\t" ".section\t.fixup,\"ax\"\n\t" "4:\tli\t%1, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=&r" (value), "=r" (res) : "r" (addr), "i" (-EFAULT)); if (res) goto fault; *newvalue = value; *regptr = ®s->regs[insn.i_format.rt]; break; case lwu_op: #ifdef CONFIG_64BIT /* * A 32-bit kernel might be running on a 64-bit processor. But * if we're on a 32-bit processor and an i-cache incoherency * or race makes us see a 64-bit instruction here the sdl/sdr * would blow up, so for now we don't handle unaligned 64-bit * instructions on 32-bit kernels. */ if (!access_ok(VERIFY_READ, addr, 4)) goto sigbus; __asm__ __volatile__ ( #ifdef __BIG_ENDIAN "1:\tlwl\t%0, (%2)\n" "2:\tlwr\t%0, 3(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tlwl\t%0, 3(%2)\n" "2:\tlwr\t%0, (%2)\n\t" #endif "dsll\t%0, %0, 32\n\t" "dsrl\t%0, %0, 32\n\t" "li\t%1, 0\n" "3:\t.section\t.fixup,\"ax\"\n\t" "4:\tli\t%1, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=&r" (value), "=r" (res) : "r" (addr), "i" (-EFAULT)); if (res) goto fault; *newvalue = value; *regptr = ®s->regs[insn.i_format.rt]; break; #endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; case ld_op: #ifdef CONFIG_64BIT /* * A 32-bit kernel might be running on a 64-bit processor. But * if we're on a 32-bit processor and an i-cache incoherency * or race makes us see a 64-bit instruction here the sdl/sdr * would blow up, so for now we don't handle unaligned 64-bit * instructions on 32-bit kernels. */ if (!access_ok(VERIFY_READ, addr, 8)) goto sigbus; __asm__ __volatile__ ( #ifdef __BIG_ENDIAN "1:\tldl\t%0, (%2)\n" "2:\tldr\t%0, 7(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tldl\t%0, 7(%2)\n" "2:\tldr\t%0, (%2)\n\t" #endif "li\t%1, 0\n" "3:\t.section\t.fixup,\"ax\"\n\t" "4:\tli\t%1, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=&r" (value), "=r" (res) : "r" (addr), "i" (-EFAULT)); if (res) goto fault; *newvalue = value; *regptr = ®s->regs[insn.i_format.rt]; break; #endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; case sh_op: if (!access_ok(VERIFY_WRITE, addr, 2)) goto sigbus; value = regs->regs[insn.i_format.rt]; __asm__ __volatile__ ( #ifdef __BIG_ENDIAN ".set\tnoat\n" "1:\tsb\t%1, 1(%2)\n\t" "srl\t$1, %1, 0x8\n" "2:\tsb\t$1, 0(%2)\n\t" ".set\tat\n\t" #endif #ifdef __LITTLE_ENDIAN ".set\tnoat\n" "1:\tsb\t%1, 0(%2)\n\t" "srl\t$1,%1, 0x8\n" "2:\tsb\t$1, 1(%2)\n\t" ".set\tat\n\t" #endif "li\t%0, 0\n" "3:\n\t" ".section\t.fixup,\"ax\"\n\t" "4:\tli\t%0, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=r" (res) : "r" (value), "r" (addr), "i" (-EFAULT)); if (res) goto fault; break; case sw_op: if (!access_ok(VERIFY_WRITE, addr, 4)) goto sigbus; value = regs->regs[insn.i_format.rt]; __asm__ __volatile__ ( #ifdef __BIG_ENDIAN "1:\tswl\t%1,(%2)\n" "2:\tswr\t%1, 3(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tswl\t%1, 3(%2)\n" "2:\tswr\t%1, (%2)\n\t" #endif "li\t%0, 0\n" "3:\n\t" ".section\t.fixup,\"ax\"\n\t" "4:\tli\t%0, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=r" (res) : "r" (value), "r" (addr), "i" (-EFAULT)); if (res) goto fault; break; case sd_op: #ifdef CONFIG_64BIT /* * A 32-bit kernel might be running on a 64-bit processor. But * if we're on a 32-bit processor and an i-cache incoherency * or race makes us see a 64-bit instruction here the sdl/sdr * would blow up, so for now we don't handle unaligned 64-bit * instructions on 32-bit kernels. */ if (!access_ok(VERIFY_WRITE, addr, 8)) goto sigbus; value = regs->regs[insn.i_format.rt]; __asm__ __volatile__ ( #ifdef __BIG_ENDIAN "1:\tsdl\t%1,(%2)\n" "2:\tsdr\t%1, 7(%2)\n\t" #endif #ifdef __LITTLE_ENDIAN "1:\tsdl\t%1, 7(%2)\n" "2:\tsdr\t%1, (%2)\n\t" #endif "li\t%0, 0\n" "3:\n\t" ".section\t.fixup,\"ax\"\n\t" "4:\tli\t%0, %3\n\t" "j\t3b\n\t" ".previous\n\t" ".section\t__ex_table,\"a\"\n\t" STR(PTR)"\t1b, 4b\n\t" STR(PTR)"\t2b, 4b\n\t" ".previous" : "=r" (res) : "r" (value), "r" (addr), "i" (-EFAULT)); if (res) goto fault; break; #endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; case lwc1_op: case ldc1_op: case swc1_op: case sdc1_op: /* * I herewith declare: this does not happen. So send SIGBUS. */ goto sigbus; case lwc2_op: case ldc2_op: case swc2_op: case sdc2_op: /* * These are the coprocessor 2 load/stores. The current * implementations don't use cp2 and cp2 should always be * disabled in c0_status. So send SIGILL. * (No longer true: The Sony Praystation uses cp2 for * 3D matrix operations. Dunno if that thingy has a MMU ...) */ default: /* * Pheeee... We encountered an yet unknown instruction or * cache coherence problem. Die sucker, die ... */ goto sigill; } #ifdef CONFIG_PROC_FS unaligned_instructions++; #endif return 0; fault: /* Did we have an exception handler installed? */ if (fixup_exception(regs)) return 1; die_if_kernel ("Unhandled kernel unaligned access", regs); send_sig(SIGSEGV, current, 1); return 0; sigbus: die_if_kernel("Unhandled kernel unaligned access", regs); send_sig(SIGBUS, current, 1); return 0; sigill: die_if_kernel("Unhandled kernel unaligned access or invalid instruction", regs); send_sig(SIGILL, current, 1); return 0; } asmlinkage void do_ade(struct pt_regs *regs) { unsigned long *regptr, newval; extern int do_dsemulret(struct pt_regs *); unsigned int __user *pc; mm_segment_t seg; /* * Address errors may be deliberately induced by the FPU emulator to * retake control of the CPU after executing the instruction in the * delay slot of an emulated branch. */ /* Terminate if exception was recognized as a delay slot return */ if (do_dsemulret(regs)) return; /* Otherwise handle as normal */ /* * Did we catch a fault trying to load an instruction? * Or are we running in MIPS16 mode? */ if ((regs->cp0_badvaddr == regs->cp0_epc) || (regs->cp0_epc & 0x1)) goto sigbus; pc = (unsigned int __user *) exception_epc(regs); if ((current->thread.mflags & MF_FIXADE) == 0) goto sigbus; /* * Do branch emulation only if we didn't forward the exception. * This is all so but ugly ... */ seg = get_fs(); if (!user_mode(regs)) set_fs(KERNEL_DS); if (!emulate_load_store_insn(regs, (void __user *)regs->cp0_badvaddr, pc, ®ptr, &newval)) { compute_return_epc(regs); /* * Now that branch is evaluated, update the dest * register if necessary */ if (regptr) *regptr = newval; } set_fs(seg); return; sigbus: die_if_kernel("Kernel unaligned instruction access", regs); force_sig(SIGBUS, current); /* * XXX On return from the signal handler we should advance the epc */ }