/* * 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. * Copyright (C) 2014 Imagination Technologies Ltd. * * 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 <sys/sysmips.h> * * ... * 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 <stdio.h> * #include <sys/sysmips.h> * * 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 <linux/context_tracking.h>#include <linux/mm.h>#include <linux/signal.h>#include <linux/smp.h>#include <linux/sched.h>#include <linux/debugfs.h>#include <linux/perf_event.h> #include <asm/asm.h>#include <asm/branch.h>#include <asm/byteorder.h>#include <asm/cop2.h>#include <asm/debug.h>#include <asm/fpu.h>#include <asm/fpu_emulator.h>#include <asm/inst.h>#include <asm/unaligned-emul.h>#include <asm/mmu_context.h>#include <linux/uaccess.h> #include "access-helper.h" enum { UNALIGNED_ACTION_QUIET, UNALIGNED_ACTION_SIGNAL, UNALIGNED_ACTION_SHOW,};#ifdef CONFIG_DEBUG_FSstatic u32 unaligned_instructions;static u32 unaligned_action;#else#define unaligned_action UNALIGNED_ACTION_QUIET#endifextern void show_registers(struct pt_regs *regs); static void emulate_load_store_insn(struct pt_regs *regs, void __user *addr, unsigned int *pc){ unsigned long origpc, orig31, value; union mips_instruction insn; unsigned int res; bool user = user_mode(regs); origpc = (unsigned long)pc; orig31 = regs->regs[31]; perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0); /* * This load never faults. */ __get_inst32(&insn.word, pc, user); 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 spec3_op: if (insn.dsp_format.func == lx_op) { switch (insn.dsp_format.op) { case lwx_op: if (user && !access_ok(addr, 4)) goto sigbus; LoadW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.dsp_format.rd] = value; break; case lhx_op: if (user && !access_ok(addr, 2)) goto sigbus; LoadHW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.dsp_format.rd] = value; break; default: goto sigill; } }#ifdef CONFIG_EVA else { /* * we can land here only from kernel accessing user * memory, so we need to "switch" the address limit to * user space, so that address check can work properly. */ switch (insn.spec3_format.func) { case lhe_op: if (!access_ok(addr, 2)) goto sigbus; LoadHWE(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.spec3_format.rt] = value; break; case lwe_op: if (!access_ok(addr, 4)) goto sigbus; LoadWE(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.spec3_format.rt] = value; break; case lhue_op: if (!access_ok(addr, 2)) goto sigbus; LoadHWUE(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.spec3_format.rt] = value; break; case she_op: if (!access_ok(addr, 2)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.spec3_format.rt]; StoreHWE(addr, value, res); if (res) goto fault; break; case swe_op: if (!access_ok(addr, 4)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.spec3_format.rt]; StoreWE(addr, value, res); if (res) goto fault; break; default: goto sigill; } }#endif break; case lh_op: if (user && !access_ok(addr, 2)) goto sigbus; if (IS_ENABLED(CONFIG_EVA) && user) LoadHWE(addr, value, res); else LoadHW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; break; case lw_op: if (user && !access_ok(addr, 4)) goto sigbus; if (IS_ENABLED(CONFIG_EVA) && user) LoadWE(addr, value, res); else LoadW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; break; case lhu_op: if (user && !access_ok(addr, 2)) goto sigbus; if (IS_ENABLED(CONFIG_EVA) && user) LoadHWUE(addr, value, res); else LoadHWU(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; 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 (user && !access_ok(addr, 4)) goto sigbus; LoadWU(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; 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 (user && !access_ok(addr, 8)) goto sigbus; LoadDW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; break;#endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; case sh_op: if (user && !access_ok(addr, 2)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.i_format.rt]; if (IS_ENABLED(CONFIG_EVA) && user) StoreHWE(addr, value, res); else StoreHW(addr, value, res); if (res) goto fault; break; case sw_op: if (user && !access_ok(addr, 4)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.i_format.rt]; if (IS_ENABLED(CONFIG_EVA) && user) StoreWE(addr, value, res); else StoreW(addr, value, res); 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 (user && !access_ok(addr, 8)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.i_format.rt]; StoreDW(addr, value, res); if (res) goto fault; break;#endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; #ifdef CONFIG_MIPS_FP_SUPPORT case lwc1_op: case ldc1_op: case swc1_op: case sdc1_op: case cop1x_op: { void __user *fault_addr = NULL; die_if_kernel("Unaligned FP access in kernel code", regs); BUG_ON(!used_math()); res = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1, &fault_addr); own_fpu(1); /* Restore FPU state. */ /* Signal if something went wrong. */ process_fpemu_return(res, fault_addr, 0); if (res == 0) break; return; }#endif /* CONFIG_MIPS_FP_SUPPORT */ #ifdef CONFIG_CPU_HAS_MSA case msa_op: { unsigned int wd, preempted; enum msa_2b_fmt df; union fpureg *fpr; if (!cpu_has_msa) goto sigill; /* * If we've reached this point then userland should have taken * the MSA disabled exception & initialised vector context at * some point in the past. */ BUG_ON(!thread_msa_context_live()); df = insn.msa_mi10_format.df; wd = insn.msa_mi10_format.wd; fpr = ¤t->thread.fpu.fpr[wd]; switch (insn.msa_mi10_format.func) { case msa_ld_op: if (!access_ok(addr, sizeof(*fpr))) goto sigbus; do { /* * If we have live MSA context keep track of * whether we get preempted in order to avoid * the register context we load being clobbered * by the live context as it's saved during * preemption. If we don't have live context * then it can't be saved to clobber the value * we load. */ preempted = test_thread_flag(TIF_USEDMSA); res = __copy_from_user_inatomic(fpr, addr, sizeof(*fpr)); if (res) goto fault; /* * Update the hardware register if it is in use * by the task in this quantum, in order to * avoid having to save & restore the whole * vector context. */ preempt_disable(); if (test_thread_flag(TIF_USEDMSA)) { write_msa_wr(wd, fpr, df); preempted = 0; } preempt_enable(); } while (preempted); break; case msa_st_op: if (!access_ok(addr, sizeof(*fpr))) goto sigbus; /* * Update from the hardware register if it is in use by * the task in this quantum, in order to avoid having to * save & restore the whole vector context. */ preempt_disable(); if (test_thread_flag(TIF_USEDMSA)) read_msa_wr(wd, fpr, df); preempt_enable(); res = __copy_to_user_inatomic(addr, fpr, sizeof(*fpr)); if (res) goto fault; break; default: goto sigbus; } compute_return_epc(regs); break;Lines 1–500 of 1555. 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/* * 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. * Copyright (C) 2014 Imagination Technologies Ltd. * * 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 <sys/sysmips.h> * * ... * 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 <stdio.h> * #include <sys/sysmips.h> * * 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 <linux/context_tracking.h> #include <linux/mm.h> #include <linux/signal.h> #include <linux/smp.h> #include <linux/sched.h> #include <linux/debugfs.h> #include <linux/perf_event.h> #include <asm/asm.h> #include <asm/branch.h> #include <asm/byteorder.h> #include <asm/cop2.h> #include <asm/debug.h> #include <asm/fpu.h> #include <asm/fpu_emulator.h> #include <asm/inst.h> #include <asm/unaligned-emul.h> #include <asm/mmu_context.h> #include <linux/uaccess.h> #include "access-helper.h" enum { UNALIGNED_ACTION_QUIET, UNALIGNED_ACTION_SIGNAL, UNALIGNED_ACTION_SHOW, }; #ifdef CONFIG_DEBUG_FS static u32 unaligned_instructions; static u32 unaligned_action; #else #define unaligned_action UNALIGNED_ACTION_QUIET #endif extern void show_registers(struct pt_regs *regs); static void emulate_load_store_insn(struct pt_regs *regs, void __user *addr, unsigned int *pc) { unsigned long origpc, orig31, value; union mips_instruction insn; unsigned int res; bool user = user_mode(regs); origpc = (unsigned long)pc; orig31 = regs->regs[31]; perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0); /* * This load never faults. */ __get_inst32(&insn.word, pc, user); 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 spec3_op: if (insn.dsp_format.func == lx_op) { switch (insn.dsp_format.op) { case lwx_op: if (user && !access_ok(addr, 4)) goto sigbus; LoadW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.dsp_format.rd] = value; break; case lhx_op: if (user && !access_ok(addr, 2)) goto sigbus; LoadHW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.dsp_format.rd] = value; break; default: goto sigill; } } #ifdef CONFIG_EVA else { /* * we can land here only from kernel accessing user * memory, so we need to "switch" the address limit to * user space, so that address check can work properly. */ switch (insn.spec3_format.func) { case lhe_op: if (!access_ok(addr, 2)) goto sigbus; LoadHWE(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.spec3_format.rt] = value; break; case lwe_op: if (!access_ok(addr, 4)) goto sigbus; LoadWE(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.spec3_format.rt] = value; break; case lhue_op: if (!access_ok(addr, 2)) goto sigbus; LoadHWUE(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.spec3_format.rt] = value; break; case she_op: if (!access_ok(addr, 2)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.spec3_format.rt]; StoreHWE(addr, value, res); if (res) goto fault; break; case swe_op: if (!access_ok(addr, 4)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.spec3_format.rt]; StoreWE(addr, value, res); if (res) goto fault; break; default: goto sigill; } } #endif break; case lh_op: if (user && !access_ok(addr, 2)) goto sigbus; if (IS_ENABLED(CONFIG_EVA) && user) LoadHWE(addr, value, res); else LoadHW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; break; case lw_op: if (user && !access_ok(addr, 4)) goto sigbus; if (IS_ENABLED(CONFIG_EVA) && user) LoadWE(addr, value, res); else LoadW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; break; case lhu_op: if (user && !access_ok(addr, 2)) goto sigbus; if (IS_ENABLED(CONFIG_EVA) && user) LoadHWUE(addr, value, res); else LoadHWU(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; 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 (user && !access_ok(addr, 4)) goto sigbus; LoadWU(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; 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 (user && !access_ok(addr, 8)) goto sigbus; LoadDW(addr, value, res); if (res) goto fault; compute_return_epc(regs); regs->regs[insn.i_format.rt] = value; break; #endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; case sh_op: if (user && !access_ok(addr, 2)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.i_format.rt]; if (IS_ENABLED(CONFIG_EVA) && user) StoreHWE(addr, value, res); else StoreHW(addr, value, res); if (res) goto fault; break; case sw_op: if (user && !access_ok(addr, 4)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.i_format.rt]; if (IS_ENABLED(CONFIG_EVA) && user) StoreWE(addr, value, res); else StoreW(addr, value, res); 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 (user && !access_ok(addr, 8)) goto sigbus; compute_return_epc(regs); value = regs->regs[insn.i_format.rt]; StoreDW(addr, value, res); if (res) goto fault; break; #endif /* CONFIG_64BIT */ /* Cannot handle 64-bit instructions in 32-bit kernel */ goto sigill; #ifdef CONFIG_MIPS_FP_SUPPORT case lwc1_op: case ldc1_op: case swc1_op: case sdc1_op: case cop1x_op: { void __user *fault_addr = NULL; die_if_kernel("Unaligned FP access in kernel code", regs); BUG_ON(!used_math()); res = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1, &fault_addr); own_fpu(1); /* Restore FPU state. */ /* Signal if something went wrong. */ process_fpemu_return(res, fault_addr, 0); if (res == 0) break; return; } #endif /* CONFIG_MIPS_FP_SUPPORT */ #ifdef CONFIG_CPU_HAS_MSA case msa_op: { unsigned int wd, preempted; enum msa_2b_fmt df; union fpureg *fpr; if (!cpu_has_msa) goto sigill; /* * If we've reached this point then userland should have taken * the MSA disabled exception & initialised vector context at * some point in the past. */ BUG_ON(!thread_msa_context_live()); df = insn.msa_mi10_format.df; wd = insn.msa_mi10_format.wd; fpr = ¤t->thread.fpu.fpr[wd]; switch (insn.msa_mi10_format.func) { case msa_ld_op: if (!access_ok(addr, sizeof(*fpr))) goto sigbus; do { /* * If we have live MSA context keep track of * whether we get preempted in order to avoid * the register context we load being clobbered * by the live context as it's saved during * preemption. If we don't have live context * then it can't be saved to clobber the value * we load. */ preempted = test_thread_flag(TIF_USEDMSA); res = __copy_from_user_inatomic(fpr, addr, sizeof(*fpr)); if (res) goto fault; /* * Update the hardware register if it is in use * by the task in this quantum, in order to * avoid having to save & restore the whole * vector context. */ preempt_disable(); if (test_thread_flag(TIF_USEDMSA)) { write_msa_wr(wd, fpr, df); preempted = 0; } preempt_enable(); } while (preempted); break; case msa_st_op: if (!access_ok(addr, sizeof(*fpr))) goto sigbus; /* * Update from the hardware register if it is in use by * the task in this quantum, in order to avoid having to * save & restore the whole vector context. */ preempt_disable(); if (test_thread_flag(TIF_USEDMSA)) read_msa_wr(wd, fpr, df); preempt_enable(); res = __copy_to_user_inatomic(addr, fpr, sizeof(*fpr)); if (res) goto fault; break; default: goto sigbus; } compute_return_epc(regs); break;