diff options
Diffstat (limited to 'arch/arm64/kernel/armv8_deprecated.c')
| -rw-r--r-- | arch/arm64/kernel/armv8_deprecated.c | 638 |
1 files changed, 638 insertions, 0 deletions
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c new file mode 100644 index 000000000..f0ba854f0 --- /dev/null +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -0,0 +1,638 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2014 ARM Limited + */ + +#include <linux/cpu.h> +#include <linux/init.h> +#include <linux/list.h> +#include <linux/perf_event.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/sysctl.h> +#include <linux/uaccess.h> + +#include <asm/cpufeature.h> +#include <asm/insn.h> +#include <asm/sysreg.h> +#include <asm/system_misc.h> +#include <asm/traps.h> + +#define CREATE_TRACE_POINTS +#include "trace-events-emulation.h" + +/* + * The runtime support for deprecated instruction support can be in one of + * following three states - + * + * 0 = undef + * 1 = emulate (software emulation) + * 2 = hw (supported in hardware) + */ +enum insn_emulation_mode { + INSN_UNDEF, + INSN_EMULATE, + INSN_HW, +}; + +enum legacy_insn_status { + INSN_DEPRECATED, + INSN_OBSOLETE, + INSN_UNAVAILABLE, +}; + +struct insn_emulation { + const char *name; + enum legacy_insn_status status; + bool (*try_emulate)(struct pt_regs *regs, + u32 insn); + int (*set_hw_mode)(bool enable); + + int current_mode; + int min; + int max; + + /* + * sysctl for this emulation + a sentinal entry. + */ + struct ctl_table sysctl[2]; +}; + +#define ARM_OPCODE_CONDTEST_FAIL 0 +#define ARM_OPCODE_CONDTEST_PASS 1 +#define ARM_OPCODE_CONDTEST_UNCOND 2 + +#define ARM_OPCODE_CONDITION_UNCOND 0xf + +static unsigned int __maybe_unused aarch32_check_condition(u32 opcode, u32 psr) +{ + u32 cc_bits = opcode >> 28; + + if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) { + if ((*aarch32_opcode_cond_checks[cc_bits])(psr)) + return ARM_OPCODE_CONDTEST_PASS; + else + return ARM_OPCODE_CONDTEST_FAIL; + } + return ARM_OPCODE_CONDTEST_UNCOND; +} + +#ifdef CONFIG_SWP_EMULATION +/* + * Implement emulation of the SWP/SWPB instructions using load-exclusive and + * store-exclusive. + * + * Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>] + * Where: Rt = destination + * Rt2 = source + * Rn = address + */ + +/* + * Error-checking SWP macros implemented using ldxr{b}/stxr{b} + */ + +/* Arbitrary constant to ensure forward-progress of the LL/SC loop */ +#define __SWP_LL_SC_LOOPS 4 + +#define __user_swpX_asm(data, addr, res, temp, temp2, B) \ +do { \ + uaccess_enable(); \ + __asm__ __volatile__( \ + " mov %w3, %w7\n" \ + "0: ldxr"B" %w2, [%4]\n" \ + "1: stxr"B" %w0, %w1, [%4]\n" \ + " cbz %w0, 2f\n" \ + " sub %w3, %w3, #1\n" \ + " cbnz %w3, 0b\n" \ + " mov %w0, %w5\n" \ + " b 3f\n" \ + "2:\n" \ + " mov %w1, %w2\n" \ + "3:\n" \ + " .pushsection .fixup,\"ax\"\n" \ + " .align 2\n" \ + "4: mov %w0, %w6\n" \ + " b 3b\n" \ + " .popsection" \ + _ASM_EXTABLE(0b, 4b) \ + _ASM_EXTABLE(1b, 4b) \ + : "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2) \ + : "r" ((unsigned long)addr), "i" (-EAGAIN), \ + "i" (-EFAULT), \ + "i" (__SWP_LL_SC_LOOPS) \ + : "memory"); \ + uaccess_disable(); \ +} while (0) + +#define __user_swp_asm(data, addr, res, temp, temp2) \ + __user_swpX_asm(data, addr, res, temp, temp2, "") +#define __user_swpb_asm(data, addr, res, temp, temp2) \ + __user_swpX_asm(data, addr, res, temp, temp2, "b") + +/* + * Bit 22 of the instruction encoding distinguishes between + * the SWP and SWPB variants (bit set means SWPB). + */ +#define TYPE_SWPB (1 << 22) + +static int emulate_swpX(unsigned int address, unsigned int *data, + unsigned int type) +{ + unsigned int res = 0; + + if ((type != TYPE_SWPB) && (address & 0x3)) { + /* SWP to unaligned address not permitted */ + pr_debug("SWP instruction on unaligned pointer!\n"); + return -EFAULT; + } + + while (1) { + unsigned long temp, temp2; + + if (type == TYPE_SWPB) + __user_swpb_asm(*data, address, res, temp, temp2); + else + __user_swp_asm(*data, address, res, temp, temp2); + + if (likely(res != -EAGAIN) || signal_pending(current)) + break; + + cond_resched(); + } + + return res; +} + +/* + * swp_handler logs the id of calling process, dissects the instruction, sanity + * checks the memory location, calls emulate_swpX for the actual operation and + * deals with fixup/error handling before returning + */ +static int swp_handler(struct pt_regs *regs, u32 instr) +{ + u32 destreg, data, type, address = 0; + const void __user *user_ptr; + int rn, rt2, res = 0; + + perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc); + + type = instr & TYPE_SWPB; + + switch (aarch32_check_condition(instr, regs->pstate)) { + case ARM_OPCODE_CONDTEST_PASS: + break; + case ARM_OPCODE_CONDTEST_FAIL: + /* Condition failed - return to next instruction */ + goto ret; + case ARM_OPCODE_CONDTEST_UNCOND: + /* If unconditional encoding - not a SWP, undef */ + return -EFAULT; + default: + return -EINVAL; + } + + rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET); + rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET); + + address = (u32)regs->user_regs.regs[rn]; + data = (u32)regs->user_regs.regs[rt2]; + destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET); + + pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n", + rn, address, destreg, + aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data); + + /* Check access in reasonable access range for both SWP and SWPB */ + user_ptr = (const void __user *)(unsigned long)(address & ~3); + if (!access_ok(user_ptr, 4)) { + pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n", + address); + goto fault; + } + + res = emulate_swpX(address, &data, type); + if (res == -EFAULT) + goto fault; + else if (res == 0) + regs->user_regs.regs[destreg] = data; + +ret: + if (type == TYPE_SWPB) + trace_instruction_emulation("swpb", regs->pc); + else + trace_instruction_emulation("swp", regs->pc); + + pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n", + current->comm, (unsigned long)current->pid, regs->pc); + + arm64_skip_faulting_instruction(regs, 4); + return 0; + +fault: + pr_debug("SWP{B} emulation: access caused memory abort!\n"); + arm64_notify_segfault(address); + + return 0; +} + +static bool try_emulate_swp(struct pt_regs *regs, u32 insn) +{ + /* SWP{B} only exists in ARM state and does not exist in Thumb */ + if (!compat_user_mode(regs) || compat_thumb_mode(regs)) + return false; + + if ((insn & 0x0fb00ff0) != 0x01000090) + return false; + + return swp_handler(regs, insn) == 0; +} + +static struct insn_emulation insn_swp = { + .name = "swp", + .status = INSN_OBSOLETE, + .try_emulate = try_emulate_swp, + .set_hw_mode = NULL, +}; +#endif /* CONFIG_SWP_EMULATION */ + +#ifdef CONFIG_CP15_BARRIER_EMULATION +static int cp15barrier_handler(struct pt_regs *regs, u32 instr) +{ + perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc); + + switch (aarch32_check_condition(instr, regs->pstate)) { + case ARM_OPCODE_CONDTEST_PASS: + break; + case ARM_OPCODE_CONDTEST_FAIL: + /* Condition failed - return to next instruction */ + goto ret; + case ARM_OPCODE_CONDTEST_UNCOND: + /* If unconditional encoding - not a barrier instruction */ + return -EFAULT; + default: + return -EINVAL; + } + + switch (aarch32_insn_mcr_extract_crm(instr)) { + case 10: + /* + * dmb - mcr p15, 0, Rt, c7, c10, 5 + * dsb - mcr p15, 0, Rt, c7, c10, 4 + */ + if (aarch32_insn_mcr_extract_opc2(instr) == 5) { + dmb(sy); + trace_instruction_emulation( + "mcr p15, 0, Rt, c7, c10, 5 ; dmb", regs->pc); + } else { + dsb(sy); + trace_instruction_emulation( + "mcr p15, 0, Rt, c7, c10, 4 ; dsb", regs->pc); + } + break; + case 5: + /* + * isb - mcr p15, 0, Rt, c7, c5, 4 + * + * Taking an exception or returning from one acts as an + * instruction barrier. So no explicit barrier needed here. + */ + trace_instruction_emulation( + "mcr p15, 0, Rt, c7, c5, 4 ; isb", regs->pc); + break; + } + +ret: + pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n", + current->comm, (unsigned long)current->pid, regs->pc); + + arm64_skip_faulting_instruction(regs, 4); + return 0; +} + +static int cp15_barrier_set_hw_mode(bool enable) +{ + if (enable) + sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_CP15BEN); + else + sysreg_clear_set(sctlr_el1, SCTLR_EL1_CP15BEN, 0); + return 0; +} + +static bool try_emulate_cp15_barrier(struct pt_regs *regs, u32 insn) +{ + if (!compat_user_mode(regs) || compat_thumb_mode(regs)) + return false; + + if ((insn & 0x0fff0fdf) == 0x0e070f9a) + return cp15barrier_handler(regs, insn) == 0; + + if ((insn & 0x0fff0fff) == 0x0e070f95) + return cp15barrier_handler(regs, insn) == 0; + + return false; +} + +static struct insn_emulation insn_cp15_barrier = { + .name = "cp15_barrier", + .status = INSN_DEPRECATED, + .try_emulate = try_emulate_cp15_barrier, + .set_hw_mode = cp15_barrier_set_hw_mode, +}; +#endif /* CONFIG_CP15_BARRIER_EMULATION */ + +#ifdef CONFIG_SETEND_EMULATION +static int setend_set_hw_mode(bool enable) +{ + if (!cpu_supports_mixed_endian_el0()) + return -EINVAL; + + if (enable) + sysreg_clear_set(sctlr_el1, SCTLR_EL1_SED, 0); + else + sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_SED); + return 0; +} + +static int compat_setend_handler(struct pt_regs *regs, u32 big_endian) +{ + char *insn; + + perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc); + + if (big_endian) { + insn = "setend be"; + regs->pstate |= PSR_AA32_E_BIT; + } else { + insn = "setend le"; + regs->pstate &= ~PSR_AA32_E_BIT; + } + + trace_instruction_emulation(insn, regs->pc); + pr_warn_ratelimited("\"%s\" (%ld) uses deprecated setend instruction at 0x%llx\n", + current->comm, (unsigned long)current->pid, regs->pc); + + return 0; +} + +static int a32_setend_handler(struct pt_regs *regs, u32 instr) +{ + int rc = compat_setend_handler(regs, (instr >> 9) & 1); + arm64_skip_faulting_instruction(regs, 4); + return rc; +} + +static int t16_setend_handler(struct pt_regs *regs, u32 instr) +{ + int rc = compat_setend_handler(regs, (instr >> 3) & 1); + arm64_skip_faulting_instruction(regs, 2); + return rc; +} + +static bool try_emulate_setend(struct pt_regs *regs, u32 insn) +{ + if (compat_thumb_mode(regs) && + (insn & 0xfffffff7) == 0x0000b650) + return t16_setend_handler(regs, insn) == 0; + + if (compat_user_mode(regs) && + (insn & 0xfffffdff) == 0xf1010000) + return a32_setend_handler(regs, insn) == 0; + + return false; +} + +static struct insn_emulation insn_setend = { + .name = "setend", + .status = INSN_DEPRECATED, + .try_emulate = try_emulate_setend, + .set_hw_mode = setend_set_hw_mode, +}; +#endif /* CONFIG_SETEND_EMULATION */ + +static struct insn_emulation *insn_emulations[] = { +#ifdef CONFIG_SWP_EMULATION + &insn_swp, +#endif +#ifdef CONFIG_CP15_BARRIER_EMULATION + &insn_cp15_barrier, +#endif +#ifdef CONFIG_SETEND_EMULATION + &insn_setend, +#endif +}; + +static DEFINE_MUTEX(insn_emulation_mutex); + +static void enable_insn_hw_mode(void *data) +{ + struct insn_emulation *insn = (struct insn_emulation *)data; + if (insn->set_hw_mode) + insn->set_hw_mode(true); +} + +static void disable_insn_hw_mode(void *data) +{ + struct insn_emulation *insn = (struct insn_emulation *)data; + if (insn->set_hw_mode) + insn->set_hw_mode(false); +} + +/* Run set_hw_mode(mode) on all active CPUs */ +static int run_all_cpu_set_hw_mode(struct insn_emulation *insn, bool enable) +{ + if (!insn->set_hw_mode) + return -EINVAL; + if (enable) + on_each_cpu(enable_insn_hw_mode, (void *)insn, true); + else + on_each_cpu(disable_insn_hw_mode, (void *)insn, true); + return 0; +} + +/* + * Run set_hw_mode for all insns on a starting CPU. + * Returns: + * 0 - If all the hooks ran successfully. + * -EINVAL - At least one hook is not supported by the CPU. + */ +static int run_all_insn_set_hw_mode(unsigned int cpu) +{ + int i; + int rc = 0; + unsigned long flags; + + /* + * Disable IRQs to serialize against an IPI from + * run_all_cpu_set_hw_mode(), ensuring the HW is programmed to the most + * recent enablement state if the two race with one another. + */ + local_irq_save(flags); + for (i = 0; i < ARRAY_SIZE(insn_emulations); i++) { + struct insn_emulation *insn = insn_emulations[i]; + bool enable = READ_ONCE(insn->current_mode) == INSN_HW; + if (insn->set_hw_mode && insn->set_hw_mode(enable)) { + pr_warn("CPU[%u] cannot support the emulation of %s", + cpu, insn->name); + rc = -EINVAL; + } + } + local_irq_restore(flags); + + return rc; +} + +static int update_insn_emulation_mode(struct insn_emulation *insn, + enum insn_emulation_mode prev) +{ + int ret = 0; + + switch (prev) { + case INSN_UNDEF: /* Nothing to be done */ + break; + case INSN_EMULATE: + break; + case INSN_HW: + if (!run_all_cpu_set_hw_mode(insn, false)) + pr_notice("Disabled %s support\n", insn->name); + break; + } + + switch (insn->current_mode) { + case INSN_UNDEF: + break; + case INSN_EMULATE: + break; + case INSN_HW: + ret = run_all_cpu_set_hw_mode(insn, true); + if (!ret) + pr_notice("Enabled %s support\n", insn->name); + break; + } + + return ret; +} + +static int emulation_proc_handler(struct ctl_table *table, int write, + void *buffer, size_t *lenp, + loff_t *ppos) +{ + int ret = 0; + struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode); + enum insn_emulation_mode prev_mode = insn->current_mode; + + mutex_lock(&insn_emulation_mutex); + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + + if (ret || !write || prev_mode == insn->current_mode) + goto ret; + + ret = update_insn_emulation_mode(insn, prev_mode); + if (ret) { + /* Mode change failed, revert to previous mode. */ + WRITE_ONCE(insn->current_mode, prev_mode); + update_insn_emulation_mode(insn, INSN_UNDEF); + } +ret: + mutex_unlock(&insn_emulation_mutex); + return ret; +} + +static void __init register_insn_emulation(struct insn_emulation *insn) +{ + struct ctl_table *sysctl; + + insn->min = INSN_UNDEF; + + switch (insn->status) { + case INSN_DEPRECATED: + insn->current_mode = INSN_EMULATE; + /* Disable the HW mode if it was turned on at early boot time */ + run_all_cpu_set_hw_mode(insn, false); + insn->max = INSN_HW; + break; + case INSN_OBSOLETE: + insn->current_mode = INSN_UNDEF; + insn->max = INSN_EMULATE; + break; + case INSN_UNAVAILABLE: + insn->current_mode = INSN_UNDEF; + insn->max = INSN_UNDEF; + break; + } + + /* Program the HW if required */ + update_insn_emulation_mode(insn, INSN_UNDEF); + + if (insn->status != INSN_UNAVAILABLE) { + sysctl = &insn->sysctl[0]; + + sysctl->mode = 0644; + sysctl->maxlen = sizeof(int); + + sysctl->procname = insn->name; + sysctl->data = &insn->current_mode; + sysctl->extra1 = &insn->min; + sysctl->extra2 = &insn->max; + sysctl->proc_handler = emulation_proc_handler; + + register_sysctl("abi", sysctl); + } +} + +bool try_emulate_armv8_deprecated(struct pt_regs *regs, u32 insn) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(insn_emulations); i++) { + struct insn_emulation *ie = insn_emulations[i]; + + if (ie->status == INSN_UNAVAILABLE) + continue; + + /* + * A trap may race with the mode being changed + * INSN_EMULATE<->INSN_HW. Try to emulate the instruction to + * avoid a spurious UNDEF. + */ + if (READ_ONCE(ie->current_mode) == INSN_UNDEF) + continue; + + if (ie->try_emulate(regs, insn)) + return true; + } + + return false; +} + +/* + * Invoked as core_initcall, which guarantees that the instruction + * emulation is ready for userspace. + */ +static int __init armv8_deprecated_init(void) +{ + int i; + +#ifdef CONFIG_SETEND_EMULATION + if (!system_supports_mixed_endian_el0()) { + insn_setend.status = INSN_UNAVAILABLE; + pr_info("setend instruction emulation is not supported on this system\n"); + } + +#endif + for (i = 0; i < ARRAY_SIZE(insn_emulations); i++) { + struct insn_emulation *ie = insn_emulations[i]; + + if (ie->status == INSN_UNAVAILABLE) + continue; + + register_insn_emulation(ie); + } + + cpuhp_setup_state_nocalls(CPUHP_AP_ARM64_ISNDEP_STARTING, + "arm64/isndep:starting", + run_all_insn_set_hw_mode, NULL); + return 0; +} + +core_initcall(armv8_deprecated_init); |