// SPDX-License-Identifier: GPL-2.0-only /* * Based on arch/arm/kernel/process.c * * Original Copyright (C) 1995 Linus Torvalds * Copyright (C) 1996-2000 Russell King - Converted to ARM. * Copyright (C) 2012 ARM Ltd. */ #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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) #include unsigned long __stack_chk_guard __ro_after_init; EXPORT_SYMBOL(__stack_chk_guard); #endif /* * Function pointers to optional machine specific functions */ void (*pm_power_off)(void); EXPORT_SYMBOL_GPL(pm_power_off); #ifdef CONFIG_HOTPLUG_CPU void __noreturn arch_cpu_idle_dead(void) { cpu_die(); } #endif /* * Called by kexec, immediately prior to machine_kexec(). * * This must completely disable all secondary CPUs; simply causing those CPUs * to execute e.g. a RAM-based pin loop is not sufficient. This allows the * kexec'd kernel to use any and all RAM as it sees fit, without having to * avoid any code or data used by any SW CPU pin loop. The CPU hotplug * functionality embodied in smpt_shutdown_nonboot_cpus() to achieve this. */ void machine_shutdown(void) { smp_shutdown_nonboot_cpus(reboot_cpu); } /* * Halting simply requires that the secondary CPUs stop performing any * activity (executing tasks, handling interrupts). smp_send_stop() * achieves this. */ void machine_halt(void) { local_irq_disable(); smp_send_stop(); while (1); } /* * Power-off simply requires that the secondary CPUs stop performing any * activity (executing tasks, handling interrupts). smp_send_stop() * achieves this. When the system power is turned off, it will take all CPUs * with it. */ void machine_power_off(void) { local_irq_disable(); smp_send_stop(); do_kernel_power_off(); } /* * Restart requires that the secondary CPUs stop performing any activity * while the primary CPU resets the system. Systems with multiple CPUs must * provide a HW restart implementation, to ensure that all CPUs reset at once. * This is required so that any code running after reset on the primary CPU * doesn't have to co-ordinate with other CPUs to ensure they aren't still * executing pre-reset code, and using RAM that the primary CPU's code wishes * to use. Implementing such co-ordination would be essentially impossible. */ void machine_restart(char *cmd) { /* Disable interrupts first */ local_irq_disable(); smp_send_stop(); /* * UpdateCapsule() depends on the system being reset via * ResetSystem(). */ if (efi_enabled(EFI_RUNTIME_SERVICES)) efi_reboot(reboot_mode, NULL); /* Now call the architecture specific reboot code. */ do_kernel_restart(cmd); /* * Whoops - the architecture was unable to reboot. */ printk("Reboot failed -- System halted\n"); while (1); } #define bstr(suffix, str) [PSR_BTYPE_ ## suffix >> PSR_BTYPE_SHIFT] = str static const char *const btypes[] = { bstr(NONE, "--"), bstr( JC, "jc"), bstr( C, "-c"), bstr( J , "j-") }; #undef bstr static void print_pstate(struct pt_regs *regs) { u64 pstate = regs->pstate; if (compat_user_mode(regs)) { printk("pstate: %08llx (%c%c%c%c %c %s %s %c%c%c %cDIT %cSSBS)\n", pstate, pstate & PSR_AA32_N_BIT ? 'N' : 'n', pstate & PSR_AA32_Z_BIT ? 'Z' : 'z', pstate & PSR_AA32_C_BIT ? 'C' : 'c', pstate & PSR_AA32_V_BIT ? 'V' : 'v', pstate & PSR_AA32_Q_BIT ? 'Q' : 'q', pstate & PSR_AA32_T_BIT ? "T32" : "A32", pstate & PSR_AA32_E_BIT ? "BE" : "LE", pstate & PSR_AA32_A_BIT ? 'A' : 'a', pstate & PSR_AA32_I_BIT ? 'I' : 'i', pstate & PSR_AA32_F_BIT ? 'F' : 'f', pstate & PSR_AA32_DIT_BIT ? '+' : '-', pstate & PSR_AA32_SSBS_BIT ? '+' : '-'); } else { const char *btype_str = btypes[(pstate & PSR_BTYPE_MASK) >> PSR_BTYPE_SHIFT]; printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO %cTCO %cDIT %cSSBS BTYPE=%s)\n", pstate, pstate & PSR_N_BIT ? 'N' : 'n', pstate & PSR_Z_BIT ? 'Z' : 'z', pstate & PSR_C_BIT ? 'C' : 'c', pstate & PSR_V_BIT ? 'V' : 'v', pstate & PSR_D_BIT ? 'D' : 'd', pstate & PSR_A_BIT ? 'A' : 'a', pstate & PSR_I_BIT ? 'I' : 'i', pstate & PSR_F_BIT ? 'F' : 'f', pstate & PSR_PAN_BIT ? '+' : '-', pstate & PSR_UAO_BIT ? '+' : '-', pstate & PSR_TCO_BIT ? '+' : '-', pstate & PSR_DIT_BIT ? '+' : '-', pstate & PSR_SSBS_BIT ? '+' : '-', btype_str); } } void __show_regs(struct pt_regs *regs) { int i, top_reg; u64 lr, sp; if (compat_user_mode(regs)) { lr = regs->compat_lr; sp = regs->compat_sp; top_reg = 12; } else { lr = regs->regs[30]; sp = regs->sp; top_reg = 29; } show_regs_print_info(KERN_DEFAULT); print_pstate(regs); if (!user_mode(regs)) { printk("pc : %pS\n", (void *)regs->pc); printk("lr : %pS\n", (void *)ptrauth_strip_kernel_insn_pac(lr)); } else { printk("pc : %016llx\n", regs->pc); printk("lr : %016llx\n", lr); } printk("sp : %016llx\n", sp); if (system_uses_irq_prio_masking()) printk("pmr_save: %08llx\n", regs->pmr_save); i = top_reg; while (i >= 0) { printk("x%-2d: %016llx", i, regs->regs[i]); while (i-- % 3) pr_cont(" x%-2d: %016llx", i, regs->regs[i]); pr_cont("\n"); } } void show_regs(struct pt_regs *regs) { __show_regs(regs); dump_backtrace(regs, NULL, KERN_DEFAULT); } static void tls_thread_flush(void) { write_sysreg(0, tpidr_el0); if (system_supports_tpidr2()) write_sysreg_s(0, SYS_TPIDR2_EL0); if (is_compat_task()) { current->thread.uw.tp_value = 0; /* * We need to ensure ordering between the shadow state and the * hardware state, so that we don't corrupt the hardware state * with a stale shadow state during context switch. */ barrier(); write_sysreg(0, tpidrro_el0); } } static void flush_tagged_addr_state(void) { if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI)) clear_thread_flag(TIF_TAGGED_ADDR); } static void flush_poe(void) { if (!system_supports_poe()) return; write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0); } void flush_thread(void) { fpsimd_flush_thread(); tls_thread_flush(); flush_ptrace_hw_breakpoint(current); flush_tagged_addr_state(); flush_poe(); } void arch_release_task_struct(struct task_struct *tsk) { fpsimd_release_task(tsk); } int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { if (current->mm) fpsimd_preserve_current_state(); *dst = *src; /* * Detach src's sve_state (if any) from dst so that it does not * get erroneously used or freed prematurely. dst's copies * will be allocated on demand later on if dst uses SVE. * For consistency, also clear TIF_SVE here: this could be done * later in copy_process(), but to avoid tripping up future * maintainers it is best not to leave TIF flags and buffers in * an inconsistent state, even temporarily. */ dst->thread.sve_state = NULL; clear_tsk_thread_flag(dst, TIF_SVE); /* * In the unlikely event that we create a new thread with ZA * enabled we should retain the ZA and ZT state so duplicate * it here. This may be shortly freed if we exec() or if * CLONE_SETTLS but it's simpler to do it here. To avoid * confusing the rest of the code ensure that we have a * sve_state allocated whenever sme_state is allocated. */ if (thread_za_enabled(&src->thread)) { dst->thread.sve_state = kzalloc(sve_state_size(src), GFP_KERNEL); if (!dst->thread.sve_state) return -ENOMEM; dst->thread.sme_state = kmemdup(src->thread.sme_state, sme_state_size(src), GFP_KERNEL); if (!dst->thread.sme_state) { kfree(dst->thread.sve_state); dst->thread.sve_state = NULL; return -ENOMEM; } } else { dst->thread.sme_state = NULL; clear_tsk_thread_flag(dst, TIF_SME); } dst->thread.fp_type = FP_STATE_FPSIMD; /* clear any pending asynchronous tag fault raised by the parent */ clear_tsk_thread_flag(dst, TIF_MTE_ASYNC_FAULT); return 0; } asmlinkage void ret_from_fork(void) asm("ret_from_fork"); int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) { unsigned long clone_flags = args->flags; unsigned long stack_start = args->stack; unsigned long tls = args->tls; struct pt_regs *childregs = task_pt_regs(p); memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context)); /* * In case p was allocated the same task_struct pointer as some * other recently-exited task, make sure p is disassociated from * any cpu that may have run that now-exited task recently. * Otherwise we could erroneously skip reloading the FPSIMD * registers for p. */ fpsimd_flush_task_state(p); ptrauth_thread_init_kernel(p); if (likely(!args->fn)) { *childregs = *current_pt_regs(); childregs->regs[0] = 0; /* * Read the current TLS pointer from tpidr_el0 as it may be * out-of-sync with the saved value. */ *task_user_tls(p) = read_sysreg(tpidr_el0); if (system_supports_tpidr2()) p->thread.tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0); if (system_supports_poe()) p->thread.por_el0 = read_sysreg_s(SYS_POR_EL0); if (stack_start) { if (is_compat_thread(task_thread_info(p))) childregs->compat_sp = stack_start; else childregs->sp = stack_start; } /* * If a TLS pointer was passed to clone, use it for the new * thread. We also reset TPIDR2 if it's in use. */ if (clone_flags & CLONE_SETTLS) { p->thread.uw.tp_value = tls; p->thread.tpidr2_el0 = 0; } } else { /* * A kthread has no context to ERET to, so ensure any buggy * ERET is treated as an illegal exception return. * * When a user task is created from a kthread, childregs will * be initialized by start_thread() or start_compat_thread(). */ memset(childregs, 0, sizeof(struct pt_regs)); childregs->pstate = PSR_MODE_EL1h | PSR_IL_BIT; p->thread.cpu_context.x19 = (unsigned long)args->fn; p->thread.cpu_context.x20 = (unsigned long)args->fn_arg; } p->thread.cpu_context.pc = (unsigned long)ret_from_fork; p->thread.cpu_context.sp = (unsigned long)childregs; /* * For the benefit of the unwinder, set up childregs->stackframe * as the final frame for the new task. */ p->thread.cpu_context.fp = (unsigned long)childregs->stackframe; ptrace_hw_copy_thread(p); return 0; } void tls_preserve_current_state(void) { *task_user_tls(current) = read_sysreg(tpidr_el0); if (system_supports_tpidr2() && !is_compat_task()) current->thread.tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0); } static void tls_thread_switch(struct task_struct *next) { tls_preserve_current_state(); if (is_compat_thread(task_thread_info(next))) write_sysreg(next->thread.uw.tp_value, tpidrro_el0); else if (!arm64_kernel_unmapped_at_el0()) write_sysreg(0, tpidrro_el0); write_sysreg(*task_user_tls(next), tpidr_el0); if (system_supports_tpidr2()) write_sysreg_s(next->thread.tpidr2_el0, SYS_TPIDR2_EL0); } /* * Force SSBS state on context-switch, since it may be lost after migrating * from a CPU which treats the bit as RES0 in a heterogeneous system. */ static void ssbs_thread_switch(struct task_struct *next) { /* * Nothing to do for kernel threads, but 'regs' may be junk * (e.g. idle task) so check the flags and bail early. */ if (unlikely(next->flags & PF_KTHREAD)) return; /* * If all CPUs implement the SSBS extension, then we just need to * context-switch the PSTATE field. */ if (alternative_has_cap_unlikely(ARM64_SSBS)) return; spectre_v4_enable_task_mitigation(next); } /* * We store our current task in sp_el0, which is clobbered by userspace. Keep a * shadow copy so that we can restore this upon entry from userspace. * * This is *only* for exception entry from EL0, and is not valid until we * __switch_to() a user task. */ DEFINE_PER_CPU(struct task_struct *, __entry_task); static void entry_task_switch(struct task_struct *next) { __this_cpu_write(__entry_task, next); } /* * Handle sysreg updates for ARM erratum 1418040 which affects the 32bit view of * CNTVCT, various other errata which require trapping all CNTVCT{,_EL0} * accesses and prctl(PR_SET_TSC). Ensure access is disabled iff a workaround is * required or PR_TSC_SIGSEGV is set. */ static void update_cntkctl_el1(struct task_struct *next) { struct thread_info *ti = task_thread_info(next); if (test_ti_thread_flag(ti, TIF_TSC_SIGSEGV) || has_erratum_handler(read_cntvct_el0) || (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) && this_cpu_has_cap(ARM64_WORKAROUND_1418040) && is_compat_thread(ti))) sysreg_clear_set(cntkctl_el1, ARCH_TIMER_USR_VCT_ACCESS_EN, 0); else sysreg_clear_set(cntkctl_el1, 0, ARCH_TIMER_USR_VCT_ACCESS_EN); } static void cntkctl_thread_switch(struct task_struct *prev, struct task_struct *next) { if ((read_ti_thread_flags(task_thread_info(prev)) & (_TIF_32BIT | _TIF_TSC_SIGSEGV)) != (read_ti_thread_flags(task_thread_info(next)) & (_TIF_32BIT | _TIF_TSC_SIGSEGV))) update_cntkctl_el1(next); } static int do_set_tsc_mode(unsigned int val) { bool tsc_sigsegv; if (val == PR_TSC_SIGSEGV) tsc_sigsegv = true; else if (val == PR_TSC_ENABLE) tsc_sigsegv = false; else return -EINVAL; preempt_disable(); update_thread_flag(TIF_TSC_SIGSEGV, tsc_sigsegv); update_cntkctl_el1(current); preempt_enable(); return 0; } static void permission_overlay_switch(struct task_struct *next) { if (!system_supports_poe()) return; current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0); if (current->thread.por_el0 != next->thread.por_el0) { write_sysreg_s(next->thread.por_el0, SYS_POR_EL0); } } /* * __switch_to() checks current->thread.sctlr_user as an optimisation. Therefore * this function must be called with preemption disabled and the update to * sctlr_user must be made in the same preemption disabled block so that * __switch_to() does not see the variable update before the SCTLR_EL1 one. */ void update_sctlr_el1(u64 sctlr) { /* * EnIA must not be cleared while in the kernel as this is necessary for * in-kernel PAC. It will be cleared on kernel exit if needed. */ sysreg_clear_set(sctlr_el1, SCTLR_USER_MASK & ~SCTLR_ELx_ENIA, sctlr); /* ISB required for the kernel uaccess routines when setting TCF0. */ isb(); } /* * Thread switching. */ __notrace_funcgraph __sched struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next) { struct task_struct *last; fpsimd_thread_switch(next); tls_thread_switch(next); hw_breakpoint_thread_switch(next); contextidr_thread_switch(next); entry_task_switch(next); ssbs_thread_switch(next); cntkctl_thread_switch(prev, next); ptrauth_thread_switch_user(next); permission_overlay_switch(next); /* * Complete any pending TLB or cache maintenance on this CPU in case * the thread migrates to a different CPU. * This full barrier is also required by the membarrier system * call. */ dsb(ish); /* * MTE thread switching must happen after the DSB above to ensure that * any asynchronous tag check faults have been logged in the TFSR*_EL1 * registers. */ mte_thread_switch(next); /* avoid expensive SCTLR_EL1 accesses if no change */ if (prev->thread.sctlr_user != next->thread.sctlr_user) update_sctlr_el1(next->thread.sctlr_user); /* the actual thread switch */ last = cpu_switch_to(prev, next); return last; } struct wchan_info { unsigned long pc; int count; }; static bool get_wchan_cb(void *arg, unsigned long pc) { struct wchan_info *wchan_info = arg; if (!in_sched_functions(pc)) { wchan_info->pc = pc; return false; } return wchan_info->count++ < 16; } unsigned long __get_wchan(struct task_struct *p) { struct wchan_info wchan_info = { .pc = 0, .count = 0, }; if (!try_get_task_stack(p)) return 0; arch_stack_walk(get_wchan_cb, &wchan_info, p, NULL); put_task_stack(p); return wchan_info.pc; } unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) sp -= get_random_u32_below(PAGE_SIZE); return sp & ~0xf; } #ifdef CONFIG_COMPAT int compat_elf_check_arch(const struct elf32_hdr *hdr) { if (!system_supports_32bit_el0()) return false; if ((hdr)->e_machine != EM_ARM) return false; if (!((hdr)->e_flags & EF_ARM_EABI_MASK)) return false; /* * Prevent execve() of a 32-bit program from a deadline task * if the restricted affinity mask would be inadmissible on an * asymmetric system. */ return !static_branch_unlikely(&arm64_mismatched_32bit_el0) || !dl_task_check_affinity(current, system_32bit_el0_cpumask()); } #endif /* * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY. */ void arch_setup_new_exec(void) { unsigned long mmflags = 0; if (is_compat_task()) { mmflags = MMCF_AARCH32; /* * Restrict the CPU affinity mask for a 32-bit task so that * it contains only 32-bit-capable CPUs. * * From the perspective of the task, this looks similar to * what would happen if the 64-bit-only CPUs were hot-unplugged * at the point of execve(), although we try a bit harder to * honour the cpuset hierarchy. */ if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) force_compatible_cpus_allowed_ptr(current); } else if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) { relax_compatible_cpus_allowed_ptr(current); } current->mm->context.flags = mmflags; ptrauth_thread_init_user(); mte_thread_init_user(); do_set_tsc_mode(PR_TSC_ENABLE); if (task_spec_ssb_noexec(current)) { arch_prctl_spec_ctrl_set(current, PR_SPEC_STORE_BYPASS, PR_SPEC_ENABLE); } } #ifdef CONFIG_ARM64_TAGGED_ADDR_ABI /* * Control the relaxed ABI allowing tagged user addresses into the kernel. */ static unsigned int tagged_addr_disabled; long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg) { unsigned long valid_mask = PR_TAGGED_ADDR_ENABLE; struct thread_info *ti = task_thread_info(task); if (is_compat_thread(ti)) return -EINVAL; if (system_supports_mte()) valid_mask |= PR_MTE_TCF_SYNC | PR_MTE_TCF_ASYNC \ | PR_MTE_TAG_MASK; if (arg & ~valid_mask) return -EINVAL; /* * Do not allow the enabling of the tagged address ABI if globally * disabled via sysctl abi.tagged_addr_disabled. */ if (arg & PR_TAGGED_ADDR_ENABLE && tagged_addr_disabled) return -EINVAL; if (set_mte_ctrl(task, arg) != 0) return -EINVAL; update_ti_thread_flag(ti, TIF_TAGGED_ADDR, arg & PR_TAGGED_ADDR_ENABLE); return 0; } long get_tagged_addr_ctrl(struct task_struct *task) { long ret = 0; struct thread_info *ti = task_thread_info(task); if (is_compat_thread(ti)) return -EINVAL; if (test_ti_thread_flag(ti, TIF_TAGGED_ADDR)) ret = PR_TAGGED_ADDR_ENABLE; ret |= get_mte_ctrl(task); return ret; } /* * Global sysctl to disable the tagged user addresses support. This control * only prevents the tagged address ABI enabling via prctl() and does not * disable it for tasks that already opted in to the relaxed ABI. */ static struct ctl_table tagged_addr_sysctl_table[] = { { .procname = "tagged_addr_disabled", .mode = 0644, .data = &tagged_addr_disabled, .maxlen = sizeof(int), .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, }, }; static int __init tagged_addr_init(void) { if (!register_sysctl("abi", tagged_addr_sysctl_table)) return -EINVAL; return 0; } core_initcall(tagged_addr_init); #endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ #ifdef CONFIG_BINFMT_ELF int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, bool has_interp, bool is_interp) { /* * For dynamically linked executables the interpreter is * responsible for setting PROT_BTI on everything except * itself. */ if (is_interp != has_interp) return prot; if (!(state->flags & ARM64_ELF_BTI)) return prot; if (prot & PROT_EXEC) prot |= PROT_BTI; return prot; } #endif int get_tsc_mode(unsigned long adr) { unsigned int val; if (is_compat_task()) return -EINVAL; if (test_thread_flag(TIF_TSC_SIGSEGV)) val = PR_TSC_SIGSEGV; else val = PR_TSC_ENABLE; return put_user(val, (unsigned int __user *)adr); } int set_tsc_mode(unsigned int val) { if (is_compat_task()) return -EINVAL; return do_set_tsc_mode(val); }