Merge tag 'sched-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel...

[linux/fpc-iii.git] / arch / arm64 / kernel / process.c

// 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 <stdarg.h>

#include <linux/compat.h>
#include <linux/efi.h>
#include <linux/elf.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/lockdep.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/nospec.h>
#include <linux/stddef.h>
#include <linux/sysctl.h>
#include <linux/unistd.h>
#include <linux/user.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/elfcore.h>
#include <linux/pm.h>
#include <linux/tick.h>
#include <linux/utsname.h>
#include <linux/uaccess.h>
#include <linux/random.h>
#include <linux/hw_breakpoint.h>
#include <linux/personality.h>
#include <linux/notifier.h>
#include <trace/events/power.h>
#include <linux/percpu.h>
#include <linux/thread_info.h>
#include <linux/prctl.h>

#include <asm/alternative.h>
#include <asm/arch_gicv3.h>
#include <asm/compat.h>
#include <asm/cpufeature.h>
#include <asm/cacheflush.h>
#include <asm/exec.h>
#include <asm/fpsimd.h>
#include <asm/mmu_context.h>
#include <asm/mte.h>
#include <asm/processor.h>
#include <asm/pointer_auth.h>
#include <asm/stacktrace.h>

#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
#include <linux/stackprotector.h>
unsigned long __stack_chk_guard __read_mostly;
EXPORT_SYMBOL(__stack_chk_guard);
#endif

/*
 * Function pointers to optional machine specific functions
 */
void (*pm_power_off)(void);
EXPORT_SYMBOL_GPL(pm_power_off);

void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);

static void noinstr __cpu_do_idle(void)
{
        dsb(sy);
        wfi();
}

static void noinstr __cpu_do_idle_irqprio(void)
{
        unsigned long pmr;
        unsigned long daif_bits;

        daif_bits = read_sysreg(daif);
        write_sysreg(daif_bits | PSR_I_BIT, daif);

        /*
         * Unmask PMR before going idle to make sure interrupts can
         * be raised.
         */
        pmr = gic_read_pmr();
        gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);

        __cpu_do_idle();

        gic_write_pmr(pmr);
        write_sysreg(daif_bits, daif);
}

/*
 *      cpu_do_idle()
 *
 *      Idle the processor (wait for interrupt).
 *
 *      If the CPU supports priority masking we must do additional work to
 *      ensure that interrupts are not masked at the PMR (because the core will
 *      not wake up if we block the wake up signal in the interrupt controller).
 */
void noinstr cpu_do_idle(void)
{
        if (system_uses_irq_prio_masking())
                __cpu_do_idle_irqprio();
        else
                __cpu_do_idle();
}

/*
 * This is our default idle handler.
 */
void noinstr arch_cpu_idle(void)
{
        /*
         * This should do all the clock switching and wait for interrupt
         * tricks
         */
        cpu_do_idle();
        raw_local_irq_enable();
}

#ifdef CONFIG_HOTPLUG_CPU
void 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();
        if (pm_power_off)
                pm_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. */
        if (arm_pm_restart)
                arm_pm_restart(reboot_mode, cmd);
        else
                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)\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');
        } 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 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 ? '+' : '-',
                        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_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]);
                i--;

                if (i % 2 == 0) {
                        pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
                        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 (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);
}

void flush_thread(void)
{
        fpsimd_flush_thread();
        tls_thread_flush();
        flush_ptrace_hw_breakpoint(current);
        flush_tagged_addr_state();
        flush_mte_state();
}

void release_thread(struct task_struct *dead_task)
{
}

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;

        /* We rely on the above assignment to initialize dst's thread_flags: */
        BUILD_BUG_ON(!IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK));

        /*
         * Detach src's sve_state (if any) from dst so that it does not
         * get erroneously used or freed prematurely.  dst's sve_state
         * 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_SVE and sve_state in
         * an inconsistent state, even temporarily.
         */
        dst->thread.sve_state = NULL;
        clear_tsk_thread_flag(dst, TIF_SVE);

        /* 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(unsigned long clone_flags, unsigned long stack_start,
                unsigned long stk_sz, struct task_struct *p, unsigned long 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(!(p->flags & PF_KTHREAD))) {
                *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 (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.
                 */
                if (clone_flags & CLONE_SETTLS)
                        p->thread.uw.tp_value = tls;
        } 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 = stack_start;
                p->thread.cpu_context.x20 = stk_sz;
        }
        p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
        p->thread.cpu_context.sp = (unsigned long)childregs;

        ptrace_hw_copy_thread(p);

        return 0;
}

void tls_preserve_current_state(void)
{
        *task_user_tls(current) = read_sysreg(tpidr_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);
}

/*
 * 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 (cpus_have_const_cap(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);
}

/*
 * ARM erratum 1418040 handling, affecting the 32bit view of CNTVCT.
 * Assuming the virtual counter is enabled at the beginning of times:
 *
 * - disable access when switching from a 64bit task to a 32bit task
 * - enable access when switching from a 32bit task to a 64bit task
 */
static void erratum_1418040_thread_switch(struct task_struct *prev,
                                          struct task_struct *next)
{
        bool prev32, next32;
        u64 val;

        if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040))
                return;

        prev32 = is_compat_thread(task_thread_info(prev));
        next32 = is_compat_thread(task_thread_info(next));

        if (prev32 == next32 || !this_cpu_has_cap(ARM64_WORKAROUND_1418040))
                return;

        val = read_sysreg(cntkctl_el1);

        if (!next32)
                val |= ARCH_TIMER_USR_VCT_ACCESS_EN;
        else
                val &= ~ARCH_TIMER_USR_VCT_ACCESS_EN;

        write_sysreg(val, cntkctl_el1);
}

/*
 * Thread switching.
 */
__notrace_funcgraph 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);
        erratum_1418040_thread_switch(prev, 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);

        /* the actual thread switch */
        last = cpu_switch_to(prev, next);

        return last;
}

unsigned long get_wchan(struct task_struct *p)
{
        struct stackframe frame;
        unsigned long stack_page, ret = 0;
        int count = 0;
        if (!p || p == current || p->state == TASK_RUNNING)
                return 0;

        stack_page = (unsigned long)try_get_task_stack(p);
        if (!stack_page)
                return 0;

        start_backtrace(&frame, thread_saved_fp(p), thread_saved_pc(p));

        do {
                if (unwind_frame(p, &frame))
                        goto out;
                if (!in_sched_functions(frame.pc)) {
                        ret = frame.pc;
                        goto out;
                }
        } while (count ++ < 16);

out:
        put_task_stack(p);
        return ret;
}

unsigned long arch_align_stack(unsigned long sp)
{
        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
                sp -= get_random_int() & ~PAGE_MASK;
        return sp & ~0xf;
}

/*
 * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY.
 */
void arch_setup_new_exec(void)
{
        current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;

        ptrauth_thread_init_user(current);

        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_MASK | 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 */

asmlinkage void __sched arm64_preempt_schedule_irq(void)
{
        lockdep_assert_irqs_disabled();

        /*
         * Preempting a task from an IRQ means we leave copies of PSTATE
         * on the stack. cpufeature's enable calls may modify PSTATE, but
         * resuming one of these preempted tasks would undo those changes.
         *
         * Only allow a task to be preempted once cpufeatures have been
         * enabled.
         */
        if (system_capabilities_finalized())
                preempt_schedule_irq();
}

#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