[linux-2.6-block.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 <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/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 <linux/stacktrace.h>

#include <asm/alternative.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>
#include <asm/switch_to.h>
#include <asm/system_misc.h>

#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
#include <linux/stackprotector.h>
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);
}

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

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 (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);
}

/*
 * ARM erratum 1418040 handling, affecting the 32bit view of CNTVCT.
 * Ensure access is disabled when switching to a 32bit task, ensure
 * access is enabled when switching to a 64bit task.
 */
static void erratum_1418040_thread_switch(struct task_struct *next)
{
        if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) ||
            !this_cpu_has_cap(ARM64_WORKAROUND_1418040))
                return;

        if (is_compat_thread(task_thread_info(next)))
                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 erratum_1418040_new_exec(void)
{
        preempt_disable();
        erratum_1418040_thread_switch(current);
        preempt_enable();
}

/*
 * __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);
        erratum_1418040_thread_switch(next);
        ptrauth_thread_switch_user(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();
        erratum_1418040_new_exec();

        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