// SPDX-License-Identifier: GPL-2.0
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/pgtable.h>
#include <linux/cpuidle.h>
#include <asm/alternative.h>
#include <asm/cacheflush.h>
#include <asm/cpufeature.h>
#include <asm/cpuidle.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
#include <asm/exec.h>
#include <asm/fpsimd.h>
#include <asm/mte.h>
#include <asm/memory.h>
#include <asm/mmu_context.h>
#include <asm/smp_plat.h>
#include <asm/suspend.h>

/*
 * This is allocated by cpu_suspend_init(), and used to store a pointer to
 * the 'struct sleep_stack_data' the contains a particular CPUs state.
 */
unsigned long *sleep_save_stash;

/*
 * This hook is provided so that cpu_suspend code can restore HW
 * breakpoints as early as possible in the resume path, before reenabling
 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
 * time the notifier runs debug exceptions might have been enabled already,
 * with HW breakpoints registers content still in an unknown state.
 */
static int (*hw_breakpoint_restore)(unsigned int);
void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
{
        /* Prevent multiple restore hook initializations */
        if (WARN_ON(hw_breakpoint_restore))
                return;
        hw_breakpoint_restore = hw_bp_restore;
}

void notrace __cpu_suspend_exit(void)
{
        unsigned int cpu = smp_processor_id();

        mte_suspend_exit();

        /*
         * We are resuming from reset with the idmap active in TTBR0_EL1.
         * We must uninstall the idmap and restore the expected MMU
         * state before we can possibly return to userspace.
         */
        cpu_uninstall_idmap();

        /* Restore CnP bit in TTBR1_EL1 */
        if (system_supports_cnp())
                cpu_enable_swapper_cnp();

        /*
         * PSTATE was not saved over suspend/resume, re-enable any detected
         * features that might not have been set correctly.
         */
        if (alternative_has_cap_unlikely(ARM64_HAS_DIT))
                set_pstate_dit(1);
        __uaccess_enable_hw_pan();

        /*
         * Restore HW breakpoint registers to sane values
         * before debug exceptions are possibly reenabled
         * by cpu_suspend()s local_daif_restore() call.
         */
        if (hw_breakpoint_restore)
                hw_breakpoint_restore(cpu);

        /*
         * On resume, firmware implementing dynamic mitigation will
         * have turned the mitigation on. If the user has forcefully
         * disabled it, make sure their wishes are obeyed.
         */
        spectre_v4_enable_mitigation(NULL);

        sme_suspend_exit();

        /* Restore additional feature-specific configuration */
        ptrauth_suspend_exit();
}

/*
 * cpu_suspend
 *
 * arg: argument to pass to the finisher function
 * fn: finisher function pointer
 *
 */
int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
{
        int ret = 0;
        unsigned long flags;
        struct sleep_stack_data state;
        struct arm_cpuidle_irq_context context;

        /*
         * Some portions of CPU state (e.g. PSTATE.{PAN,DIT}) are initialized
         * before alternatives are patched, but are only restored by
         * __cpu_suspend_exit() after alternatives are patched. To avoid
         * accidentally losing these bits we must not attempt to suspend until
         * after alternatives have been patched.
         */
        WARN_ON(!system_capabilities_finalized());

        /* Report any MTE async fault before going to suspend */
        mte_suspend_enter();

        /*
         * From this point debug exceptions are disabled to prevent
         * updates to mdscr register (saved and restored along with
         * general purpose registers) from kernel debuggers.
         *
         * Strictly speaking the trace_hardirqs_off() here is superfluous,
         * hardirqs should be firmly off by now. This really ought to use
         * something like raw_local_daif_save().
         */
        flags = local_daif_save();

        /*
         * Function graph tracer state gets inconsistent when the kernel
         * calls functions that never return (aka suspend finishers) hence
         * disable graph tracing during their execution.
         */
        pause_graph_tracing();

        /*
         * Switch to using DAIF.IF instead of PMR in order to reliably
         * resume if we're using pseudo-NMIs.
         */
        arm_cpuidle_save_irq_context(&context);

        ct_cpuidle_enter();

        if (__cpu_suspend_enter(&state)) {
                /* Call the suspend finisher */
                ret = fn(arg);

                /*
                 * Never gets here, unless the suspend finisher fails.
                 * Successful cpu_suspend() should return from cpu_resume(),
                 * returning through this code path is considered an error
                 * If the return value is set to 0 force ret = -EOPNOTSUPP
                 * to make sure a proper error condition is propagated
                 */
                if (!ret)
                        ret = -EOPNOTSUPP;

                ct_cpuidle_exit();
        } else {
                ct_cpuidle_exit();
                __cpu_suspend_exit();
        }

        arm_cpuidle_restore_irq_context(&context);

        unpause_graph_tracing();

        /*
         * Restore pstate flags. OS lock and mdscr have been already
         * restored, so from this point onwards, debugging is fully
         * reenabled if it was enabled when core started shutdown.
         */
        local_daif_restore(flags);

        return ret;
}

static int __init cpu_suspend_init(void)
{
        /* ctx_ptr is an array of physical addresses */
        sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
                                   GFP_KERNEL);

        if (WARN_ON(!sleep_save_stash))
                return -ENOMEM;

        return 0;
}
early_initcall(cpu_suspend_init);