// SPDX-License-Identifier: GPL-2.0-or-later

#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/prctl.h>
#include <linux/sched.h>

#include <asm/cpu_has_feature.h>
#include <asm/cputable.h>
#include <asm/processor.h>
#include <asm/reg.h>

static int __init init_task_dexcr(void)
{
        if (!early_cpu_has_feature(CPU_FTR_ARCH_31))
                return 0;

        current->thread.dexcr_onexec = mfspr(SPRN_DEXCR);

        return 0;
}
early_initcall(init_task_dexcr)

/* Allow thread local configuration of these by default */
#define DEXCR_PRCTL_EDITABLE ( \
        DEXCR_PR_IBRTPD | \
        DEXCR_PR_SRAPD | \
        DEXCR_PR_NPHIE)

static int prctl_to_aspect(unsigned long which, unsigned int *aspect)
{
        switch (which) {
        case PR_PPC_DEXCR_SBHE:
                *aspect = DEXCR_PR_SBHE;
                break;
        case PR_PPC_DEXCR_IBRTPD:
                *aspect = DEXCR_PR_IBRTPD;
                break;
        case PR_PPC_DEXCR_SRAPD:
                *aspect = DEXCR_PR_SRAPD;
                break;
        case PR_PPC_DEXCR_NPHIE:
                *aspect = DEXCR_PR_NPHIE;
                break;
        default:
                return -ENODEV;
        }

        return 0;
}

int get_dexcr_prctl(struct task_struct *task, unsigned long which)
{
        unsigned int aspect;
        int ret;

        ret = prctl_to_aspect(which, &aspect);
        if (ret)
                return ret;

        if (aspect & DEXCR_PRCTL_EDITABLE)
                ret |= PR_PPC_DEXCR_CTRL_EDITABLE;

        if (aspect & mfspr(SPRN_DEXCR))
                ret |= PR_PPC_DEXCR_CTRL_SET;
        else
                ret |= PR_PPC_DEXCR_CTRL_CLEAR;

        if (aspect & task->thread.dexcr_onexec)
                ret |= PR_PPC_DEXCR_CTRL_SET_ONEXEC;
        else
                ret |= PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC;

        return ret;
}

int set_dexcr_prctl(struct task_struct *task, unsigned long which, unsigned long ctrl)
{
        unsigned long dexcr;
        unsigned int aspect;
        int err = 0;

        err = prctl_to_aspect(which, &aspect);
        if (err)
                return err;

        if (!(aspect & DEXCR_PRCTL_EDITABLE))
                return -EPERM;

        if (ctrl & ~PR_PPC_DEXCR_CTRL_MASK)
                return -EINVAL;

        if (ctrl & PR_PPC_DEXCR_CTRL_SET && ctrl & PR_PPC_DEXCR_CTRL_CLEAR)
                return -EINVAL;

        if (ctrl & PR_PPC_DEXCR_CTRL_SET_ONEXEC && ctrl & PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC)
                return -EINVAL;

        /*
         * We do not want an unprivileged process being able to disable
         * a setuid process's hash check instructions
         */
        if (aspect == DEXCR_PR_NPHIE &&
            ctrl & PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC &&
            !capable(CAP_SYS_ADMIN))
                return -EPERM;

        dexcr = mfspr(SPRN_DEXCR);

        if (ctrl & PR_PPC_DEXCR_CTRL_SET)
                dexcr |= aspect;
        else if (ctrl & PR_PPC_DEXCR_CTRL_CLEAR)
                dexcr &= ~aspect;

        if (ctrl & PR_PPC_DEXCR_CTRL_SET_ONEXEC)
                task->thread.dexcr_onexec |= aspect;
        else if (ctrl & PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC)
                task->thread.dexcr_onexec &= ~aspect;

        mtspr(SPRN_DEXCR, dexcr);

        return 0;
}