// SPDX-License-Identifier: GPL-2.0
/*
 * General MIPS MT support routines, usable in AP/SP and SMVP.
 * Copyright (C) 2005 Mips Technologies, Inc
 */
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/cpumask.h>
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/cred.h>
#include <linux/security.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <asm/syscalls.h>

/*
 * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
 */
cpumask_t mt_fpu_cpumask;

static int fpaff_threshold = -1;
unsigned long mt_fpemul_threshold;

/*
 * Replacement functions for the sys_sched_setaffinity() and
 * sys_sched_getaffinity() system calls, so that we can integrate
 * FPU affinity with the user's requested processor affinity.
 * This code is 98% identical with the sys_sched_setaffinity()
 * and sys_sched_getaffinity() system calls, and should be
 * updated when kernel/sched/core.c changes.
 */

/*
 * find_process_by_pid - find a process with a matching PID value.
 * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
 * cloned here.
 */
static inline struct task_struct *find_process_by_pid(pid_t pid)
{
        return pid ? find_task_by_vpid(pid) : current;
}

/*
 * check the target process has a UID that matches the current process's
 */
static bool check_same_owner(struct task_struct *p)
{
        const struct cred *cred = current_cred(), *pcred;
        bool match;

        rcu_read_lock();
        pcred = __task_cred(p);
        match = (uid_eq(cred->euid, pcred->euid) ||
                 uid_eq(cred->euid, pcred->uid));
        rcu_read_unlock();
        return match;
}

/*
 * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
 */
asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
                                      unsigned long __user *user_mask_ptr)
{
        cpumask_var_t cpus_allowed, new_mask, effective_mask;
        struct thread_info *ti;
        struct task_struct *p;
        int retval;

        if (len < sizeof(new_mask))
                return -EINVAL;

        if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
                return -EFAULT;

        cpus_read_lock();
        rcu_read_lock();

        p = find_process_by_pid(pid);
        if (!p) {
                rcu_read_unlock();
                cpus_read_unlock();
                return -ESRCH;
        }

        /* Prevent p going away */
        get_task_struct(p);
        rcu_read_unlock();

        if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
                retval = -ENOMEM;
                goto out_put_task;
        }
        if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
                retval = -ENOMEM;
                goto out_free_cpus_allowed;
        }
        if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
                retval = -ENOMEM;
                goto out_free_new_mask;
        }
        if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) {
                retval = -EPERM;
                goto out_unlock;
        }

        retval = security_task_setscheduler(p);
        if (retval)
                goto out_unlock;

        /* Record new user-specified CPU set for future reference */
        cpumask_copy(&p->thread.user_cpus_allowed, new_mask);

 again:
        /* Compute new global allowed CPU set if necessary */
        ti = task_thread_info(p);
        if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
            cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
                cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
                retval = set_cpus_allowed_ptr(p, effective_mask);
        } else {
                cpumask_copy(effective_mask, new_mask);
                clear_ti_thread_flag(ti, TIF_FPUBOUND);
                retval = set_cpus_allowed_ptr(p, new_mask);
        }

        if (!retval) {
                cpuset_cpus_allowed(p, cpus_allowed);
                if (!cpumask_subset(effective_mask, cpus_allowed)) {
                        /*
                         * We must have raced with a concurrent cpuset
                         * update. Just reset the cpus_allowed to the
                         * cpuset's cpus_allowed
                         */
                        cpumask_copy(new_mask, cpus_allowed);
                        goto again;
                }
        }
out_unlock:
        free_cpumask_var(effective_mask);
out_free_new_mask:
        free_cpumask_var(new_mask);
out_free_cpus_allowed:
        free_cpumask_var(cpus_allowed);
out_put_task:
        put_task_struct(p);
        cpus_read_unlock();
        return retval;
}

/*
 * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
 */
asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
                                      unsigned long __user *user_mask_ptr)
{
        unsigned int real_len;
        cpumask_t allowed, mask;
        int retval;
        struct task_struct *p;

        real_len = sizeof(mask);
        if (len < real_len)
                return -EINVAL;

        cpus_read_lock();
        rcu_read_lock();

        retval = -ESRCH;
        p = find_process_by_pid(pid);
        if (!p)
                goto out_unlock;
        retval = security_task_getscheduler(p);
        if (retval)
                goto out_unlock;

        cpumask_or(&allowed, &p->thread.user_cpus_allowed, p->cpus_ptr);
        cpumask_and(&mask, &allowed, cpu_active_mask);

out_unlock:
        rcu_read_unlock();
        cpus_read_unlock();
        if (retval)
                return retval;
        if (copy_to_user(user_mask_ptr, &mask, real_len))
                return -EFAULT;
        return real_len;
}


static int __init fpaff_thresh(char *str)
{
        get_option(&str, &fpaff_threshold);
        return 1;
}
__setup("fpaff=", fpaff_thresh);

/*
 * FPU Use Factor empirically derived from experiments on 34K
 */
#define FPUSEFACTOR 2000

static __init int mt_fp_affinity_init(void)
{
        if (fpaff_threshold >= 0) {
                mt_fpemul_threshold = fpaff_threshold;
        } else {
                mt_fpemul_threshold =
                        (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
        }
        printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
               mt_fpemul_threshold);

        return 0;
}
arch_initcall(mt_fp_affinity_init);