1// SPDX-License-Identifier: GPL-2.0
2/*
3 * General MIPS MT support routines, usable in AP/SP and SMVP.
4 * Copyright (C) 2005 Mips Technologies, Inc
5 */
6#include <linux/cpu.h>
7#include <linux/cpuset.h>
8#include <linux/cpumask.h>
9#include <linux/delay.h>
10#include <linux/kernel.h>
11#include <linux/init.h>
12#include <linux/sched.h>
13#include <linux/sched/task.h>
14#include <linux/cred.h>
15#include <linux/security.h>
16#include <linux/types.h>
17#include <linux/uaccess.h>
18#include <asm/syscalls.h>
19
20/*
21 * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
22 */
23cpumask_t mt_fpu_cpumask;
24
25static int fpaff_threshold = -1;
26unsigned long mt_fpemul_threshold;
27
28/*
29 * Replacement functions for the sys_sched_setaffinity() and
30 * sys_sched_getaffinity() system calls, so that we can integrate
31 * FPU affinity with the user's requested processor affinity.
32 * This code is 98% identical with the sys_sched_setaffinity()
33 * and sys_sched_getaffinity() system calls, and should be
34 * updated when kernel/sched/core.c changes.
35 */
36
37/*
38 * find_process_by_pid - find a process with a matching PID value.
39 * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
40 * cloned here.
41 */
42static inline struct task_struct *find_process_by_pid(pid_t pid)
43{
44	return pid ? find_task_by_vpid(pid) : current;
45}
46
47/*
48 * check the target process has a UID that matches the current process's
49 */
50static bool check_same_owner(struct task_struct *p)
51{
52	const struct cred *cred = current_cred(), *pcred;
53	bool match;
54
55	rcu_read_lock();
56	pcred = __task_cred(p);
57	match = (uid_eq(cred->euid, pcred->euid) ||
58		 uid_eq(cred->euid, pcred->uid));
59	rcu_read_unlock();
60	return match;
61}
62
63/*
64 * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
65 */
66asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
67				      unsigned long __user *user_mask_ptr)
68{
69	cpumask_var_t cpus_allowed, new_mask, effective_mask;
70	struct thread_info *ti;
71	struct task_struct *p;
72	int retval;
73
74	if (len < sizeof(new_mask))
75		return -EINVAL;
76
77	if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
78		return -EFAULT;
79
80	cpus_read_lock();
81	rcu_read_lock();
82
83	p = find_process_by_pid(pid);
84	if (!p) {
85		rcu_read_unlock();
86		cpus_read_unlock();
87		return -ESRCH;
88	}
89
90	/* Prevent p going away */
91	get_task_struct(p);
92	rcu_read_unlock();
93
94	if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
95		retval = -ENOMEM;
96		goto out_put_task;
97	}
98	if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
99		retval = -ENOMEM;
100		goto out_free_cpus_allowed;
101	}
102	if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
103		retval = -ENOMEM;
104		goto out_free_new_mask;
105	}
106	if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) {
107		retval = -EPERM;
108		goto out_unlock;
109	}
110
111	retval = security_task_setscheduler(p);
112	if (retval)
113		goto out_unlock;
114
115	/* Record new user-specified CPU set for future reference */
116	cpumask_copy(&p->thread.user_cpus_allowed, new_mask);
117
118 again:
119	/* Compute new global allowed CPU set if necessary */
120	ti = task_thread_info(p);
121	if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
122	    cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
123		cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
124		retval = set_cpus_allowed_ptr(p, effective_mask);
125	} else {
126		cpumask_copy(effective_mask, new_mask);
127		clear_ti_thread_flag(ti, TIF_FPUBOUND);
128		retval = set_cpus_allowed_ptr(p, new_mask);
129	}
130
131	if (!retval) {
132		cpuset_cpus_allowed(p, cpus_allowed);
133		if (!cpumask_subset(effective_mask, cpus_allowed)) {
134			/*
135			 * We must have raced with a concurrent cpuset
136			 * update. Just reset the cpus_allowed to the
137			 * cpuset's cpus_allowed
138			 */
139			cpumask_copy(new_mask, cpus_allowed);
140			goto again;
141		}
142	}
143out_unlock:
144	free_cpumask_var(effective_mask);
145out_free_new_mask:
146	free_cpumask_var(new_mask);
147out_free_cpus_allowed:
148	free_cpumask_var(cpus_allowed);
149out_put_task:
150	put_task_struct(p);
151	cpus_read_unlock();
152	return retval;
153}
154
155/*
156 * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
157 */
158asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
159				      unsigned long __user *user_mask_ptr)
160{
161	unsigned int real_len;
162	cpumask_t allowed, mask;
163	int retval;
164	struct task_struct *p;
165
166	real_len = sizeof(mask);
167	if (len < real_len)
168		return -EINVAL;
169
170	cpus_read_lock();
171	rcu_read_lock();
172
173	retval = -ESRCH;
174	p = find_process_by_pid(pid);
175	if (!p)
176		goto out_unlock;
177	retval = security_task_getscheduler(p);
178	if (retval)
179		goto out_unlock;
180
181	cpumask_or(&allowed, &p->thread.user_cpus_allowed, p->cpus_ptr);
182	cpumask_and(&mask, &allowed, cpu_active_mask);
183
184out_unlock:
185	rcu_read_unlock();
186	cpus_read_unlock();
187	if (retval)
188		return retval;
189	if (copy_to_user(user_mask_ptr, &mask, real_len))
190		return -EFAULT;
191	return real_len;
192}
193
194
195static int __init fpaff_thresh(char *str)
196{
197	get_option(&str, &fpaff_threshold);
198	return 1;
199}
200__setup("fpaff=", fpaff_thresh);
201
202/*
203 * FPU Use Factor empirically derived from experiments on 34K
204 */
205#define FPUSEFACTOR 2000
206
207static __init int mt_fp_affinity_init(void)
208{
209	if (fpaff_threshold >= 0) {
210		mt_fpemul_threshold = fpaff_threshold;
211	} else {
212		mt_fpemul_threshold =
213			(FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
214	}
215	printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
216	       mt_fpemul_threshold);
217
218	return 0;
219}
220arch_initcall(mt_fp_affinity_init);
221