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