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 */
23 cpumask_t mt_fpu_cpumask;
24
25 static int fpaff_threshold = -1;
26 unsigned 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 */
42 static 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 */
50 static 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 */
66 asmlinkage 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 }
143 out_unlock:
144 free_cpumask_var(effective_mask);
145 out_free_new_mask:
146 free_cpumask_var(new_mask);
147 out_free_cpus_allowed:
148 free_cpumask_var(cpus_allowed);
149 out_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 */
158 asmlinkage 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
184 out_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
195 static 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
207 static __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 }
220 arch_initcall(mt_fp_affinity_init);
221
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.