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