arch/openrisc/kernel/process.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * OpenRISC process.c
   4  *
   5  * Linux architectural port borrowing liberally from similar works of
   6  * others.  All original copyrights apply as per the original source
   7  * declaration.
   8  *
   9  * Modifications for the OpenRISC architecture:
  10  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  11  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  12  *
  13  * This file handles the architecture-dependent parts of process handling...
  14  */
  15
  16 #define __KERNEL_SYSCALLS__
  17 #include <linux/cpu.h>
  18 #include <linux/errno.h>
  19 #include <linux/sched.h>
  20 #include <linux/sched/debug.h>
  21 #include <linux/sched/task.h>
  22 #include <linux/sched/task_stack.h>
  23 #include <linux/kernel.h>
  24 #include <linux/export.h>
  25 #include <linux/mm.h>
  26 #include <linux/stddef.h>
  27 #include <linux/unistd.h>
  28 #include <linux/ptrace.h>
  29 #include <linux/slab.h>
  30 #include <linux/elfcore.h>
  31 #include <linux/interrupt.h>
  32 #include <linux/delay.h>
  33 #include <linux/init_task.h>
  34 #include <linux/mqueue.h>
  35 #include <linux/fs.h>
  36 #include <linux/reboot.h>
  37
  38 #include <linux/uaccess.h>
  39 #include <asm/fpu.h>
  40 #include <asm/io.h>
  41 #include <asm/processor.h>
  42 #include <asm/spr_defs.h>
  43 #include <asm/switch_to.h>
  44
  45 #include <linux/smp.h>
  46
  47 /*
  48  * Pointer to Current thread info structure.
  49  *
  50  * Used at user space -> kernel transitions.
  51  */
  52 struct thread_info *current_thread_info_set[NR_CPUS] = { &init_thread_info, };
  53
  54 void machine_restart(char *cmd)
  55 {
  56         do_kernel_restart(cmd);
  57
  58         __asm__("l.nop 13");
  59
  60         /* Give a grace period for failure to restart of 1s */
  61         mdelay(1000);
  62
  63         /* Whoops - the platform was unable to reboot. Tell the user! */
  64         pr_emerg("Reboot failed -- System halted\n");
  65         while (1);
  66 }
  67
  68 /*
  69  * This is used if a sys-off handler was not set by a power management
  70  * driver, in this case we can assume we are on a simulator.  On
  71  * OpenRISC simulators l.nop 1 will trigger the simulator exit.
  72  */
  73 static void default_power_off(void)
  74 {
  75         __asm__("l.nop 1");
  76 }
  77
  78 /*
  79  * Similar to machine_power_off, but don't shut off power.  Add code
  80  * here to freeze the system for e.g. post-mortem debug purpose when
  81  * possible.  This halt has nothing to do with the idle halt.
  82  */
  83 void machine_halt(void)
  84 {
  85         printk(KERN_INFO "*** MACHINE HALT ***\n");
  86         __asm__("l.nop 1");
  87 }
  88
  89 /* If or when software power-off is implemented, add code here.  */
  90 void machine_power_off(void)
  91 {
  92         printk(KERN_INFO "*** MACHINE POWER OFF ***\n");
  93         do_kernel_power_off();
  94         default_power_off();
  95 }
  96
  97 /*
  98  * Send the doze signal to the cpu if available.
  99  * Make sure, that all interrupts are enabled
 100  */
 101 void arch_cpu_idle(void)
 102 {
 103         raw_local_irq_enable();
 104         if (mfspr(SPR_UPR) & SPR_UPR_PMP)
 105                 mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME);
 106         raw_local_irq_disable();
 107 }
 108
 109 void (*pm_power_off)(void) = NULL;
 110 EXPORT_SYMBOL(pm_power_off);
 111
 112 /*
 113  * When a process does an "exec", machine state like FPU and debug
 114  * registers need to be reset.  This is a hook function for that.
 115  * Currently we don't have any such state to reset, so this is empty.
 116  */
 117 void flush_thread(void)
 118 {
 119 }
 120
 121 void show_regs(struct pt_regs *regs)
 122 {
 123         show_regs_print_info(KERN_DEFAULT);
 124         /* __PHX__ cleanup this mess */
 125         show_registers(regs);
 126 }
 127
 128 /*
 129  * Copy the thread-specific (arch specific) info from the current
 130  * process to the new one p
 131  */
 132 extern asmlinkage void ret_from_fork(void);
 133
 134 /*
 135  * copy_thread
 136  * @clone_flags: flags
 137  * @usp: user stack pointer or fn for kernel thread
 138  * @arg: arg to fn for kernel thread; always NULL for userspace thread
 139  * @p: the newly created task
 140  * @tls: the Thread Local Storage pointer for the new process
 141  *
 142  * At the top of a newly initialized kernel stack are two stacked pt_reg
 143  * structures.  The first (topmost) is the userspace context of the thread.
 144  * The second is the kernelspace context of the thread.
 145  *
 146  * A kernel thread will not be returning to userspace, so the topmost pt_regs
 147  * struct can be uninitialized; it _does_ need to exist, though, because
 148  * a kernel thread can become a userspace thread by doing a kernel_execve, in
 149  * which case the topmost context will be initialized and used for 'returning'
 150  * to userspace.
 151  *
 152  * The second pt_reg struct needs to be initialized to 'return' to
 153  * ret_from_fork.  A kernel thread will need to set r20 to the address of
 154  * a function to call into (with arg in r22); userspace threads need to set
 155  * r20 to NULL in which case ret_from_fork will just continue a return to
 156  * userspace.
 157  *
 158  * A kernel thread 'fn' may return; this is effectively what happens when
 159  * kernel_execve is called.  In that case, the userspace pt_regs must have
 160  * been initialized (which kernel_execve takes care of, see start_thread
 161  * below); ret_from_fork will then continue its execution causing the
 162  * 'kernel thread' to return to userspace as a userspace thread.
 163  */
 164
 165 int
 166 copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 167 {
 168         unsigned long clone_flags = args->flags;
 169         unsigned long usp = args->stack;
 170         unsigned long tls = args->tls;
 171         struct pt_regs *userregs;
 172         struct pt_regs *kregs;
 173         unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 174         unsigned long top_of_kernel_stack;
 175
 176         top_of_kernel_stack = sp;
 177
 178         /* Locate userspace context on stack... */
 179         sp -= STACK_FRAME_OVERHEAD;     /* redzone */
 180         sp -= sizeof(struct pt_regs);
 181         userregs = (struct pt_regs *) sp;
 182
 183         /* ...and kernel context */
 184         sp -= STACK_FRAME_OVERHEAD;     /* redzone */
 185         sp -= sizeof(struct pt_regs);
 186         kregs = (struct pt_regs *)sp;
 187
 188         if (unlikely(args->fn)) {
 189                 memset(kregs, 0, sizeof(struct pt_regs));
 190                 kregs->gpr[20] = (unsigned long)args->fn;
 191                 kregs->gpr[22] = (unsigned long)args->fn_arg;
 192         } else {
 193                 *userregs = *current_pt_regs();
 194
 195                 if (usp)
 196                         userregs->sp = usp;
 197
 198                 /*
 199                  * For CLONE_SETTLS set "tp" (r10) to the TLS pointer.
 200                  */
 201                 if (clone_flags & CLONE_SETTLS)
 202                         userregs->gpr[10] = tls;
 203
 204                 userregs->gpr[11] = 0;  /* Result from fork() */
 205
 206                 kregs->gpr[20] = 0;     /* Userspace thread */
 207         }
 208
 209         /*
 210          * _switch wants the kernel stack page in pt_regs->sp so that it
 211          * can restore it to thread_info->ksp... see _switch for details.
 212          */
 213         kregs->sp = top_of_kernel_stack;
 214         kregs->gpr[9] = (unsigned long)ret_from_fork;
 215
 216         task_thread_info(p)->ksp = (unsigned long)kregs;
 217
 218         return 0;
 219 }
 220
 221 /*
 222  * Set up a thread for executing a new program
 223  */
 224 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
 225 {
 226         unsigned long sr = mfspr(SPR_SR) & ~SPR_SR_SM;
 227
 228         memset(regs, 0, sizeof(struct pt_regs));
 229
 230         regs->pc = pc;
 231         regs->sr = sr;
 232         regs->sp = sp;
 233 }
 234
 235 extern struct thread_info *_switch(struct thread_info *old_ti,
 236                                    struct thread_info *new_ti);
 237 extern int lwa_flag;
 238
 239 struct task_struct *__switch_to(struct task_struct *old,
 240                                 struct task_struct *new)
 241 {
 242         struct task_struct *last;
 243         struct thread_info *new_ti, *old_ti;
 244         unsigned long flags;
 245
 246         local_irq_save(flags);
 247
 248         save_fpu(current);
 249
 250         /* current_set is an array of saved current pointers
 251          * (one for each cpu). we need them at user->kernel transition,
 252          * while we save them at kernel->user transition
 253          */
 254         new_ti = new->stack;
 255         old_ti = old->stack;
 256
 257         lwa_flag = 0;
 258
 259         current_thread_info_set[smp_processor_id()] = new_ti;
 260         last = (_switch(old_ti, new_ti))->task;
 261
 262         restore_fpu(current);
 263
 264         local_irq_restore(flags);
 265
 266         return last;
 267 }
 268
 269 /*
 270  * Write out registers in core dump format, as defined by the
 271  * struct user_regs_struct
 272  */
 273 void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
 274 {
 275         dest[0] = 0; /* r0 */
 276         memcpy(dest+1, regs->gpr+1, 31*sizeof(unsigned long));
 277         dest[32] = regs->pc;
 278         dest[33] = regs->sr;
 279         dest[34] = 0;
 280         dest[35] = 0;
 281 }
 282
 283 unsigned long __get_wchan(struct task_struct *p)
 284 {
 285         /* TODO */
 286
 287         return 0;
 288 }