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 <stdarg.h>
  18
  19 #include <linux/errno.h>
  20 #include <linux/sched.h>
  21 #include <linux/sched/debug.h>
  22 #include <linux/sched/task.h>
  23 #include <linux/sched/task_stack.h>
  24 #include <linux/kernel.h>
  25 #include <linux/export.h>
  26 #include <linux/mm.h>
  27 #include <linux/stddef.h>
  28 #include <linux/unistd.h>
  29 #include <linux/ptrace.h>
  30 #include <linux/slab.h>
  31 #include <linux/elfcore.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/delay.h>
  34 #include <linux/init_task.h>
  35 #include <linux/mqueue.h>
  36 #include <linux/fs.h>
  37
  38 #include <linux/uaccess.h>
  39 #include <asm/pgtable.h>
  40 #include <asm/io.h>
  41 #include <asm/processor.h>
  42 #include <asm/spr_defs.h>
  43
  44 #include <linux/smp.h>
  45
  46 /*
  47  * Pointer to Current thread info structure.
  48  *
  49  * Used at user space -> kernel transitions.
  50  */
  51 struct thread_info *current_thread_info_set[NR_CPUS] = { &init_thread_info, };
  52
  53 void machine_restart(void)
  54 {
  55         printk(KERN_INFO "*** MACHINE RESTART ***\n");
  56         __asm__("l.nop 1");
  57 }
  58
  59 /*
  60  * Similar to machine_power_off, but don't shut off power.  Add code
  61  * here to freeze the system for e.g. post-mortem debug purpose when
  62  * possible.  This halt has nothing to do with the idle halt.
  63  */
  64 void machine_halt(void)
  65 {
  66         printk(KERN_INFO "*** MACHINE HALT ***\n");
  67         __asm__("l.nop 1");
  68 }
  69
  70 /* If or when software power-off is implemented, add code here.  */
  71 void machine_power_off(void)
  72 {
  73         printk(KERN_INFO "*** MACHINE POWER OFF ***\n");
  74         __asm__("l.nop 1");
  75 }
  76
  77 /*
  78  * Send the doze signal to the cpu if available.
  79  * Make sure, that all interrupts are enabled
  80  */
  81 void arch_cpu_idle(void)
  82 {
  83         local_irq_enable();
  84         if (mfspr(SPR_UPR) & SPR_UPR_PMP)
  85                 mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME);
  86 }
  87
  88 void (*pm_power_off) (void) = machine_power_off;
  89 EXPORT_SYMBOL(pm_power_off);
  90
  91 /*
  92  * When a process does an "exec", machine state like FPU and debug
  93  * registers need to be reset.  This is a hook function for that.
  94  * Currently we don't have any such state to reset, so this is empty.
  95  */
  96 void flush_thread(void)
  97 {
  98 }
  99
 100 void show_regs(struct pt_regs *regs)
 101 {
 102         extern void show_registers(struct pt_regs *regs);
 103
 104         show_regs_print_info(KERN_DEFAULT);
 105         /* __PHX__ cleanup this mess */
 106         show_registers(regs);
 107 }
 108
 109 void release_thread(struct task_struct *dead_task)
 110 {
 111 }
 112
 113 /*
 114  * Copy the thread-specific (arch specific) info from the current
 115  * process to the new one p
 116  */
 117 extern asmlinkage void ret_from_fork(void);
 118
 119 /*
 120  * copy_thread
 121  * @clone_flags: flags
 122  * @usp: user stack pointer or fn for kernel thread
 123  * @arg: arg to fn for kernel thread; always NULL for userspace thread
 124  * @p: the newly created task
 125  * @regs: CPU context to copy for userspace thread; always NULL for kthread
 126  *
 127  * At the top of a newly initialized kernel stack are two stacked pt_reg
 128  * structures.  The first (topmost) is the userspace context of the thread.
 129  * The second is the kernelspace context of the thread.
 130  *
 131  * A kernel thread will not be returning to userspace, so the topmost pt_regs
 132  * struct can be uninitialized; it _does_ need to exist, though, because
 133  * a kernel thread can become a userspace thread by doing a kernel_execve, in
 134  * which case the topmost context will be initialized and used for 'returning'
 135  * to userspace.
 136  *
 137  * The second pt_reg struct needs to be initialized to 'return' to
 138  * ret_from_fork.  A kernel thread will need to set r20 to the address of
 139  * a function to call into (with arg in r22); userspace threads need to set
 140  * r20 to NULL in which case ret_from_fork will just continue a return to
 141  * userspace.
 142  *
 143  * A kernel thread 'fn' may return; this is effectively what happens when
 144  * kernel_execve is called.  In that case, the userspace pt_regs must have
 145  * been initialized (which kernel_execve takes care of, see start_thread
 146  * below); ret_from_fork will then continue its execution causing the
 147  * 'kernel thread' to return to userspace as a userspace thread.
 148  */
 149
 150 int
 151 copy_thread(unsigned long clone_flags, unsigned long usp,
 152             unsigned long arg, struct task_struct *p)
 153 {
 154         struct pt_regs *userregs;
 155         struct pt_regs *kregs;
 156         unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 157         unsigned long top_of_kernel_stack;
 158
 159         top_of_kernel_stack = sp;
 160
 161         /* Locate userspace context on stack... */
 162         sp -= STACK_FRAME_OVERHEAD;     /* redzone */
 163         sp -= sizeof(struct pt_regs);
 164         userregs = (struct pt_regs *) sp;
 165
 166         /* ...and kernel context */
 167         sp -= STACK_FRAME_OVERHEAD;     /* redzone */
 168         sp -= sizeof(struct pt_regs);
 169         kregs = (struct pt_regs *)sp;
 170
 171         if (unlikely(p->flags & PF_KTHREAD)) {
 172                 memset(kregs, 0, sizeof(struct pt_regs));
 173                 kregs->gpr[20] = usp; /* fn, kernel thread */
 174                 kregs->gpr[22] = arg;
 175         } else {
 176                 *userregs = *current_pt_regs();
 177
 178                 if (usp)
 179                         userregs->sp = usp;
 180
 181                 /*
 182                  * For CLONE_SETTLS set "tp" (r10) to the TLS pointer passed to sys_clone.
 183                  *
 184                  * The kernel entry is:
 185                  *      int clone (long flags, void *child_stack, int *parent_tid,
 186                  *              int *child_tid, struct void *tls)
 187                  *
 188                  * This makes the source r7 in the kernel registers.
 189                  */
 190                 if (clone_flags & CLONE_SETTLS)
 191                         userregs->gpr[10] = userregs->gpr[7];
 192
 193                 userregs->gpr[11] = 0;  /* Result from fork() */
 194
 195                 kregs->gpr[20] = 0;     /* Userspace thread */
 196         }
 197
 198         /*
 199          * _switch wants the kernel stack page in pt_regs->sp so that it
 200          * can restore it to thread_info->ksp... see _switch for details.
 201          */
 202         kregs->sp = top_of_kernel_stack;
 203         kregs->gpr[9] = (unsigned long)ret_from_fork;
 204
 205         task_thread_info(p)->ksp = (unsigned long)kregs;
 206
 207         return 0;
 208 }
 209
 210 /*
 211  * Set up a thread for executing a new program
 212  */
 213 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
 214 {
 215         unsigned long sr = mfspr(SPR_SR) & ~SPR_SR_SM;
 216
 217         memset(regs, 0, sizeof(struct pt_regs));
 218
 219         regs->pc = pc;
 220         regs->sr = sr;
 221         regs->sp = sp;
 222 }
 223
 224 /* Fill in the fpu structure for a core dump.  */
 225 int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
 226 {
 227         /* TODO */
 228         return 0;
 229 }
 230
 231 extern struct thread_info *_switch(struct thread_info *old_ti,
 232                                    struct thread_info *new_ti);
 233 extern int lwa_flag;
 234
 235 struct task_struct *__switch_to(struct task_struct *old,
 236                                 struct task_struct *new)
 237 {
 238         struct task_struct *last;
 239         struct thread_info *new_ti, *old_ti;
 240         unsigned long flags;
 241
 242         local_irq_save(flags);
 243
 244         /* current_set is an array of saved current pointers
 245          * (one for each cpu). we need them at user->kernel transition,
 246          * while we save them at kernel->user transition
 247          */
 248         new_ti = new->stack;
 249         old_ti = old->stack;
 250
 251         lwa_flag = 0;
 252
 253         current_thread_info_set[smp_processor_id()] = new_ti;
 254         last = (_switch(old_ti, new_ti))->task;
 255
 256         local_irq_restore(flags);
 257
 258         return last;
 259 }
 260
 261 /*
 262  * Write out registers in core dump format, as defined by the
 263  * struct user_regs_struct
 264  */
 265 void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
 266 {
 267         dest[0] = 0; /* r0 */
 268         memcpy(dest+1, regs->gpr+1, 31*sizeof(unsigned long));
 269         dest[32] = regs->pc;
 270         dest[33] = regs->sr;
 271         dest[34] = 0;
 272         dest[35] = 0;
 273 }
 274
 275 unsigned long get_wchan(struct task_struct *p)
 276 {
 277         /* TODO */
 278
 279         return 0;
 280 }