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Linux/arch/openrisc/kernel/process.c

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  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 }
281 

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