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Linux/arch/openrisc/kernel/process.c

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  1 /*
  2  * OpenRISC process.c
  3  *
  4  * Linux architectural port borrowing liberally from similar works of
  5  * others.  All original copyrights apply as per the original source
  6  * declaration.
  7  *
  8  * Modifications for the OpenRISC architecture:
  9  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 11  *
 12  *      This program is free software; you can redistribute it and/or
 13  *      modify it under the terms of the GNU General Public License
 14  *      as published by the Free Software Foundation; either version
 15  *      2 of the License, or (at your option) any later version.
 16  *
 17  * This file handles the architecture-dependent parts of process handling...
 18  */
 19 
 20 #define __KERNEL_SYSCALLS__
 21 #include <stdarg.h>
 22 
 23 #include <linux/errno.h>
 24 #include <linux/sched.h>
 25 #include <linux/kernel.h>
 26 #include <linux/module.h>
 27 #include <linux/mm.h>
 28 #include <linux/stddef.h>
 29 #include <linux/unistd.h>
 30 #include <linux/ptrace.h>
 31 #include <linux/slab.h>
 32 #include <linux/elfcore.h>
 33 #include <linux/interrupt.h>
 34 #include <linux/delay.h>
 35 #include <linux/init_task.h>
 36 #include <linux/mqueue.h>
 37 #include <linux/fs.h>
 38 
 39 #include <linux/uaccess.h>
 40 #include <asm/pgtable.h>
 41 #include <asm/io.h>
 42 #include <asm/processor.h>
 43 #include <asm/spr_defs.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(void)
 55 {
 56         printk(KERN_INFO "*** MACHINE RESTART ***\n");
 57         __asm__("l.nop 1");
 58 }
 59 
 60 /*
 61  * Similar to machine_power_off, but don't shut off power.  Add code
 62  * here to freeze the system for e.g. post-mortem debug purpose when
 63  * possible.  This halt has nothing to do with the idle halt.
 64  */
 65 void machine_halt(void)
 66 {
 67         printk(KERN_INFO "*** MACHINE HALT ***\n");
 68         __asm__("l.nop 1");
 69 }
 70 
 71 /* If or when software power-off is implemented, add code here.  */
 72 void machine_power_off(void)
 73 {
 74         printk(KERN_INFO "*** MACHINE POWER OFF ***\n");
 75         __asm__("l.nop 1");
 76 }
 77 
 78 void (*pm_power_off) (void) = machine_power_off;
 79 
 80 /*
 81  * When a process does an "exec", machine state like FPU and debug
 82  * registers need to be reset.  This is a hook function for that.
 83  * Currently we don't have any such state to reset, so this is empty.
 84  */
 85 void flush_thread(void)
 86 {
 87 }
 88 
 89 void show_regs(struct pt_regs *regs)
 90 {
 91         extern void show_registers(struct pt_regs *regs);
 92 
 93         show_regs_print_info(KERN_DEFAULT);
 94         /* __PHX__ cleanup this mess */
 95         show_registers(regs);
 96 }
 97 
 98 unsigned long thread_saved_pc(struct task_struct *t)
 99 {
100         return (unsigned long)user_regs(t->stack)->pc;
101 }
102 
103 void release_thread(struct task_struct *dead_task)
104 {
105 }
106 
107 /*
108  * Copy the thread-specific (arch specific) info from the current
109  * process to the new one p
110  */
111 extern asmlinkage void ret_from_fork(void);
112 
113 /*
114  * copy_thread
115  * @clone_flags: flags
116  * @usp: user stack pointer or fn for kernel thread
117  * @arg: arg to fn for kernel thread; always NULL for userspace thread
118  * @p: the newly created task
119  * @regs: CPU context to copy for userspace thread; always NULL for kthread
120  *
121  * At the top of a newly initialized kernel stack are two stacked pt_reg
122  * structures.  The first (topmost) is the userspace context of the thread.
123  * The second is the kernelspace context of the thread.
124  *
125  * A kernel thread will not be returning to userspace, so the topmost pt_regs
126  * struct can be uninitialized; it _does_ need to exist, though, because
127  * a kernel thread can become a userspace thread by doing a kernel_execve, in
128  * which case the topmost context will be initialized and used for 'returning'
129  * to userspace.
130  *
131  * The second pt_reg struct needs to be initialized to 'return' to
132  * ret_from_fork.  A kernel thread will need to set r20 to the address of
133  * a function to call into (with arg in r22); userspace threads need to set
134  * r20 to NULL in which case ret_from_fork will just continue a return to
135  * userspace.
136  *
137  * A kernel thread 'fn' may return; this is effectively what happens when
138  * kernel_execve is called.  In that case, the userspace pt_regs must have
139  * been initialized (which kernel_execve takes care of, see start_thread
140  * below); ret_from_fork will then continue its execution causing the
141  * 'kernel thread' to return to userspace as a userspace thread.
142  */
143 
144 int
145 copy_thread(unsigned long clone_flags, unsigned long usp,
146             unsigned long arg, struct task_struct *p)
147 {
148         struct pt_regs *userregs;
149         struct pt_regs *kregs;
150         unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
151         unsigned long top_of_kernel_stack;
152 
153         top_of_kernel_stack = sp;
154 
155         p->set_child_tid = p->clear_child_tid = NULL;
156 
157         /* Locate userspace context on stack... */
158         sp -= STACK_FRAME_OVERHEAD;     /* redzone */
159         sp -= sizeof(struct pt_regs);
160         userregs = (struct pt_regs *) sp;
161 
162         /* ...and kernel context */
163         sp -= STACK_FRAME_OVERHEAD;     /* redzone */
164         sp -= sizeof(struct pt_regs);
165         kregs = (struct pt_regs *)sp;
166 
167         if (unlikely(p->flags & PF_KTHREAD)) {
168                 memset(kregs, 0, sizeof(struct pt_regs));
169                 kregs->gpr[20] = usp; /* fn, kernel thread */
170                 kregs->gpr[22] = arg;
171         } else {
172                 *userregs = *current_pt_regs();
173 
174                 if (usp)
175                         userregs->sp = usp;
176 
177                 /*
178                  * For CLONE_SETTLS set "tp" (r10) to the TLS pointer passed to sys_clone.
179                  *
180                  * The kernel entry is:
181                  *      int clone (long flags, void *child_stack, int *parent_tid,
182                  *              int *child_tid, struct void *tls)
183                  *
184                  * This makes the source r7 in the kernel registers.
185                  */
186                 if (clone_flags & CLONE_SETTLS)
187                         userregs->gpr[10] = userregs->gpr[7];
188 
189                 userregs->gpr[11] = 0;  /* Result from fork() */
190 
191                 kregs->gpr[20] = 0;     /* Userspace thread */
192         }
193 
194         /*
195          * _switch wants the kernel stack page in pt_regs->sp so that it
196          * can restore it to thread_info->ksp... see _switch for details.
197          */
198         kregs->sp = top_of_kernel_stack;
199         kregs->gpr[9] = (unsigned long)ret_from_fork;
200 
201         task_thread_info(p)->ksp = (unsigned long)kregs;
202 
203         return 0;
204 }
205 
206 /*
207  * Set up a thread for executing a new program
208  */
209 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
210 {
211         unsigned long sr = mfspr(SPR_SR) & ~SPR_SR_SM;
212 
213         memset(regs, 0, sizeof(struct pt_regs));
214 
215         regs->pc = pc;
216         regs->sr = sr;
217         regs->sp = sp;
218 }
219 
220 /* Fill in the fpu structure for a core dump.  */
221 int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
222 {
223         /* TODO */
224         return 0;
225 }
226 
227 extern struct thread_info *_switch(struct thread_info *old_ti,
228                                    struct thread_info *new_ti);
229 
230 struct task_struct *__switch_to(struct task_struct *old,
231                                 struct task_struct *new)
232 {
233         struct task_struct *last;
234         struct thread_info *new_ti, *old_ti;
235         unsigned long flags;
236 
237         local_irq_save(flags);
238 
239         /* current_set is an array of saved current pointers
240          * (one for each cpu). we need them at user->kernel transition,
241          * while we save them at kernel->user transition
242          */
243         new_ti = new->stack;
244         old_ti = old->stack;
245 
246         current_thread_info_set[smp_processor_id()] = new_ti;
247         last = (_switch(old_ti, new_ti))->task;
248 
249         local_irq_restore(flags);
250 
251         return last;
252 }
253 
254 /*
255  * Write out registers in core dump format, as defined by the
256  * struct user_regs_struct
257  */
258 void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
259 {
260         dest[0] = 0; /* r0 */
261         memcpy(dest+1, regs->gpr+1, 31*sizeof(unsigned long));
262         dest[32] = regs->pc;
263         dest[33] = regs->sr;
264         dest[34] = 0;
265         dest[35] = 0;
266 }
267 
268 unsigned long get_wchan(struct task_struct *p)
269 {
270         /* TODO */
271 
272         return 0;
273 }
274 

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