xref: /linux/arch/openrisc/kernel/process.c (revision b889fcf63cb62e7fdb7816565e28f44dbe4a76a5)
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 <asm/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 	/* __PHX__ cleanup this mess */
94 	show_registers(regs);
95 }
96 
97 unsigned long thread_saved_pc(struct task_struct *t)
98 {
99 	return (unsigned long)user_regs(t->stack)->pc;
100 }
101 
102 void release_thread(struct task_struct *dead_task)
103 {
104 }
105 
106 /*
107  * Copy the thread-specific (arch specific) info from the current
108  * process to the new one p
109  */
110 extern asmlinkage void ret_from_fork(void);
111 
112 /*
113  * copy_thread
114  * @clone_flags: flags
115  * @usp: user stack pointer or fn for kernel thread
116  * @arg: arg to fn for kernel thread; always NULL for userspace thread
117  * @p: the newly created task
118  * @regs: CPU context to copy for userspace thread; always NULL for kthread
119  *
120  * At the top of a newly initialized kernel stack are two stacked pt_reg
121  * structures.  The first (topmost) is the userspace context of the thread.
122  * The second is the kernelspace context of the thread.
123  *
124  * A kernel thread will not be returning to userspace, so the topmost pt_regs
125  * struct can be uninitialized; it _does_ need to exist, though, because
126  * a kernel thread can become a userspace thread by doing a kernel_execve, in
127  * which case the topmost context will be initialized and used for 'returning'
128  * to userspace.
129  *
130  * The second pt_reg struct needs to be initialized to 'return' to
131  * ret_from_fork.  A kernel thread will need to set r20 to the address of
132  * a function to call into (with arg in r22); userspace threads need to set
133  * r20 to NULL in which case ret_from_fork will just continue a return to
134  * userspace.
135  *
136  * A kernel thread 'fn' may return; this is effectively what happens when
137  * kernel_execve is called.  In that case, the userspace pt_regs must have
138  * been initialized (which kernel_execve takes care of, see start_thread
139  * below); ret_from_fork will then continue its execution causing the
140  * 'kernel thread' to return to userspace as a userspace thread.
141  */
142 
143 int
144 copy_thread(unsigned long clone_flags, unsigned long usp,
145 	    unsigned long arg, struct task_struct *p)
146 {
147 	struct pt_regs *userregs;
148 	struct pt_regs *kregs;
149 	unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
150 	unsigned long top_of_kernel_stack;
151 
152 	top_of_kernel_stack = sp;
153 
154 	p->set_child_tid = p->clear_child_tid = NULL;
155 
156 	/* Locate userspace context on stack... */
157 	sp -= STACK_FRAME_OVERHEAD;	/* redzone */
158 	sp -= sizeof(struct pt_regs);
159 	userregs = (struct pt_regs *) sp;
160 
161 	/* ...and kernel context */
162 	sp -= STACK_FRAME_OVERHEAD;	/* redzone */
163 	sp -= sizeof(struct pt_regs);
164 	kregs = (struct pt_regs *)sp;
165 
166 	if (unlikely(p->flags & PF_KTHREAD)) {
167 		memset(kregs, 0, sizeof(struct pt_regs));
168 		kregs->gpr[20] = usp; /* fn, kernel thread */
169 		kregs->gpr[22] = arg;
170 	} else {
171 		*userregs = *current_pt_regs();
172 
173 		if (usp)
174 			userregs->sp = usp;
175 		userregs->gpr[11] = 0;	/* Result from fork() */
176 
177 		kregs->gpr[20] = 0;	/* Userspace thread */
178 	}
179 
180 	/*
181 	 * _switch wants the kernel stack page in pt_regs->sp so that it
182 	 * can restore it to thread_info->ksp... see _switch for details.
183 	 */
184 	kregs->sp = top_of_kernel_stack;
185 	kregs->gpr[9] = (unsigned long)ret_from_fork;
186 
187 	task_thread_info(p)->ksp = (unsigned long)kregs;
188 
189 	return 0;
190 }
191 
192 /*
193  * Set up a thread for executing a new program
194  */
195 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
196 {
197 	unsigned long sr = mfspr(SPR_SR) & ~SPR_SR_SM;
198 
199 	set_fs(USER_DS);
200 	memset(regs, 0, sizeof(struct pt_regs));
201 
202 	regs->pc = pc;
203 	regs->sr = sr;
204 	regs->sp = sp;
205 }
206 
207 /* Fill in the fpu structure for a core dump.  */
208 int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
209 {
210 	/* TODO */
211 	return 0;
212 }
213 
214 extern struct thread_info *_switch(struct thread_info *old_ti,
215 				   struct thread_info *new_ti);
216 
217 struct task_struct *__switch_to(struct task_struct *old,
218 				struct task_struct *new)
219 {
220 	struct task_struct *last;
221 	struct thread_info *new_ti, *old_ti;
222 	unsigned long flags;
223 
224 	local_irq_save(flags);
225 
226 	/* current_set is an array of saved current pointers
227 	 * (one for each cpu). we need them at user->kernel transition,
228 	 * while we save them at kernel->user transition
229 	 */
230 	new_ti = new->stack;
231 	old_ti = old->stack;
232 
233 	current_thread_info_set[smp_processor_id()] = new_ti;
234 	last = (_switch(old_ti, new_ti))->task;
235 
236 	local_irq_restore(flags);
237 
238 	return last;
239 }
240 
241 /*
242  * Write out registers in core dump format, as defined by the
243  * struct user_regs_struct
244  */
245 void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
246 {
247 	dest[0] = 0; /* r0 */
248 	memcpy(dest+1, regs->gpr+1, 31*sizeof(unsigned long));
249 	dest[32] = regs->pc;
250 	dest[33] = regs->sr;
251 	dest[34] = 0;
252 	dest[35] = 0;
253 }
254 
255 unsigned long get_wchan(struct task_struct *p)
256 {
257 	/* TODO */
258 
259 	return 0;
260 }
261