xref: /openbmc/linux/arch/openrisc/kernel/process.c (revision a36954f5)
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/sched/debug.h>
26 #include <linux/sched/task.h>
27 #include <linux/sched/task_stack.h>
28 #include <linux/kernel.h>
29 #include <linux/module.h>
30 #include <linux/mm.h>
31 #include <linux/stddef.h>
32 #include <linux/unistd.h>
33 #include <linux/ptrace.h>
34 #include <linux/slab.h>
35 #include <linux/elfcore.h>
36 #include <linux/interrupt.h>
37 #include <linux/delay.h>
38 #include <linux/init_task.h>
39 #include <linux/mqueue.h>
40 #include <linux/fs.h>
41 
42 #include <linux/uaccess.h>
43 #include <asm/pgtable.h>
44 #include <asm/io.h>
45 #include <asm/processor.h>
46 #include <asm/spr_defs.h>
47 
48 #include <linux/smp.h>
49 
50 /*
51  * Pointer to Current thread info structure.
52  *
53  * Used at user space -> kernel transitions.
54  */
55 struct thread_info *current_thread_info_set[NR_CPUS] = { &init_thread_info, };
56 
57 void machine_restart(void)
58 {
59 	printk(KERN_INFO "*** MACHINE RESTART ***\n");
60 	__asm__("l.nop 1");
61 }
62 
63 /*
64  * Similar to machine_power_off, but don't shut off power.  Add code
65  * here to freeze the system for e.g. post-mortem debug purpose when
66  * possible.  This halt has nothing to do with the idle halt.
67  */
68 void machine_halt(void)
69 {
70 	printk(KERN_INFO "*** MACHINE HALT ***\n");
71 	__asm__("l.nop 1");
72 }
73 
74 /* If or when software power-off is implemented, add code here.  */
75 void machine_power_off(void)
76 {
77 	printk(KERN_INFO "*** MACHINE POWER OFF ***\n");
78 	__asm__("l.nop 1");
79 }
80 
81 /*
82  * Send the doze signal to the cpu if available.
83  * Make sure, that all interrupts are enabled
84  */
85 void arch_cpu_idle(void)
86 {
87 	local_irq_enable();
88 	if (mfspr(SPR_UPR) & SPR_UPR_PMP)
89 		mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME);
90 }
91 
92 void (*pm_power_off) (void) = machine_power_off;
93 EXPORT_SYMBOL(pm_power_off);
94 
95 /*
96  * When a process does an "exec", machine state like FPU and debug
97  * registers need to be reset.  This is a hook function for that.
98  * Currently we don't have any such state to reset, so this is empty.
99  */
100 void flush_thread(void)
101 {
102 }
103 
104 void show_regs(struct pt_regs *regs)
105 {
106 	extern void show_registers(struct pt_regs *regs);
107 
108 	show_regs_print_info(KERN_DEFAULT);
109 	/* __PHX__ cleanup this mess */
110 	show_registers(regs);
111 }
112 
113 unsigned long thread_saved_pc(struct task_struct *t)
114 {
115 	return (unsigned long)user_regs(t->stack)->pc;
116 }
117 
118 void release_thread(struct task_struct *dead_task)
119 {
120 }
121 
122 /*
123  * Copy the thread-specific (arch specific) info from the current
124  * process to the new one p
125  */
126 extern asmlinkage void ret_from_fork(void);
127 
128 /*
129  * copy_thread
130  * @clone_flags: flags
131  * @usp: user stack pointer or fn for kernel thread
132  * @arg: arg to fn for kernel thread; always NULL for userspace thread
133  * @p: the newly created task
134  * @regs: CPU context to copy for userspace thread; always NULL for kthread
135  *
136  * At the top of a newly initialized kernel stack are two stacked pt_reg
137  * structures.  The first (topmost) is the userspace context of the thread.
138  * The second is the kernelspace context of the thread.
139  *
140  * A kernel thread will not be returning to userspace, so the topmost pt_regs
141  * struct can be uninitialized; it _does_ need to exist, though, because
142  * a kernel thread can become a userspace thread by doing a kernel_execve, in
143  * which case the topmost context will be initialized and used for 'returning'
144  * to userspace.
145  *
146  * The second pt_reg struct needs to be initialized to 'return' to
147  * ret_from_fork.  A kernel thread will need to set r20 to the address of
148  * a function to call into (with arg in r22); userspace threads need to set
149  * r20 to NULL in which case ret_from_fork will just continue a return to
150  * userspace.
151  *
152  * A kernel thread 'fn' may return; this is effectively what happens when
153  * kernel_execve is called.  In that case, the userspace pt_regs must have
154  * been initialized (which kernel_execve takes care of, see start_thread
155  * below); ret_from_fork will then continue its execution causing the
156  * 'kernel thread' to return to userspace as a userspace thread.
157  */
158 
159 int
160 copy_thread(unsigned long clone_flags, unsigned long usp,
161 	    unsigned long arg, struct task_struct *p)
162 {
163 	struct pt_regs *userregs;
164 	struct pt_regs *kregs;
165 	unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
166 	unsigned long top_of_kernel_stack;
167 
168 	top_of_kernel_stack = sp;
169 
170 	p->set_child_tid = p->clear_child_tid = NULL;
171 
172 	/* Locate userspace context on stack... */
173 	sp -= STACK_FRAME_OVERHEAD;	/* redzone */
174 	sp -= sizeof(struct pt_regs);
175 	userregs = (struct pt_regs *) sp;
176 
177 	/* ...and kernel context */
178 	sp -= STACK_FRAME_OVERHEAD;	/* redzone */
179 	sp -= sizeof(struct pt_regs);
180 	kregs = (struct pt_regs *)sp;
181 
182 	if (unlikely(p->flags & PF_KTHREAD)) {
183 		memset(kregs, 0, sizeof(struct pt_regs));
184 		kregs->gpr[20] = usp; /* fn, kernel thread */
185 		kregs->gpr[22] = arg;
186 	} else {
187 		*userregs = *current_pt_regs();
188 
189 		if (usp)
190 			userregs->sp = usp;
191 
192 		/*
193 		 * For CLONE_SETTLS set "tp" (r10) to the TLS pointer passed to sys_clone.
194 		 *
195 		 * The kernel entry is:
196 		 *	int clone (long flags, void *child_stack, int *parent_tid,
197 		 *		int *child_tid, struct void *tls)
198 		 *
199 		 * This makes the source r7 in the kernel registers.
200 		 */
201 		if (clone_flags & CLONE_SETTLS)
202 			userregs->gpr[10] = userregs->gpr[7];
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 /* Fill in the fpu structure for a core dump.  */
236 int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
237 {
238 	/* TODO */
239 	return 0;
240 }
241 
242 extern struct thread_info *_switch(struct thread_info *old_ti,
243 				   struct thread_info *new_ti);
244 extern int lwa_flag;
245 
246 struct task_struct *__switch_to(struct task_struct *old,
247 				struct task_struct *new)
248 {
249 	struct task_struct *last;
250 	struct thread_info *new_ti, *old_ti;
251 	unsigned long flags;
252 
253 	local_irq_save(flags);
254 
255 	/* current_set is an array of saved current pointers
256 	 * (one for each cpu). we need them at user->kernel transition,
257 	 * while we save them at kernel->user transition
258 	 */
259 	new_ti = new->stack;
260 	old_ti = old->stack;
261 
262 	lwa_flag = 0;
263 
264 	current_thread_info_set[smp_processor_id()] = new_ti;
265 	last = (_switch(old_ti, new_ti))->task;
266 
267 	local_irq_restore(flags);
268 
269 	return last;
270 }
271 
272 /*
273  * Write out registers in core dump format, as defined by the
274  * struct user_regs_struct
275  */
276 void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
277 {
278 	dest[0] = 0; /* r0 */
279 	memcpy(dest+1, regs->gpr+1, 31*sizeof(unsigned long));
280 	dest[32] = regs->pc;
281 	dest[33] = regs->sr;
282 	dest[34] = 0;
283 	dest[35] = 0;
284 }
285 
286 unsigned long get_wchan(struct task_struct *p)
287 {
288 	/* TODO */
289 
290 	return 0;
291 }
292