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-rw-r--r--arch/hexagon/kernel/process.c279
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diff --git a/arch/hexagon/kernel/process.c b/arch/hexagon/kernel/process.c
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1/*
2 * Process creation support for Hexagon
3 *
4 * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 and
8 * only version 2 as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 * 02110-1301, USA.
19 */
20
21#include <linux/sched.h>
22#include <linux/types.h>
23#include <linux/module.h>
24#include <linux/tick.h>
25#include <linux/uaccess.h>
26#include <linux/slab.h>
27
28/*
29 * Kernel thread creation. The desired kernel function is "wrapped"
30 * in the kernel_thread_helper function, which does cleanup
31 * afterwards.
32 */
33static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
34{
35 do_exit(fn(arg));
36}
37
38int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
39{
40 struct pt_regs regs;
41
42 memset(&regs, 0, sizeof(regs));
43 /*
44 * Yes, we're exploting illicit knowledge of the ABI here.
45 */
46 regs.r00 = (unsigned long) arg;
47 regs.r01 = (unsigned long) fn;
48 pt_set_elr(&regs, (unsigned long)kernel_thread_helper);
49 pt_set_kmode(&regs);
50
51 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
52}
53EXPORT_SYMBOL(kernel_thread);
54
55/*
56 * Program thread launch. Often defined as a macro in processor.h,
57 * but we're shooting for a small footprint and it's not an inner-loop
58 * performance-critical operation.
59 *
60 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
61 * so that gets automatically done here. If we ever stop doing that here,
62 * we'll probably want to define the ELF_PLAT_INIT macro.
63 */
64void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
65{
66 /* Set to run with user-mode data segmentation */
67 set_fs(USER_DS);
68 /* We want to zero all data-containing registers. Is this overkill? */
69 memset(regs, 0, sizeof(*regs));
70 /* We might want to also zero all Processor registers here */
71 pt_set_usermode(regs);
72 pt_set_elr(regs, pc);
73 pt_set_rte_sp(regs, sp);
74}
75
76/*
77 * Spin, or better still, do a hardware or VM wait instruction
78 * If hardware or VM offer wait termination even though interrupts
79 * are disabled.
80 */
81static void default_idle(void)
82{
83 __vmwait();
84}
85
86void (*idle_sleep)(void) = default_idle;
87
88void cpu_idle(void)
89{
90 while (1) {
91 tick_nohz_stop_sched_tick(1);
92 local_irq_disable();
93 while (!need_resched()) {
94 idle_sleep();
95 /* interrupts wake us up, but aren't serviced */
96 local_irq_enable(); /* service interrupt */
97 local_irq_disable();
98 }
99 local_irq_enable();
100 tick_nohz_restart_sched_tick();
101 schedule();
102 }
103}
104
105/*
106 * Return saved PC of a blocked thread
107 */
108unsigned long thread_saved_pc(struct task_struct *tsk)
109{
110 return 0;
111}
112
113/*
114 * Copy architecture-specific thread state
115 */
116int copy_thread(unsigned long clone_flags, unsigned long usp,
117 unsigned long unused, struct task_struct *p,
118 struct pt_regs *regs)
119{
120 struct thread_info *ti = task_thread_info(p);
121 struct hexagon_switch_stack *ss;
122 struct pt_regs *childregs;
123 asmlinkage void ret_from_fork(void);
124
125 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
126 sizeof(*childregs));
127
128 memcpy(childregs, regs, sizeof(*childregs));
129 ti->regs = childregs;
130
131 /*
132 * Establish kernel stack pointer and initial PC for new thread
133 */
134 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
135 sizeof(*ss));
136 ss->lr = (unsigned long)ret_from_fork;
137 p->thread.switch_sp = ss;
138
139 /* If User mode thread, set pt_reg stack pointer as per parameter */
140 if (user_mode(childregs)) {
141 pt_set_rte_sp(childregs, usp);
142
143 /* Child sees zero return value */
144 childregs->r00 = 0;
145
146 /*
147 * The clone syscall has the C signature:
148 * int [r0] clone(int flags [r0],
149 * void *child_frame [r1],
150 * void *parent_tid [r2],
151 * void *child_tid [r3],
152 * void *thread_control_block [r4]);
153 * ugp is used to provide TLS support.
154 */
155 if (clone_flags & CLONE_SETTLS)
156 childregs->ugp = childregs->r04;
157
158 /*
159 * Parent sees new pid -- not necessary, not even possible at
160 * this point in the fork process
161 * Might also want to set things like ti->addr_limit
162 */
163 } else {
164 /*
165 * If kernel thread, resume stack is kernel stack base.
166 * Note that this is pointer arithmetic on pt_regs *
167 */
168 pt_set_rte_sp(childregs, (unsigned long)(childregs + 1));
169 /*
170 * We need the current thread_info fast path pointer
171 * set up in pt_regs. The register to be used is
172 * parametric for assembler code, but the mechanism
173 * doesn't drop neatly into C. Needs to be fixed.
174 */
175 childregs->THREADINFO_REG = (unsigned long) ti;
176 }
177
178 /*
179 * thread_info pointer is pulled out of task_struct "stack"
180 * field on switch_to.
181 */
182 p->stack = (void *)ti;
183
184 return 0;
185}
186
187/*
188 * Release any architecture-specific resources locked by thread
189 */
190void release_thread(struct task_struct *dead_task)
191{
192}
193
194/*
195 * Free any architecture-specific thread data structures, etc.
196 */
197void exit_thread(void)
198{
199}
200
201/*
202 * Some archs flush debug and FPU info here
203 */
204void flush_thread(void)
205{
206}
207
208/*
209 * The "wait channel" terminology is archaic, but what we want
210 * is an identification of the point at which the scheduler
211 * was invoked by a blocked thread.
212 */
213unsigned long get_wchan(struct task_struct *p)
214{
215 unsigned long fp, pc;
216 unsigned long stack_page;
217 int count = 0;
218 if (!p || p == current || p->state == TASK_RUNNING)
219 return 0;
220
221 stack_page = (unsigned long)task_stack_page(p);
222 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
223 do {
224 if (fp < (stack_page + sizeof(struct thread_info)) ||
225 fp >= (THREAD_SIZE - 8 + stack_page))
226 return 0;
227 pc = ((unsigned long *)fp)[1];
228 if (!in_sched_functions(pc))
229 return pc;
230 fp = *(unsigned long *) fp;
231 } while (count++ < 16);
232
233 return 0;
234}
235
236/*
237 * Borrowed from PowerPC -- basically allow smaller kernel stacks if we
238 * go crazy with the page sizes.
239 */
240#if THREAD_SHIFT < PAGE_SHIFT
241
242static struct kmem_cache *thread_info_cache;
243
244struct thread_info *alloc_thread_info_node(struct task_struct *tsk, int node)
245{
246 struct thread_info *ti;
247
248 ti = kmem_cache_alloc_node(thread_info_cache, GFP_KERNEL, node);
249 if (unlikely(ti == NULL))
250 return NULL;
251#ifdef CONFIG_DEBUG_STACK_USAGE
252 memset(ti, 0, THREAD_SIZE);
253#endif
254 return ti;
255}
256
257void free_thread_info(struct thread_info *ti)
258{
259 kmem_cache_free(thread_info_cache, ti);
260}
261
262/* Weak symbol; called by init/main.c */
263
264void thread_info_cache_init(void)
265{
266 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
267 THREAD_SIZE, 0, NULL);
268 BUG_ON(thread_info_cache == NULL);
269}
270
271#endif /* THREAD_SHIFT < PAGE_SHIFT */
272
273/*
274 * Required placeholder.
275 */
276int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
277{
278 return 0;
279}