1/*
2 * Process creation support for Hexagon
3 *
4 * Copyright (c) 2010-2012, The Linux Foundation. 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#include <linux/tracehook.h>
28
29/*
30 * Program thread launch.  Often defined as a macro in processor.h,
31 * but we're shooting for a small footprint and it's not an inner-loop
32 * performance-critical operation.
33 *
34 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
35 * so that gets automatically done here.  If we ever stop doing that here,
36 * we'll probably want to define the ELF_PLAT_INIT macro.
37 */
38void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
39{
40	/* We want to zero all data-containing registers. Is this overkill? */
41	memset(regs, 0, sizeof(*regs));
42	/* We might want to also zero all Processor registers here */
43	pt_set_usermode(regs);
44	pt_set_elr(regs, pc);
45	pt_set_rte_sp(regs, sp);
46}
47
48/*
49 *  Spin, or better still, do a hardware or VM wait instruction
50 *  If hardware or VM offer wait termination even though interrupts
51 *  are disabled.
52 */
53void arch_cpu_idle(void)
54{
55	__vmwait();
56	/*  interrupts wake us up, but irqs are still disabled */
57	local_irq_enable();
58}
59
60/*
61 *  Return saved PC of a blocked thread
62 */
63unsigned long thread_saved_pc(struct task_struct *tsk)
64{
65	return 0;
66}
67
68/*
69 * Copy architecture-specific thread state
70 */
71int copy_thread(unsigned long clone_flags, unsigned long usp,
72		unsigned long arg, struct task_struct *p)
73{
74	struct thread_info *ti = task_thread_info(p);
75	struct hexagon_switch_stack *ss;
76	struct pt_regs *childregs;
77	asmlinkage void ret_from_fork(void);
78
79	childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
80					sizeof(*childregs));
81
82	ti->regs = childregs;
83
84	/*
85	 * Establish kernel stack pointer and initial PC for new thread
86	 * Note that unlike the usual situation, we do not copy the
87	 * parent's callee-saved here; those are in pt_regs and whatever
88	 * we leave here will be overridden on return to userland.
89	 */
90	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
91						    sizeof(*ss));
92	ss->lr = (unsigned long)ret_from_fork;
93	p->thread.switch_sp = ss;
94	if (unlikely(p->flags & PF_KTHREAD)) {
95		memset(childregs, 0, sizeof(struct pt_regs));
96		/* r24 <- fn, r25 <- arg */
97		ss->r24 = usp;
98		ss->r25 = arg;
99		pt_set_kmode(childregs);
100		return 0;
101	}
102	memcpy(childregs, current_pt_regs(), sizeof(*childregs));
103	ss->r2524 = 0;
104
105	if (usp)
106		pt_set_rte_sp(childregs, usp);
107
108	/* Child sees zero return value */
109	childregs->r00 = 0;
110
111	/*
112	 * The clone syscall has the C signature:
113	 * int [r0] clone(int flags [r0],
114	 *           void *child_frame [r1],
115	 *           void *parent_tid [r2],
116	 *           void *child_tid [r3],
117	 *           void *thread_control_block [r4]);
118	 * ugp is used to provide TLS support.
119	 */
120	if (clone_flags & CLONE_SETTLS)
121		childregs->ugp = childregs->r04;
122
123	/*
124	 * Parent sees new pid -- not necessary, not even possible at
125	 * this point in the fork process
126	 * Might also want to set things like ti->addr_limit
127	 */
128
129	return 0;
130}
131
132/*
133 * Release any architecture-specific resources locked by thread
134 */
135void release_thread(struct task_struct *dead_task)
136{
137}
138
139/*
140 * Free any architecture-specific thread data structures, etc.
141 */
142void exit_thread(void)
143{
144}
145
146/*
147 * Some archs flush debug and FPU info here
148 */
149void flush_thread(void)
150{
151}
152
153/*
154 * The "wait channel" terminology is archaic, but what we want
155 * is an identification of the point at which the scheduler
156 * was invoked by a blocked thread.
157 */
158unsigned long get_wchan(struct task_struct *p)
159{
160	unsigned long fp, pc;
161	unsigned long stack_page;
162	int count = 0;
163	if (!p || p == current || p->state == TASK_RUNNING)
164		return 0;
165
166	stack_page = (unsigned long)task_stack_page(p);
167	fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
168	do {
169		if (fp < (stack_page + sizeof(struct thread_info)) ||
170			fp >= (THREAD_SIZE - 8 + stack_page))
171			return 0;
172		pc = ((unsigned long *)fp)[1];
173		if (!in_sched_functions(pc))
174			return pc;
175		fp = *(unsigned long *) fp;
176	} while (count++ < 16);
177
178	return 0;
179}
180
181/*
182 * Required placeholder.
183 */
184int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
185{
186	return 0;
187}
188
189
190/*
191 * Called on the exit path of event entry; see vm_entry.S
192 *
193 * Interrupts will already be disabled.
194 *
195 * Returns 0 if there's no need to re-check for more work.
196 */
197
198int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
199{
200	if (!(thread_info_flags & _TIF_WORK_MASK)) {
201		return 0;
202	}  /* shortcut -- no work to be done */
203
204	local_irq_enable();
205
206	if (thread_info_flags & _TIF_NEED_RESCHED) {
207		schedule();
208		return 1;
209	}
210
211	if (thread_info_flags & _TIF_SIGPENDING) {
212		do_signal(regs);
213		return 1;
214	}
215
216	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
217		clear_thread_flag(TIF_NOTIFY_RESUME);
218		tracehook_notify_resume(regs);
219		return 1;
220	}
221
222	/* Should not even reach here */
223	panic("%s: bad thread_info flags 0x%08x\n", __func__,
224		thread_info_flags);
225}
226