1/*
2 * arch/xtensa/kernel/process.c
3 *
4 * Xtensa Processor version.
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License.  See the file "COPYING" in the main directory of this archive
8 * for more details.
9 *
10 * Copyright (C) 2001 - 2005 Tensilica Inc.
11 *
12 * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
13 * Chris Zankel <chris@zankel.net>
14 * Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
15 * Kevin Chea
16 */
17
18#include <linux/errno.h>
19#include <linux/sched.h>
20#include <linux/kernel.h>
21#include <linux/mm.h>
22#include <linux/smp.h>
23#include <linux/stddef.h>
24#include <linux/unistd.h>
25#include <linux/ptrace.h>
26#include <linux/elf.h>
27#include <linux/init.h>
28#include <linux/prctl.h>
29#include <linux/init_task.h>
30#include <linux/module.h>
31#include <linux/mqueue.h>
32#include <linux/fs.h>
33#include <linux/slab.h>
34#include <linux/rcupdate.h>
35
36#include <asm/pgtable.h>
37#include <asm/uaccess.h>
38#include <asm/io.h>
39#include <asm/processor.h>
40#include <asm/platform.h>
41#include <asm/mmu.h>
42#include <asm/irq.h>
43#include <linux/atomic.h>
44#include <asm/asm-offsets.h>
45#include <asm/regs.h>
46
47extern void ret_from_fork(void);
48extern void ret_from_kernel_thread(void);
49
50struct task_struct *current_set[NR_CPUS] = {&init_task, };
51
52void (*pm_power_off)(void) = NULL;
53EXPORT_SYMBOL(pm_power_off);
54
55
56#if XTENSA_HAVE_COPROCESSORS
57
58void coprocessor_release_all(struct thread_info *ti)
59{
60	unsigned long cpenable;
61	int i;
62
63	/* Make sure we don't switch tasks during this operation. */
64
65	preempt_disable();
66
67	/* Walk through all cp owners and release it for the requested one. */
68
69	cpenable = ti->cpenable;
70
71	for (i = 0; i < XCHAL_CP_MAX; i++) {
72		if (coprocessor_owner[i] == ti) {
73			coprocessor_owner[i] = 0;
74			cpenable &= ~(1 << i);
75		}
76	}
77
78	ti->cpenable = cpenable;
79	coprocessor_clear_cpenable();
80
81	preempt_enable();
82}
83
84void coprocessor_flush_all(struct thread_info *ti)
85{
86	unsigned long cpenable;
87	int i;
88
89	preempt_disable();
90
91	cpenable = ti->cpenable;
92
93	for (i = 0; i < XCHAL_CP_MAX; i++) {
94		if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
95			coprocessor_flush(ti, i);
96		cpenable >>= 1;
97	}
98
99	preempt_enable();
100}
101
102#endif
103
104
105/*
106 * Powermanagement idle function, if any is provided by the platform.
107 */
108void arch_cpu_idle(void)
109{
110	platform_idle();
111}
112
113/*
114 * This is called when the thread calls exit().
115 */
116void exit_thread(void)
117{
118#if XTENSA_HAVE_COPROCESSORS
119	coprocessor_release_all(current_thread_info());
120#endif
121}
122
123/*
124 * Flush thread state. This is called when a thread does an execve()
125 * Note that we flush coprocessor registers for the case execve fails.
126 */
127void flush_thread(void)
128{
129#if XTENSA_HAVE_COPROCESSORS
130	struct thread_info *ti = current_thread_info();
131	coprocessor_flush_all(ti);
132	coprocessor_release_all(ti);
133#endif
134}
135
136/*
137 * this gets called so that we can store coprocessor state into memory and
138 * copy the current task into the new thread.
139 */
140int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
141{
142#if XTENSA_HAVE_COPROCESSORS
143	coprocessor_flush_all(task_thread_info(src));
144#endif
145	*dst = *src;
146	return 0;
147}
148
149/*
150 * Copy thread.
151 *
152 * There are two modes in which this function is called:
153 * 1) Userspace thread creation,
154 *    regs != NULL, usp_thread_fn is userspace stack pointer.
155 *    It is expected to copy parent regs (in case CLONE_VM is not set
156 *    in the clone_flags) and set up passed usp in the childregs.
157 * 2) Kernel thread creation,
158 *    regs == NULL, usp_thread_fn is the function to run in the new thread
159 *    and thread_fn_arg is its parameter.
160 *    childregs are not used for the kernel threads.
161 *
162 * The stack layout for the new thread looks like this:
163 *
164 *	+------------------------+
165 *	|       childregs        |
166 *	+------------------------+ <- thread.sp = sp in dummy-frame
167 *	|      dummy-frame       |    (saved in dummy-frame spill-area)
168 *	+------------------------+
169 *
170 * We create a dummy frame to return to either ret_from_fork or
171 *   ret_from_kernel_thread:
172 *   a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
173 *   sp points to itself (thread.sp)
174 *   a2, a3 are unused for userspace threads,
175 *   a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
176 *
177 * Note: This is a pristine frame, so we don't need any spill region on top of
178 *       childregs.
179 *
180 * The fun part:  if we're keeping the same VM (i.e. cloning a thread,
181 * not an entire process), we're normally given a new usp, and we CANNOT share
182 * any live address register windows.  If we just copy those live frames over,
183 * the two threads (parent and child) will overflow the same frames onto the
184 * parent stack at different times, likely corrupting the parent stack (esp.
185 * if the parent returns from functions that called clone() and calls new
186 * ones, before the child overflows its now old copies of its parent windows).
187 * One solution is to spill windows to the parent stack, but that's fairly
188 * involved.  Much simpler to just not copy those live frames across.
189 */
190
191int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
192		unsigned long thread_fn_arg, struct task_struct *p)
193{
194	struct pt_regs *childregs = task_pt_regs(p);
195
196#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
197	struct thread_info *ti;
198#endif
199
200	/* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
201	*((int*)childregs - 3) = (unsigned long)childregs;
202	*((int*)childregs - 4) = 0;
203
204	p->thread.sp = (unsigned long)childregs;
205
206	if (!(p->flags & PF_KTHREAD)) {
207		struct pt_regs *regs = current_pt_regs();
208		unsigned long usp = usp_thread_fn ?
209			usp_thread_fn : regs->areg[1];
210
211		p->thread.ra = MAKE_RA_FOR_CALL(
212				(unsigned long)ret_from_fork, 0x1);
213
214		/* This does not copy all the regs.
215		 * In a bout of brilliance or madness,
216		 * ARs beyond a0-a15 exist past the end of the struct.
217		 */
218		*childregs = *regs;
219		childregs->areg[1] = usp;
220		childregs->areg[2] = 0;
221
222		/* When sharing memory with the parent thread, the child
223		   usually starts on a pristine stack, so we have to reset
224		   windowbase, windowstart and wmask.
225		   (Note that such a new thread is required to always create
226		   an initial call4 frame)
227		   The exception is vfork, where the new thread continues to
228		   run on the parent's stack until it calls execve. This could
229		   be a call8 or call12, which requires a legal stack frame
230		   of the previous caller for the overflow handlers to work.
231		   (Note that it's always legal to overflow live registers).
232		   In this case, ensure to spill at least the stack pointer
233		   of that frame. */
234
235		if (clone_flags & CLONE_VM) {
236			/* check that caller window is live and same stack */
237			int len = childregs->wmask & ~0xf;
238			if (regs->areg[1] == usp && len != 0) {
239				int callinc = (regs->areg[0] >> 30) & 3;
240				int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
241				put_user(regs->areg[caller_ars+1],
242					 (unsigned __user*)(usp - 12));
243			}
244			childregs->wmask = 1;
245			childregs->windowstart = 1;
246			childregs->windowbase = 0;
247		} else {
248			int len = childregs->wmask & ~0xf;
249			memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
250			       &regs->areg[XCHAL_NUM_AREGS - len/4], len);
251		}
252
253		/* The thread pointer is passed in the '4th argument' (= a5) */
254		if (clone_flags & CLONE_SETTLS)
255			childregs->threadptr = childregs->areg[5];
256	} else {
257		p->thread.ra = MAKE_RA_FOR_CALL(
258				(unsigned long)ret_from_kernel_thread, 1);
259
260		/* pass parameters to ret_from_kernel_thread:
261		 * a2 = thread_fn, a3 = thread_fn arg
262		 */
263		*((int *)childregs - 1) = thread_fn_arg;
264		*((int *)childregs - 2) = usp_thread_fn;
265
266		/* Childregs are only used when we're going to userspace
267		 * in which case start_thread will set them up.
268		 */
269	}
270
271#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
272	ti = task_thread_info(p);
273	ti->cpenable = 0;
274#endif
275
276	return 0;
277}
278
279
280/*
281 * These bracket the sleeping functions..
282 */
283
284unsigned long get_wchan(struct task_struct *p)
285{
286	unsigned long sp, pc;
287	unsigned long stack_page = (unsigned long) task_stack_page(p);
288	int count = 0;
289
290	if (!p || p == current || p->state == TASK_RUNNING)
291		return 0;
292
293	sp = p->thread.sp;
294	pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
295
296	do {
297		if (sp < stack_page + sizeof(struct task_struct) ||
298		    sp >= (stack_page + THREAD_SIZE) ||
299		    pc == 0)
300			return 0;
301		if (!in_sched_functions(pc))
302			return pc;
303
304		/* Stack layout: sp-4: ra, sp-3: sp' */
305
306		pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
307		sp = *(unsigned long *)sp - 3;
308	} while (count++ < 16);
309	return 0;
310}
311
312/*
313 * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
314 * of processor registers.  Besides different ordering,
315 * xtensa_gregset_t contains non-live register information that
316 * 'struct pt_regs' does not.  Exception handling (primarily) uses
317 * 'struct pt_regs'.  Core files and ptrace use xtensa_gregset_t.
318 *
319 */
320
321void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
322{
323	unsigned long wb, ws, wm;
324	int live, last;
325
326	wb = regs->windowbase;
327	ws = regs->windowstart;
328	wm = regs->wmask;
329	ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
330
331	/* Don't leak any random bits. */
332
333	memset(elfregs, 0, sizeof(*elfregs));
334
335	/* Note:  PS.EXCM is not set while user task is running; its
336	 * being set in regs->ps is for exception handling convenience.
337	 */
338
339	elfregs->pc		= regs->pc;
340	elfregs->ps		= (regs->ps & ~(1 << PS_EXCM_BIT));
341	elfregs->lbeg		= regs->lbeg;
342	elfregs->lend		= regs->lend;
343	elfregs->lcount		= regs->lcount;
344	elfregs->sar		= regs->sar;
345	elfregs->windowstart	= ws;
346
347	live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
348	last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
349	memcpy(elfregs->a, regs->areg, live * 4);
350	memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);
351}
352
353int dump_fpu(void)
354{
355	return 0;
356}
357