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/sched/debug.h>
21 #include <linux/sched/task.h>
22 #include <linux/sched/task_stack.h>
23 #include <linux/kernel.h>
24 #include <linux/mm.h>
25 #include <linux/smp.h>
26 #include <linux/stddef.h>
27 #include <linux/unistd.h>
28 #include <linux/ptrace.h>
29 #include <linux/elf.h>
30 #include <linux/hw_breakpoint.h>
31 #include <linux/init.h>
32 #include <linux/prctl.h>
33 #include <linux/init_task.h>
34 #include <linux/module.h>
35 #include <linux/mqueue.h>
36 #include <linux/fs.h>
37 #include <linux/slab.h>
38 #include <linux/rcupdate.h>
39 
40 #include <linux/uaccess.h>
41 #include <asm/io.h>
42 #include <asm/processor.h>
43 #include <asm/platform.h>
44 #include <asm/mmu.h>
45 #include <asm/irq.h>
46 #include <linux/atomic.h>
47 #include <asm/asm-offsets.h>
48 #include <asm/regs.h>
49 #include <asm/hw_breakpoint.h>
50 #include <asm/traps.h>
51 
52 extern void ret_from_fork(void);
53 extern void ret_from_kernel_thread(void);
54 
55 void (*pm_power_off)(void) = NULL;
56 EXPORT_SYMBOL(pm_power_off);
57 
58 
59 #ifdef CONFIG_STACKPROTECTOR
60 #include <linux/stackprotector.h>
61 unsigned long __stack_chk_guard __read_mostly;
62 EXPORT_SYMBOL(__stack_chk_guard);
63 #endif
64 
65 #if XTENSA_HAVE_COPROCESSORS
66 
local_coprocessors_flush_release_all(void)67 void local_coprocessors_flush_release_all(void)
68 {
69 	struct thread_info **coprocessor_owner;
70 	struct thread_info *unique_owner[XCHAL_CP_MAX];
71 	int n = 0;
72 	int i, j;
73 
74 	coprocessor_owner = this_cpu_ptr(&exc_table)->coprocessor_owner;
75 	xtensa_set_sr(XCHAL_CP_MASK, cpenable);
76 
77 	for (i = 0; i < XCHAL_CP_MAX; i++) {
78 		struct thread_info *ti = coprocessor_owner[i];
79 
80 		if (ti) {
81 			coprocessor_flush(ti, i);
82 
83 			for (j = 0; j < n; j++)
84 				if (unique_owner[j] == ti)
85 					break;
86 			if (j == n)
87 				unique_owner[n++] = ti;
88 
89 			coprocessor_owner[i] = NULL;
90 		}
91 	}
92 	for (i = 0; i < n; i++) {
93 		/* pairs with memw (1) in fast_coprocessor and memw in switch_to */
94 		smp_wmb();
95 		unique_owner[i]->cpenable = 0;
96 	}
97 	xtensa_set_sr(0, cpenable);
98 }
99 
local_coprocessor_release_all(void * info)100 static void local_coprocessor_release_all(void *info)
101 {
102 	struct thread_info *ti = info;
103 	struct thread_info **coprocessor_owner;
104 	int i;
105 
106 	coprocessor_owner = this_cpu_ptr(&exc_table)->coprocessor_owner;
107 
108 	/* Walk through all cp owners and release it for the requested one. */
109 
110 	for (i = 0; i < XCHAL_CP_MAX; i++) {
111 		if (coprocessor_owner[i] == ti)
112 			coprocessor_owner[i] = NULL;
113 	}
114 	/* pairs with memw (1) in fast_coprocessor and memw in switch_to */
115 	smp_wmb();
116 	ti->cpenable = 0;
117 	if (ti == current_thread_info())
118 		xtensa_set_sr(0, cpenable);
119 }
120 
coprocessor_release_all(struct thread_info * ti)121 void coprocessor_release_all(struct thread_info *ti)
122 {
123 	if (ti->cpenable) {
124 		/* pairs with memw (2) in fast_coprocessor */
125 		smp_rmb();
126 		smp_call_function_single(ti->cp_owner_cpu,
127 					 local_coprocessor_release_all,
128 					 ti, true);
129 	}
130 }
131 
local_coprocessor_flush_all(void * info)132 static void local_coprocessor_flush_all(void *info)
133 {
134 	struct thread_info *ti = info;
135 	struct thread_info **coprocessor_owner;
136 	unsigned long old_cpenable;
137 	int i;
138 
139 	coprocessor_owner = this_cpu_ptr(&exc_table)->coprocessor_owner;
140 	old_cpenable = xtensa_xsr(ti->cpenable, cpenable);
141 
142 	for (i = 0; i < XCHAL_CP_MAX; i++) {
143 		if (coprocessor_owner[i] == ti)
144 			coprocessor_flush(ti, i);
145 	}
146 	xtensa_set_sr(old_cpenable, cpenable);
147 }
148 
coprocessor_flush_all(struct thread_info * ti)149 void coprocessor_flush_all(struct thread_info *ti)
150 {
151 	if (ti->cpenable) {
152 		/* pairs with memw (2) in fast_coprocessor */
153 		smp_rmb();
154 		smp_call_function_single(ti->cp_owner_cpu,
155 					 local_coprocessor_flush_all,
156 					 ti, true);
157 	}
158 }
159 
local_coprocessor_flush_release_all(void * info)160 static void local_coprocessor_flush_release_all(void *info)
161 {
162 	local_coprocessor_flush_all(info);
163 	local_coprocessor_release_all(info);
164 }
165 
coprocessor_flush_release_all(struct thread_info * ti)166 void coprocessor_flush_release_all(struct thread_info *ti)
167 {
168 	if (ti->cpenable) {
169 		/* pairs with memw (2) in fast_coprocessor */
170 		smp_rmb();
171 		smp_call_function_single(ti->cp_owner_cpu,
172 					 local_coprocessor_flush_release_all,
173 					 ti, true);
174 	}
175 }
176 
177 #endif
178 
179 
180 /*
181  * Powermanagement idle function, if any is provided by the platform.
182  */
arch_cpu_idle(void)183 void arch_cpu_idle(void)
184 {
185 	platform_idle();
186 }
187 
188 /*
189  * This is called when the thread calls exit().
190  */
exit_thread(struct task_struct * tsk)191 void exit_thread(struct task_struct *tsk)
192 {
193 #if XTENSA_HAVE_COPROCESSORS
194 	coprocessor_release_all(task_thread_info(tsk));
195 #endif
196 }
197 
198 /*
199  * Flush thread state. This is called when a thread does an execve()
200  * Note that we flush coprocessor registers for the case execve fails.
201  */
flush_thread(void)202 void flush_thread(void)
203 {
204 #if XTENSA_HAVE_COPROCESSORS
205 	struct thread_info *ti = current_thread_info();
206 	coprocessor_flush_release_all(ti);
207 #endif
208 	flush_ptrace_hw_breakpoint(current);
209 }
210 
211 /*
212  * this gets called so that we can store coprocessor state into memory and
213  * copy the current task into the new thread.
214  */
arch_dup_task_struct(struct task_struct * dst,struct task_struct * src)215 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
216 {
217 #if XTENSA_HAVE_COPROCESSORS
218 	coprocessor_flush_all(task_thread_info(src));
219 #endif
220 	*dst = *src;
221 	return 0;
222 }
223 
224 /*
225  * Copy thread.
226  *
227  * There are two modes in which this function is called:
228  * 1) Userspace thread creation,
229  *    regs != NULL, usp_thread_fn is userspace stack pointer.
230  *    It is expected to copy parent regs (in case CLONE_VM is not set
231  *    in the clone_flags) and set up passed usp in the childregs.
232  * 2) Kernel thread creation,
233  *    regs == NULL, usp_thread_fn is the function to run in the new thread
234  *    and thread_fn_arg is its parameter.
235  *    childregs are not used for the kernel threads.
236  *
237  * The stack layout for the new thread looks like this:
238  *
239  *	+------------------------+
240  *	|       childregs        |
241  *	+------------------------+ <- thread.sp = sp in dummy-frame
242  *	|      dummy-frame       |    (saved in dummy-frame spill-area)
243  *	+------------------------+
244  *
245  * We create a dummy frame to return to either ret_from_fork or
246  *   ret_from_kernel_thread:
247  *   a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
248  *   sp points to itself (thread.sp)
249  *   a2, a3 are unused for userspace threads,
250  *   a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
251  *
252  * Note: This is a pristine frame, so we don't need any spill region on top of
253  *       childregs.
254  *
255  * The fun part:  if we're keeping the same VM (i.e. cloning a thread,
256  * not an entire process), we're normally given a new usp, and we CANNOT share
257  * any live address register windows.  If we just copy those live frames over,
258  * the two threads (parent and child) will overflow the same frames onto the
259  * parent stack at different times, likely corrupting the parent stack (esp.
260  * if the parent returns from functions that called clone() and calls new
261  * ones, before the child overflows its now old copies of its parent windows).
262  * One solution is to spill windows to the parent stack, but that's fairly
263  * involved.  Much simpler to just not copy those live frames across.
264  */
265 
copy_thread(struct task_struct * p,const struct kernel_clone_args * args)266 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
267 {
268 	unsigned long clone_flags = args->flags;
269 	unsigned long usp_thread_fn = args->stack;
270 	unsigned long tls = args->tls;
271 	struct pt_regs *childregs = task_pt_regs(p);
272 
273 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
274 	struct thread_info *ti;
275 #endif
276 
277 #if defined(__XTENSA_WINDOWED_ABI__)
278 	/* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
279 	SPILL_SLOT(childregs, 1) = (unsigned long)childregs;
280 	SPILL_SLOT(childregs, 0) = 0;
281 
282 	p->thread.sp = (unsigned long)childregs;
283 #elif defined(__XTENSA_CALL0_ABI__)
284 	/* Reserve 16 bytes for the _switch_to stack frame. */
285 	p->thread.sp = (unsigned long)childregs - 16;
286 #else
287 #error Unsupported Xtensa ABI
288 #endif
289 
290 	if (!args->fn) {
291 		struct pt_regs *regs = current_pt_regs();
292 		unsigned long usp = usp_thread_fn ?
293 			usp_thread_fn : regs->areg[1];
294 
295 		p->thread.ra = MAKE_RA_FOR_CALL(
296 				(unsigned long)ret_from_fork, 0x1);
297 
298 		*childregs = *regs;
299 		childregs->areg[1] = usp;
300 		childregs->areg[2] = 0;
301 
302 		/* When sharing memory with the parent thread, the child
303 		   usually starts on a pristine stack, so we have to reset
304 		   windowbase, windowstart and wmask.
305 		   (Note that such a new thread is required to always create
306 		   an initial call4 frame)
307 		   The exception is vfork, where the new thread continues to
308 		   run on the parent's stack until it calls execve. This could
309 		   be a call8 or call12, which requires a legal stack frame
310 		   of the previous caller for the overflow handlers to work.
311 		   (Note that it's always legal to overflow live registers).
312 		   In this case, ensure to spill at least the stack pointer
313 		   of that frame. */
314 
315 		if (clone_flags & CLONE_VM) {
316 			/* check that caller window is live and same stack */
317 			int len = childregs->wmask & ~0xf;
318 			if (regs->areg[1] == usp && len != 0) {
319 				int callinc = (regs->areg[0] >> 30) & 3;
320 				int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
321 				put_user(regs->areg[caller_ars+1],
322 					 (unsigned __user*)(usp - 12));
323 			}
324 			childregs->wmask = 1;
325 			childregs->windowstart = 1;
326 			childregs->windowbase = 0;
327 		}
328 
329 		if (clone_flags & CLONE_SETTLS)
330 			childregs->threadptr = tls;
331 	} else {
332 		p->thread.ra = MAKE_RA_FOR_CALL(
333 				(unsigned long)ret_from_kernel_thread, 1);
334 
335 		/* pass parameters to ret_from_kernel_thread: */
336 #if defined(__XTENSA_WINDOWED_ABI__)
337 		/*
338 		 * a2 = thread_fn, a3 = thread_fn arg.
339 		 * Window underflow will load registers from the
340 		 * spill slots on the stack on return from _switch_to.
341 		 */
342 		SPILL_SLOT(childregs, 2) = (unsigned long)args->fn;
343 		SPILL_SLOT(childregs, 3) = (unsigned long)args->fn_arg;
344 #elif defined(__XTENSA_CALL0_ABI__)
345 		/*
346 		 * a12 = thread_fn, a13 = thread_fn arg.
347 		 * _switch_to epilogue will load registers from the stack.
348 		 */
349 		((unsigned long *)p->thread.sp)[0] = (unsigned long)args->fn;
350 		((unsigned long *)p->thread.sp)[1] = (unsigned long)args->fn_arg;
351 #else
352 #error Unsupported Xtensa ABI
353 #endif
354 
355 		/* Childregs are only used when we're going to userspace
356 		 * in which case start_thread will set them up.
357 		 */
358 	}
359 
360 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
361 	ti = task_thread_info(p);
362 	ti->cpenable = 0;
363 #endif
364 
365 	clear_ptrace_hw_breakpoint(p);
366 
367 	return 0;
368 }
369 
370 
371 /*
372  * These bracket the sleeping functions..
373  */
374 
__get_wchan(struct task_struct * p)375 unsigned long __get_wchan(struct task_struct *p)
376 {
377 	unsigned long sp, pc;
378 	unsigned long stack_page = (unsigned long) task_stack_page(p);
379 	int count = 0;
380 
381 	sp = p->thread.sp;
382 	pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
383 
384 	do {
385 		if (sp < stack_page + sizeof(struct task_struct) ||
386 		    sp >= (stack_page + THREAD_SIZE) ||
387 		    pc == 0)
388 			return 0;
389 		if (!in_sched_functions(pc))
390 			return pc;
391 
392 		/* Stack layout: sp-4: ra, sp-3: sp' */
393 
394 		pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), sp);
395 		sp = SPILL_SLOT(sp, 1);
396 	} while (count++ < 16);
397 	return 0;
398 }
399