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 <asm/pgtable.h>
41 #include <linux/uaccess.h>
42 #include <asm/io.h>
43 #include <asm/processor.h>
44 #include <asm/platform.h>
45 #include <asm/mmu.h>
46 #include <asm/irq.h>
47 #include <linux/atomic.h>
48 #include <asm/asm-offsets.h>
49 #include <asm/regs.h>
50 #include <asm/hw_breakpoint.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
67 void coprocessor_release_all(struct thread_info *ti)
68 {
69 unsigned long cpenable;
70 int i;
71
72 /* Make sure we don't switch tasks during this operation. */
73
74 preempt_disable();
75
76 /* Walk through all cp owners and release it for the requested one. */
77
78 cpenable = ti->cpenable;
79
80 for (i = 0; i < XCHAL_CP_MAX; i++) {
81 if (coprocessor_owner[i] == ti) {
82 coprocessor_owner[i] = 0;
83 cpenable &= ~(1 << i);
84 }
85 }
86
87 ti->cpenable = cpenable;
88 if (ti == current_thread_info())
89 xtensa_set_sr(0, cpenable);
90
91 preempt_enable();
92 }
93
94 void coprocessor_flush_all(struct thread_info *ti)
95 {
96 unsigned long cpenable, old_cpenable;
97 int i;
98
99 preempt_disable();
100
101 old_cpenable = xtensa_get_sr(cpenable);
102 cpenable = ti->cpenable;
103 xtensa_set_sr(cpenable, cpenable);
104
105 for (i = 0; i < XCHAL_CP_MAX; i++) {
106 if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
107 coprocessor_flush(ti, i);
108 cpenable >>= 1;
109 }
110 xtensa_set_sr(old_cpenable, cpenable);
111
112 preempt_enable();
113 }
114
115 #endif
116
117
118 /*
119 * Powermanagement idle function, if any is provided by the platform.
120 */
121 void arch_cpu_idle(void)
122 {
123 platform_idle();
124 }
125
126 /*
127 * This is called when the thread calls exit().
128 */
129 void exit_thread(struct task_struct *tsk)
130 {
131 #if XTENSA_HAVE_COPROCESSORS
132 coprocessor_release_all(task_thread_info(tsk));
133 #endif
134 }
135
136 /*
137 * Flush thread state. This is called when a thread does an execve()
138 * Note that we flush coprocessor registers for the case execve fails.
139 */
140 void flush_thread(void)
141 {
142 #if XTENSA_HAVE_COPROCESSORS
143 struct thread_info *ti = current_thread_info();
144 coprocessor_flush_all(ti);
145 coprocessor_release_all(ti);
146 #endif
147 flush_ptrace_hw_breakpoint(current);
148 }
149
150 /*
151 * this gets called so that we can store coprocessor state into memory and
152 * copy the current task into the new thread.
153 */
154 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
155 {
156 #if XTENSA_HAVE_COPROCESSORS
157 coprocessor_flush_all(task_thread_info(src));
158 #endif
159 *dst = *src;
160 return 0;
161 }
162
163 /*
164 * Copy thread.
165 *
166 * There are two modes in which this function is called:
167 * 1) Userspace thread creation,
168 * regs != NULL, usp_thread_fn is userspace stack pointer.
169 * It is expected to copy parent regs (in case CLONE_VM is not set
170 * in the clone_flags) and set up passed usp in the childregs.
171 * 2) Kernel thread creation,
172 * regs == NULL, usp_thread_fn is the function to run in the new thread
173 * and thread_fn_arg is its parameter.
174 * childregs are not used for the kernel threads.
175 *
176 * The stack layout for the new thread looks like this:
177 *
178 * +------------------------+
179 * | childregs |
180 * +------------------------+ <- thread.sp = sp in dummy-frame
181 * | dummy-frame | (saved in dummy-frame spill-area)
182 * +------------------------+
183 *
184 * We create a dummy frame to return to either ret_from_fork or
185 * ret_from_kernel_thread:
186 * a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
187 * sp points to itself (thread.sp)
188 * a2, a3 are unused for userspace threads,
189 * a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
190 *
191 * Note: This is a pristine frame, so we don't need any spill region on top of
192 * childregs.
193 *
194 * The fun part: if we're keeping the same VM (i.e. cloning a thread,
195 * not an entire process), we're normally given a new usp, and we CANNOT share
196 * any live address register windows. If we just copy those live frames over,
197 * the two threads (parent and child) will overflow the same frames onto the
198 * parent stack at different times, likely corrupting the parent stack (esp.
199 * if the parent returns from functions that called clone() and calls new
200 * ones, before the child overflows its now old copies of its parent windows).
201 * One solution is to spill windows to the parent stack, but that's fairly
202 * involved. Much simpler to just not copy those live frames across.
203 */
204
205 int copy_thread_tls(unsigned long clone_flags, unsigned long usp_thread_fn,
206 unsigned long thread_fn_arg, struct task_struct *p,
207 unsigned long tls)
208 {
209 struct pt_regs *childregs = task_pt_regs(p);
210
211 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
212 struct thread_info *ti;
213 #endif
214
215 /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
216 SPILL_SLOT(childregs, 1) = (unsigned long)childregs;
217 SPILL_SLOT(childregs, 0) = 0;
218
219 p->thread.sp = (unsigned long)childregs;
220
221 if (!(p->flags & PF_KTHREAD)) {
222 struct pt_regs *regs = current_pt_regs();
223 unsigned long usp = usp_thread_fn ?
224 usp_thread_fn : regs->areg[1];
225
226 p->thread.ra = MAKE_RA_FOR_CALL(
227 (unsigned long)ret_from_fork, 0x1);
228
229 /* This does not copy all the regs.
230 * In a bout of brilliance or madness,
231 * ARs beyond a0-a15 exist past the end of the struct.
232 */
233 *childregs = *regs;
234 childregs->areg[1] = usp;
235 childregs->areg[2] = 0;
236
237 /* When sharing memory with the parent thread, the child
238 usually starts on a pristine stack, so we have to reset
239 windowbase, windowstart and wmask.
240 (Note that such a new thread is required to always create
241 an initial call4 frame)
242 The exception is vfork, where the new thread continues to
243 run on the parent's stack until it calls execve. This could
244 be a call8 or call12, which requires a legal stack frame
245 of the previous caller for the overflow handlers to work.
246 (Note that it's always legal to overflow live registers).
247 In this case, ensure to spill at least the stack pointer
248 of that frame. */
249
250 if (clone_flags & CLONE_VM) {
251 /* check that caller window is live and same stack */
252 int len = childregs->wmask & ~0xf;
253 if (regs->areg[1] == usp && len != 0) {
254 int callinc = (regs->areg[0] >> 30) & 3;
255 int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
256 put_user(regs->areg[caller_ars+1],
257 (unsigned __user*)(usp - 12));
258 }
259 childregs->wmask = 1;
260 childregs->windowstart = 1;
261 childregs->windowbase = 0;
262 } else {
263 int len = childregs->wmask & ~0xf;
264 memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
265 ®s->areg[XCHAL_NUM_AREGS - len/4], len);
266 }
267
268 if (clone_flags & CLONE_SETTLS)
269 childregs->threadptr = tls;
270 } else {
271 p->thread.ra = MAKE_RA_FOR_CALL(
272 (unsigned long)ret_from_kernel_thread, 1);
273
274 /* pass parameters to ret_from_kernel_thread:
275 * a2 = thread_fn, a3 = thread_fn arg
276 */
277 SPILL_SLOT(childregs, 3) = thread_fn_arg;
278 SPILL_SLOT(childregs, 2) = usp_thread_fn;
279
280 /* Childregs are only used when we're going to userspace
281 * in which case start_thread will set them up.
282 */
283 }
284
285 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
286 ti = task_thread_info(p);
287 ti->cpenable = 0;
288 #endif
289
290 clear_ptrace_hw_breakpoint(p);
291
292 return 0;
293 }
294
295
296 /*
297 * These bracket the sleeping functions..
298 */
299
300 unsigned long get_wchan(struct task_struct *p)
301 {
302 unsigned long sp, pc;
303 unsigned long stack_page = (unsigned long) task_stack_page(p);
304 int count = 0;
305
306 if (!p || p == current || p->state == TASK_RUNNING)
307 return 0;
308
309 sp = p->thread.sp;
310 pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
311
312 do {
313 if (sp < stack_page + sizeof(struct task_struct) ||
314 sp >= (stack_page + THREAD_SIZE) ||
315 pc == 0)
316 return 0;
317 if (!in_sched_functions(pc))
318 return pc;
319
320 /* Stack layout: sp-4: ra, sp-3: sp' */
321
322 pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), sp);
323 sp = SPILL_SLOT(sp, 1);
324 } while (count++ < 16);
325 return 0;
326 }