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 struct task_struct *current_set[NR_CPUS] = {&init_task, };
56
57 void (*pm_power_off)(void) = NULL;
58 EXPORT_SYMBOL(pm_power_off);
59
60
61 #if XTENSA_HAVE_COPROCESSORS
62
coprocessor_release_all(struct thread_info * ti)63 void coprocessor_release_all(struct thread_info *ti)
64 {
65 unsigned long cpenable;
66 int i;
67
68 /* Make sure we don't switch tasks during this operation. */
69
70 preempt_disable();
71
72 /* Walk through all cp owners and release it for the requested one. */
73
74 cpenable = ti->cpenable;
75
76 for (i = 0; i < XCHAL_CP_MAX; i++) {
77 if (coprocessor_owner[i] == ti) {
78 coprocessor_owner[i] = 0;
79 cpenable &= ~(1 << i);
80 }
81 }
82
83 ti->cpenable = cpenable;
84 coprocessor_clear_cpenable();
85
86 preempt_enable();
87 }
88
coprocessor_flush_all(struct thread_info * ti)89 void coprocessor_flush_all(struct thread_info *ti)
90 {
91 unsigned long cpenable, old_cpenable;
92 int i;
93
94 preempt_disable();
95
96 RSR_CPENABLE(old_cpenable);
97 cpenable = ti->cpenable;
98 WSR_CPENABLE(cpenable);
99
100 for (i = 0; i < XCHAL_CP_MAX; i++) {
101 if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
102 coprocessor_flush(ti, i);
103 cpenable >>= 1;
104 }
105 WSR_CPENABLE(old_cpenable);
106
107 preempt_enable();
108 }
109
110 #endif
111
112
113 /*
114 * Powermanagement idle function, if any is provided by the platform.
115 */
arch_cpu_idle(void)116 void arch_cpu_idle(void)
117 {
118 platform_idle();
119 }
120
121 /*
122 * This is called when the thread calls exit().
123 */
exit_thread(struct task_struct * tsk)124 void exit_thread(struct task_struct *tsk)
125 {
126 #if XTENSA_HAVE_COPROCESSORS
127 coprocessor_release_all(task_thread_info(tsk));
128 #endif
129 }
130
131 /*
132 * Flush thread state. This is called when a thread does an execve()
133 * Note that we flush coprocessor registers for the case execve fails.
134 */
flush_thread(void)135 void flush_thread(void)
136 {
137 #if XTENSA_HAVE_COPROCESSORS
138 struct thread_info *ti = current_thread_info();
139 coprocessor_flush_all(ti);
140 coprocessor_release_all(ti);
141 #endif
142 flush_ptrace_hw_breakpoint(current);
143 }
144
145 /*
146 * this gets called so that we can store coprocessor state into memory and
147 * copy the current task into the new thread.
148 */
arch_dup_task_struct(struct task_struct * dst,struct task_struct * src)149 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
150 {
151 #if XTENSA_HAVE_COPROCESSORS
152 coprocessor_flush_all(task_thread_info(src));
153 #endif
154 *dst = *src;
155 return 0;
156 }
157
158 /*
159 * Copy thread.
160 *
161 * There are two modes in which this function is called:
162 * 1) Userspace thread creation,
163 * regs != NULL, usp_thread_fn is userspace stack pointer.
164 * It is expected to copy parent regs (in case CLONE_VM is not set
165 * in the clone_flags) and set up passed usp in the childregs.
166 * 2) Kernel thread creation,
167 * regs == NULL, usp_thread_fn is the function to run in the new thread
168 * and thread_fn_arg is its parameter.
169 * childregs are not used for the kernel threads.
170 *
171 * The stack layout for the new thread looks like this:
172 *
173 * +------------------------+
174 * | childregs |
175 * +------------------------+ <- thread.sp = sp in dummy-frame
176 * | dummy-frame | (saved in dummy-frame spill-area)
177 * +------------------------+
178 *
179 * We create a dummy frame to return to either ret_from_fork or
180 * ret_from_kernel_thread:
181 * a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
182 * sp points to itself (thread.sp)
183 * a2, a3 are unused for userspace threads,
184 * a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
185 *
186 * Note: This is a pristine frame, so we don't need any spill region on top of
187 * childregs.
188 *
189 * The fun part: if we're keeping the same VM (i.e. cloning a thread,
190 * not an entire process), we're normally given a new usp, and we CANNOT share
191 * any live address register windows. If we just copy those live frames over,
192 * the two threads (parent and child) will overflow the same frames onto the
193 * parent stack at different times, likely corrupting the parent stack (esp.
194 * if the parent returns from functions that called clone() and calls new
195 * ones, before the child overflows its now old copies of its parent windows).
196 * One solution is to spill windows to the parent stack, but that's fairly
197 * involved. Much simpler to just not copy those live frames across.
198 */
199
copy_thread(unsigned long clone_flags,unsigned long usp_thread_fn,unsigned long thread_fn_arg,struct task_struct * p)200 int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
201 unsigned long thread_fn_arg, struct task_struct *p)
202 {
203 struct pt_regs *childregs = task_pt_regs(p);
204
205 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
206 struct thread_info *ti;
207 #endif
208
209 /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
210 SPILL_SLOT(childregs, 1) = (unsigned long)childregs;
211 SPILL_SLOT(childregs, 0) = 0;
212
213 p->thread.sp = (unsigned long)childregs;
214
215 if (!(p->flags & PF_KTHREAD)) {
216 struct pt_regs *regs = current_pt_regs();
217 unsigned long usp = usp_thread_fn ?
218 usp_thread_fn : regs->areg[1];
219
220 p->thread.ra = MAKE_RA_FOR_CALL(
221 (unsigned long)ret_from_fork, 0x1);
222
223 /* This does not copy all the regs.
224 * In a bout of brilliance or madness,
225 * ARs beyond a0-a15 exist past the end of the struct.
226 */
227 *childregs = *regs;
228 childregs->areg[1] = usp;
229 childregs->areg[2] = 0;
230
231 /* When sharing memory with the parent thread, the child
232 usually starts on a pristine stack, so we have to reset
233 windowbase, windowstart and wmask.
234 (Note that such a new thread is required to always create
235 an initial call4 frame)
236 The exception is vfork, where the new thread continues to
237 run on the parent's stack until it calls execve. This could
238 be a call8 or call12, which requires a legal stack frame
239 of the previous caller for the overflow handlers to work.
240 (Note that it's always legal to overflow live registers).
241 In this case, ensure to spill at least the stack pointer
242 of that frame. */
243
244 if (clone_flags & CLONE_VM) {
245 /* check that caller window is live and same stack */
246 int len = childregs->wmask & ~0xf;
247 if (regs->areg[1] == usp && len != 0) {
248 int callinc = (regs->areg[0] >> 30) & 3;
249 int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
250 put_user(regs->areg[caller_ars+1],
251 (unsigned __user*)(usp - 12));
252 }
253 childregs->wmask = 1;
254 childregs->windowstart = 1;
255 childregs->windowbase = 0;
256 } else {
257 int len = childregs->wmask & ~0xf;
258 memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
259 ®s->areg[XCHAL_NUM_AREGS - len/4], len);
260 }
261
262 /* The thread pointer is passed in the '4th argument' (= a5) */
263 if (clone_flags & CLONE_SETTLS)
264 childregs->threadptr = childregs->areg[5];
265 } else {
266 p->thread.ra = MAKE_RA_FOR_CALL(
267 (unsigned long)ret_from_kernel_thread, 1);
268
269 /* pass parameters to ret_from_kernel_thread:
270 * a2 = thread_fn, a3 = thread_fn arg
271 */
272 SPILL_SLOT(childregs, 3) = thread_fn_arg;
273 SPILL_SLOT(childregs, 2) = usp_thread_fn;
274
275 /* Childregs are only used when we're going to userspace
276 * in which case start_thread will set them up.
277 */
278 }
279
280 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
281 ti = task_thread_info(p);
282 ti->cpenable = 0;
283 #endif
284
285 clear_ptrace_hw_breakpoint(p);
286
287 return 0;
288 }
289
290
291 /*
292 * These bracket the sleeping functions..
293 */
294
get_wchan(struct task_struct * p)295 unsigned long get_wchan(struct task_struct *p)
296 {
297 unsigned long sp, pc;
298 unsigned long stack_page = (unsigned long) task_stack_page(p);
299 int count = 0;
300
301 if (!p || p == current || p->state == TASK_RUNNING)
302 return 0;
303
304 sp = p->thread.sp;
305 pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
306
307 do {
308 if (sp < stack_page + sizeof(struct task_struct) ||
309 sp >= (stack_page + THREAD_SIZE) ||
310 pc == 0)
311 return 0;
312 if (!in_sched_functions(pc))
313 return pc;
314
315 /* Stack layout: sp-4: ra, sp-3: sp' */
316
317 pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), sp);
318 sp = SPILL_SLOT(sp, 1);
319 } while (count++ < 16);
320 return 0;
321 }
322
323 /*
324 * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
325 * of processor registers. Besides different ordering,
326 * xtensa_gregset_t contains non-live register information that
327 * 'struct pt_regs' does not. Exception handling (primarily) uses
328 * 'struct pt_regs'. Core files and ptrace use xtensa_gregset_t.
329 *
330 */
331
xtensa_elf_core_copy_regs(xtensa_gregset_t * elfregs,struct pt_regs * regs)332 void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
333 {
334 unsigned long wb, ws, wm;
335 int live, last;
336
337 wb = regs->windowbase;
338 ws = regs->windowstart;
339 wm = regs->wmask;
340 ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
341
342 /* Don't leak any random bits. */
343
344 memset(elfregs, 0, sizeof(*elfregs));
345
346 /* Note: PS.EXCM is not set while user task is running; its
347 * being set in regs->ps is for exception handling convenience.
348 */
349
350 elfregs->pc = regs->pc;
351 elfregs->ps = (regs->ps & ~(1 << PS_EXCM_BIT));
352 elfregs->lbeg = regs->lbeg;
353 elfregs->lend = regs->lend;
354 elfregs->lcount = regs->lcount;
355 elfregs->sar = regs->sar;
356 elfregs->windowstart = ws;
357
358 live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
359 last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
360 memcpy(elfregs->a, regs->areg, live * 4);
361 memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);
362 }
363
dump_fpu(void)364 int dump_fpu(void)
365 {
366 return 0;
367 }
368