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Linux/arch/xtensa/kernel/process.c

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  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 
 47 extern void ret_from_fork(void);
 48 extern void ret_from_kernel_thread(void);
 49 
 50 struct task_struct *current_set[NR_CPUS] = {&init_task, };
 51 
 52 void (*pm_power_off)(void) = NULL;
 53 EXPORT_SYMBOL(pm_power_off);
 54 
 55 
 56 #if XTENSA_HAVE_COPROCESSORS
 57 
 58 void 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 
 84 void 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  */
108 
109 void cpu_idle(void)
110 {
111         local_irq_enable();
112 
113         /* endless idle loop with no priority at all */
114         while (1) {
115                 rcu_idle_enter();
116                 while (!need_resched())
117                         platform_idle();
118                 rcu_idle_exit();
119                 schedule_preempt_disabled();
120         }
121 }
122 
123 /*
124  * This is called when the thread calls exit().
125  */
126 void exit_thread(void)
127 {
128 #if XTENSA_HAVE_COPROCESSORS
129         coprocessor_release_all(current_thread_info());
130 #endif
131 }
132 
133 /*
134  * Flush thread state. This is called when a thread does an execve()
135  * Note that we flush coprocessor registers for the case execve fails.
136  */
137 void flush_thread(void)
138 {
139 #if XTENSA_HAVE_COPROCESSORS
140         struct thread_info *ti = current_thread_info();
141         coprocessor_flush_all(ti);
142         coprocessor_release_all(ti);
143 #endif
144 }
145 
146 /*
147  * this gets called so that we can store coprocessor state into memory and
148  * copy the current task into the new thread.
149  */
150 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
151 {
152 #if XTENSA_HAVE_COPROCESSORS
153         coprocessor_flush_all(task_thread_info(src));
154 #endif
155         *dst = *src;
156         return 0;
157 }
158 
159 /*
160  * Copy thread.
161  *
162  * There are two modes in which this function is called:
163  * 1) Userspace thread creation,
164  *    regs != NULL, usp_thread_fn is userspace stack pointer.
165  *    It is expected to copy parent regs (in case CLONE_VM is not set
166  *    in the clone_flags) and set up passed usp in the childregs.
167  * 2) Kernel thread creation,
168  *    regs == NULL, usp_thread_fn is the function to run in the new thread
169  *    and thread_fn_arg is its parameter.
170  *    childregs are not used for the kernel threads.
171  *
172  * The stack layout for the new thread looks like this:
173  *
174  *      +------------------------+
175  *      |       childregs        |
176  *      +------------------------+ <- thread.sp = sp in dummy-frame
177  *      |      dummy-frame       |    (saved in dummy-frame spill-area)
178  *      +------------------------+
179  *
180  * We create a dummy frame to return to either ret_from_fork or
181  *   ret_from_kernel_thread:
182  *   a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
183  *   sp points to itself (thread.sp)
184  *   a2, a3 are unused for userspace threads,
185  *   a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
186  *
187  * Note: This is a pristine frame, so we don't need any spill region on top of
188  *       childregs.
189  *
190  * The fun part:  if we're keeping the same VM (i.e. cloning a thread,
191  * not an entire process), we're normally given a new usp, and we CANNOT share
192  * any live address register windows.  If we just copy those live frames over,
193  * the two threads (parent and child) will overflow the same frames onto the
194  * parent stack at different times, likely corrupting the parent stack (esp.
195  * if the parent returns from functions that called clone() and calls new
196  * ones, before the child overflows its now old copies of its parent windows).
197  * One solution is to spill windows to the parent stack, but that's fairly
198  * involved.  Much simpler to just not copy those live frames across.
199  */
200 
201 int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
202                 unsigned long thread_fn_arg, struct task_struct *p)
203 {
204         struct pt_regs *childregs = task_pt_regs(p);
205 
206 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
207         struct thread_info *ti;
208 #endif
209 
210         /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
211         *((int*)childregs - 3) = (unsigned long)childregs;
212         *((int*)childregs - 4) = 0;
213 
214         p->thread.sp = (unsigned long)childregs;
215 
216         if (!(p->flags & PF_KTHREAD)) {
217                 struct pt_regs *regs = current_pt_regs();
218                 unsigned long usp = usp_thread_fn ?
219                         usp_thread_fn : regs->areg[1];
220 
221                 p->thread.ra = MAKE_RA_FOR_CALL(
222                                 (unsigned long)ret_from_fork, 0x1);
223 
224                 /* This does not copy all the regs.
225                  * In a bout of brilliance or madness,
226                  * ARs beyond a0-a15 exist past the end of the struct.
227                  */
228                 *childregs = *regs;
229                 childregs->areg[1] = usp;
230                 childregs->areg[2] = 0;
231 
232                 /* When sharing memory with the parent thread, the child
233                    usually starts on a pristine stack, so we have to reset
234                    windowbase, windowstart and wmask.
235                    (Note that such a new thread is required to always create
236                    an initial call4 frame)
237                    The exception is vfork, where the new thread continues to
238                    run on the parent's stack until it calls execve. This could
239                    be a call8 or call12, which requires a legal stack frame
240                    of the previous caller for the overflow handlers to work.
241                    (Note that it's always legal to overflow live registers).
242                    In this case, ensure to spill at least the stack pointer
243                    of that frame. */
244 
245                 if (clone_flags & CLONE_VM) {
246                         /* check that caller window is live and same stack */
247                         int len = childregs->wmask & ~0xf;
248                         if (regs->areg[1] == usp && len != 0) {
249                                 int callinc = (regs->areg[0] >> 30) & 3;
250                                 int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
251                                 put_user(regs->areg[caller_ars+1],
252                                          (unsigned __user*)(usp - 12));
253                         }
254                         childregs->wmask = 1;
255                         childregs->windowstart = 1;
256                         childregs->windowbase = 0;
257                 } else {
258                         int len = childregs->wmask & ~0xf;
259                         memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
260                                &regs->areg[XCHAL_NUM_AREGS - len/4], len);
261                 }
262 // FIXME: we need to set THREADPTR in thread_info...
263                 if (clone_flags & CLONE_SETTLS)
264                         childregs->areg[2] = childregs->areg[6];
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                 *((int *)childregs - 1) = thread_fn_arg;
273                 *((int *)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         return 0;
286 }
287 
288 
289 /*
290  * These bracket the sleeping functions..
291  */
292 
293 unsigned long get_wchan(struct task_struct *p)
294 {
295         unsigned long sp, pc;
296         unsigned long stack_page = (unsigned long) task_stack_page(p);
297         int count = 0;
298 
299         if (!p || p == current || p->state == TASK_RUNNING)
300                 return 0;
301 
302         sp = p->thread.sp;
303         pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
304 
305         do {
306                 if (sp < stack_page + sizeof(struct task_struct) ||
307                     sp >= (stack_page + THREAD_SIZE) ||
308                     pc == 0)
309                         return 0;
310                 if (!in_sched_functions(pc))
311                         return pc;
312 
313                 /* Stack layout: sp-4: ra, sp-3: sp' */
314 
315                 pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
316                 sp = *(unsigned long *)sp - 3;
317         } while (count++ < 16);
318         return 0;
319 }
320 
321 /*
322  * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
323  * of processor registers.  Besides different ordering,
324  * xtensa_gregset_t contains non-live register information that
325  * 'struct pt_regs' does not.  Exception handling (primarily) uses
326  * 'struct pt_regs'.  Core files and ptrace use xtensa_gregset_t.
327  *
328  */
329 
330 void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
331 {
332         unsigned long wb, ws, wm;
333         int live, last;
334 
335         wb = regs->windowbase;
336         ws = regs->windowstart;
337         wm = regs->wmask;
338         ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
339 
340         /* Don't leak any random bits. */
341 
342         memset(elfregs, 0, sizeof(*elfregs));
343 
344         /* Note:  PS.EXCM is not set while user task is running; its
345          * being set in regs->ps is for exception handling convenience.
346          */
347 
348         elfregs->pc             = regs->pc;
349         elfregs->ps             = (regs->ps & ~(1 << PS_EXCM_BIT));
350         elfregs->lbeg           = regs->lbeg;
351         elfregs->lend           = regs->lend;
352         elfregs->lcount         = regs->lcount;
353         elfregs->sar            = regs->sar;
354         elfregs->windowstart    = ws;
355 
356         live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
357         last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
358         memcpy(elfregs->a, regs->areg, live * 4);
359         memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);
360 }
361 
362 int dump_fpu(void)
363 {
364         return 0;
365 }
366 

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