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, 203 struct task_struct *p, struct pt_regs *unused) 204 { 205 struct pt_regs *childregs = task_pt_regs(p); 206 207 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 208 struct thread_info *ti; 209 #endif 210 211 /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */ 212 *((int*)childregs - 3) = (unsigned long)childregs; 213 *((int*)childregs - 4) = 0; 214 215 p->thread.sp = (unsigned long)childregs; 216 217 if (!(p->flags & PF_KTHREAD)) { 218 struct pt_regs *regs = current_pt_regs(); 219 unsigned long usp = usp_thread_fn ? 220 usp_thread_fn : regs->areg[1]; 221 222 p->thread.ra = MAKE_RA_FOR_CALL( 223 (unsigned long)ret_from_fork, 0x1); 224 225 /* This does not copy all the regs. 226 * In a bout of brilliance or madness, 227 * ARs beyond a0-a15 exist past the end of the struct. 228 */ 229 *childregs = *regs; 230 childregs->areg[1] = usp; 231 childregs->areg[2] = 0; 232 233 /* When sharing memory with the parent thread, the child 234 usually starts on a pristine stack, so we have to reset 235 windowbase, windowstart and wmask. 236 (Note that such a new thread is required to always create 237 an initial call4 frame) 238 The exception is vfork, where the new thread continues to 239 run on the parent's stack until it calls execve. This could 240 be a call8 or call12, which requires a legal stack frame 241 of the previous caller for the overflow handlers to work. 242 (Note that it's always legal to overflow live registers). 243 In this case, ensure to spill at least the stack pointer 244 of that frame. */ 245 246 if (clone_flags & CLONE_VM) { 247 /* check that caller window is live and same stack */ 248 int len = childregs->wmask & ~0xf; 249 if (regs->areg[1] == usp && len != 0) { 250 int callinc = (regs->areg[0] >> 30) & 3; 251 int caller_ars = XCHAL_NUM_AREGS - callinc * 4; 252 put_user(regs->areg[caller_ars+1], 253 (unsigned __user*)(usp - 12)); 254 } 255 childregs->wmask = 1; 256 childregs->windowstart = 1; 257 childregs->windowbase = 0; 258 } else { 259 int len = childregs->wmask & ~0xf; 260 memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4], 261 ®s->areg[XCHAL_NUM_AREGS - len/4], len); 262 } 263 // FIXME: we need to set THREADPTR in thread_info... 264 if (clone_flags & CLONE_SETTLS) 265 childregs->areg[2] = childregs->areg[6]; 266 } else { 267 p->thread.ra = MAKE_RA_FOR_CALL( 268 (unsigned long)ret_from_kernel_thread, 1); 269 270 /* pass parameters to ret_from_kernel_thread: 271 * a2 = thread_fn, a3 = thread_fn arg 272 */ 273 *((int *)childregs - 1) = thread_fn_arg; 274 *((int *)childregs - 2) = usp_thread_fn; 275 276 /* Childregs are only used when we're going to userspace 277 * in which case start_thread will set them up. 278 */ 279 } 280 281 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 282 ti = task_thread_info(p); 283 ti->cpenable = 0; 284 #endif 285 286 return 0; 287 } 288 289 290 /* 291 * These bracket the sleeping functions.. 292 */ 293 294 unsigned long get_wchan(struct task_struct *p) 295 { 296 unsigned long sp, pc; 297 unsigned long stack_page = (unsigned long) task_stack_page(p); 298 int count = 0; 299 300 if (!p || p == current || p->state == TASK_RUNNING) 301 return 0; 302 303 sp = p->thread.sp; 304 pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp); 305 306 do { 307 if (sp < stack_page + sizeof(struct task_struct) || 308 sp >= (stack_page + THREAD_SIZE) || 309 pc == 0) 310 return 0; 311 if (!in_sched_functions(pc)) 312 return pc; 313 314 /* Stack layout: sp-4: ra, sp-3: sp' */ 315 316 pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp); 317 sp = *(unsigned long *)sp - 3; 318 } while (count++ < 16); 319 return 0; 320 } 321 322 /* 323 * xtensa_gregset_t and 'struct pt_regs' are vastly different formats 324 * of processor registers. Besides different ordering, 325 * xtensa_gregset_t contains non-live register information that 326 * 'struct pt_regs' does not. Exception handling (primarily) uses 327 * 'struct pt_regs'. Core files and ptrace use xtensa_gregset_t. 328 * 329 */ 330 331 void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs) 332 { 333 unsigned long wb, ws, wm; 334 int live, last; 335 336 wb = regs->windowbase; 337 ws = regs->windowstart; 338 wm = regs->wmask; 339 ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1); 340 341 /* Don't leak any random bits. */ 342 343 memset(elfregs, 0, sizeof(*elfregs)); 344 345 /* Note: PS.EXCM is not set while user task is running; its 346 * being set in regs->ps is for exception handling convenience. 347 */ 348 349 elfregs->pc = regs->pc; 350 elfregs->ps = (regs->ps & ~(1 << PS_EXCM_BIT)); 351 elfregs->lbeg = regs->lbeg; 352 elfregs->lend = regs->lend; 353 elfregs->lcount = regs->lcount; 354 elfregs->sar = regs->sar; 355 elfregs->windowstart = ws; 356 357 live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16; 358 last = XCHAL_NUM_AREGS - (wm >> 4) * 4; 359 memcpy(elfregs->a, regs->areg, live * 4); 360 memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16); 361 } 362 363 int dump_fpu(void) 364 { 365 return 0; 366 } 367 368 asmlinkage 369 long xtensa_clone(unsigned long clone_flags, unsigned long newsp, 370 void __user *parent_tid, void *child_tls, 371 void __user *child_tid, long a5, 372 struct pt_regs *regs) 373 { 374 return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid); 375 } 376