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 ®s->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