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 <linux/uaccess.h> 41 #include <asm/io.h> 42 #include <asm/processor.h> 43 #include <asm/platform.h> 44 #include <asm/mmu.h> 45 #include <asm/irq.h> 46 #include <linux/atomic.h> 47 #include <asm/asm-offsets.h> 48 #include <asm/regs.h> 49 #include <asm/hw_breakpoint.h> 50 #include <asm/sections.h> 51 #include <asm/traps.h> 52 53 extern void ret_from_fork(void); 54 extern void ret_from_kernel_thread(void); 55 56 void (*pm_power_off)(void) = NULL; 57 EXPORT_SYMBOL(pm_power_off); 58 59 60 #ifdef CONFIG_STACKPROTECTOR 61 #include <linux/stackprotector.h> 62 unsigned long __stack_chk_guard __read_mostly; 63 EXPORT_SYMBOL(__stack_chk_guard); 64 #endif 65 66 #if XTENSA_HAVE_COPROCESSORS 67 68 void local_coprocessors_flush_release_all(void) 69 { 70 struct thread_info **coprocessor_owner; 71 struct thread_info *unique_owner[XCHAL_CP_MAX]; 72 int n = 0; 73 int i, j; 74 75 coprocessor_owner = this_cpu_ptr(&exc_table)->coprocessor_owner; 76 xtensa_set_sr(XCHAL_CP_MASK, cpenable); 77 78 for (i = 0; i < XCHAL_CP_MAX; i++) { 79 struct thread_info *ti = coprocessor_owner[i]; 80 81 if (ti) { 82 coprocessor_flush(ti, i); 83 84 for (j = 0; j < n; j++) 85 if (unique_owner[j] == ti) 86 break; 87 if (j == n) 88 unique_owner[n++] = ti; 89 90 coprocessor_owner[i] = NULL; 91 } 92 } 93 for (i = 0; i < n; i++) { 94 /* pairs with memw (1) in fast_coprocessor and memw in switch_to */ 95 smp_wmb(); 96 unique_owner[i]->cpenable = 0; 97 } 98 xtensa_set_sr(0, cpenable); 99 } 100 101 static void local_coprocessor_release_all(void *info) 102 { 103 struct thread_info *ti = info; 104 struct thread_info **coprocessor_owner; 105 int i; 106 107 coprocessor_owner = this_cpu_ptr(&exc_table)->coprocessor_owner; 108 109 /* Walk through all cp owners and release it for the requested one. */ 110 111 for (i = 0; i < XCHAL_CP_MAX; i++) { 112 if (coprocessor_owner[i] == ti) 113 coprocessor_owner[i] = NULL; 114 } 115 /* pairs with memw (1) in fast_coprocessor and memw in switch_to */ 116 smp_wmb(); 117 ti->cpenable = 0; 118 if (ti == current_thread_info()) 119 xtensa_set_sr(0, cpenable); 120 } 121 122 void coprocessor_release_all(struct thread_info *ti) 123 { 124 if (ti->cpenable) { 125 /* pairs with memw (2) in fast_coprocessor */ 126 smp_rmb(); 127 smp_call_function_single(ti->cp_owner_cpu, 128 local_coprocessor_release_all, 129 ti, true); 130 } 131 } 132 133 static void local_coprocessor_flush_all(void *info) 134 { 135 struct thread_info *ti = info; 136 struct thread_info **coprocessor_owner; 137 unsigned long old_cpenable; 138 int i; 139 140 coprocessor_owner = this_cpu_ptr(&exc_table)->coprocessor_owner; 141 old_cpenable = xtensa_xsr(ti->cpenable, cpenable); 142 143 for (i = 0; i < XCHAL_CP_MAX; i++) { 144 if (coprocessor_owner[i] == ti) 145 coprocessor_flush(ti, i); 146 } 147 xtensa_set_sr(old_cpenable, cpenable); 148 } 149 150 void coprocessor_flush_all(struct thread_info *ti) 151 { 152 if (ti->cpenable) { 153 /* pairs with memw (2) in fast_coprocessor */ 154 smp_rmb(); 155 smp_call_function_single(ti->cp_owner_cpu, 156 local_coprocessor_flush_all, 157 ti, true); 158 } 159 } 160 161 static void local_coprocessor_flush_release_all(void *info) 162 { 163 local_coprocessor_flush_all(info); 164 local_coprocessor_release_all(info); 165 } 166 167 void coprocessor_flush_release_all(struct thread_info *ti) 168 { 169 if (ti->cpenable) { 170 /* pairs with memw (2) in fast_coprocessor */ 171 smp_rmb(); 172 smp_call_function_single(ti->cp_owner_cpu, 173 local_coprocessor_flush_release_all, 174 ti, true); 175 } 176 } 177 178 #endif 179 180 181 /* 182 * Powermanagement idle function, if any is provided by the platform. 183 */ 184 void arch_cpu_idle(void) 185 { 186 platform_idle(); 187 raw_local_irq_disable(); 188 } 189 190 /* 191 * This is called when the thread calls exit(). 192 */ 193 void exit_thread(struct task_struct *tsk) 194 { 195 #if XTENSA_HAVE_COPROCESSORS 196 coprocessor_release_all(task_thread_info(tsk)); 197 #endif 198 } 199 200 /* 201 * Flush thread state. This is called when a thread does an execve() 202 * Note that we flush coprocessor registers for the case execve fails. 203 */ 204 void flush_thread(void) 205 { 206 #if XTENSA_HAVE_COPROCESSORS 207 struct thread_info *ti = current_thread_info(); 208 coprocessor_flush_release_all(ti); 209 #endif 210 flush_ptrace_hw_breakpoint(current); 211 } 212 213 /* 214 * this gets called so that we can store coprocessor state into memory and 215 * copy the current task into the new thread. 216 */ 217 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) 218 { 219 #if XTENSA_HAVE_COPROCESSORS 220 coprocessor_flush_all(task_thread_info(src)); 221 #endif 222 *dst = *src; 223 return 0; 224 } 225 226 /* 227 * Copy thread. 228 * 229 * There are two modes in which this function is called: 230 * 1) Userspace thread creation, 231 * regs != NULL, usp_thread_fn is userspace stack pointer. 232 * It is expected to copy parent regs (in case CLONE_VM is not set 233 * in the clone_flags) and set up passed usp in the childregs. 234 * 2) Kernel thread creation, 235 * regs == NULL, usp_thread_fn is the function to run in the new thread 236 * and thread_fn_arg is its parameter. 237 * childregs are not used for the kernel threads. 238 * 239 * The stack layout for the new thread looks like this: 240 * 241 * +------------------------+ 242 * | childregs | 243 * +------------------------+ <- thread.sp = sp in dummy-frame 244 * | dummy-frame | (saved in dummy-frame spill-area) 245 * +------------------------+ 246 * 247 * We create a dummy frame to return to either ret_from_fork or 248 * ret_from_kernel_thread: 249 * a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4) 250 * sp points to itself (thread.sp) 251 * a2, a3 are unused for userspace threads, 252 * a2 points to thread_fn, a3 holds thread_fn arg for kernel threads. 253 * 254 * Note: This is a pristine frame, so we don't need any spill region on top of 255 * childregs. 256 * 257 * The fun part: if we're keeping the same VM (i.e. cloning a thread, 258 * not an entire process), we're normally given a new usp, and we CANNOT share 259 * any live address register windows. If we just copy those live frames over, 260 * the two threads (parent and child) will overflow the same frames onto the 261 * parent stack at different times, likely corrupting the parent stack (esp. 262 * if the parent returns from functions that called clone() and calls new 263 * ones, before the child overflows its now old copies of its parent windows). 264 * One solution is to spill windows to the parent stack, but that's fairly 265 * involved. Much simpler to just not copy those live frames across. 266 */ 267 268 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) 269 { 270 unsigned long clone_flags = args->flags; 271 unsigned long usp_thread_fn = args->stack; 272 unsigned long tls = args->tls; 273 struct pt_regs *childregs = task_pt_regs(p); 274 275 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 276 struct thread_info *ti; 277 #endif 278 279 #if defined(__XTENSA_WINDOWED_ABI__) 280 /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */ 281 SPILL_SLOT(childregs, 1) = (unsigned long)childregs; 282 SPILL_SLOT(childregs, 0) = 0; 283 284 p->thread.sp = (unsigned long)childregs; 285 #elif defined(__XTENSA_CALL0_ABI__) 286 /* Reserve 16 bytes for the _switch_to stack frame. */ 287 p->thread.sp = (unsigned long)childregs - 16; 288 #else 289 #error Unsupported Xtensa ABI 290 #endif 291 292 if (!args->fn) { 293 struct pt_regs *regs = current_pt_regs(); 294 unsigned long usp = usp_thread_fn ? 295 usp_thread_fn : regs->areg[1]; 296 297 p->thread.ra = MAKE_RA_FOR_CALL( 298 (unsigned long)ret_from_fork, 0x1); 299 300 *childregs = *regs; 301 childregs->areg[1] = usp; 302 childregs->areg[2] = 0; 303 304 /* When sharing memory with the parent thread, the child 305 usually starts on a pristine stack, so we have to reset 306 windowbase, windowstart and wmask. 307 (Note that such a new thread is required to always create 308 an initial call4 frame) 309 The exception is vfork, where the new thread continues to 310 run on the parent's stack until it calls execve. This could 311 be a call8 or call12, which requires a legal stack frame 312 of the previous caller for the overflow handlers to work. 313 (Note that it's always legal to overflow live registers). 314 In this case, ensure to spill at least the stack pointer 315 of that frame. */ 316 317 if (clone_flags & CLONE_VM) { 318 /* check that caller window is live and same stack */ 319 int len = childregs->wmask & ~0xf; 320 if (regs->areg[1] == usp && len != 0) { 321 int callinc = (regs->areg[0] >> 30) & 3; 322 int caller_ars = XCHAL_NUM_AREGS - callinc * 4; 323 put_user(regs->areg[caller_ars+1], 324 (unsigned __user*)(usp - 12)); 325 } 326 childregs->wmask = 1; 327 childregs->windowstart = 1; 328 childregs->windowbase = 0; 329 } 330 331 if (clone_flags & CLONE_SETTLS) 332 childregs->threadptr = tls; 333 } else { 334 p->thread.ra = MAKE_RA_FOR_CALL( 335 (unsigned long)ret_from_kernel_thread, 1); 336 337 /* pass parameters to ret_from_kernel_thread: */ 338 #if defined(__XTENSA_WINDOWED_ABI__) 339 /* 340 * a2 = thread_fn, a3 = thread_fn arg. 341 * Window underflow will load registers from the 342 * spill slots on the stack on return from _switch_to. 343 */ 344 SPILL_SLOT(childregs, 2) = (unsigned long)args->fn; 345 SPILL_SLOT(childregs, 3) = (unsigned long)args->fn_arg; 346 #elif defined(__XTENSA_CALL0_ABI__) 347 /* 348 * a12 = thread_fn, a13 = thread_fn arg. 349 * _switch_to epilogue will load registers from the stack. 350 */ 351 ((unsigned long *)p->thread.sp)[0] = (unsigned long)args->fn; 352 ((unsigned long *)p->thread.sp)[1] = (unsigned long)args->fn_arg; 353 #else 354 #error Unsupported Xtensa ABI 355 #endif 356 357 /* Childregs are only used when we're going to userspace 358 * in which case start_thread will set them up. 359 */ 360 } 361 362 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 363 ti = task_thread_info(p); 364 ti->cpenable = 0; 365 #endif 366 367 clear_ptrace_hw_breakpoint(p); 368 369 return 0; 370 } 371 372 373 /* 374 * These bracket the sleeping functions.. 375 */ 376 377 unsigned long __get_wchan(struct task_struct *p) 378 { 379 unsigned long sp, pc; 380 unsigned long stack_page = (unsigned long) task_stack_page(p); 381 int count = 0; 382 383 sp = p->thread.sp; 384 pc = MAKE_PC_FROM_RA(p->thread.ra, _text); 385 386 do { 387 if (sp < stack_page + sizeof(struct task_struct) || 388 sp >= (stack_page + THREAD_SIZE) || 389 pc == 0) 390 return 0; 391 if (!in_sched_functions(pc)) 392 return pc; 393 394 /* Stack layout: sp-4: ra, sp-3: sp' */ 395 396 pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), _text); 397 sp = SPILL_SLOT(sp, 1); 398 } while (count++ < 16); 399 return 0; 400 } 401