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