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 <asm/pgtable.h> 41 #include <linux/uaccess.h> 42 #include <asm/io.h> 43 #include <asm/processor.h> 44 #include <asm/platform.h> 45 #include <asm/mmu.h> 46 #include <asm/irq.h> 47 #include <linux/atomic.h> 48 #include <asm/asm-offsets.h> 49 #include <asm/regs.h> 50 #include <asm/hw_breakpoint.h> 51 52 extern void ret_from_fork(void); 53 extern void ret_from_kernel_thread(void); 54 55 struct task_struct *current_set[NR_CPUS] = {&init_task, }; 56 57 void (*pm_power_off)(void) = NULL; 58 EXPORT_SYMBOL(pm_power_off); 59 60 61 #ifdef CONFIG_STACKPROTECTOR 62 #include <linux/stackprotector.h> 63 unsigned long __stack_chk_guard __read_mostly; 64 EXPORT_SYMBOL(__stack_chk_guard); 65 #endif 66 67 #if XTENSA_HAVE_COPROCESSORS 68 69 void coprocessor_release_all(struct thread_info *ti) 70 { 71 unsigned long cpenable; 72 int i; 73 74 /* Make sure we don't switch tasks during this operation. */ 75 76 preempt_disable(); 77 78 /* Walk through all cp owners and release it for the requested one. */ 79 80 cpenable = ti->cpenable; 81 82 for (i = 0; i < XCHAL_CP_MAX; i++) { 83 if (coprocessor_owner[i] == ti) { 84 coprocessor_owner[i] = 0; 85 cpenable &= ~(1 << i); 86 } 87 } 88 89 ti->cpenable = cpenable; 90 coprocessor_clear_cpenable(); 91 92 preempt_enable(); 93 } 94 95 void coprocessor_flush_all(struct thread_info *ti) 96 { 97 unsigned long cpenable, old_cpenable; 98 int i; 99 100 preempt_disable(); 101 102 RSR_CPENABLE(old_cpenable); 103 cpenable = ti->cpenable; 104 WSR_CPENABLE(cpenable); 105 106 for (i = 0; i < XCHAL_CP_MAX; i++) { 107 if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti) 108 coprocessor_flush(ti, i); 109 cpenable >>= 1; 110 } 111 WSR_CPENABLE(old_cpenable); 112 113 preempt_enable(); 114 } 115 116 #endif 117 118 119 /* 120 * Powermanagement idle function, if any is provided by the platform. 121 */ 122 void arch_cpu_idle(void) 123 { 124 platform_idle(); 125 } 126 127 /* 128 * This is called when the thread calls exit(). 129 */ 130 void exit_thread(struct task_struct *tsk) 131 { 132 #if XTENSA_HAVE_COPROCESSORS 133 coprocessor_release_all(task_thread_info(tsk)); 134 #endif 135 } 136 137 /* 138 * Flush thread state. This is called when a thread does an execve() 139 * Note that we flush coprocessor registers for the case execve fails. 140 */ 141 void flush_thread(void) 142 { 143 #if XTENSA_HAVE_COPROCESSORS 144 struct thread_info *ti = current_thread_info(); 145 coprocessor_flush_all(ti); 146 coprocessor_release_all(ti); 147 #endif 148 flush_ptrace_hw_breakpoint(current); 149 } 150 151 /* 152 * this gets called so that we can store coprocessor state into memory and 153 * copy the current task into the new thread. 154 */ 155 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) 156 { 157 #if XTENSA_HAVE_COPROCESSORS 158 coprocessor_flush_all(task_thread_info(src)); 159 #endif 160 *dst = *src; 161 return 0; 162 } 163 164 /* 165 * Copy thread. 166 * 167 * There are two modes in which this function is called: 168 * 1) Userspace thread creation, 169 * regs != NULL, usp_thread_fn is userspace stack pointer. 170 * It is expected to copy parent regs (in case CLONE_VM is not set 171 * in the clone_flags) and set up passed usp in the childregs. 172 * 2) Kernel thread creation, 173 * regs == NULL, usp_thread_fn is the function to run in the new thread 174 * and thread_fn_arg is its parameter. 175 * childregs are not used for the kernel threads. 176 * 177 * The stack layout for the new thread looks like this: 178 * 179 * +------------------------+ 180 * | childregs | 181 * +------------------------+ <- thread.sp = sp in dummy-frame 182 * | dummy-frame | (saved in dummy-frame spill-area) 183 * +------------------------+ 184 * 185 * We create a dummy frame to return to either ret_from_fork or 186 * ret_from_kernel_thread: 187 * a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4) 188 * sp points to itself (thread.sp) 189 * a2, a3 are unused for userspace threads, 190 * a2 points to thread_fn, a3 holds thread_fn arg for kernel threads. 191 * 192 * Note: This is a pristine frame, so we don't need any spill region on top of 193 * childregs. 194 * 195 * The fun part: if we're keeping the same VM (i.e. cloning a thread, 196 * not an entire process), we're normally given a new usp, and we CANNOT share 197 * any live address register windows. If we just copy those live frames over, 198 * the two threads (parent and child) will overflow the same frames onto the 199 * parent stack at different times, likely corrupting the parent stack (esp. 200 * if the parent returns from functions that called clone() and calls new 201 * ones, before the child overflows its now old copies of its parent windows). 202 * One solution is to spill windows to the parent stack, but that's fairly 203 * involved. Much simpler to just not copy those live frames across. 204 */ 205 206 int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn, 207 unsigned long thread_fn_arg, struct task_struct *p) 208 { 209 struct pt_regs *childregs = task_pt_regs(p); 210 211 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 212 struct thread_info *ti; 213 #endif 214 215 /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */ 216 SPILL_SLOT(childregs, 1) = (unsigned long)childregs; 217 SPILL_SLOT(childregs, 0) = 0; 218 219 p->thread.sp = (unsigned long)childregs; 220 221 if (!(p->flags & PF_KTHREAD)) { 222 struct pt_regs *regs = current_pt_regs(); 223 unsigned long usp = usp_thread_fn ? 224 usp_thread_fn : regs->areg[1]; 225 226 p->thread.ra = MAKE_RA_FOR_CALL( 227 (unsigned long)ret_from_fork, 0x1); 228 229 /* This does not copy all the regs. 230 * In a bout of brilliance or madness, 231 * ARs beyond a0-a15 exist past the end of the struct. 232 */ 233 *childregs = *regs; 234 childregs->areg[1] = usp; 235 childregs->areg[2] = 0; 236 237 /* When sharing memory with the parent thread, the child 238 usually starts on a pristine stack, so we have to reset 239 windowbase, windowstart and wmask. 240 (Note that such a new thread is required to always create 241 an initial call4 frame) 242 The exception is vfork, where the new thread continues to 243 run on the parent's stack until it calls execve. This could 244 be a call8 or call12, which requires a legal stack frame 245 of the previous caller for the overflow handlers to work. 246 (Note that it's always legal to overflow live registers). 247 In this case, ensure to spill at least the stack pointer 248 of that frame. */ 249 250 if (clone_flags & CLONE_VM) { 251 /* check that caller window is live and same stack */ 252 int len = childregs->wmask & ~0xf; 253 if (regs->areg[1] == usp && len != 0) { 254 int callinc = (regs->areg[0] >> 30) & 3; 255 int caller_ars = XCHAL_NUM_AREGS - callinc * 4; 256 put_user(regs->areg[caller_ars+1], 257 (unsigned __user*)(usp - 12)); 258 } 259 childregs->wmask = 1; 260 childregs->windowstart = 1; 261 childregs->windowbase = 0; 262 } else { 263 int len = childregs->wmask & ~0xf; 264 memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4], 265 ®s->areg[XCHAL_NUM_AREGS - len/4], len); 266 } 267 268 /* The thread pointer is passed in the '4th argument' (= a5) */ 269 if (clone_flags & CLONE_SETTLS) 270 childregs->threadptr = childregs->areg[5]; 271 } else { 272 p->thread.ra = MAKE_RA_FOR_CALL( 273 (unsigned long)ret_from_kernel_thread, 1); 274 275 /* pass parameters to ret_from_kernel_thread: 276 * a2 = thread_fn, a3 = thread_fn arg 277 */ 278 SPILL_SLOT(childregs, 3) = thread_fn_arg; 279 SPILL_SLOT(childregs, 2) = usp_thread_fn; 280 281 /* Childregs are only used when we're going to userspace 282 * in which case start_thread will set them up. 283 */ 284 } 285 286 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 287 ti = task_thread_info(p); 288 ti->cpenable = 0; 289 #endif 290 291 clear_ptrace_hw_breakpoint(p); 292 293 return 0; 294 } 295 296 297 /* 298 * These bracket the sleeping functions.. 299 */ 300 301 unsigned long get_wchan(struct task_struct *p) 302 { 303 unsigned long sp, pc; 304 unsigned long stack_page = (unsigned long) task_stack_page(p); 305 int count = 0; 306 307 if (!p || p == current || p->state == TASK_RUNNING) 308 return 0; 309 310 sp = p->thread.sp; 311 pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp); 312 313 do { 314 if (sp < stack_page + sizeof(struct task_struct) || 315 sp >= (stack_page + THREAD_SIZE) || 316 pc == 0) 317 return 0; 318 if (!in_sched_functions(pc)) 319 return pc; 320 321 /* Stack layout: sp-4: ra, sp-3: sp' */ 322 323 pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp); 324 sp = *(unsigned long *)sp - 3; 325 } while (count++ < 16); 326 return 0; 327 } 328 329 /* 330 * xtensa_gregset_t and 'struct pt_regs' are vastly different formats 331 * of processor registers. Besides different ordering, 332 * xtensa_gregset_t contains non-live register information that 333 * 'struct pt_regs' does not. Exception handling (primarily) uses 334 * 'struct pt_regs'. Core files and ptrace use xtensa_gregset_t. 335 * 336 */ 337 338 void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs) 339 { 340 unsigned long wb, ws, wm; 341 int live, last; 342 343 wb = regs->windowbase; 344 ws = regs->windowstart; 345 wm = regs->wmask; 346 ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1); 347 348 /* Don't leak any random bits. */ 349 350 memset(elfregs, 0, sizeof(*elfregs)); 351 352 /* Note: PS.EXCM is not set while user task is running; its 353 * being set in regs->ps is for exception handling convenience. 354 */ 355 356 elfregs->pc = regs->pc; 357 elfregs->ps = (regs->ps & ~(1 << PS_EXCM_BIT)); 358 elfregs->lbeg = regs->lbeg; 359 elfregs->lend = regs->lend; 360 elfregs->lcount = regs->lcount; 361 elfregs->sar = regs->sar; 362 elfregs->windowstart = ws; 363 364 live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16; 365 last = XCHAL_NUM_AREGS - (wm >> 4) * 4; 366 memcpy(elfregs->a, regs->areg, live * 4); 367 memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16); 368 } 369 370 int dump_fpu(void) 371 { 372 return 0; 373 } 374