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