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