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