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