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_tls(unsigned long clone_flags, unsigned long usp_thread_fn, 206 unsigned long thread_fn_arg, struct task_struct *p, 207 unsigned long tls) 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 childregs->syscall = regs->syscall; 269 270 if (clone_flags & CLONE_SETTLS) 271 childregs->threadptr = tls; 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(SPILL_SLOT(sp, 0), sp); 325 sp = SPILL_SLOT(sp, 1); 326 } while (count++ < 16); 327 return 0; 328 } 329