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Linux/arch/arm64/kernel/process.c

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  1 /*
  2  * Based on arch/arm/kernel/process.c
  3  *
  4  * Original Copyright (C) 1995  Linus Torvalds
  5  * Copyright (C) 1996-2000 Russell King - Converted to ARM.
  6  * Copyright (C) 2012 ARM Ltd.
  7  *
  8  * This program is free software; you can redistribute it and/or modify
  9  * it under the terms of the GNU General Public License version 2 as
 10  * published by the Free Software Foundation.
 11  *
 12  * This program is distributed in the hope that it will be useful,
 13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15  * GNU General Public License for more details.
 16  *
 17  * You should have received a copy of the GNU General Public License
 18  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 19  */
 20 
 21 #include <stdarg.h>
 22 
 23 #include <linux/compat.h>
 24 #include <linux/efi.h>
 25 #include <linux/export.h>
 26 #include <linux/sched.h>
 27 #include <linux/sched/debug.h>
 28 #include <linux/sched/task.h>
 29 #include <linux/sched/task_stack.h>
 30 #include <linux/kernel.h>
 31 #include <linux/mm.h>
 32 #include <linux/stddef.h>
 33 #include <linux/unistd.h>
 34 #include <linux/user.h>
 35 #include <linux/delay.h>
 36 #include <linux/reboot.h>
 37 #include <linux/interrupt.h>
 38 #include <linux/init.h>
 39 #include <linux/cpu.h>
 40 #include <linux/elfcore.h>
 41 #include <linux/pm.h>
 42 #include <linux/tick.h>
 43 #include <linux/utsname.h>
 44 #include <linux/uaccess.h>
 45 #include <linux/random.h>
 46 #include <linux/hw_breakpoint.h>
 47 #include <linux/personality.h>
 48 #include <linux/notifier.h>
 49 #include <trace/events/power.h>
 50 #include <linux/percpu.h>
 51 #include <linux/thread_info.h>
 52 
 53 #include <asm/alternative.h>
 54 #include <asm/compat.h>
 55 #include <asm/cacheflush.h>
 56 #include <asm/exec.h>
 57 #include <asm/fpsimd.h>
 58 #include <asm/mmu_context.h>
 59 #include <asm/processor.h>
 60 #include <asm/stacktrace.h>
 61 
 62 #ifdef CONFIG_CC_STACKPROTECTOR
 63 #include <linux/stackprotector.h>
 64 unsigned long __stack_chk_guard __read_mostly;
 65 EXPORT_SYMBOL(__stack_chk_guard);
 66 #endif
 67 
 68 /*
 69  * Function pointers to optional machine specific functions
 70  */
 71 void (*pm_power_off)(void);
 72 EXPORT_SYMBOL_GPL(pm_power_off);
 73 
 74 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 75 
 76 /*
 77  * This is our default idle handler.
 78  */
 79 void arch_cpu_idle(void)
 80 {
 81         /*
 82          * This should do all the clock switching and wait for interrupt
 83          * tricks
 84          */
 85         trace_cpu_idle_rcuidle(1, smp_processor_id());
 86         cpu_do_idle();
 87         local_irq_enable();
 88         trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 89 }
 90 
 91 #ifdef CONFIG_HOTPLUG_CPU
 92 void arch_cpu_idle_dead(void)
 93 {
 94        cpu_die();
 95 }
 96 #endif
 97 
 98 /*
 99  * Called by kexec, immediately prior to machine_kexec().
100  *
101  * This must completely disable all secondary CPUs; simply causing those CPUs
102  * to execute e.g. a RAM-based pin loop is not sufficient. This allows the
103  * kexec'd kernel to use any and all RAM as it sees fit, without having to
104  * avoid any code or data used by any SW CPU pin loop. The CPU hotplug
105  * functionality embodied in disable_nonboot_cpus() to achieve this.
106  */
107 void machine_shutdown(void)
108 {
109         disable_nonboot_cpus();
110 }
111 
112 /*
113  * Halting simply requires that the secondary CPUs stop performing any
114  * activity (executing tasks, handling interrupts). smp_send_stop()
115  * achieves this.
116  */
117 void machine_halt(void)
118 {
119         local_irq_disable();
120         smp_send_stop();
121         while (1);
122 }
123 
124 /*
125  * Power-off simply requires that the secondary CPUs stop performing any
126  * activity (executing tasks, handling interrupts). smp_send_stop()
127  * achieves this. When the system power is turned off, it will take all CPUs
128  * with it.
129  */
130 void machine_power_off(void)
131 {
132         local_irq_disable();
133         smp_send_stop();
134         if (pm_power_off)
135                 pm_power_off();
136 }
137 
138 /*
139  * Restart requires that the secondary CPUs stop performing any activity
140  * while the primary CPU resets the system. Systems with multiple CPUs must
141  * provide a HW restart implementation, to ensure that all CPUs reset at once.
142  * This is required so that any code running after reset on the primary CPU
143  * doesn't have to co-ordinate with other CPUs to ensure they aren't still
144  * executing pre-reset code, and using RAM that the primary CPU's code wishes
145  * to use. Implementing such co-ordination would be essentially impossible.
146  */
147 void machine_restart(char *cmd)
148 {
149         /* Disable interrupts first */
150         local_irq_disable();
151         smp_send_stop();
152 
153         /*
154          * UpdateCapsule() depends on the system being reset via
155          * ResetSystem().
156          */
157         if (efi_enabled(EFI_RUNTIME_SERVICES))
158                 efi_reboot(reboot_mode, NULL);
159 
160         /* Now call the architecture specific reboot code. */
161         if (arm_pm_restart)
162                 arm_pm_restart(reboot_mode, cmd);
163         else
164                 do_kernel_restart(cmd);
165 
166         /*
167          * Whoops - the architecture was unable to reboot.
168          */
169         printk("Reboot failed -- System halted\n");
170         while (1);
171 }
172 
173 static void print_pstate(struct pt_regs *regs)
174 {
175         u64 pstate = regs->pstate;
176 
177         if (compat_user_mode(regs)) {
178                 printk("pstate: %08llx (%c%c%c%c %c %s %s %c%c%c)\n",
179                         pstate,
180                         pstate & COMPAT_PSR_N_BIT ? 'N' : 'n',
181                         pstate & COMPAT_PSR_Z_BIT ? 'Z' : 'z',
182                         pstate & COMPAT_PSR_C_BIT ? 'C' : 'c',
183                         pstate & COMPAT_PSR_V_BIT ? 'V' : 'v',
184                         pstate & COMPAT_PSR_Q_BIT ? 'Q' : 'q',
185                         pstate & COMPAT_PSR_T_BIT ? "T32" : "A32",
186                         pstate & COMPAT_PSR_E_BIT ? "BE" : "LE",
187                         pstate & COMPAT_PSR_A_BIT ? 'A' : 'a',
188                         pstate & COMPAT_PSR_I_BIT ? 'I' : 'i',
189                         pstate & COMPAT_PSR_F_BIT ? 'F' : 'f');
190         } else {
191                 printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO)\n",
192                         pstate,
193                         pstate & PSR_N_BIT ? 'N' : 'n',
194                         pstate & PSR_Z_BIT ? 'Z' : 'z',
195                         pstate & PSR_C_BIT ? 'C' : 'c',
196                         pstate & PSR_V_BIT ? 'V' : 'v',
197                         pstate & PSR_D_BIT ? 'D' : 'd',
198                         pstate & PSR_A_BIT ? 'A' : 'a',
199                         pstate & PSR_I_BIT ? 'I' : 'i',
200                         pstate & PSR_F_BIT ? 'F' : 'f',
201                         pstate & PSR_PAN_BIT ? '+' : '-',
202                         pstate & PSR_UAO_BIT ? '+' : '-');
203         }
204 }
205 
206 void __show_regs(struct pt_regs *regs)
207 {
208         int i, top_reg;
209         u64 lr, sp;
210 
211         if (compat_user_mode(regs)) {
212                 lr = regs->compat_lr;
213                 sp = regs->compat_sp;
214                 top_reg = 12;
215         } else {
216                 lr = regs->regs[30];
217                 sp = regs->sp;
218                 top_reg = 29;
219         }
220 
221         show_regs_print_info(KERN_DEFAULT);
222         print_pstate(regs);
223 
224         if (!user_mode(regs)) {
225                 printk("pc : %pS\n", (void *)regs->pc);
226                 printk("lr : %pS\n", (void *)lr);
227         } else {
228                 printk("pc : %016llx\n", regs->pc);
229                 printk("lr : %016llx\n", lr);
230         }
231 
232         printk("sp : %016llx\n", sp);
233 
234         i = top_reg;
235 
236         while (i >= 0) {
237                 printk("x%-2d: %016llx ", i, regs->regs[i]);
238                 i--;
239 
240                 if (i % 2 == 0) {
241                         pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
242                         i--;
243                 }
244 
245                 pr_cont("\n");
246         }
247 }
248 
249 void show_regs(struct pt_regs * regs)
250 {
251         __show_regs(regs);
252         dump_backtrace(regs, NULL);
253 }
254 
255 static void tls_thread_flush(void)
256 {
257         write_sysreg(0, tpidr_el0);
258 
259         if (is_compat_task()) {
260                 current->thread.uw.tp_value = 0;
261 
262                 /*
263                  * We need to ensure ordering between the shadow state and the
264                  * hardware state, so that we don't corrupt the hardware state
265                  * with a stale shadow state during context switch.
266                  */
267                 barrier();
268                 write_sysreg(0, tpidrro_el0);
269         }
270 }
271 
272 void flush_thread(void)
273 {
274         fpsimd_flush_thread();
275         tls_thread_flush();
276         flush_ptrace_hw_breakpoint(current);
277 }
278 
279 void release_thread(struct task_struct *dead_task)
280 {
281 }
282 
283 void arch_release_task_struct(struct task_struct *tsk)
284 {
285         fpsimd_release_task(tsk);
286 }
287 
288 /*
289  * src and dst may temporarily have aliased sve_state after task_struct
290  * is copied.  We cannot fix this properly here, because src may have
291  * live SVE state and dst's thread_info may not exist yet, so tweaking
292  * either src's or dst's TIF_SVE is not safe.
293  *
294  * The unaliasing is done in copy_thread() instead.  This works because
295  * dst is not schedulable or traceable until both of these functions
296  * have been called.
297  */
298 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
299 {
300         if (current->mm)
301                 fpsimd_preserve_current_state();
302         *dst = *src;
303 
304         return 0;
305 }
306 
307 asmlinkage void ret_from_fork(void) asm("ret_from_fork");
308 
309 int copy_thread(unsigned long clone_flags, unsigned long stack_start,
310                 unsigned long stk_sz, struct task_struct *p)
311 {
312         struct pt_regs *childregs = task_pt_regs(p);
313 
314         memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
315 
316         /*
317          * Unalias p->thread.sve_state (if any) from the parent task
318          * and disable discard SVE state for p:
319          */
320         clear_tsk_thread_flag(p, TIF_SVE);
321         p->thread.sve_state = NULL;
322 
323         /*
324          * In case p was allocated the same task_struct pointer as some
325          * other recently-exited task, make sure p is disassociated from
326          * any cpu that may have run that now-exited task recently.
327          * Otherwise we could erroneously skip reloading the FPSIMD
328          * registers for p.
329          */
330         fpsimd_flush_task_state(p);
331 
332         if (likely(!(p->flags & PF_KTHREAD))) {
333                 *childregs = *current_pt_regs();
334                 childregs->regs[0] = 0;
335 
336                 /*
337                  * Read the current TLS pointer from tpidr_el0 as it may be
338                  * out-of-sync with the saved value.
339                  */
340                 *task_user_tls(p) = read_sysreg(tpidr_el0);
341 
342                 if (stack_start) {
343                         if (is_compat_thread(task_thread_info(p)))
344                                 childregs->compat_sp = stack_start;
345                         else
346                                 childregs->sp = stack_start;
347                 }
348 
349                 /*
350                  * If a TLS pointer was passed to clone (4th argument), use it
351                  * for the new thread.
352                  */
353                 if (clone_flags & CLONE_SETTLS)
354                         p->thread.uw.tp_value = childregs->regs[3];
355         } else {
356                 memset(childregs, 0, sizeof(struct pt_regs));
357                 childregs->pstate = PSR_MODE_EL1h;
358                 if (IS_ENABLED(CONFIG_ARM64_UAO) &&
359                     cpus_have_const_cap(ARM64_HAS_UAO))
360                         childregs->pstate |= PSR_UAO_BIT;
361                 p->thread.cpu_context.x19 = stack_start;
362                 p->thread.cpu_context.x20 = stk_sz;
363         }
364         p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
365         p->thread.cpu_context.sp = (unsigned long)childregs;
366 
367         ptrace_hw_copy_thread(p);
368 
369         return 0;
370 }
371 
372 void tls_preserve_current_state(void)
373 {
374         *task_user_tls(current) = read_sysreg(tpidr_el0);
375 }
376 
377 static void tls_thread_switch(struct task_struct *next)
378 {
379         tls_preserve_current_state();
380 
381         if (is_compat_thread(task_thread_info(next)))
382                 write_sysreg(next->thread.uw.tp_value, tpidrro_el0);
383         else if (!arm64_kernel_unmapped_at_el0())
384                 write_sysreg(0, tpidrro_el0);
385 
386         write_sysreg(*task_user_tls(next), tpidr_el0);
387 }
388 
389 /* Restore the UAO state depending on next's addr_limit */
390 void uao_thread_switch(struct task_struct *next)
391 {
392         if (IS_ENABLED(CONFIG_ARM64_UAO)) {
393                 if (task_thread_info(next)->addr_limit == KERNEL_DS)
394                         asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
395                 else
396                         asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO));
397         }
398 }
399 
400 /*
401  * We store our current task in sp_el0, which is clobbered by userspace. Keep a
402  * shadow copy so that we can restore this upon entry from userspace.
403  *
404  * This is *only* for exception entry from EL0, and is not valid until we
405  * __switch_to() a user task.
406  */
407 DEFINE_PER_CPU(struct task_struct *, __entry_task);
408 
409 static void entry_task_switch(struct task_struct *next)
410 {
411         __this_cpu_write(__entry_task, next);
412 }
413 
414 /*
415  * Thread switching.
416  */
417 __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
418                                 struct task_struct *next)
419 {
420         struct task_struct *last;
421 
422         fpsimd_thread_switch(next);
423         tls_thread_switch(next);
424         hw_breakpoint_thread_switch(next);
425         contextidr_thread_switch(next);
426         entry_task_switch(next);
427         uao_thread_switch(next);
428 
429         /*
430          * Complete any pending TLB or cache maintenance on this CPU in case
431          * the thread migrates to a different CPU.
432          * This full barrier is also required by the membarrier system
433          * call.
434          */
435         dsb(ish);
436 
437         /* the actual thread switch */
438         last = cpu_switch_to(prev, next);
439 
440         return last;
441 }
442 
443 unsigned long get_wchan(struct task_struct *p)
444 {
445         struct stackframe frame;
446         unsigned long stack_page, ret = 0;
447         int count = 0;
448         if (!p || p == current || p->state == TASK_RUNNING)
449                 return 0;
450 
451         stack_page = (unsigned long)try_get_task_stack(p);
452         if (!stack_page)
453                 return 0;
454 
455         frame.fp = thread_saved_fp(p);
456         frame.pc = thread_saved_pc(p);
457 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
458         frame.graph = p->curr_ret_stack;
459 #endif
460         do {
461                 if (unwind_frame(p, &frame))
462                         goto out;
463                 if (!in_sched_functions(frame.pc)) {
464                         ret = frame.pc;
465                         goto out;
466                 }
467         } while (count ++ < 16);
468 
469 out:
470         put_task_stack(p);
471         return ret;
472 }
473 
474 unsigned long arch_align_stack(unsigned long sp)
475 {
476         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
477                 sp -= get_random_int() & ~PAGE_MASK;
478         return sp & ~0xf;
479 }
480 
481 unsigned long arch_randomize_brk(struct mm_struct *mm)
482 {
483         if (is_compat_task())
484                 return randomize_page(mm->brk, SZ_32M);
485         else
486                 return randomize_page(mm->brk, SZ_1G);
487 }
488 
489 /*
490  * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY.
491  */
492 void arch_setup_new_exec(void)
493 {
494         current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
495 }
496 

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