kernel/entry/common.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/context_tracking.h>
   4 #include <linux/entry-common.h>
   5 #include <linux/resume_user_mode.h>
   6 #include <linux/highmem.h>
   7 #include <linux/jump_label.h>
   8 #include <linux/livepatch.h>
   9 #include <linux/audit.h>
  10 #include <linux/tick.h>
  11
  12 #include "common.h"
  13
  14 #define CREATE_TRACE_POINTS
  15 #include <trace/events/syscalls.h>
  16
  17 /* See comment for enter_from_user_mode() in entry-common.h */
  18 static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
  19 {
  20         arch_enter_from_user_mode(regs);
  21         lockdep_hardirqs_off(CALLER_ADDR0);
  22
  23         CT_WARN_ON(ct_state() != CONTEXT_USER);
  24         user_exit_irqoff();
  25
  26         instrumentation_begin();
  27         trace_hardirqs_off_finish();
  28         instrumentation_end();
  29 }
  30
  31 void noinstr enter_from_user_mode(struct pt_regs *regs)
  32 {
  33         __enter_from_user_mode(regs);
  34 }
  35
  36 static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
  37 {
  38         if (unlikely(audit_context())) {
  39                 unsigned long args[6];
  40
  41                 syscall_get_arguments(current, regs, args);
  42                 audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
  43         }
  44 }
  45
  46 static long syscall_trace_enter(struct pt_regs *regs, long syscall,
  47                                 unsigned long work)
  48 {
  49         long ret = 0;
  50
  51         /*
  52          * Handle Syscall User Dispatch.  This must comes first, since
  53          * the ABI here can be something that doesn't make sense for
  54          * other syscall_work features.
  55          */
  56         if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
  57                 if (syscall_user_dispatch(regs))
  58                         return -1L;
  59         }
  60
  61         /* Handle ptrace */
  62         if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
  63                 ret = ptrace_report_syscall_entry(regs);
  64                 if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
  65                         return -1L;
  66         }
  67
  68         /* Do seccomp after ptrace, to catch any tracer changes. */
  69         if (work & SYSCALL_WORK_SECCOMP) {
  70                 ret = __secure_computing(NULL);
  71                 if (ret == -1L)
  72                         return ret;
  73         }
  74
  75         /* Either of the above might have changed the syscall number */
  76         syscall = syscall_get_nr(current, regs);
  77
  78         if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
  79                 trace_sys_enter(regs, syscall);
  80
  81         syscall_enter_audit(regs, syscall);
  82
  83         return ret ? : syscall;
  84 }
  85
  86 static __always_inline long
  87 __syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
  88 {
  89         unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
  90
  91         if (work & SYSCALL_WORK_ENTER)
  92                 syscall = syscall_trace_enter(regs, syscall, work);
  93
  94         return syscall;
  95 }
  96
  97 long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
  98 {
  99         return __syscall_enter_from_user_work(regs, syscall);
 100 }
 101
 102 noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
 103 {
 104         long ret;
 105
 106         __enter_from_user_mode(regs);
 107
 108         instrumentation_begin();
 109         local_irq_enable();
 110         ret = __syscall_enter_from_user_work(regs, syscall);
 111         instrumentation_end();
 112
 113         return ret;
 114 }
 115
 116 noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
 117 {
 118         __enter_from_user_mode(regs);
 119         instrumentation_begin();
 120         local_irq_enable();
 121         instrumentation_end();
 122 }
 123
 124 /* See comment for exit_to_user_mode() in entry-common.h */
 125 static __always_inline void __exit_to_user_mode(void)
 126 {
 127         instrumentation_begin();
 128         trace_hardirqs_on_prepare();
 129         lockdep_hardirqs_on_prepare();
 130         instrumentation_end();
 131
 132         user_enter_irqoff();
 133         arch_exit_to_user_mode();
 134         lockdep_hardirqs_on(CALLER_ADDR0);
 135 }
 136
 137 void noinstr exit_to_user_mode(void)
 138 {
 139         __exit_to_user_mode();
 140 }
 141
 142 /* Workaround to allow gradual conversion of architecture code */
 143 void __weak arch_do_signal_or_restart(struct pt_regs *regs) { }
 144
 145 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 146                                             unsigned long ti_work)
 147 {
 148         /*
 149          * Before returning to user space ensure that all pending work
 150          * items have been completed.
 151          */
 152         while (ti_work & EXIT_TO_USER_MODE_WORK) {
 153
 154                 local_irq_enable_exit_to_user(ti_work);
 155
 156                 if (ti_work & _TIF_NEED_RESCHED)
 157                         schedule();
 158
 159                 if (ti_work & _TIF_UPROBE)
 160                         uprobe_notify_resume(regs);
 161
 162                 if (ti_work & _TIF_PATCH_PENDING)
 163                         klp_update_patch_state(current);
 164
 165                 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 166                         arch_do_signal_or_restart(regs);
 167
 168                 if (ti_work & _TIF_NOTIFY_RESUME)
 169                         resume_user_mode_work(regs);
 170
 171                 /* Architecture specific TIF work */
 172                 arch_exit_to_user_mode_work(regs, ti_work);
 173
 174                 /*
 175                  * Disable interrupts and reevaluate the work flags as they
 176                  * might have changed while interrupts and preemption was
 177                  * enabled above.
 178                  */
 179                 local_irq_disable_exit_to_user();
 180
 181                 /* Check if any of the above work has queued a deferred wakeup */
 182                 tick_nohz_user_enter_prepare();
 183
 184                 ti_work = read_thread_flags();
 185         }
 186
 187         /* Return the latest work state for arch_exit_to_user_mode() */
 188         return ti_work;
 189 }
 190
 191 static void exit_to_user_mode_prepare(struct pt_regs *regs)
 192 {
 193         unsigned long ti_work = read_thread_flags();
 194
 195         lockdep_assert_irqs_disabled();
 196
 197         /* Flush pending rcuog wakeup before the last need_resched() check */
 198         tick_nohz_user_enter_prepare();
 199
 200         if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
 201                 ti_work = exit_to_user_mode_loop(regs, ti_work);
 202
 203         arch_exit_to_user_mode_prepare(regs, ti_work);
 204
 205         /* Ensure that the address limit is intact and no locks are held */
 206         addr_limit_user_check();
 207         kmap_assert_nomap();
 208         lockdep_assert_irqs_disabled();
 209         lockdep_sys_exit();
 210 }
 211
 212 /*
 213  * If SYSCALL_EMU is set, then the only reason to report is when
 214  * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
 215  * instruction has been already reported in syscall_enter_from_user_mode().
 216  */
 217 static inline bool report_single_step(unsigned long work)
 218 {
 219         if (work & SYSCALL_WORK_SYSCALL_EMU)
 220                 return false;
 221
 222         return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
 223 }
 224
 225 static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
 226 {
 227         bool step;
 228
 229         /*
 230          * If the syscall was rolled back due to syscall user dispatching,
 231          * then the tracers below are not invoked for the same reason as
 232          * the entry side was not invoked in syscall_trace_enter(): The ABI
 233          * of these syscalls is unknown.
 234          */
 235         if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
 236                 if (unlikely(current->syscall_dispatch.on_dispatch)) {
 237                         current->syscall_dispatch.on_dispatch = false;
 238                         return;
 239                 }
 240         }
 241
 242         audit_syscall_exit(regs);
 243
 244         if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
 245                 trace_sys_exit(regs, syscall_get_return_value(current, regs));
 246
 247         step = report_single_step(work);
 248         if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
 249                 ptrace_report_syscall_exit(regs, step);
 250 }
 251
 252 /*
 253  * Syscall specific exit to user mode preparation. Runs with interrupts
 254  * enabled.
 255  */
 256 static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
 257 {
 258         unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 259         unsigned long nr = syscall_get_nr(current, regs);
 260
 261         CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
 262
 263         if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
 264                 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
 265                         local_irq_enable();
 266         }
 267
 268         rseq_syscall(regs);
 269
 270         /*
 271          * Do one-time syscall specific work. If these work items are
 272          * enabled, we want to run them exactly once per syscall exit with
 273          * interrupts enabled.
 274          */
 275         if (unlikely(work & SYSCALL_WORK_EXIT))
 276                 syscall_exit_work(regs, work);
 277 }
 278
 279 static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
 280 {
 281         syscall_exit_to_user_mode_prepare(regs);
 282         local_irq_disable_exit_to_user();
 283         exit_to_user_mode_prepare(regs);
 284 }
 285
 286 void syscall_exit_to_user_mode_work(struct pt_regs *regs)
 287 {
 288         __syscall_exit_to_user_mode_work(regs);
 289 }
 290
 291 __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
 292 {
 293         instrumentation_begin();
 294         __syscall_exit_to_user_mode_work(regs);
 295         instrumentation_end();
 296         __exit_to_user_mode();
 297 }
 298
 299 noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
 300 {
 301         __enter_from_user_mode(regs);
 302 }
 303
 304 noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
 305 {
 306         instrumentation_begin();
 307         exit_to_user_mode_prepare(regs);
 308         instrumentation_end();
 309         __exit_to_user_mode();
 310 }
 311
 312 noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 313 {
 314         irqentry_state_t ret = {
 315                 .exit_rcu = false,
 316         };
 317
 318         if (user_mode(regs)) {
 319                 irqentry_enter_from_user_mode(regs);
 320                 return ret;
 321         }
 322
 323         /*
 324          * If this entry hit the idle task invoke ct_irq_enter() whether
 325          * RCU is watching or not.
 326          *
 327          * Interrupts can nest when the first interrupt invokes softirq
 328          * processing on return which enables interrupts.
 329          *
 330          * Scheduler ticks in the idle task can mark quiescent state and
 331          * terminate a grace period, if and only if the timer interrupt is
 332          * not nested into another interrupt.
 333          *
 334          * Checking for rcu_is_watching() here would prevent the nesting
 335          * interrupt to invoke ct_irq_enter(). If that nested interrupt is
 336          * the tick then rcu_flavor_sched_clock_irq() would wrongfully
 337          * assume that it is the first interrupt and eventually claim
 338          * quiescent state and end grace periods prematurely.
 339          *
 340          * Unconditionally invoke ct_irq_enter() so RCU state stays
 341          * consistent.
 342          *
 343          * TINY_RCU does not support EQS, so let the compiler eliminate
 344          * this part when enabled.
 345          */
 346         if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
 347                 /*
 348                  * If RCU is not watching then the same careful
 349                  * sequence vs. lockdep and tracing is required
 350                  * as in irqentry_enter_from_user_mode().
 351                  */
 352                 lockdep_hardirqs_off(CALLER_ADDR0);
 353                 ct_irq_enter();
 354                 instrumentation_begin();
 355                 trace_hardirqs_off_finish();
 356                 instrumentation_end();
 357
 358                 ret.exit_rcu = true;
 359                 return ret;
 360         }
 361
 362         /*
 363          * If RCU is watching then RCU only wants to check whether it needs
 364          * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
 365          * already contains a warning when RCU is not watching, so no point
 366          * in having another one here.
 367          */
 368         lockdep_hardirqs_off(CALLER_ADDR0);
 369         instrumentation_begin();
 370         rcu_irq_enter_check_tick();
 371         trace_hardirqs_off_finish();
 372         instrumentation_end();
 373
 374         return ret;
 375 }
 376
 377 void raw_irqentry_exit_cond_resched(void)
 378 {
 379         if (!preempt_count()) {
 380                 /* Sanity check RCU and thread stack */
 381                 rcu_irq_exit_check_preempt();
 382                 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
 383                         WARN_ON_ONCE(!on_thread_stack());
 384                 if (need_resched())
 385                         preempt_schedule_irq();
 386         }
 387 }
 388 #ifdef CONFIG_PREEMPT_DYNAMIC
 389 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
 390 DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
 391 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
 392 DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
 393 void dynamic_irqentry_exit_cond_resched(void)
 394 {
 395         if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
 396                 return;
 397         raw_irqentry_exit_cond_resched();
 398 }
 399 #endif
 400 #endif
 401
 402 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 403 {
 404         lockdep_assert_irqs_disabled();
 405
 406         /* Check whether this returns to user mode */
 407         if (user_mode(regs)) {
 408                 irqentry_exit_to_user_mode(regs);
 409         } else if (!regs_irqs_disabled(regs)) {
 410                 /*
 411                  * If RCU was not watching on entry this needs to be done
 412                  * carefully and needs the same ordering of lockdep/tracing
 413                  * and RCU as the return to user mode path.
 414                  */
 415                 if (state.exit_rcu) {
 416                         instrumentation_begin();
 417                         /* Tell the tracer that IRET will enable interrupts */
 418                         trace_hardirqs_on_prepare();
 419                         lockdep_hardirqs_on_prepare();
 420                         instrumentation_end();
 421                         ct_irq_exit();
 422                         lockdep_hardirqs_on(CALLER_ADDR0);
 423                         return;
 424                 }
 425
 426                 instrumentation_begin();
 427                 if (IS_ENABLED(CONFIG_PREEMPTION))
 428                         irqentry_exit_cond_resched();
 429
 430                 /* Covers both tracing and lockdep */
 431                 trace_hardirqs_on();
 432                 instrumentation_end();
 433         } else {
 434                 /*
 435                  * IRQ flags state is correct already. Just tell RCU if it
 436                  * was not watching on entry.
 437                  */
 438                 if (state.exit_rcu)
 439                         ct_irq_exit();
 440         }
 441 }
 442
 443 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
 444 {
 445         irqentry_state_t irq_state;
 446
 447         irq_state.lockdep = lockdep_hardirqs_enabled();
 448
 449         __nmi_enter();
 450         lockdep_hardirqs_off(CALLER_ADDR0);
 451         lockdep_hardirq_enter();
 452         ct_nmi_enter();
 453
 454         instrumentation_begin();
 455         trace_hardirqs_off_finish();
 456         ftrace_nmi_enter();
 457         instrumentation_end();
 458
 459         return irq_state;
 460 }
 461
 462 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
 463 {
 464         instrumentation_begin();
 465         ftrace_nmi_exit();
 466         if (irq_state.lockdep) {
 467                 trace_hardirqs_on_prepare();
 468                 lockdep_hardirqs_on_prepare();
 469         }
 470         instrumentation_end();
 471
 472         ct_nmi_exit();
 473         lockdep_hardirq_exit();
 474         if (irq_state.lockdep)
 475                 lockdep_hardirqs_on(CALLER_ADDR0);
 476         __nmi_exit();
 477 }