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