include/linux/entry-common.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_ENTRYCOMMON_H
   3 #define __LINUX_ENTRYCOMMON_H
   4
   5 #include <linux/static_call_types.h>
   6 #include <linux/ptrace.h>
   7 #include <linux/syscalls.h>
   8 #include <linux/seccomp.h>
   9 #include <linux/sched.h>
  10
  11 #include <asm/entry-common.h>
  12
  13 /*
  14  * Define dummy _TIF work flags if not defined by the architecture or for
  15  * disabled functionality.
  16  */
  17 #ifndef _TIF_PATCH_PENDING
  18 # define _TIF_PATCH_PENDING             (0)
  19 #endif
  20
  21 #ifndef _TIF_UPROBE
  22 # define _TIF_UPROBE                    (0)
  23 #endif
  24
  25 /*
  26  * SYSCALL_WORK flags handled in syscall_enter_from_user_mode()
  27  */
  28 #ifndef ARCH_SYSCALL_WORK_ENTER
  29 # define ARCH_SYSCALL_WORK_ENTER        (0)
  30 #endif
  31
  32 /*
  33  * SYSCALL_WORK flags handled in syscall_exit_to_user_mode()
  34  */
  35 #ifndef ARCH_SYSCALL_WORK_EXIT
  36 # define ARCH_SYSCALL_WORK_EXIT         (0)
  37 #endif
  38
  39 #define SYSCALL_WORK_ENTER      (SYSCALL_WORK_SECCOMP |                 \
  40                                  SYSCALL_WORK_SYSCALL_TRACEPOINT |      \
  41                                  SYSCALL_WORK_SYSCALL_TRACE |           \
  42                                  SYSCALL_WORK_SYSCALL_EMU |             \
  43                                  SYSCALL_WORK_SYSCALL_AUDIT |           \
  44                                  SYSCALL_WORK_SYSCALL_USER_DISPATCH |   \
  45                                  ARCH_SYSCALL_WORK_ENTER)
  46 #define SYSCALL_WORK_EXIT       (SYSCALL_WORK_SYSCALL_TRACEPOINT |      \
  47                                  SYSCALL_WORK_SYSCALL_TRACE |           \
  48                                  SYSCALL_WORK_SYSCALL_AUDIT |           \
  49                                  SYSCALL_WORK_SYSCALL_USER_DISPATCH |   \
  50                                  SYSCALL_WORK_SYSCALL_EXIT_TRAP |       \
  51                                  ARCH_SYSCALL_WORK_EXIT)
  52
  53 /*
  54  * TIF flags handled in exit_to_user_mode_loop()
  55  */
  56 #ifndef ARCH_EXIT_TO_USER_MODE_WORK
  57 # define ARCH_EXIT_TO_USER_MODE_WORK            (0)
  58 #endif
  59
  60 #define EXIT_TO_USER_MODE_WORK                                          \
  61         (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |           \
  62          _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL |  \
  63          ARCH_EXIT_TO_USER_MODE_WORK)
  64
  65 /**
  66  * arch_check_user_regs - Architecture specific sanity check for user mode regs
  67  * @regs:       Pointer to currents pt_regs
  68  *
  69  * Defaults to an empty implementation. Can be replaced by architecture
  70  * specific code.
  71  *
  72  * Invoked from syscall_enter_from_user_mode() in the non-instrumentable
  73  * section. Use __always_inline so the compiler cannot push it out of line
  74  * and make it instrumentable.
  75  */
  76 static __always_inline void arch_check_user_regs(struct pt_regs *regs);
  77
  78 #ifndef arch_check_user_regs
  79 static __always_inline void arch_check_user_regs(struct pt_regs *regs) {}
  80 #endif
  81
  82 /**
  83  * enter_from_user_mode - Establish state when coming from user mode
  84  *
  85  * Syscall/interrupt entry disables interrupts, but user mode is traced as
  86  * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
  87  *
  88  * 1) Tell lockdep that interrupts are disabled
  89  * 2) Invoke context tracking if enabled to reactivate RCU
  90  * 3) Trace interrupts off state
  91  *
  92  * Invoked from architecture specific syscall entry code with interrupts
  93  * disabled. The calling code has to be non-instrumentable. When the
  94  * function returns all state is correct and interrupts are still
  95  * disabled. The subsequent functions can be instrumented.
  96  *
  97  * This is invoked when there is architecture specific functionality to be
  98  * done between establishing state and enabling interrupts. The caller must
  99  * enable interrupts before invoking syscall_enter_from_user_mode_work().
 100  */
 101 void enter_from_user_mode(struct pt_regs *regs);
 102
 103 /**
 104  * syscall_enter_from_user_mode_prepare - Establish state and enable interrupts
 105  * @regs:       Pointer to currents pt_regs
 106  *
 107  * Invoked from architecture specific syscall entry code with interrupts
 108  * disabled. The calling code has to be non-instrumentable. When the
 109  * function returns all state is correct, interrupts are enabled and the
 110  * subsequent functions can be instrumented.
 111  *
 112  * This handles lockdep, RCU (context tracking) and tracing state, i.e.
 113  * the functionality provided by enter_from_user_mode().
 114  *
 115  * This is invoked when there is extra architecture specific functionality
 116  * to be done between establishing state and handling user mode entry work.
 117  */
 118 void syscall_enter_from_user_mode_prepare(struct pt_regs *regs);
 119
 120 /**
 121  * syscall_enter_from_user_mode_work - Check and handle work before invoking
 122  *                                     a syscall
 123  * @regs:       Pointer to currents pt_regs
 124  * @syscall:    The syscall number
 125  *
 126  * Invoked from architecture specific syscall entry code with interrupts
 127  * enabled after invoking syscall_enter_from_user_mode_prepare() and extra
 128  * architecture specific work.
 129  *
 130  * Returns: The original or a modified syscall number
 131  *
 132  * If the returned syscall number is -1 then the syscall should be
 133  * skipped. In this case the caller may invoke syscall_set_error() or
 134  * syscall_set_return_value() first.  If neither of those are called and -1
 135  * is returned, then the syscall will fail with ENOSYS.
 136  *
 137  * It handles the following work items:
 138  *
 139  *  1) syscall_work flag dependent invocations of
 140  *     ptrace_report_syscall_entry(), __secure_computing(), trace_sys_enter()
 141  *  2) Invocation of audit_syscall_entry()
 142  */
 143 long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall);
 144
 145 /**
 146  * syscall_enter_from_user_mode - Establish state and check and handle work
 147  *                                before invoking a syscall
 148  * @regs:       Pointer to currents pt_regs
 149  * @syscall:    The syscall number
 150  *
 151  * Invoked from architecture specific syscall entry code with interrupts
 152  * disabled. The calling code has to be non-instrumentable. When the
 153  * function returns all state is correct, interrupts are enabled and the
 154  * subsequent functions can be instrumented.
 155  *
 156  * This is combination of syscall_enter_from_user_mode_prepare() and
 157  * syscall_enter_from_user_mode_work().
 158  *
 159  * Returns: The original or a modified syscall number. See
 160  * syscall_enter_from_user_mode_work() for further explanation.
 161  */
 162 long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);
 163
 164 /**
 165  * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
 166  * @ti_work:    Cached TIF flags gathered with interrupts disabled
 167  *
 168  * Defaults to local_irq_enable(). Can be supplied by architecture specific
 169  * code.
 170  */
 171 static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
 172
 173 #ifndef local_irq_enable_exit_to_user
 174 static inline void local_irq_enable_exit_to_user(unsigned long ti_work)
 175 {
 176         local_irq_enable();
 177 }
 178 #endif
 179
 180 /**
 181  * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
 182  *
 183  * Defaults to local_irq_disable(). Can be supplied by architecture specific
 184  * code.
 185  */
 186 static inline void local_irq_disable_exit_to_user(void);
 187
 188 #ifndef local_irq_disable_exit_to_user
 189 static inline void local_irq_disable_exit_to_user(void)
 190 {
 191         local_irq_disable();
 192 }
 193 #endif
 194
 195 /**
 196  * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
 197  *                               to user mode.
 198  * @regs:       Pointer to currents pt_regs
 199  * @ti_work:    Cached TIF flags gathered with interrupts disabled
 200  *
 201  * Invoked from exit_to_user_mode_loop() with interrupt enabled
 202  *
 203  * Defaults to NOOP. Can be supplied by architecture specific code.
 204  */
 205 static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
 206                                                unsigned long ti_work);
 207
 208 #ifndef arch_exit_to_user_mode_work
 209 static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
 210                                                unsigned long ti_work)
 211 {
 212 }
 213 #endif
 214
 215 /**
 216  * arch_exit_to_user_mode_prepare - Architecture specific preparation for
 217  *                                  exit to user mode.
 218  * @regs:       Pointer to currents pt_regs
 219  * @ti_work:    Cached TIF flags gathered with interrupts disabled
 220  *
 221  * Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
 222  * function before return. Defaults to NOOP.
 223  */
 224 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
 225                                                   unsigned long ti_work);
 226
 227 #ifndef arch_exit_to_user_mode_prepare
 228 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
 229                                                   unsigned long ti_work)
 230 {
 231 }
 232 #endif
 233
 234 /**
 235  * arch_exit_to_user_mode - Architecture specific final work before
 236  *                          exit to user mode.
 237  *
 238  * Invoked from exit_to_user_mode() with interrupt disabled as the last
 239  * function before return. Defaults to NOOP.
 240  *
 241  * This needs to be __always_inline because it is non-instrumentable code
 242  * invoked after context tracking switched to user mode.
 243  *
 244  * An architecture implementation must not do anything complex, no locking
 245  * etc. The main purpose is for speculation mitigations.
 246  */
 247 static __always_inline void arch_exit_to_user_mode(void);
 248
 249 #ifndef arch_exit_to_user_mode
 250 static __always_inline void arch_exit_to_user_mode(void) { }
 251 #endif
 252
 253 /**
 254  * arch_do_signal_or_restart -  Architecture specific signal delivery function
 255  * @regs:       Pointer to currents pt_regs
 256  * @has_signal: actual signal to handle
 257  *
 258  * Invoked from exit_to_user_mode_loop().
 259  */
 260 void arch_do_signal_or_restart(struct pt_regs *regs);
 261
 262 /**
 263  * exit_to_user_mode - Fixup state when exiting to user mode
 264  *
 265  * Syscall/interrupt exit enables interrupts, but the kernel state is
 266  * interrupts disabled when this is invoked. Also tell RCU about it.
 267  *
 268  * 1) Trace interrupts on state
 269  * 2) Invoke context tracking if enabled to adjust RCU state
 270  * 3) Invoke architecture specific last minute exit code, e.g. speculation
 271  *    mitigations, etc.: arch_exit_to_user_mode()
 272  * 4) Tell lockdep that interrupts are enabled
 273  *
 274  * Invoked from architecture specific code when syscall_exit_to_user_mode()
 275  * is not suitable as the last step before returning to userspace. Must be
 276  * invoked with interrupts disabled and the caller must be
 277  * non-instrumentable.
 278  * The caller has to invoke syscall_exit_to_user_mode_work() before this.
 279  */
 280 void exit_to_user_mode(void);
 281
 282 /**
 283  * syscall_exit_to_user_mode_work - Handle work before returning to user mode
 284  * @regs:       Pointer to currents pt_regs
 285  *
 286  * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
 287  * exit_to_user_mode() to perform the final transition to user mode.
 288  *
 289  * Calling convention is the same as for syscall_exit_to_user_mode() and it
 290  * returns with all work handled and interrupts disabled. The caller must
 291  * invoke exit_to_user_mode() before actually switching to user mode to
 292  * make the final state transitions. Interrupts must stay disabled between
 293  * return from this function and the invocation of exit_to_user_mode().
 294  */
 295 void syscall_exit_to_user_mode_work(struct pt_regs *regs);
 296
 297 /**
 298  * syscall_exit_to_user_mode - Handle work before returning to user mode
 299  * @regs:       Pointer to currents pt_regs
 300  *
 301  * Invoked with interrupts enabled and fully valid regs. Returns with all
 302  * work handled, interrupts disabled such that the caller can immediately
 303  * switch to user mode. Called from architecture specific syscall and ret
 304  * from fork code.
 305  *
 306  * The call order is:
 307  *  1) One-time syscall exit work:
 308  *      - rseq syscall exit
 309  *      - audit
 310  *      - syscall tracing
 311  *      - ptrace (single stepping)
 312  *
 313  *  2) Preparatory work
 314  *      - Exit to user mode loop (common TIF handling). Invokes
 315  *        arch_exit_to_user_mode_work() for architecture specific TIF work
 316  *      - Architecture specific one time work arch_exit_to_user_mode_prepare()
 317  *      - Address limit and lockdep checks
 318  *
 319  *  3) Final transition (lockdep, tracing, context tracking, RCU), i.e. the
 320  *     functionality in exit_to_user_mode().
 321  *
 322  * This is a combination of syscall_exit_to_user_mode_work() (1,2) and
 323  * exit_to_user_mode(). This function is preferred unless there is a
 324  * compelling architectural reason to use the separate functions.
 325  */
 326 void syscall_exit_to_user_mode(struct pt_regs *regs);
 327
 328 /**
 329  * irqentry_enter_from_user_mode - Establish state before invoking the irq handler
 330  * @regs:       Pointer to currents pt_regs
 331  *
 332  * Invoked from architecture specific entry code with interrupts disabled.
 333  * Can only be called when the interrupt entry came from user mode. The
 334  * calling code must be non-instrumentable.  When the function returns all
 335  * state is correct and the subsequent functions can be instrumented.
 336  *
 337  * The function establishes state (lockdep, RCU (context tracking), tracing)
 338  */
 339 void irqentry_enter_from_user_mode(struct pt_regs *regs);
 340
 341 /**
 342  * irqentry_exit_to_user_mode - Interrupt exit work
 343  * @regs:       Pointer to current's pt_regs
 344  *
 345  * Invoked with interrupts disabled and fully valid regs. Returns with all
 346  * work handled, interrupts disabled such that the caller can immediately
 347  * switch to user mode. Called from architecture specific interrupt
 348  * handling code.
 349  *
 350  * The call order is #2 and #3 as described in syscall_exit_to_user_mode().
 351  * Interrupt exit is not invoking #1 which is the syscall specific one time
 352  * work.
 353  */
 354 void irqentry_exit_to_user_mode(struct pt_regs *regs);
 355
 356 #ifndef irqentry_state
 357 /**
 358  * struct irqentry_state - Opaque object for exception state storage
 359  * @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
 360  *            exit path has to invoke rcu_irq_exit().
 361  * @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
 362  *           lockdep state is restored correctly on exit from nmi.
 363  *
 364  * This opaque object is filled in by the irqentry_*_enter() functions and
 365  * must be passed back into the corresponding irqentry_*_exit() functions
 366  * when the exception is complete.
 367  *
 368  * Callers of irqentry_*_[enter|exit]() must consider this structure opaque
 369  * and all members private.  Descriptions of the members are provided to aid in
 370  * the maintenance of the irqentry_*() functions.
 371  */
 372 typedef struct irqentry_state {
 373         union {
 374                 bool    exit_rcu;
 375                 bool    lockdep;
 376         };
 377 } irqentry_state_t;
 378 #endif
 379
 380 /**
 381  * irqentry_enter - Handle state tracking on ordinary interrupt entries
 382  * @regs:       Pointer to pt_regs of interrupted context
 383  *
 384  * Invokes:
 385  *  - lockdep irqflag state tracking as low level ASM entry disabled
 386  *    interrupts.
 387  *
 388  *  - Context tracking if the exception hit user mode.
 389  *
 390  *  - The hardirq tracer to keep the state consistent as low level ASM
 391  *    entry disabled interrupts.
 392  *
 393  * As a precondition, this requires that the entry came from user mode,
 394  * idle, or a kernel context in which RCU is watching.
 395  *
 396  * For kernel mode entries RCU handling is done conditional. If RCU is
 397  * watching then the only RCU requirement is to check whether the tick has
 398  * to be restarted. If RCU is not watching then rcu_irq_enter() has to be
 399  * invoked on entry and rcu_irq_exit() on exit.
 400  *
 401  * Avoiding the rcu_irq_enter/exit() calls is an optimization but also
 402  * solves the problem of kernel mode pagefaults which can schedule, which
 403  * is not possible after invoking rcu_irq_enter() without undoing it.
 404  *
 405  * For user mode entries irqentry_enter_from_user_mode() is invoked to
 406  * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
 407  * would not be possible.
 408  *
 409  * Returns: An opaque object that must be passed to idtentry_exit()
 410  */
 411 irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
 412
 413 /**
 414  * irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
 415  *
 416  * Conditional reschedule with additional sanity checks.
 417  */
 418 void raw_irqentry_exit_cond_resched(void);
 419 #ifdef CONFIG_PREEMPT_DYNAMIC
 420 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
 421 #define irqentry_exit_cond_resched_dynamic_enabled      raw_irqentry_exit_cond_resched
 422 #define irqentry_exit_cond_resched_dynamic_disabled     NULL
 423 DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
 424 #define irqentry_exit_cond_resched()    static_call(irqentry_exit_cond_resched)()
 425 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
 426 DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
 427 void dynamic_irqentry_exit_cond_resched(void);
 428 #define irqentry_exit_cond_resched()    dynamic_irqentry_exit_cond_resched()
 429 #endif
 430 #else /* CONFIG_PREEMPT_DYNAMIC */
 431 #define irqentry_exit_cond_resched()    raw_irqentry_exit_cond_resched()
 432 #endif /* CONFIG_PREEMPT_DYNAMIC */
 433
 434 /**
 435  * irqentry_exit - Handle return from exception that used irqentry_enter()
 436  * @regs:       Pointer to pt_regs (exception entry regs)
 437  * @state:      Return value from matching call to irqentry_enter()
 438  *
 439  * Depending on the return target (kernel/user) this runs the necessary
 440  * preemption and work checks if possible and required and returns to
 441  * the caller with interrupts disabled and no further work pending.
 442  *
 443  * This is the last action before returning to the low level ASM code which
 444  * just needs to return to the appropriate context.
 445  *
 446  * Counterpart to irqentry_enter().
 447  */
 448 void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
 449
 450 /**
 451  * irqentry_nmi_enter - Handle NMI entry
 452  * @regs:       Pointer to currents pt_regs
 453  *
 454  * Similar to irqentry_enter() but taking care of the NMI constraints.
 455  */
 456 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
 457
 458 /**
 459  * irqentry_nmi_exit - Handle return from NMI handling
 460  * @regs:       Pointer to pt_regs (NMI entry regs)
 461  * @irq_state:  Return value from matching call to irqentry_nmi_enter()
 462  *
 463  * Last action before returning to the low level assembly code.
 464  *
 465  * Counterpart to irqentry_nmi_enter().
 466  */
 467 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
 468
 469 #endif