Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 | // SPDX-License-Identifier: GPL-2.0 #include <linux/context_tracking.h> #include <linux/entry-common.h> #include <linux/livepatch.h> #include <linux/audit.h> #define CREATE_TRACE_POINTS #include <trace/events/syscalls.h> /** * enter_from_user_mode - Establish state when coming from user mode * * Syscall/interrupt entry disables interrupts, but user mode is traced as * interrupts enabled. Also with NO_HZ_FULL RCU might be idle. * * 1) Tell lockdep that interrupts are disabled * 2) Invoke context tracking if enabled to reactivate RCU * 3) Trace interrupts off state */ static __always_inline void enter_from_user_mode(struct pt_regs *regs) { arch_check_user_regs(regs); lockdep_hardirqs_off(CALLER_ADDR0); CT_WARN_ON(ct_state() != CONTEXT_USER); user_exit_irqoff(); instrumentation_begin(); trace_hardirqs_off_finish(); instrumentation_end(); } static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) { if (unlikely(audit_context())) { unsigned long args[6]; syscall_get_arguments(current, regs, args); audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]); } } static long syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long ti_work) { long ret = 0; /* Handle ptrace */ if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) { ret = arch_syscall_enter_tracehook(regs); if (ret || (ti_work & _TIF_SYSCALL_EMU)) return -1L; } /* Do seccomp after ptrace, to catch any tracer changes. */ if (ti_work & _TIF_SECCOMP) { ret = __secure_computing(NULL); if (ret == -1L) return ret; } /* Either of the above might have changed the syscall number */ syscall = syscall_get_nr(current, regs); if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT)) trace_sys_enter(regs, syscall); syscall_enter_audit(regs, syscall); return ret ? : syscall; } static __always_inline long __syscall_enter_from_user_work(struct pt_regs *regs, long syscall) { unsigned long ti_work; ti_work = READ_ONCE(current_thread_info()->flags); if (ti_work & SYSCALL_ENTER_WORK) syscall = syscall_trace_enter(regs, syscall, ti_work); return syscall; } long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall) { return __syscall_enter_from_user_work(regs, syscall); } noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) { long ret; enter_from_user_mode(regs); instrumentation_begin(); local_irq_enable(); ret = __syscall_enter_from_user_work(regs, syscall); instrumentation_end(); return ret; } noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) { enter_from_user_mode(regs); instrumentation_begin(); local_irq_enable(); instrumentation_end(); } /** * exit_to_user_mode - Fixup state when exiting to user mode * * Syscall/interupt exit enables interrupts, but the kernel state is * interrupts disabled when this is invoked. Also tell RCU about it. * * 1) Trace interrupts on state * 2) Invoke context tracking if enabled to adjust RCU state * 3) Invoke architecture specific last minute exit code, e.g. speculation * mitigations, etc. * 4) Tell lockdep that interrupts are enabled */ static __always_inline void exit_to_user_mode(void) { instrumentation_begin(); trace_hardirqs_on_prepare(); lockdep_hardirqs_on_prepare(CALLER_ADDR0); instrumentation_end(); user_enter_irqoff(); arch_exit_to_user_mode(); lockdep_hardirqs_on(CALLER_ADDR0); } /* Workaround to allow gradual conversion of architecture code */ void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { } static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work) { if (ti_work & _TIF_NOTIFY_SIGNAL) tracehook_notify_signal(); arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING); } static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, unsigned long ti_work) { /* * Before returning to user space ensure that all pending work * items have been completed. */ while (ti_work & EXIT_TO_USER_MODE_WORK) { local_irq_enable_exit_to_user(ti_work); if (ti_work & _TIF_NEED_RESCHED) schedule(); if (ti_work & _TIF_UPROBE) uprobe_notify_resume(regs); if (ti_work & _TIF_PATCH_PENDING) klp_update_patch_state(current); if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) handle_signal_work(regs, ti_work); if (ti_work & _TIF_NOTIFY_RESUME) { tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); } /* Architecture specific TIF work */ arch_exit_to_user_mode_work(regs, ti_work); /* * Disable interrupts and reevaluate the work flags as they * might have changed while interrupts and preemption was * enabled above. */ local_irq_disable_exit_to_user(); ti_work = READ_ONCE(current_thread_info()->flags); } /* Return the latest work state for arch_exit_to_user_mode() */ return ti_work; } static void exit_to_user_mode_prepare(struct pt_regs *regs) { unsigned long ti_work = READ_ONCE(current_thread_info()->flags); lockdep_assert_irqs_disabled(); if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) ti_work = exit_to_user_mode_loop(regs, ti_work); arch_exit_to_user_mode_prepare(regs, ti_work); /* Ensure that the address limit is intact and no locks are held */ addr_limit_user_check(); lockdep_assert_irqs_disabled(); lockdep_sys_exit(); } #ifndef _TIF_SINGLESTEP static inline bool report_single_step(unsigned long ti_work) { return false; } #else /* * If TIF_SYSCALL_EMU is set, then the only reason to report is when * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall * instruction has been already reported in syscall_enter_from_user_mode(). */ #define SYSEMU_STEP (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU) static inline bool report_single_step(unsigned long ti_work) { return (ti_work & SYSEMU_STEP) == _TIF_SINGLESTEP; } #endif static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work) { bool step; audit_syscall_exit(regs); if (ti_work & _TIF_SYSCALL_TRACEPOINT) trace_sys_exit(regs, syscall_get_return_value(current, regs)); step = report_single_step(ti_work); if (step || ti_work & _TIF_SYSCALL_TRACE) arch_syscall_exit_tracehook(regs, step); } /* * Syscall specific exit to user mode preparation. Runs with interrupts * enabled. */ static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs) { u32 cached_flags = READ_ONCE(current_thread_info()->flags); unsigned long nr = syscall_get_nr(current, regs); CT_WARN_ON(ct_state() != CONTEXT_KERNEL); if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr)) local_irq_enable(); } rseq_syscall(regs); /* * Do one-time syscall specific work. If these work items are * enabled, we want to run them exactly once per syscall exit with * interrupts enabled. */ if (unlikely(cached_flags & SYSCALL_EXIT_WORK)) syscall_exit_work(regs, cached_flags); } __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs) { instrumentation_begin(); syscall_exit_to_user_mode_prepare(regs); local_irq_disable_exit_to_user(); exit_to_user_mode_prepare(regs); instrumentation_end(); exit_to_user_mode(); } noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs) { enter_from_user_mode(regs); } noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs) { instrumentation_begin(); exit_to_user_mode_prepare(regs); instrumentation_end(); exit_to_user_mode(); } noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs) { irqentry_state_t ret = { .exit_rcu = false, }; if (user_mode(regs)) { irqentry_enter_from_user_mode(regs); return ret; } /* * If this entry hit the idle task invoke rcu_irq_enter() whether * RCU is watching or not. * * Interupts can nest when the first interrupt invokes softirq * processing on return which enables interrupts. * * Scheduler ticks in the idle task can mark quiescent state and * terminate a grace period, if and only if the timer interrupt is * not nested into another interrupt. * * Checking for rcu_is_watching() here would prevent the nesting * interrupt to invoke rcu_irq_enter(). If that nested interrupt is * the tick then rcu_flavor_sched_clock_irq() would wrongfully * assume that it is the first interupt and eventually claim * quiescient state and end grace periods prematurely. * * Unconditionally invoke rcu_irq_enter() so RCU state stays * consistent. * * TINY_RCU does not support EQS, so let the compiler eliminate * this part when enabled. */ if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) { /* * If RCU is not watching then the same careful * sequence vs. lockdep and tracing is required * as in irq_enter_from_user_mode(). */ lockdep_hardirqs_off(CALLER_ADDR0); rcu_irq_enter(); instrumentation_begin(); trace_hardirqs_off_finish(); instrumentation_end(); ret.exit_rcu = true; return ret; } /* * If RCU is watching then RCU only wants to check whether it needs * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick() * already contains a warning when RCU is not watching, so no point * in having another one here. */ lockdep_hardirqs_off(CALLER_ADDR0); instrumentation_begin(); rcu_irq_enter_check_tick(); trace_hardirqs_off_finish(); instrumentation_end(); return ret; } void irqentry_exit_cond_resched(void) { if (!preempt_count()) { /* Sanity check RCU and thread stack */ rcu_irq_exit_check_preempt(); if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) WARN_ON_ONCE(!on_thread_stack()); if (need_resched()) preempt_schedule_irq(); } } noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state) { lockdep_assert_irqs_disabled(); /* Check whether this returns to user mode */ if (user_mode(regs)) { irqentry_exit_to_user_mode(regs); } else if (!regs_irqs_disabled(regs)) { /* * If RCU was not watching on entry this needs to be done * carefully and needs the same ordering of lockdep/tracing * and RCU as the return to user mode path. */ if (state.exit_rcu) { instrumentation_begin(); /* Tell the tracer that IRET will enable interrupts */ trace_hardirqs_on_prepare(); lockdep_hardirqs_on_prepare(CALLER_ADDR0); instrumentation_end(); rcu_irq_exit(); lockdep_hardirqs_on(CALLER_ADDR0); return; } instrumentation_begin(); if (IS_ENABLED(CONFIG_PREEMPTION)) irqentry_exit_cond_resched(); /* Covers both tracing and lockdep */ trace_hardirqs_on(); instrumentation_end(); } else { /* * IRQ flags state is correct already. Just tell RCU if it * was not watching on entry. */ if (state.exit_rcu) rcu_irq_exit(); } } irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs) { irqentry_state_t irq_state; irq_state.lockdep = lockdep_hardirqs_enabled(); __nmi_enter(); lockdep_hardirqs_off(CALLER_ADDR0); lockdep_hardirq_enter(); rcu_nmi_enter(); instrumentation_begin(); trace_hardirqs_off_finish(); ftrace_nmi_enter(); instrumentation_end(); return irq_state; } void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state) { instrumentation_begin(); ftrace_nmi_exit(); if (irq_state.lockdep) { trace_hardirqs_on_prepare(); lockdep_hardirqs_on_prepare(CALLER_ADDR0); } instrumentation_end(); rcu_nmi_exit(); lockdep_hardirq_exit(); if (irq_state.lockdep) lockdep_hardirqs_on(CALLER_ADDR0); __nmi_exit(); } |