1 // SPDX-License-Identifier: GPL-2.0 2 3 #include <linux/context_tracking.h> 4 #include <linux/entry-common.h> 5 #include <linux/highmem.h> 6 #include <linux/livepatch.h> 7 #include <linux/audit.h> 8 #include <linux/tick.h> 9 10 #include "common.h" 11 12 #define CREATE_TRACE_POINTS 13 #include <trace/events/syscalls.h> 14 15 /* See comment for enter_from_user_mode() in entry-common.h */ 16 static __always_inline void __enter_from_user_mode(struct pt_regs *regs) 17 { 18 arch_check_user_regs(regs); 19 lockdep_hardirqs_off(CALLER_ADDR0); 20 21 CT_WARN_ON(ct_state() != CONTEXT_USER); 22 user_exit_irqoff(); 23 24 instrumentation_begin(); 25 trace_hardirqs_off_finish(); 26 instrumentation_end(); 27 } 28 29 void noinstr enter_from_user_mode(struct pt_regs *regs) 30 { 31 __enter_from_user_mode(regs); 32 } 33 34 static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) 35 { 36 if (unlikely(audit_context())) { 37 unsigned long args[6]; 38 39 syscall_get_arguments(current, regs, args); 40 audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]); 41 } 42 } 43 44 static long syscall_trace_enter(struct pt_regs *regs, long syscall, 45 unsigned long work) 46 { 47 long ret = 0; 48 49 /* 50 * Handle Syscall User Dispatch. This must comes first, since 51 * the ABI here can be something that doesn't make sense for 52 * other syscall_work features. 53 */ 54 if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) { 55 if (syscall_user_dispatch(regs)) 56 return -1L; 57 } 58 59 /* Handle ptrace */ 60 if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) { 61 ret = arch_syscall_enter_tracehook(regs); 62 if (ret || (work & SYSCALL_WORK_SYSCALL_EMU)) 63 return -1L; 64 } 65 66 /* Do seccomp after ptrace, to catch any tracer changes. */ 67 if (work & SYSCALL_WORK_SECCOMP) { 68 ret = __secure_computing(NULL); 69 if (ret == -1L) 70 return ret; 71 } 72 73 /* Either of the above might have changed the syscall number */ 74 syscall = syscall_get_nr(current, regs); 75 76 if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) 77 trace_sys_enter(regs, syscall); 78 79 syscall_enter_audit(regs, syscall); 80 81 return ret ? : syscall; 82 } 83 84 static __always_inline long 85 __syscall_enter_from_user_work(struct pt_regs *regs, long syscall) 86 { 87 unsigned long work = READ_ONCE(current_thread_info()->syscall_work); 88 89 if (work & SYSCALL_WORK_ENTER) 90 syscall = syscall_trace_enter(regs, syscall, work); 91 92 return syscall; 93 } 94 95 long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall) 96 { 97 return __syscall_enter_from_user_work(regs, syscall); 98 } 99 100 noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) 101 { 102 long ret; 103 104 __enter_from_user_mode(regs); 105 106 instrumentation_begin(); 107 local_irq_enable(); 108 ret = __syscall_enter_from_user_work(regs, syscall); 109 instrumentation_end(); 110 111 return ret; 112 } 113 114 noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) 115 { 116 __enter_from_user_mode(regs); 117 instrumentation_begin(); 118 local_irq_enable(); 119 instrumentation_end(); 120 } 121 122 /* See comment for exit_to_user_mode() in entry-common.h */ 123 static __always_inline void __exit_to_user_mode(void) 124 { 125 instrumentation_begin(); 126 trace_hardirqs_on_prepare(); 127 lockdep_hardirqs_on_prepare(CALLER_ADDR0); 128 instrumentation_end(); 129 130 user_enter_irqoff(); 131 arch_exit_to_user_mode(); 132 lockdep_hardirqs_on(CALLER_ADDR0); 133 } 134 135 void noinstr exit_to_user_mode(void) 136 { 137 __exit_to_user_mode(); 138 } 139 140 /* Workaround to allow gradual conversion of architecture code */ 141 void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { } 142 143 static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work) 144 { 145 if (ti_work & _TIF_NOTIFY_SIGNAL) 146 tracehook_notify_signal(); 147 148 arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING); 149 } 150 151 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, 152 unsigned long ti_work) 153 { 154 /* 155 * Before returning to user space ensure that all pending work 156 * items have been completed. 157 */ 158 while (ti_work & EXIT_TO_USER_MODE_WORK) { 159 160 local_irq_enable_exit_to_user(ti_work); 161 162 if (ti_work & _TIF_NEED_RESCHED) 163 schedule(); 164 165 if (ti_work & _TIF_UPROBE) 166 uprobe_notify_resume(regs); 167 168 if (ti_work & _TIF_PATCH_PENDING) 169 klp_update_patch_state(current); 170 171 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) 172 handle_signal_work(regs, ti_work); 173 174 if (ti_work & _TIF_NOTIFY_RESUME) { 175 tracehook_notify_resume(regs); 176 rseq_handle_notify_resume(NULL, regs); 177 } 178 179 /* Architecture specific TIF work */ 180 arch_exit_to_user_mode_work(regs, ti_work); 181 182 /* 183 * Disable interrupts and reevaluate the work flags as they 184 * might have changed while interrupts and preemption was 185 * enabled above. 186 */ 187 local_irq_disable_exit_to_user(); 188 189 /* Check if any of the above work has queued a deferred wakeup */ 190 tick_nohz_user_enter_prepare(); 191 192 ti_work = READ_ONCE(current_thread_info()->flags); 193 } 194 195 /* Return the latest work state for arch_exit_to_user_mode() */ 196 return ti_work; 197 } 198 199 static void exit_to_user_mode_prepare(struct pt_regs *regs) 200 { 201 unsigned long ti_work = READ_ONCE(current_thread_info()->flags); 202 203 lockdep_assert_irqs_disabled(); 204 205 /* Flush pending rcuog wakeup before the last need_resched() check */ 206 tick_nohz_user_enter_prepare(); 207 208 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) 209 ti_work = exit_to_user_mode_loop(regs, ti_work); 210 211 arch_exit_to_user_mode_prepare(regs, ti_work); 212 213 /* Ensure that the address limit is intact and no locks are held */ 214 addr_limit_user_check(); 215 kmap_assert_nomap(); 216 lockdep_assert_irqs_disabled(); 217 lockdep_sys_exit(); 218 } 219 220 /* 221 * If SYSCALL_EMU is set, then the only reason to report is when 222 * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall 223 * instruction has been already reported in syscall_enter_from_user_mode(). 224 */ 225 static inline bool report_single_step(unsigned long work) 226 { 227 if (work & SYSCALL_WORK_SYSCALL_EMU) 228 return false; 229 230 return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP; 231 } 232 233 static void syscall_exit_work(struct pt_regs *regs, unsigned long work) 234 { 235 bool step; 236 237 /* 238 * If the syscall was rolled back due to syscall user dispatching, 239 * then the tracers below are not invoked for the same reason as 240 * the entry side was not invoked in syscall_trace_enter(): The ABI 241 * of these syscalls is unknown. 242 */ 243 if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) { 244 if (unlikely(current->syscall_dispatch.on_dispatch)) { 245 current->syscall_dispatch.on_dispatch = false; 246 return; 247 } 248 } 249 250 audit_syscall_exit(regs); 251 252 if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT) 253 trace_sys_exit(regs, syscall_get_return_value(current, regs)); 254 255 step = report_single_step(work); 256 if (step || work & SYSCALL_WORK_SYSCALL_TRACE) 257 arch_syscall_exit_tracehook(regs, step); 258 } 259 260 /* 261 * Syscall specific exit to user mode preparation. Runs with interrupts 262 * enabled. 263 */ 264 static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs) 265 { 266 unsigned long work = READ_ONCE(current_thread_info()->syscall_work); 267 unsigned long nr = syscall_get_nr(current, regs); 268 269 CT_WARN_ON(ct_state() != CONTEXT_KERNEL); 270 271 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { 272 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr)) 273 local_irq_enable(); 274 } 275 276 rseq_syscall(regs); 277 278 /* 279 * Do one-time syscall specific work. If these work items are 280 * enabled, we want to run them exactly once per syscall exit with 281 * interrupts enabled. 282 */ 283 if (unlikely(work & SYSCALL_WORK_EXIT)) 284 syscall_exit_work(regs, work); 285 } 286 287 static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs) 288 { 289 syscall_exit_to_user_mode_prepare(regs); 290 local_irq_disable_exit_to_user(); 291 exit_to_user_mode_prepare(regs); 292 } 293 294 void syscall_exit_to_user_mode_work(struct pt_regs *regs) 295 { 296 __syscall_exit_to_user_mode_work(regs); 297 } 298 299 __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs) 300 { 301 instrumentation_begin(); 302 __syscall_exit_to_user_mode_work(regs); 303 instrumentation_end(); 304 __exit_to_user_mode(); 305 } 306 307 noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs) 308 { 309 __enter_from_user_mode(regs); 310 } 311 312 noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs) 313 { 314 instrumentation_begin(); 315 exit_to_user_mode_prepare(regs); 316 instrumentation_end(); 317 __exit_to_user_mode(); 318 } 319 320 noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs) 321 { 322 irqentry_state_t ret = { 323 .exit_rcu = false, 324 }; 325 326 if (user_mode(regs)) { 327 irqentry_enter_from_user_mode(regs); 328 return ret; 329 } 330 331 /* 332 * If this entry hit the idle task invoke rcu_irq_enter() whether 333 * RCU is watching or not. 334 * 335 * Interrupts can nest when the first interrupt invokes softirq 336 * processing on return which enables interrupts. 337 * 338 * Scheduler ticks in the idle task can mark quiescent state and 339 * terminate a grace period, if and only if the timer interrupt is 340 * not nested into another interrupt. 341 * 342 * Checking for rcu_is_watching() here would prevent the nesting 343 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is 344 * the tick then rcu_flavor_sched_clock_irq() would wrongfully 345 * assume that it is the first interrupt and eventually claim 346 * quiescent state and end grace periods prematurely. 347 * 348 * Unconditionally invoke rcu_irq_enter() so RCU state stays 349 * consistent. 350 * 351 * TINY_RCU does not support EQS, so let the compiler eliminate 352 * this part when enabled. 353 */ 354 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) { 355 /* 356 * If RCU is not watching then the same careful 357 * sequence vs. lockdep and tracing is required 358 * as in irqentry_enter_from_user_mode(). 359 */ 360 lockdep_hardirqs_off(CALLER_ADDR0); 361 rcu_irq_enter(); 362 instrumentation_begin(); 363 trace_hardirqs_off_finish(); 364 instrumentation_end(); 365 366 ret.exit_rcu = true; 367 return ret; 368 } 369 370 /* 371 * If RCU is watching then RCU only wants to check whether it needs 372 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick() 373 * already contains a warning when RCU is not watching, so no point 374 * in having another one here. 375 */ 376 lockdep_hardirqs_off(CALLER_ADDR0); 377 instrumentation_begin(); 378 rcu_irq_enter_check_tick(); 379 trace_hardirqs_off_finish(); 380 instrumentation_end(); 381 382 return ret; 383 } 384 385 void irqentry_exit_cond_resched(void) 386 { 387 if (!preempt_count()) { 388 /* Sanity check RCU and thread stack */ 389 rcu_irq_exit_check_preempt(); 390 if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) 391 WARN_ON_ONCE(!on_thread_stack()); 392 if (need_resched()) 393 preempt_schedule_irq(); 394 } 395 } 396 #ifdef CONFIG_PREEMPT_DYNAMIC 397 DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched); 398 #endif 399 400 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state) 401 { 402 lockdep_assert_irqs_disabled(); 403 404 /* Check whether this returns to user mode */ 405 if (user_mode(regs)) { 406 irqentry_exit_to_user_mode(regs); 407 } else if (!regs_irqs_disabled(regs)) { 408 /* 409 * If RCU was not watching on entry this needs to be done 410 * carefully and needs the same ordering of lockdep/tracing 411 * and RCU as the return to user mode path. 412 */ 413 if (state.exit_rcu) { 414 instrumentation_begin(); 415 /* Tell the tracer that IRET will enable interrupts */ 416 trace_hardirqs_on_prepare(); 417 lockdep_hardirqs_on_prepare(CALLER_ADDR0); 418 instrumentation_end(); 419 rcu_irq_exit(); 420 lockdep_hardirqs_on(CALLER_ADDR0); 421 return; 422 } 423 424 instrumentation_begin(); 425 if (IS_ENABLED(CONFIG_PREEMPTION)) { 426 #ifdef CONFIG_PREEMPT_DYNAMIC 427 static_call(irqentry_exit_cond_resched)(); 428 #else 429 irqentry_exit_cond_resched(); 430 #endif 431 } 432 /* Covers both tracing and lockdep */ 433 trace_hardirqs_on(); 434 instrumentation_end(); 435 } else { 436 /* 437 * IRQ flags state is correct already. Just tell RCU if it 438 * was not watching on entry. 439 */ 440 if (state.exit_rcu) 441 rcu_irq_exit(); 442 } 443 } 444 445 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs) 446 { 447 irqentry_state_t irq_state; 448 449 irq_state.lockdep = lockdep_hardirqs_enabled(); 450 451 __nmi_enter(); 452 lockdep_hardirqs_off(CALLER_ADDR0); 453 lockdep_hardirq_enter(); 454 rcu_nmi_enter(); 455 456 instrumentation_begin(); 457 trace_hardirqs_off_finish(); 458 ftrace_nmi_enter(); 459 instrumentation_end(); 460 461 return irq_state; 462 } 463 464 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state) 465 { 466 instrumentation_begin(); 467 ftrace_nmi_exit(); 468 if (irq_state.lockdep) { 469 trace_hardirqs_on_prepare(); 470 lockdep_hardirqs_on_prepare(CALLER_ADDR0); 471 } 472 instrumentation_end(); 473 474 rcu_nmi_exit(); 475 lockdep_hardirq_exit(); 476 if (irq_state.lockdep) 477 lockdep_hardirqs_on(CALLER_ADDR0); 478 __nmi_exit(); 479 } 480