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 9 #include "common.h" 10 11 #define CREATE_TRACE_POINTS 12 #include <trace/events/syscalls.h> 13 14 /* See comment for enter_from_user_mode() in entry-common.h */ 15 static __always_inline void __enter_from_user_mode(struct pt_regs *regs) 16 { 17 arch_check_user_regs(regs); 18 lockdep_hardirqs_off(CALLER_ADDR0); 19 20 CT_WARN_ON(ct_state() != CONTEXT_USER); 21 user_exit_irqoff(); 22 23 instrumentation_begin(); 24 trace_hardirqs_off_finish(); 25 instrumentation_end(); 26 } 27 28 void noinstr enter_from_user_mode(struct pt_regs *regs) 29 { 30 __enter_from_user_mode(regs); 31 } 32 33 static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) 34 { 35 if (unlikely(audit_context())) { 36 unsigned long args[6]; 37 38 syscall_get_arguments(current, regs, args); 39 audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]); 40 } 41 } 42 43 static long syscall_trace_enter(struct pt_regs *regs, long syscall, 44 unsigned long work) 45 { 46 long ret = 0; 47 48 /* 49 * Handle Syscall User Dispatch. This must comes first, since 50 * the ABI here can be something that doesn't make sense for 51 * other syscall_work features. 52 */ 53 if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) { 54 if (syscall_user_dispatch(regs)) 55 return -1L; 56 } 57 58 /* Handle ptrace */ 59 if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) { 60 ret = arch_syscall_enter_tracehook(regs); 61 if (ret || (work & SYSCALL_WORK_SYSCALL_EMU)) 62 return -1L; 63 } 64 65 /* Do seccomp after ptrace, to catch any tracer changes. */ 66 if (work & SYSCALL_WORK_SECCOMP) { 67 ret = __secure_computing(NULL); 68 if (ret == -1L) 69 return ret; 70 } 71 72 /* Either of the above might have changed the syscall number */ 73 syscall = syscall_get_nr(current, regs); 74 75 if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) 76 trace_sys_enter(regs, syscall); 77 78 syscall_enter_audit(regs, syscall); 79 80 return ret ? : syscall; 81 } 82 83 static __always_inline long 84 __syscall_enter_from_user_work(struct pt_regs *regs, long syscall) 85 { 86 unsigned long work = READ_ONCE(current_thread_info()->syscall_work); 87 88 if (work & SYSCALL_WORK_ENTER) 89 syscall = syscall_trace_enter(regs, syscall, work); 90 91 return syscall; 92 } 93 94 long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall) 95 { 96 return __syscall_enter_from_user_work(regs, syscall); 97 } 98 99 noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) 100 { 101 long ret; 102 103 __enter_from_user_mode(regs); 104 105 instrumentation_begin(); 106 local_irq_enable(); 107 ret = __syscall_enter_from_user_work(regs, syscall); 108 instrumentation_end(); 109 110 return ret; 111 } 112 113 noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) 114 { 115 __enter_from_user_mode(regs); 116 instrumentation_begin(); 117 local_irq_enable(); 118 instrumentation_end(); 119 } 120 121 /* See comment for exit_to_user_mode() in entry-common.h */ 122 static __always_inline void __exit_to_user_mode(void) 123 { 124 instrumentation_begin(); 125 trace_hardirqs_on_prepare(); 126 lockdep_hardirqs_on_prepare(CALLER_ADDR0); 127 instrumentation_end(); 128 129 user_enter_irqoff(); 130 arch_exit_to_user_mode(); 131 lockdep_hardirqs_on(CALLER_ADDR0); 132 } 133 134 void noinstr exit_to_user_mode(void) 135 { 136 __exit_to_user_mode(); 137 } 138 139 /* Workaround to allow gradual conversion of architecture code */ 140 void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { } 141 142 static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work) 143 { 144 if (ti_work & _TIF_NOTIFY_SIGNAL) 145 tracehook_notify_signal(); 146 147 arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING); 148 } 149 150 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, 151 unsigned long ti_work) 152 { 153 /* 154 * Before returning to user space ensure that all pending work 155 * items have been completed. 156 */ 157 while (ti_work & EXIT_TO_USER_MODE_WORK) { 158 159 local_irq_enable_exit_to_user(ti_work); 160 161 if (ti_work & _TIF_NEED_RESCHED) 162 schedule(); 163 164 if (ti_work & _TIF_UPROBE) 165 uprobe_notify_resume(regs); 166 167 if (ti_work & _TIF_PATCH_PENDING) 168 klp_update_patch_state(current); 169 170 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) 171 handle_signal_work(regs, ti_work); 172 173 if (ti_work & _TIF_NOTIFY_RESUME) { 174 tracehook_notify_resume(regs); 175 rseq_handle_notify_resume(NULL, regs); 176 } 177 178 /* Architecture specific TIF work */ 179 arch_exit_to_user_mode_work(regs, ti_work); 180 181 /* 182 * Disable interrupts and reevaluate the work flags as they 183 * might have changed while interrupts and preemption was 184 * enabled above. 185 */ 186 local_irq_disable_exit_to_user(); 187 ti_work = READ_ONCE(current_thread_info()->flags); 188 } 189 190 /* Return the latest work state for arch_exit_to_user_mode() */ 191 return ti_work; 192 } 193 194 static void exit_to_user_mode_prepare(struct pt_regs *regs) 195 { 196 unsigned long ti_work = READ_ONCE(current_thread_info()->flags); 197 198 lockdep_assert_irqs_disabled(); 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 #ifndef _TIF_SINGLESTEP 213 static inline bool report_single_step(unsigned long work) 214 { 215 return false; 216 } 217 #else 218 /* 219 * If SYSCALL_EMU is set, then the only reason to report is when 220 * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall 221 * instruction has been already reported in syscall_enter_from_user_mode(). 222 */ 223 static inline bool report_single_step(unsigned long work) 224 { 225 if (!(work & SYSCALL_WORK_SYSCALL_EMU)) 226 return false; 227 228 return !!(current_thread_info()->flags & _TIF_SINGLESTEP); 229 } 230 #endif 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 interupt 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 } 396 397 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state) 398 { 399 lockdep_assert_irqs_disabled(); 400 401 /* Check whether this returns to user mode */ 402 if (user_mode(regs)) { 403 irqentry_exit_to_user_mode(regs); 404 } else if (!regs_irqs_disabled(regs)) { 405 /* 406 * If RCU was not watching on entry this needs to be done 407 * carefully and needs the same ordering of lockdep/tracing 408 * and RCU as the return to user mode path. 409 */ 410 if (state.exit_rcu) { 411 instrumentation_begin(); 412 /* Tell the tracer that IRET will enable interrupts */ 413 trace_hardirqs_on_prepare(); 414 lockdep_hardirqs_on_prepare(CALLER_ADDR0); 415 instrumentation_end(); 416 rcu_irq_exit(); 417 lockdep_hardirqs_on(CALLER_ADDR0); 418 return; 419 } 420 421 instrumentation_begin(); 422 if (IS_ENABLED(CONFIG_PREEMPTION)) 423 irqentry_exit_cond_resched(); 424 /* Covers both tracing and lockdep */ 425 trace_hardirqs_on(); 426 instrumentation_end(); 427 } else { 428 /* 429 * IRQ flags state is correct already. Just tell RCU if it 430 * was not watching on entry. 431 */ 432 if (state.exit_rcu) 433 rcu_irq_exit(); 434 } 435 } 436 437 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs) 438 { 439 irqentry_state_t irq_state; 440 441 irq_state.lockdep = lockdep_hardirqs_enabled(); 442 443 __nmi_enter(); 444 lockdep_hardirqs_off(CALLER_ADDR0); 445 lockdep_hardirq_enter(); 446 rcu_nmi_enter(); 447 448 instrumentation_begin(); 449 trace_hardirqs_off_finish(); 450 ftrace_nmi_enter(); 451 instrumentation_end(); 452 453 return irq_state; 454 } 455 456 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state) 457 { 458 instrumentation_begin(); 459 ftrace_nmi_exit(); 460 if (irq_state.lockdep) { 461 trace_hardirqs_on_prepare(); 462 lockdep_hardirqs_on_prepare(CALLER_ADDR0); 463 } 464 instrumentation_end(); 465 466 rcu_nmi_exit(); 467 lockdep_hardirq_exit(); 468 if (irq_state.lockdep) 469 lockdep_hardirqs_on(CALLER_ADDR0); 470 __nmi_exit(); 471 } 472