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