1 /*- 2 * SPDX-License-Identifier: BSD-4-Clause 3 * 4 * Copyright (C) 1994, David Greenman 5 * Copyright (c) 1990, 1993 6 * The Regents of the University of California. All rights reserved. 7 * Copyright (c) 2007, 2022 The FreeBSD Foundation 8 * 9 * This code is derived from software contributed to Berkeley by 10 * the University of Utah, and William Jolitz. 11 * 12 * Portions of this software were developed by A. Joseph Koshy under 13 * sponsorship from the FreeBSD Foundation and Google, Inc. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 3. All advertising materials mentioning features or use of this software 24 * must display the following acknowledgement: 25 * This product includes software developed by the University of 26 * California, Berkeley and its contributors. 27 * 4. Neither the name of the University nor the names of its contributors 28 * may be used to endorse or promote products derived from this software 29 * without specific prior written permission. 30 * 31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 41 * SUCH DAMAGE. 42 */ 43 44 #include <sys/cdefs.h> 45 #include "opt_hwpmc_hooks.h" 46 47 #include <sys/param.h> 48 #include <sys/kernel.h> 49 #include <sys/limits.h> 50 #include <sys/lock.h> 51 #include <sys/msan.h> 52 #include <sys/mutex.h> 53 #include <sys/proc.h> 54 #include <sys/ktr.h> 55 #include <sys/resourcevar.h> 56 #include <sys/sched.h> 57 #include <sys/syscall.h> 58 #include <sys/syscallsubr.h> 59 #include <sys/sysent.h> 60 #include <sys/systm.h> 61 #include <sys/vmmeter.h> 62 63 #include <machine/cpu.h> 64 65 #ifdef VIMAGE 66 #include <net/vnet.h> 67 #endif 68 69 #ifdef HWPMC_HOOKS 70 #include <sys/pmckern.h> 71 #endif 72 73 #ifdef EPOCH_TRACE 74 #include <sys/epoch.h> 75 #endif 76 77 volatile uint32_t __read_frequently hpts_that_need_softclock = 0; 78 79 void (*tcp_hpts_softclock)(void); 80 81 /* 82 * Define the code needed before returning to user mode, for trap and 83 * syscall. 84 */ 85 void 86 userret(struct thread *td, struct trapframe *frame) 87 { 88 struct proc *p = td->td_proc; 89 90 CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid, 91 td->td_name); 92 KASSERT((p->p_flag & P_WEXIT) == 0, 93 ("Exiting process returns to usermode")); 94 #ifdef DIAGNOSTIC 95 /* 96 * Check that we called signotify() enough. For 97 * multi-threaded processes, where signal distribution might 98 * change due to other threads changing sigmask, the check is 99 * racy and cannot be performed reliably. 100 * If current process is vfork child, indicated by P_PPWAIT, then 101 * issignal() ignores stops, so we block the check to avoid 102 * classifying pending signals. 103 */ 104 if (p->p_numthreads == 1) { 105 PROC_LOCK(p); 106 thread_lock(td); 107 if ((p->p_flag & P_PPWAIT) == 0 && 108 (td->td_pflags & TDP_SIGFASTBLOCK) == 0 && 109 SIGPENDING(td) && !td_ast_pending(td, TDA_AST) && 110 !td_ast_pending(td, TDA_SIG)) { 111 thread_unlock(td); 112 panic( 113 "failed to set signal flags for ast p %p " 114 "td %p td_ast %#x fl %#x", 115 p, td, td->td_ast, td->td_flags); 116 } 117 thread_unlock(td); 118 PROC_UNLOCK(p); 119 } 120 #endif 121 122 /* 123 * Charge system time if profiling. 124 */ 125 if (__predict_false(p->p_flag & P_PROFIL)) 126 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio); 127 128 #ifdef HWPMC_HOOKS 129 if (PMC_THREAD_HAS_SAMPLES(td)) 130 PMC_CALL_HOOK(td, PMC_FN_THR_USERRET, NULL); 131 #endif 132 /* 133 * Calling tcp_hpts_softclock() here allows us to avoid frequent, 134 * expensive callouts that trash the cache and lead to a much higher 135 * number of interrupts and context switches. Testing on busy web 136 * servers at Netflix has shown that this improves CPU use by 7% over 137 * relying only on callouts to drive HPTS, and also results in idle 138 * power savings on mostly idle servers. 139 * This was inspired by the paper "Soft Timers: Efficient Microsecond 140 * Software Timer Support for Network Processing" 141 * by Mohit Aron and Peter Druschel. 142 */ 143 tcp_hpts_softclock(); 144 /* 145 * Let the scheduler adjust our priority etc. 146 */ 147 sched_userret(td); 148 149 /* 150 * Check for misbehavior. 151 * 152 * In case there is a callchain tracing ongoing because of 153 * hwpmc(4), skip the scheduler pinning check. 154 * hwpmc(4) subsystem, infact, will collect callchain informations 155 * at ast() checkpoint, which is past userret(). 156 */ 157 WITNESS_WARN(WARN_PANIC, NULL, "userret: returning"); 158 KASSERT(td->td_critnest == 0, 159 ("userret: Returning in a critical section")); 160 KASSERT(td->td_locks == 0, 161 ("userret: Returning with %d locks held", td->td_locks)); 162 KASSERT(td->td_rw_rlocks == 0, 163 ("userret: Returning with %d rwlocks held in read mode", 164 td->td_rw_rlocks)); 165 KASSERT(td->td_sx_slocks == 0, 166 ("userret: Returning with %d sx locks held in shared mode", 167 td->td_sx_slocks)); 168 KASSERT(td->td_lk_slocks == 0, 169 ("userret: Returning with %d lockmanager locks held in shared mode", 170 td->td_lk_slocks)); 171 KASSERT((td->td_pflags & TDP_NOFAULTING) == 0, 172 ("userret: Returning with pagefaults disabled")); 173 if (__predict_false(!THREAD_CAN_SLEEP())) { 174 #ifdef EPOCH_TRACE 175 epoch_trace_list(curthread); 176 #endif 177 KASSERT(0, ("userret: Returning with sleep disabled")); 178 } 179 KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0, 180 ("userret: Returning with pinned thread")); 181 KASSERT(td->td_vp_reserved == NULL, 182 ("userret: Returning with preallocated vnode")); 183 KASSERT((td->td_flags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0, 184 ("userret: Returning with stop signals deferred")); 185 KASSERT(td->td_vslock_sz == 0, 186 ("userret: Returning with vslock-wired space")); 187 #ifdef VIMAGE 188 /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */ 189 VNET_ASSERT(curvnet == NULL, 190 ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s", 191 __func__, td, p->p_pid, td->td_name, curvnet, 192 (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A")); 193 #endif 194 } 195 196 static void 197 ast_prep(struct thread *td, int tda __unused) 198 { 199 VM_CNT_INC(v_trap); 200 td->td_pticks = 0; 201 if (td->td_cowgen != atomic_load_int(&td->td_proc->p_cowgen)) 202 thread_cow_update(td); 203 204 } 205 206 struct ast_entry { 207 int ae_flags; 208 int ae_tdp; 209 void (*ae_f)(struct thread *td, int ast); 210 }; 211 212 _Static_assert(TDAI(TDA_MAX) <= UINT_MAX, "Too many ASTs"); 213 214 static struct ast_entry ast_entries[TDA_MAX] __read_mostly = { 215 [TDA_AST] = { .ae_f = ast_prep, .ae_flags = ASTR_UNCOND}, 216 }; 217 218 void 219 ast_register(int ast, int flags, int tdp, 220 void (*f)(struct thread *, int asts)) 221 { 222 struct ast_entry *ae; 223 224 MPASS(ast < TDA_MAX); 225 MPASS((flags & ASTR_TDP) == 0 || ((flags & ASTR_ASTF_REQUIRED) != 0 226 && __bitcount(tdp) == 1)); 227 ae = &ast_entries[ast]; 228 MPASS(ae->ae_f == NULL); 229 ae->ae_flags = flags; 230 ae->ae_tdp = tdp; 231 atomic_interrupt_fence(); 232 ae->ae_f = f; 233 } 234 235 /* 236 * XXXKIB Note that the deregistration of an AST handler does not 237 * drain threads possibly executing it, which affects unloadable 238 * modules. The issue is either handled by the subsystem using 239 * handlers, or simply ignored. Fixing the problem is considered not 240 * worth the overhead. 241 */ 242 void 243 ast_deregister(int ast) 244 { 245 struct ast_entry *ae; 246 247 MPASS(ast < TDA_MAX); 248 ae = &ast_entries[ast]; 249 MPASS(ae->ae_f != NULL); 250 ae->ae_f = NULL; 251 atomic_interrupt_fence(); 252 ae->ae_flags = 0; 253 ae->ae_tdp = 0; 254 } 255 256 void 257 ast_sched_locked(struct thread *td, int tda) 258 { 259 THREAD_LOCK_ASSERT(td, MA_OWNED); 260 MPASS(tda < TDA_MAX); 261 262 td->td_ast |= TDAI(tda); 263 } 264 265 void 266 ast_unsched_locked(struct thread *td, int tda) 267 { 268 THREAD_LOCK_ASSERT(td, MA_OWNED); 269 MPASS(tda < TDA_MAX); 270 271 td->td_ast &= ~TDAI(tda); 272 } 273 274 void 275 ast_sched(struct thread *td, int tda) 276 { 277 thread_lock(td); 278 ast_sched_locked(td, tda); 279 thread_unlock(td); 280 } 281 282 void 283 ast_sched_mask(struct thread *td, int ast) 284 { 285 thread_lock(td); 286 td->td_ast |= ast; 287 thread_unlock(td); 288 } 289 290 static bool 291 ast_handler_calc_tdp_run(struct thread *td, const struct ast_entry *ae) 292 { 293 return ((ae->ae_flags & ASTR_TDP) == 0 || 294 (td->td_pflags & ae->ae_tdp) != 0); 295 } 296 297 /* 298 * Process an asynchronous software trap. 299 */ 300 static void 301 ast_handler(struct thread *td, struct trapframe *framep, bool dtor) 302 { 303 struct ast_entry *ae; 304 void (*f)(struct thread *td, int asts); 305 int a, td_ast; 306 bool run; 307 308 if (framep != NULL) { 309 kmsan_mark(framep, sizeof(*framep), KMSAN_STATE_INITED); 310 td->td_frame = framep; 311 } 312 313 if (__predict_true(!dtor)) { 314 WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode"); 315 mtx_assert(&Giant, MA_NOTOWNED); 316 THREAD_LOCK_ASSERT(td, MA_NOTOWNED); 317 318 /* 319 * This updates the td_ast for the checks below in one 320 * atomic operation with turning off all scheduled AST's. 321 * If another AST is triggered while we are handling the 322 * AST's saved in td_ast, the td_ast is again non-zero and 323 * ast() will be called again. 324 */ 325 thread_lock(td); 326 td_ast = td->td_ast; 327 td->td_ast = 0; 328 thread_unlock(td); 329 } else { 330 /* 331 * The td thread's td_lock is not guaranteed to exist, 332 * the thread might be not initialized enough when it's 333 * destructor is called. It is safe to read and 334 * update td_ast without locking since the thread is 335 * not runnable or visible to other threads. 336 */ 337 td_ast = td->td_ast; 338 td->td_ast = 0; 339 } 340 341 CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, td->td_proc->p_pid, 342 td->td_proc->p_comm); 343 KASSERT(framep == NULL || TRAPF_USERMODE(framep), 344 ("ast in kernel mode")); 345 346 for (a = 0; a < nitems(ast_entries); a++) { 347 ae = &ast_entries[a]; 348 f = ae->ae_f; 349 if (f == NULL) 350 continue; 351 atomic_interrupt_fence(); 352 353 run = false; 354 if (__predict_false(framep == NULL)) { 355 if ((ae->ae_flags & ASTR_KCLEAR) != 0) 356 run = ast_handler_calc_tdp_run(td, ae); 357 } else { 358 if ((ae->ae_flags & ASTR_UNCOND) != 0) 359 run = true; 360 else if ((ae->ae_flags & ASTR_ASTF_REQUIRED) != 0 && 361 (td_ast & TDAI(a)) != 0) 362 run = ast_handler_calc_tdp_run(td, ae); 363 } 364 if (run) 365 f(td, td_ast); 366 } 367 } 368 369 void 370 ast(struct trapframe *framep) 371 { 372 struct thread *td; 373 374 td = curthread; 375 ast_handler(td, framep, false); 376 userret(td, framep); 377 } 378 379 void 380 ast_kclear(struct thread *td) 381 { 382 ast_handler(td, NULL, td != curthread); 383 } 384 385 const char * 386 syscallname(struct proc *p, u_int code) 387 { 388 static const char unknown[] = "unknown"; 389 struct sysentvec *sv; 390 391 sv = p->p_sysent; 392 if (sv->sv_syscallnames == NULL || code >= sv->sv_size) 393 return (unknown); 394 return (sv->sv_syscallnames[code]); 395 } 396