| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* Support for MMIO probes. |
| 3 | * Benefit many code from kprobes |
| 4 | * (C) 2002 Louis Zhuang <louis.zhuang@intel.com>. |
| 5 | * 2007 Alexander Eichner |
| 6 | * 2008 Pekka Paalanen <pq@iki.fi> |
| 7 | */ |
| 8 | |
| 9 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 10 | |
| 11 | #include <linux/list.h> |
| 12 | #include <linux/rculist.h> |
| 13 | #include <linux/spinlock.h> |
| 14 | #include <linux/hash.h> |
| 15 | #include <linux/export.h> |
| 16 | #include <linux/kernel.h> |
| 17 | #include <linux/uaccess.h> |
| 18 | #include <linux/ptrace.h> |
| 19 | #include <linux/preempt.h> |
| 20 | #include <linux/percpu.h> |
| 21 | #include <linux/kdebug.h> |
| 22 | #include <linux/mutex.h> |
| 23 | #include <linux/io.h> |
| 24 | #include <linux/slab.h> |
| 25 | #include <asm/cacheflush.h> |
| 26 | #include <asm/tlbflush.h> |
| 27 | #include <linux/errno.h> |
| 28 | #include <asm/debugreg.h> |
| 29 | #include <linux/mmiotrace.h> |
| 30 | |
| 31 | #define KMMIO_PAGE_HASH_BITS 4 |
| 32 | #define KMMIO_PAGE_TABLE_SIZE (1 << KMMIO_PAGE_HASH_BITS) |
| 33 | |
| 34 | struct kmmio_fault_page { |
| 35 | struct list_head list; |
| 36 | struct kmmio_fault_page *release_next; |
| 37 | unsigned long addr; /* the requested address */ |
| 38 | pteval_t old_presence; /* page presence prior to arming */ |
| 39 | bool armed; |
| 40 | |
| 41 | /* |
| 42 | * Number of times this page has been registered as a part |
| 43 | * of a probe. If zero, page is disarmed and this may be freed. |
| 44 | * Used only by writers (RCU) and post_kmmio_handler(). |
| 45 | * Protected by kmmio_lock, when linked into kmmio_page_table. |
| 46 | */ |
| 47 | int count; |
| 48 | |
| 49 | bool scheduled_for_release; |
| 50 | }; |
| 51 | |
| 52 | struct kmmio_delayed_release { |
| 53 | struct rcu_head rcu; |
| 54 | struct kmmio_fault_page *release_list; |
| 55 | }; |
| 56 | |
| 57 | struct kmmio_context { |
| 58 | struct kmmio_fault_page *fpage; |
| 59 | struct kmmio_probe *probe; |
| 60 | unsigned long saved_flags; |
| 61 | unsigned long addr; |
| 62 | int active; |
| 63 | }; |
| 64 | |
| 65 | /* |
| 66 | * The kmmio_lock is taken in int3 context, which is treated as NMI context. |
| 67 | * This causes lockdep to complain about it bein in both NMI and normal |
| 68 | * context. Hide it from lockdep, as it should not have any other locks |
| 69 | * taken under it, and this is only enabled for debugging mmio anyway. |
| 70 | */ |
| 71 | static arch_spinlock_t kmmio_lock = __ARCH_SPIN_LOCK_UNLOCKED; |
| 72 | |
| 73 | /* Protected by kmmio_lock */ |
| 74 | unsigned int kmmio_count; |
| 75 | |
| 76 | /* Read-protected by RCU, write-protected by kmmio_lock. */ |
| 77 | static struct list_head kmmio_page_table[KMMIO_PAGE_TABLE_SIZE]; |
| 78 | static LIST_HEAD(kmmio_probes); |
| 79 | |
| 80 | static struct list_head *kmmio_page_list(unsigned long addr) |
| 81 | { |
| 82 | unsigned int l; |
| 83 | pte_t *pte = lookup_address(addr, &l); |
| 84 | |
| 85 | if (!pte) |
| 86 | return NULL; |
| 87 | addr &= page_level_mask(l); |
| 88 | |
| 89 | return &kmmio_page_table[hash_long(addr, KMMIO_PAGE_HASH_BITS)]; |
| 90 | } |
| 91 | |
| 92 | /* Accessed per-cpu */ |
| 93 | static DEFINE_PER_CPU(struct kmmio_context, kmmio_ctx); |
| 94 | |
| 95 | /* |
| 96 | * this is basically a dynamic stabbing problem: |
| 97 | * Could use the existing prio tree code or |
| 98 | * Possible better implementations: |
| 99 | * The Interval Skip List: A Data Structure for Finding All Intervals That |
| 100 | * Overlap a Point (might be simple) |
| 101 | * Space Efficient Dynamic Stabbing with Fast Queries - Mikkel Thorup |
| 102 | */ |
| 103 | /* Get the kmmio at this addr (if any). You must be holding RCU read lock. */ |
| 104 | static struct kmmio_probe *get_kmmio_probe(unsigned long addr) |
| 105 | { |
| 106 | struct kmmio_probe *p; |
| 107 | list_for_each_entry_rcu(p, &kmmio_probes, list) { |
| 108 | if (addr >= p->addr && addr < (p->addr + p->len)) |
| 109 | return p; |
| 110 | } |
| 111 | return NULL; |
| 112 | } |
| 113 | |
| 114 | /* You must be holding RCU read lock. */ |
| 115 | static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long addr) |
| 116 | { |
| 117 | struct list_head *head; |
| 118 | struct kmmio_fault_page *f; |
| 119 | unsigned int l; |
| 120 | pte_t *pte = lookup_address(addr, &l); |
| 121 | |
| 122 | if (!pte) |
| 123 | return NULL; |
| 124 | addr &= page_level_mask(l); |
| 125 | head = kmmio_page_list(addr); |
| 126 | list_for_each_entry_rcu(f, head, list) { |
| 127 | if (f->addr == addr) |
| 128 | return f; |
| 129 | } |
| 130 | return NULL; |
| 131 | } |
| 132 | |
| 133 | static void clear_pmd_presence(pmd_t *pmd, bool clear, pmdval_t *old) |
| 134 | { |
| 135 | pmd_t new_pmd; |
| 136 | pmdval_t v = pmd_val(*pmd); |
| 137 | if (clear) { |
| 138 | *old = v; |
| 139 | new_pmd = pmd_mkinvalid(*pmd); |
| 140 | } else { |
| 141 | /* Presume this has been called with clear==true previously */ |
| 142 | new_pmd = __pmd(*old); |
| 143 | } |
| 144 | set_pmd(pmd, new_pmd); |
| 145 | } |
| 146 | |
| 147 | static void clear_pte_presence(pte_t *pte, bool clear, pteval_t *old) |
| 148 | { |
| 149 | pteval_t v = pte_val(*pte); |
| 150 | if (clear) { |
| 151 | *old = v; |
| 152 | /* Nothing should care about address */ |
| 153 | pte_clear(&init_mm, 0, pte); |
| 154 | } else { |
| 155 | /* Presume this has been called with clear==true previously */ |
| 156 | set_pte_atomic(pte, __pte(*old)); |
| 157 | } |
| 158 | } |
| 159 | |
| 160 | static int clear_page_presence(struct kmmio_fault_page *f, bool clear) |
| 161 | { |
| 162 | unsigned int level; |
| 163 | pte_t *pte = lookup_address(f->addr, &level); |
| 164 | |
| 165 | if (!pte) { |
| 166 | pr_err("no pte for addr 0x%08lx\n", f->addr); |
| 167 | return -1; |
| 168 | } |
| 169 | |
| 170 | switch (level) { |
| 171 | case PG_LEVEL_2M: |
| 172 | clear_pmd_presence((pmd_t *)pte, clear, &f->old_presence); |
| 173 | break; |
| 174 | case PG_LEVEL_4K: |
| 175 | clear_pte_presence(pte, clear, &f->old_presence); |
| 176 | break; |
| 177 | default: |
| 178 | pr_err("unexpected page level 0x%x.\n", level); |
| 179 | return -1; |
| 180 | } |
| 181 | |
| 182 | flush_tlb_one_kernel(f->addr); |
| 183 | return 0; |
| 184 | } |
| 185 | |
| 186 | /* |
| 187 | * Mark the given page as not present. Access to it will trigger a fault. |
| 188 | * |
| 189 | * Struct kmmio_fault_page is protected by RCU and kmmio_lock, but the |
| 190 | * protection is ignored here. RCU read lock is assumed held, so the struct |
| 191 | * will not disappear unexpectedly. Furthermore, the caller must guarantee, |
| 192 | * that double arming the same virtual address (page) cannot occur. |
| 193 | * |
| 194 | * Double disarming on the other hand is allowed, and may occur when a fault |
| 195 | * and mmiotrace shutdown happen simultaneously. |
| 196 | */ |
| 197 | static int arm_kmmio_fault_page(struct kmmio_fault_page *f) |
| 198 | { |
| 199 | int ret; |
| 200 | WARN_ONCE(f->armed, KERN_ERR pr_fmt("kmmio page already armed.\n")); |
| 201 | if (f->armed) { |
| 202 | pr_warn("double-arm: addr 0x%08lx, ref %d, old %d\n", |
| 203 | f->addr, f->count, !!f->old_presence); |
| 204 | } |
| 205 | ret = clear_page_presence(f, true); |
| 206 | WARN_ONCE(ret < 0, KERN_ERR pr_fmt("arming at 0x%08lx failed.\n"), |
| 207 | f->addr); |
| 208 | f->armed = true; |
| 209 | return ret; |
| 210 | } |
| 211 | |
| 212 | /** Restore the given page to saved presence state. */ |
| 213 | static void disarm_kmmio_fault_page(struct kmmio_fault_page *f) |
| 214 | { |
| 215 | int ret = clear_page_presence(f, false); |
| 216 | WARN_ONCE(ret < 0, |
| 217 | KERN_ERR "kmmio disarming at 0x%08lx failed.\n", f->addr); |
| 218 | f->armed = false; |
| 219 | } |
| 220 | |
| 221 | /* |
| 222 | * This is being called from do_page_fault(). |
| 223 | * |
| 224 | * We may be in an interrupt or a critical section. Also prefecthing may |
| 225 | * trigger a page fault. We may be in the middle of process switch. |
| 226 | * We cannot take any locks, because we could be executing especially |
| 227 | * within a kmmio critical section. |
| 228 | * |
| 229 | * Local interrupts are disabled, so preemption cannot happen. |
| 230 | * Do not enable interrupts, do not sleep, and watch out for other CPUs. |
| 231 | */ |
| 232 | /* |
| 233 | * Interrupts are disabled on entry as trap3 is an interrupt gate |
| 234 | * and they remain disabled throughout this function. |
| 235 | */ |
| 236 | int kmmio_handler(struct pt_regs *regs, unsigned long addr) |
| 237 | { |
| 238 | struct kmmio_context *ctx; |
| 239 | struct kmmio_fault_page *faultpage; |
| 240 | int ret = 0; /* default to fault not handled */ |
| 241 | unsigned long page_base = addr; |
| 242 | unsigned int l; |
| 243 | pte_t *pte = lookup_address(addr, &l); |
| 244 | if (!pte) |
| 245 | return -EINVAL; |
| 246 | page_base &= page_level_mask(l); |
| 247 | |
| 248 | /* |
| 249 | * Hold the RCU read lock over single stepping to avoid looking |
| 250 | * up the probe and kmmio_fault_page again. The rcu_read_lock_sched() |
| 251 | * also disables preemption and prevents process switch during |
| 252 | * the single stepping. We can only handle one active kmmio trace |
| 253 | * per cpu, so ensure that we finish it before something else |
| 254 | * gets to run. |
| 255 | */ |
| 256 | rcu_read_lock_sched_notrace(); |
| 257 | |
| 258 | faultpage = get_kmmio_fault_page(page_base); |
| 259 | if (!faultpage) { |
| 260 | /* |
| 261 | * Either this page fault is not caused by kmmio, or |
| 262 | * another CPU just pulled the kmmio probe from under |
| 263 | * our feet. The latter case should not be possible. |
| 264 | */ |
| 265 | goto no_kmmio; |
| 266 | } |
| 267 | |
| 268 | ctx = this_cpu_ptr(&kmmio_ctx); |
| 269 | if (ctx->active) { |
| 270 | if (page_base == ctx->addr) { |
| 271 | /* |
| 272 | * A second fault on the same page means some other |
| 273 | * condition needs handling by do_page_fault(), the |
| 274 | * page really not being present is the most common. |
| 275 | */ |
| 276 | pr_debug("secondary hit for 0x%08lx CPU %d.\n", |
| 277 | addr, smp_processor_id()); |
| 278 | |
| 279 | if (!faultpage->old_presence) |
| 280 | pr_info("unexpected secondary hit for address 0x%08lx on CPU %d.\n", |
| 281 | addr, smp_processor_id()); |
| 282 | } else { |
| 283 | /* |
| 284 | * Prevent overwriting already in-flight context. |
| 285 | * This should not happen, let's hope disarming at |
| 286 | * least prevents a panic. |
| 287 | */ |
| 288 | pr_emerg("recursive probe hit on CPU %d, for address 0x%08lx. Ignoring.\n", |
| 289 | smp_processor_id(), addr); |
| 290 | pr_emerg("previous hit was at 0x%08lx.\n", ctx->addr); |
| 291 | disarm_kmmio_fault_page(faultpage); |
| 292 | } |
| 293 | goto no_kmmio; |
| 294 | } |
| 295 | ctx->active++; |
| 296 | |
| 297 | ctx->fpage = faultpage; |
| 298 | ctx->probe = get_kmmio_probe(page_base); |
| 299 | ctx->saved_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF)); |
| 300 | ctx->addr = page_base; |
| 301 | |
| 302 | if (ctx->probe && ctx->probe->pre_handler) |
| 303 | ctx->probe->pre_handler(ctx->probe, regs, addr); |
| 304 | |
| 305 | /* |
| 306 | * Enable single-stepping and disable interrupts for the faulting |
| 307 | * context. Local interrupts must not get enabled during stepping. |
| 308 | */ |
| 309 | regs->flags |= X86_EFLAGS_TF; |
| 310 | regs->flags &= ~X86_EFLAGS_IF; |
| 311 | |
| 312 | /* Now we set present bit in PTE and single step. */ |
| 313 | disarm_kmmio_fault_page(ctx->fpage); |
| 314 | |
| 315 | /* |
| 316 | * If another cpu accesses the same page while we are stepping, |
| 317 | * the access will not be caught. It will simply succeed and the |
| 318 | * only downside is we lose the event. If this becomes a problem, |
| 319 | * the user should drop to single cpu before tracing. |
| 320 | */ |
| 321 | |
| 322 | return 1; /* fault handled */ |
| 323 | |
| 324 | no_kmmio: |
| 325 | rcu_read_unlock_sched_notrace(); |
| 326 | return ret; |
| 327 | } |
| 328 | |
| 329 | /* |
| 330 | * Interrupts are disabled on entry as trap1 is an interrupt gate |
| 331 | * and they remain disabled throughout this function. |
| 332 | * This must always get called as the pair to kmmio_handler(). |
| 333 | */ |
| 334 | static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs) |
| 335 | { |
| 336 | int ret = 0; |
| 337 | struct kmmio_context *ctx = this_cpu_ptr(&kmmio_ctx); |
| 338 | |
| 339 | if (!ctx->active) { |
| 340 | /* |
| 341 | * debug traps without an active context are due to either |
| 342 | * something external causing them (f.e. using a debugger while |
| 343 | * mmio tracing enabled), or erroneous behaviour |
| 344 | */ |
| 345 | pr_warn("unexpected debug trap on CPU %d.\n", smp_processor_id()); |
| 346 | goto out; |
| 347 | } |
| 348 | |
| 349 | if (ctx->probe && ctx->probe->post_handler) |
| 350 | ctx->probe->post_handler(ctx->probe, condition, regs); |
| 351 | |
| 352 | /* Prevent racing against release_kmmio_fault_page(). */ |
| 353 | arch_spin_lock(&kmmio_lock); |
| 354 | if (ctx->fpage->count) |
| 355 | arm_kmmio_fault_page(ctx->fpage); |
| 356 | arch_spin_unlock(&kmmio_lock); |
| 357 | |
| 358 | regs->flags &= ~X86_EFLAGS_TF; |
| 359 | regs->flags |= ctx->saved_flags; |
| 360 | |
| 361 | /* These were acquired in kmmio_handler(). */ |
| 362 | ctx->active--; |
| 363 | BUG_ON(ctx->active); |
| 364 | rcu_read_unlock_sched_notrace(); |
| 365 | |
| 366 | /* |
| 367 | * if somebody else is singlestepping across a probe point, flags |
| 368 | * will have TF set, in which case, continue the remaining processing |
| 369 | * of do_debug, as if this is not a probe hit. |
| 370 | */ |
| 371 | if (!(regs->flags & X86_EFLAGS_TF)) |
| 372 | ret = 1; |
| 373 | out: |
| 374 | return ret; |
| 375 | } |
| 376 | |
| 377 | /* You must be holding kmmio_lock. */ |
| 378 | static int add_kmmio_fault_page(unsigned long addr) |
| 379 | { |
| 380 | struct kmmio_fault_page *f; |
| 381 | |
| 382 | f = get_kmmio_fault_page(addr); |
| 383 | if (f) { |
| 384 | if (!f->count) |
| 385 | arm_kmmio_fault_page(f); |
| 386 | f->count++; |
| 387 | return 0; |
| 388 | } |
| 389 | |
| 390 | f = kzalloc(sizeof(*f), GFP_ATOMIC); |
| 391 | if (!f) |
| 392 | return -1; |
| 393 | |
| 394 | f->count = 1; |
| 395 | f->addr = addr; |
| 396 | |
| 397 | if (arm_kmmio_fault_page(f)) { |
| 398 | kfree(f); |
| 399 | return -1; |
| 400 | } |
| 401 | |
| 402 | list_add_rcu(&f->list, kmmio_page_list(f->addr)); |
| 403 | |
| 404 | return 0; |
| 405 | } |
| 406 | |
| 407 | /* You must be holding kmmio_lock. */ |
| 408 | static void release_kmmio_fault_page(unsigned long addr, |
| 409 | struct kmmio_fault_page **release_list) |
| 410 | { |
| 411 | struct kmmio_fault_page *f; |
| 412 | |
| 413 | f = get_kmmio_fault_page(addr); |
| 414 | if (!f) |
| 415 | return; |
| 416 | |
| 417 | f->count--; |
| 418 | BUG_ON(f->count < 0); |
| 419 | if (!f->count) { |
| 420 | disarm_kmmio_fault_page(f); |
| 421 | if (!f->scheduled_for_release) { |
| 422 | f->release_next = *release_list; |
| 423 | *release_list = f; |
| 424 | f->scheduled_for_release = true; |
| 425 | } |
| 426 | } |
| 427 | } |
| 428 | |
| 429 | /* |
| 430 | * With page-unaligned ioremaps, one or two armed pages may contain |
| 431 | * addresses from outside the intended mapping. Events for these addresses |
| 432 | * are currently silently dropped. The events may result only from programming |
| 433 | * mistakes by accessing addresses before the beginning or past the end of a |
| 434 | * mapping. |
| 435 | */ |
| 436 | int register_kmmio_probe(struct kmmio_probe *p) |
| 437 | { |
| 438 | unsigned long flags; |
| 439 | int ret = 0; |
| 440 | unsigned long size = 0; |
| 441 | unsigned long addr = p->addr & PAGE_MASK; |
| 442 | const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK); |
| 443 | unsigned int l; |
| 444 | pte_t *pte; |
| 445 | |
| 446 | local_irq_save(flags); |
| 447 | arch_spin_lock(&kmmio_lock); |
| 448 | if (get_kmmio_probe(addr)) { |
| 449 | ret = -EEXIST; |
| 450 | goto out; |
| 451 | } |
| 452 | |
| 453 | pte = lookup_address(addr, &l); |
| 454 | if (!pte) { |
| 455 | ret = -EINVAL; |
| 456 | goto out; |
| 457 | } |
| 458 | |
| 459 | kmmio_count++; |
| 460 | list_add_rcu(&p->list, &kmmio_probes); |
| 461 | while (size < size_lim) { |
| 462 | if (add_kmmio_fault_page(addr + size)) |
| 463 | pr_err("Unable to set page fault.\n"); |
| 464 | size += page_level_size(l); |
| 465 | } |
| 466 | out: |
| 467 | arch_spin_unlock(&kmmio_lock); |
| 468 | local_irq_restore(flags); |
| 469 | |
| 470 | /* |
| 471 | * XXX: What should I do here? |
| 472 | * Here was a call to global_flush_tlb(), but it does not exist |
| 473 | * anymore. It seems it's not needed after all. |
| 474 | */ |
| 475 | return ret; |
| 476 | } |
| 477 | EXPORT_SYMBOL(register_kmmio_probe); |
| 478 | |
| 479 | static void rcu_free_kmmio_fault_pages(struct rcu_head *head) |
| 480 | { |
| 481 | struct kmmio_delayed_release *dr = container_of( |
| 482 | head, |
| 483 | struct kmmio_delayed_release, |
| 484 | rcu); |
| 485 | struct kmmio_fault_page *f = dr->release_list; |
| 486 | while (f) { |
| 487 | struct kmmio_fault_page *next = f->release_next; |
| 488 | BUG_ON(f->count); |
| 489 | kfree(f); |
| 490 | f = next; |
| 491 | } |
| 492 | kfree(dr); |
| 493 | } |
| 494 | |
| 495 | static void remove_kmmio_fault_pages(struct rcu_head *head) |
| 496 | { |
| 497 | struct kmmio_delayed_release *dr = |
| 498 | container_of(head, struct kmmio_delayed_release, rcu); |
| 499 | struct kmmio_fault_page *f = dr->release_list; |
| 500 | struct kmmio_fault_page **prevp = &dr->release_list; |
| 501 | unsigned long flags; |
| 502 | |
| 503 | local_irq_save(flags); |
| 504 | arch_spin_lock(&kmmio_lock); |
| 505 | while (f) { |
| 506 | if (!f->count) { |
| 507 | list_del_rcu(&f->list); |
| 508 | prevp = &f->release_next; |
| 509 | } else { |
| 510 | *prevp = f->release_next; |
| 511 | f->release_next = NULL; |
| 512 | f->scheduled_for_release = false; |
| 513 | } |
| 514 | f = *prevp; |
| 515 | } |
| 516 | arch_spin_unlock(&kmmio_lock); |
| 517 | local_irq_restore(flags); |
| 518 | |
| 519 | /* This is the real RCU destroy call. */ |
| 520 | call_rcu(&dr->rcu, rcu_free_kmmio_fault_pages); |
| 521 | } |
| 522 | |
| 523 | /* |
| 524 | * Remove a kmmio probe. You have to synchronize_rcu() before you can be |
| 525 | * sure that the callbacks will not be called anymore. Only after that |
| 526 | * you may actually release your struct kmmio_probe. |
| 527 | * |
| 528 | * Unregistering a kmmio fault page has three steps: |
| 529 | * 1. release_kmmio_fault_page() |
| 530 | * Disarm the page, wait a grace period to let all faults finish. |
| 531 | * 2. remove_kmmio_fault_pages() |
| 532 | * Remove the pages from kmmio_page_table. |
| 533 | * 3. rcu_free_kmmio_fault_pages() |
| 534 | * Actually free the kmmio_fault_page structs as with RCU. |
| 535 | */ |
| 536 | void unregister_kmmio_probe(struct kmmio_probe *p) |
| 537 | { |
| 538 | unsigned long flags; |
| 539 | unsigned long size = 0; |
| 540 | unsigned long addr = p->addr & PAGE_MASK; |
| 541 | const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK); |
| 542 | struct kmmio_fault_page *release_list = NULL; |
| 543 | struct kmmio_delayed_release *drelease; |
| 544 | unsigned int l; |
| 545 | pte_t *pte; |
| 546 | |
| 547 | pte = lookup_address(addr, &l); |
| 548 | if (!pte) |
| 549 | return; |
| 550 | |
| 551 | local_irq_save(flags); |
| 552 | arch_spin_lock(&kmmio_lock); |
| 553 | while (size < size_lim) { |
| 554 | release_kmmio_fault_page(addr + size, &release_list); |
| 555 | size += page_level_size(l); |
| 556 | } |
| 557 | list_del_rcu(&p->list); |
| 558 | kmmio_count--; |
| 559 | arch_spin_unlock(&kmmio_lock); |
| 560 | local_irq_restore(flags); |
| 561 | |
| 562 | if (!release_list) |
| 563 | return; |
| 564 | |
| 565 | drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC); |
| 566 | if (!drelease) { |
| 567 | pr_crit("leaking kmmio_fault_page objects.\n"); |
| 568 | return; |
| 569 | } |
| 570 | drelease->release_list = release_list; |
| 571 | |
| 572 | /* |
| 573 | * This is not really RCU here. We have just disarmed a set of |
| 574 | * pages so that they cannot trigger page faults anymore. However, |
| 575 | * we cannot remove the pages from kmmio_page_table, |
| 576 | * because a probe hit might be in flight on another CPU. The |
| 577 | * pages are collected into a list, and they will be removed from |
| 578 | * kmmio_page_table when it is certain that no probe hit related to |
| 579 | * these pages can be in flight. RCU grace period sounds like a |
| 580 | * good choice. |
| 581 | * |
| 582 | * If we removed the pages too early, kmmio page fault handler might |
| 583 | * not find the respective kmmio_fault_page and determine it's not |
| 584 | * a kmmio fault, when it actually is. This would lead to madness. |
| 585 | */ |
| 586 | call_rcu(&drelease->rcu, remove_kmmio_fault_pages); |
| 587 | } |
| 588 | EXPORT_SYMBOL(unregister_kmmio_probe); |
| 589 | |
| 590 | static int |
| 591 | kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args) |
| 592 | { |
| 593 | struct die_args *arg = args; |
| 594 | unsigned long* dr6_p = (unsigned long *)ERR_PTR(arg->err); |
| 595 | |
| 596 | if (val == DIE_DEBUG && (*dr6_p & DR_STEP)) |
| 597 | if (post_kmmio_handler(*dr6_p, arg->regs) == 1) { |
| 598 | /* |
| 599 | * Reset the BS bit in dr6 (pointed by args->err) to |
| 600 | * denote completion of processing |
| 601 | */ |
| 602 | *dr6_p &= ~DR_STEP; |
| 603 | return NOTIFY_STOP; |
| 604 | } |
| 605 | |
| 606 | return NOTIFY_DONE; |
| 607 | } |
| 608 | |
| 609 | static struct notifier_block nb_die = { |
| 610 | .notifier_call = kmmio_die_notifier |
| 611 | }; |
| 612 | |
| 613 | int kmmio_init(void) |
| 614 | { |
| 615 | int i; |
| 616 | |
| 617 | for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) |
| 618 | INIT_LIST_HEAD(&kmmio_page_table[i]); |
| 619 | |
| 620 | return register_die_notifier(&nb_die); |
| 621 | } |
| 622 | |
| 623 | void kmmio_cleanup(void) |
| 624 | { |
| 625 | int i; |
| 626 | |
| 627 | unregister_die_notifier(&nb_die); |
| 628 | for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) { |
| 629 | WARN_ONCE(!list_empty(&kmmio_page_table[i]), |
| 630 | KERN_ERR "kmmio_page_table not empty at cleanup, any further tracing will leak memory.\n"); |
| 631 | } |
| 632 | } |