arch/x86/mm/mmio-mod.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *
   4  * Copyright (C) IBM Corporation, 2005
   5  *               Jeff Muizelaar, 2006, 2007
   6  *               Pekka Paalanen, 2008 <pq@iki.fi>
   7  *
   8  * Derived from the read-mod example from relay-examples by Tom Zanussi.
   9  */
  10
  11 #define pr_fmt(fmt) "mmiotrace: " fmt
  12
  13 #include <linux/moduleparam.h>
  14 #include <linux/debugfs.h>
  15 #include <linux/slab.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/io.h>
  18 #include <linux/mmiotrace.h>
  19 #include <linux/pgtable.h>
  20 #include <asm/e820/api.h> /* for ISA_START_ADDRESS */
  21 #include <linux/atomic.h>
  22 #include <linux/percpu.h>
  23 #include <linux/cpu.h>
  24
  25 #include "pf_in.h"
  26
  27 struct trap_reason {
  28         unsigned long addr;
  29         unsigned long ip;
  30         enum reason_type type;
  31         int active_traces;
  32 };
  33
  34 struct remap_trace {
  35         struct list_head list;
  36         struct kmmio_probe probe;
  37         resource_size_t phys;
  38         unsigned long id;
  39 };
  40
  41 /* Accessed per-cpu. */
  42 static DEFINE_PER_CPU(struct trap_reason, pf_reason);
  43 static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);
  44
  45 static DEFINE_MUTEX(mmiotrace_mutex);
  46 static DEFINE_SPINLOCK(trace_lock);
  47 static atomic_t mmiotrace_enabled;
  48 static LIST_HEAD(trace_list);           /* struct remap_trace */
  49
  50 /*
  51  * Locking in this file:
  52  * - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
  53  * - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
  54  *   and trace_lock.
  55  * - Routines depending on is_enabled() must take trace_lock.
  56  * - trace_list users must hold trace_lock.
  57  * - is_enabled() guarantees that mmio_trace_{rw,mapping} are allowed.
  58  * - pre/post callbacks assume the effect of is_enabled() being true.
  59  */
  60
  61 /* module parameters */
  62 static unsigned long    filter_offset;
  63 static bool             nommiotrace;
  64 static bool             trace_pc;
  65
  66 module_param(filter_offset, ulong, 0);
  67 module_param(nommiotrace, bool, 0);
  68 module_param(trace_pc, bool, 0);
  69
  70 MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
  71 MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
  72 MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");
  73
  74 static bool is_enabled(void)
  75 {
  76         return atomic_read(&mmiotrace_enabled);
  77 }
  78
  79 static void print_pte(unsigned long address)
  80 {
  81         unsigned int level;
  82         pte_t *pte = lookup_address(address, &level);
  83
  84         if (!pte) {
  85                 pr_err("Error in %s: no pte for page 0x%08lx\n",
  86                        __func__, address);
  87                 return;
  88         }
  89
  90         if (level == PG_LEVEL_2M) {
  91                 pr_emerg("4MB pages are not currently supported: 0x%08lx\n",
  92                          address);
  93                 BUG();
  94         }
  95         pr_info("pte for 0x%lx: 0x%llx 0x%llx\n",
  96                 address,
  97                 (unsigned long long)pte_val(*pte),
  98                 (unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
  99 }
 100
 101 /*
 102  * For some reason the pre/post pairs have been called in an
 103  * unmatched order. Report and die.
 104  */
 105 static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
 106 {
 107         const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 108         pr_emerg("unexpected fault for address: 0x%08lx, last fault for address: 0x%08lx\n",
 109                  addr, my_reason->addr);
 110         print_pte(addr);
 111         pr_emerg("faulting IP is at %pS\n", (void *)regs->ip);
 112         pr_emerg("last faulting IP was at %pS\n", (void *)my_reason->ip);
 113 #ifdef __i386__
 114         pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
 115                  regs->ax, regs->bx, regs->cx, regs->dx);
 116         pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
 117                  regs->si, regs->di, regs->bp, regs->sp);
 118 #else
 119         pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
 120                  regs->ax, regs->cx, regs->dx);
 121         pr_emerg("rsi: %016lx   rdi: %016lx   rbp: %016lx   rsp: %016lx\n",
 122                  regs->si, regs->di, regs->bp, regs->sp);
 123 #endif
 124         put_cpu_var(pf_reason);
 125         BUG();
 126 }
 127
 128 static void pre(struct kmmio_probe *p, struct pt_regs *regs,
 129                                                 unsigned long addr)
 130 {
 131         struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 132         struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
 133         const unsigned long instptr = instruction_pointer(regs);
 134         const enum reason_type type = get_ins_type(instptr);
 135         struct remap_trace *trace = p->private;
 136
 137         /* it doesn't make sense to have more than one active trace per cpu */
 138         if (my_reason->active_traces)
 139                 die_kmmio_nesting_error(regs, addr);
 140         else
 141                 my_reason->active_traces++;
 142
 143         my_reason->type = type;
 144         my_reason->addr = addr;
 145         my_reason->ip = instptr;
 146
 147         my_trace->phys = addr - trace->probe.addr + trace->phys;
 148         my_trace->map_id = trace->id;
 149
 150         /*
 151          * Only record the program counter when requested.
 152          * It may taint clean-room reverse engineering.
 153          */
 154         if (trace_pc)
 155                 my_trace->pc = instptr;
 156         else
 157                 my_trace->pc = 0;
 158
 159         /*
 160          * XXX: the timestamp recorded will be *after* the tracing has been
 161          * done, not at the time we hit the instruction. SMP implications
 162          * on event ordering?
 163          */
 164
 165         switch (type) {
 166         case REG_READ:
 167                 my_trace->opcode = MMIO_READ;
 168                 my_trace->width = get_ins_mem_width(instptr);
 169                 break;
 170         case REG_WRITE:
 171                 my_trace->opcode = MMIO_WRITE;
 172                 my_trace->width = get_ins_mem_width(instptr);
 173                 my_trace->value = get_ins_reg_val(instptr, regs);
 174                 break;
 175         case IMM_WRITE:
 176                 my_trace->opcode = MMIO_WRITE;
 177                 my_trace->width = get_ins_mem_width(instptr);
 178                 my_trace->value = get_ins_imm_val(instptr);
 179                 break;
 180         default:
 181                 {
 182                         unsigned char *ip = (unsigned char *)instptr;
 183                         my_trace->opcode = MMIO_UNKNOWN_OP;
 184                         my_trace->width = 0;
 185                         my_trace->value = (*ip) << 16 | *(ip + 1) << 8 |
 186                                                                 *(ip + 2);
 187                 }
 188         }
 189         put_cpu_var(cpu_trace);
 190         put_cpu_var(pf_reason);
 191 }
 192
 193 static void post(struct kmmio_probe *p, unsigned long condition,
 194                                                         struct pt_regs *regs)
 195 {
 196         struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 197         struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
 198
 199         /* this should always return the active_trace count to 0 */
 200         my_reason->active_traces--;
 201         if (my_reason->active_traces) {
 202                 pr_emerg("unexpected post handler");
 203                 BUG();
 204         }
 205
 206         switch (my_reason->type) {
 207         case REG_READ:
 208                 my_trace->value = get_ins_reg_val(my_reason->ip, regs);
 209                 break;
 210         default:
 211                 break;
 212         }
 213
 214         mmio_trace_rw(my_trace);
 215         put_cpu_var(cpu_trace);
 216         put_cpu_var(pf_reason);
 217 }
 218
 219 static void ioremap_trace_core(resource_size_t offset, unsigned long size,
 220                                                         void __iomem *addr)
 221 {
 222         static atomic_t next_id;
 223         struct remap_trace *trace = kmalloc(sizeof(*trace), GFP_KERNEL);
 224         /* These are page-unaligned. */
 225         struct mmiotrace_map map = {
 226                 .phys = offset,
 227                 .virt = (unsigned long)addr,
 228                 .len = size,
 229                 .opcode = MMIO_PROBE
 230         };
 231
 232         if (!trace) {
 233                 pr_err("kmalloc failed in ioremap\n");
 234                 return;
 235         }
 236
 237         *trace = (struct remap_trace) {
 238                 .probe = {
 239                         .addr = (unsigned long)addr,
 240                         .len = size,
 241                         .pre_handler = pre,
 242                         .post_handler = post,
 243                         .private = trace
 244                 },
 245                 .phys = offset,
 246                 .id = atomic_inc_return(&next_id)
 247         };
 248         map.map_id = trace->id;
 249
 250         spin_lock_irq(&trace_lock);
 251         if (!is_enabled()) {
 252                 kfree(trace);
 253                 goto not_enabled;
 254         }
 255
 256         mmio_trace_mapping(&map);
 257         list_add_tail(&trace->list, &trace_list);
 258         if (!nommiotrace)
 259                 register_kmmio_probe(&trace->probe);
 260
 261 not_enabled:
 262         spin_unlock_irq(&trace_lock);
 263 }
 264
 265 void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
 266                                                 void __iomem *addr)
 267 {
 268         if (!is_enabled()) /* recheck and proper locking in *_core() */
 269                 return;
 270
 271         pr_debug("ioremap_*(0x%llx, 0x%lx) = %p\n",
 272                  (unsigned long long)offset, size, addr);
 273         if ((filter_offset) && (offset != filter_offset))
 274                 return;
 275         ioremap_trace_core(offset, size, addr);
 276 }
 277
 278 static void iounmap_trace_core(volatile void __iomem *addr)
 279 {
 280         struct mmiotrace_map map = {
 281                 .phys = 0,
 282                 .virt = (unsigned long)addr,
 283                 .len = 0,
 284                 .opcode = MMIO_UNPROBE
 285         };
 286         struct remap_trace *trace;
 287         struct remap_trace *tmp;
 288         struct remap_trace *found_trace = NULL;
 289
 290         pr_debug("Unmapping %p.\n", addr);
 291
 292         spin_lock_irq(&trace_lock);
 293         if (!is_enabled())
 294                 goto not_enabled;
 295
 296         list_for_each_entry_safe(trace, tmp, &trace_list, list) {
 297                 if ((unsigned long)addr == trace->probe.addr) {
 298                         if (!nommiotrace)
 299                                 unregister_kmmio_probe(&trace->probe);
 300                         list_del(&trace->list);
 301                         found_trace = trace;
 302                         break;
 303                 }
 304         }
 305         map.map_id = (found_trace) ? found_trace->id : -1;
 306         mmio_trace_mapping(&map);
 307
 308 not_enabled:
 309         spin_unlock_irq(&trace_lock);
 310         if (found_trace) {
 311                 synchronize_rcu(); /* unregister_kmmio_probe() requirement */
 312                 kfree(found_trace);
 313         }
 314 }
 315
 316 void mmiotrace_iounmap(volatile void __iomem *addr)
 317 {
 318         might_sleep();
 319         if (is_enabled()) /* recheck and proper locking in *_core() */
 320                 iounmap_trace_core(addr);
 321 }
 322
 323 int mmiotrace_printk(const char *fmt, ...)
 324 {
 325         int ret = 0;
 326         va_list args;
 327         unsigned long flags;
 328         va_start(args, fmt);
 329
 330         spin_lock_irqsave(&trace_lock, flags);
 331         if (is_enabled())
 332                 ret = mmio_trace_printk(fmt, args);
 333         spin_unlock_irqrestore(&trace_lock, flags);
 334
 335         va_end(args);
 336         return ret;
 337 }
 338 EXPORT_SYMBOL(mmiotrace_printk);
 339
 340 static void clear_trace_list(void)
 341 {
 342         struct remap_trace *trace;
 343         struct remap_trace *tmp;
 344
 345         /*
 346          * No locking required, because the caller ensures we are in a
 347          * critical section via mutex, and is_enabled() is false,
 348          * i.e. nothing can traverse or modify this list.
 349          * Caller also ensures is_enabled() cannot change.
 350          */
 351         list_for_each_entry(trace, &trace_list, list) {
 352                 pr_notice("purging non-iounmapped trace @0x%08lx, size 0x%lx.\n",
 353                           trace->probe.addr, trace->probe.len);
 354                 if (!nommiotrace)
 355                         unregister_kmmio_probe(&trace->probe);
 356         }
 357         synchronize_rcu(); /* unregister_kmmio_probe() requirement */
 358
 359         list_for_each_entry_safe(trace, tmp, &trace_list, list) {
 360                 list_del(&trace->list);
 361                 kfree(trace);
 362         }
 363 }
 364
 365 #ifdef CONFIG_HOTPLUG_CPU
 366 static cpumask_var_t downed_cpus;
 367
 368 static void enter_uniprocessor(void)
 369 {
 370         int cpu;
 371         int err;
 372
 373         if (!cpumask_available(downed_cpus) &&
 374             !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
 375                 pr_notice("Failed to allocate mask\n");
 376                 goto out;
 377         }
 378
 379         cpus_read_lock();
 380         cpumask_copy(downed_cpus, cpu_online_mask);
 381         cpumask_clear_cpu(cpumask_first(cpu_online_mask), downed_cpus);
 382         if (num_online_cpus() > 1)
 383                 pr_notice("Disabling non-boot CPUs...\n");
 384         cpus_read_unlock();
 385
 386         for_each_cpu(cpu, downed_cpus) {
 387                 err = remove_cpu(cpu);
 388                 if (!err)
 389                         pr_info("CPU%d is down.\n", cpu);
 390                 else
 391                         pr_err("Error taking CPU%d down: %d\n", cpu, err);
 392         }
 393 out:
 394         if (num_online_cpus() > 1)
 395                 pr_warn("multiple CPUs still online, may miss events.\n");
 396 }
 397
 398 static void leave_uniprocessor(void)
 399 {
 400         int cpu;
 401         int err;
 402
 403         if (!cpumask_available(downed_cpus) || cpumask_empty(downed_cpus))
 404                 return;
 405         pr_notice("Re-enabling CPUs...\n");
 406         for_each_cpu(cpu, downed_cpus) {
 407                 err = add_cpu(cpu);
 408                 if (!err)
 409                         pr_info("enabled CPU%d.\n", cpu);
 410                 else
 411                         pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
 412         }
 413 }
 414
 415 #else /* !CONFIG_HOTPLUG_CPU */
 416 static void enter_uniprocessor(void)
 417 {
 418         if (num_online_cpus() > 1)
 419                 pr_warn("multiple CPUs are online, may miss events. "
 420                         "Suggest booting with maxcpus=1 kernel argument.\n");
 421 }
 422
 423 static void leave_uniprocessor(void)
 424 {
 425 }
 426 #endif
 427
 428 void enable_mmiotrace(void)
 429 {
 430         mutex_lock(&mmiotrace_mutex);
 431         if (is_enabled())
 432                 goto out;
 433
 434         if (nommiotrace)
 435                 pr_info("MMIO tracing disabled.\n");
 436         kmmio_init();
 437         enter_uniprocessor();
 438         spin_lock_irq(&trace_lock);
 439         atomic_inc(&mmiotrace_enabled);
 440         spin_unlock_irq(&trace_lock);
 441         pr_info("enabled.\n");
 442 out:
 443         mutex_unlock(&mmiotrace_mutex);
 444 }
 445
 446 void disable_mmiotrace(void)
 447 {
 448         mutex_lock(&mmiotrace_mutex);
 449         if (!is_enabled())
 450                 goto out;
 451
 452         spin_lock_irq(&trace_lock);
 453         atomic_dec(&mmiotrace_enabled);
 454         BUG_ON(is_enabled());
 455         spin_unlock_irq(&trace_lock);
 456
 457         clear_trace_list(); /* guarantees: no more kmmio callbacks */
 458         leave_uniprocessor();
 459         kmmio_cleanup();
 460         pr_info("disabled.\n");
 461 out:
 462         mutex_unlock(&mmiotrace_mutex);
 463 }