arch/x86/mm/mmio-mod.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License as published by
   4  * the Free Software Foundation; either version 2 of the License, or
   5  * (at your option) any later version.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, write to the Free Software
  14  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  15  *
  16  * Copyright (C) IBM Corporation, 2005
  17  *               Jeff Muizelaar, 2006, 2007
  18  *               Pekka Paalanen, 2008 <pq@iki.fi>
  19  *
  20  * Derived from the read-mod example from relay-examples by Tom Zanussi.
  21  */
  22
  23 #define pr_fmt(fmt) "mmiotrace: " fmt
  24
  25 #define DEBUG 1
  26
  27 #include <linux/module.h>
  28 #include <linux/debugfs.h>
  29 #include <linux/slab.h>
  30 #include <linux/uaccess.h>
  31 #include <linux/io.h>
  32 #include <linux/kallsyms.h>
  33 #include <asm/pgtable.h>
  34 #include <linux/mmiotrace.h>
  35 #include <asm/e820.h> /* for ISA_START_ADDRESS */
  36 #include <linux/atomic.h>
  37 #include <linux/percpu.h>
  38 #include <linux/cpu.h>
  39
  40 #include "pf_in.h"
  41
  42 struct trap_reason {
  43         unsigned long addr;
  44         unsigned long ip;
  45         enum reason_type type;
  46         int active_traces;
  47 };
  48
  49 struct remap_trace {
  50         struct list_head list;
  51         struct kmmio_probe probe;
  52         resource_size_t phys;
  53         unsigned long id;
  54 };
  55
  56 /* Accessed per-cpu. */
  57 static DEFINE_PER_CPU(struct trap_reason, pf_reason);
  58 static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);
  59
  60 static DEFINE_MUTEX(mmiotrace_mutex);
  61 static DEFINE_SPINLOCK(trace_lock);
  62 static atomic_t mmiotrace_enabled;
  63 static LIST_HEAD(trace_list);           /* struct remap_trace */
  64
  65 /*
  66  * Locking in this file:
  67  * - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
  68  * - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
  69  *   and trace_lock.
  70  * - Routines depending on is_enabled() must take trace_lock.
  71  * - trace_list users must hold trace_lock.
  72  * - is_enabled() guarantees that mmio_trace_{rw,mapping} are allowed.
  73  * - pre/post callbacks assume the effect of is_enabled() being true.
  74  */
  75
  76 /* module parameters */
  77 static unsigned long    filter_offset;
  78 static int              nommiotrace;
  79 static int              trace_pc;
  80
  81 module_param(filter_offset, ulong, 0);
  82 module_param(nommiotrace, bool, 0);
  83 module_param(trace_pc, bool, 0);
  84
  85 MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
  86 MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
  87 MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");
  88
  89 static bool is_enabled(void)
  90 {
  91         return atomic_read(&mmiotrace_enabled);
  92 }
  93
  94 static void print_pte(unsigned long address)
  95 {
  96         unsigned int level;
  97         pte_t *pte = lookup_address(address, &level);
  98
  99         if (!pte) {
 100                 pr_err("Error in %s: no pte for page 0x%08lx\n",
 101                        __func__, address);
 102                 return;
 103         }
 104
 105         if (level == PG_LEVEL_2M) {
 106                 pr_emerg("4MB pages are not currently supported: 0x%08lx\n",
 107                          address);
 108                 BUG();
 109         }
 110         pr_info("pte for 0x%lx: 0x%llx 0x%llx\n",
 111                 address,
 112                 (unsigned long long)pte_val(*pte),
 113                 (unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
 114 }
 115
 116 /*
 117  * For some reason the pre/post pairs have been called in an
 118  * unmatched order. Report and die.
 119  */
 120 static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
 121 {
 122         const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 123         pr_emerg("unexpected fault for address: 0x%08lx, last fault for address: 0x%08lx\n",
 124                  addr, my_reason->addr);
 125         print_pte(addr);
 126         print_symbol(KERN_EMERG "faulting IP is at %s\n", regs->ip);
 127         print_symbol(KERN_EMERG "last faulting IP was at %s\n", my_reason->ip);
 128 #ifdef __i386__
 129         pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
 130                  regs->ax, regs->bx, regs->cx, regs->dx);
 131         pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
 132                  regs->si, regs->di, regs->bp, regs->sp);
 133 #else
 134         pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
 135                  regs->ax, regs->cx, regs->dx);
 136         pr_emerg("rsi: %016lx   rdi: %016lx   rbp: %016lx   rsp: %016lx\n",
 137                  regs->si, regs->di, regs->bp, regs->sp);
 138 #endif
 139         put_cpu_var(pf_reason);
 140         BUG();
 141 }
 142
 143 static void pre(struct kmmio_probe *p, struct pt_regs *regs,
 144                                                 unsigned long addr)
 145 {
 146         struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 147         struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
 148         const unsigned long instptr = instruction_pointer(regs);
 149         const enum reason_type type = get_ins_type(instptr);
 150         struct remap_trace *trace = p->private;
 151
 152         /* it doesn't make sense to have more than one active trace per cpu */
 153         if (my_reason->active_traces)
 154                 die_kmmio_nesting_error(regs, addr);
 155         else
 156                 my_reason->active_traces++;
 157
 158         my_reason->type = type;
 159         my_reason->addr = addr;
 160         my_reason->ip = instptr;
 161
 162         my_trace->phys = addr - trace->probe.addr + trace->phys;
 163         my_trace->map_id = trace->id;
 164
 165         /*
 166          * Only record the program counter when requested.
 167          * It may taint clean-room reverse engineering.
 168          */
 169         if (trace_pc)
 170                 my_trace->pc = instptr;
 171         else
 172                 my_trace->pc = 0;
 173
 174         /*
 175          * XXX: the timestamp recorded will be *after* the tracing has been
 176          * done, not at the time we hit the instruction. SMP implications
 177          * on event ordering?
 178          */
 179
 180         switch (type) {
 181         case REG_READ:
 182                 my_trace->opcode = MMIO_READ;
 183                 my_trace->width = get_ins_mem_width(instptr);
 184                 break;
 185         case REG_WRITE:
 186                 my_trace->opcode = MMIO_WRITE;
 187                 my_trace->width = get_ins_mem_width(instptr);
 188                 my_trace->value = get_ins_reg_val(instptr, regs);
 189                 break;
 190         case IMM_WRITE:
 191                 my_trace->opcode = MMIO_WRITE;
 192                 my_trace->width = get_ins_mem_width(instptr);
 193                 my_trace->value = get_ins_imm_val(instptr);
 194                 break;
 195         default:
 196                 {
 197                         unsigned char *ip = (unsigned char *)instptr;
 198                         my_trace->opcode = MMIO_UNKNOWN_OP;
 199                         my_trace->width = 0;
 200                         my_trace->value = (*ip) << 16 | *(ip + 1) << 8 |
 201                                                                 *(ip + 2);
 202                 }
 203         }
 204         put_cpu_var(cpu_trace);
 205         put_cpu_var(pf_reason);
 206 }
 207
 208 static void post(struct kmmio_probe *p, unsigned long condition,
 209                                                         struct pt_regs *regs)
 210 {
 211         struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 212         struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
 213
 214         /* this should always return the active_trace count to 0 */
 215         my_reason->active_traces--;
 216         if (my_reason->active_traces) {
 217                 pr_emerg("unexpected post handler");
 218                 BUG();
 219         }
 220
 221         switch (my_reason->type) {
 222         case REG_READ:
 223                 my_trace->value = get_ins_reg_val(my_reason->ip, regs);
 224                 break;
 225         default:
 226                 break;
 227         }
 228
 229         mmio_trace_rw(my_trace);
 230         put_cpu_var(cpu_trace);
 231         put_cpu_var(pf_reason);
 232 }
 233
 234 static void ioremap_trace_core(resource_size_t offset, unsigned long size,
 235                                                         void __iomem *addr)
 236 {
 237         static atomic_t next_id;
 238         struct remap_trace *trace = kmalloc(sizeof(*trace), GFP_KERNEL);
 239         /* These are page-unaligned. */
 240         struct mmiotrace_map map = {
 241                 .phys = offset,
 242                 .virt = (unsigned long)addr,
 243                 .len = size,
 244                 .opcode = MMIO_PROBE
 245         };
 246
 247         if (!trace) {
 248                 pr_err("kmalloc failed in ioremap\n");
 249                 return;
 250         }
 251
 252         *trace = (struct remap_trace) {
 253                 .probe = {
 254                         .addr = (unsigned long)addr,
 255                         .len = size,
 256                         .pre_handler = pre,
 257                         .post_handler = post,
 258                         .private = trace
 259                 },
 260                 .phys = offset,
 261                 .id = atomic_inc_return(&next_id)
 262         };
 263         map.map_id = trace->id;
 264
 265         spin_lock_irq(&trace_lock);
 266         if (!is_enabled()) {
 267                 kfree(trace);
 268                 goto not_enabled;
 269         }
 270
 271         mmio_trace_mapping(&map);
 272         list_add_tail(&trace->list, &trace_list);
 273         if (!nommiotrace)
 274                 register_kmmio_probe(&trace->probe);
 275
 276 not_enabled:
 277         spin_unlock_irq(&trace_lock);
 278 }
 279
 280 void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
 281                                                 void __iomem *addr)
 282 {
 283         if (!is_enabled()) /* recheck and proper locking in *_core() */
 284                 return;
 285
 286         pr_debug("ioremap_*(0x%llx, 0x%lx) = %p\n",
 287                  (unsigned long long)offset, size, addr);
 288         if ((filter_offset) && (offset != filter_offset))
 289                 return;
 290         ioremap_trace_core(offset, size, addr);
 291 }
 292
 293 static void iounmap_trace_core(volatile void __iomem *addr)
 294 {
 295         struct mmiotrace_map map = {
 296                 .phys = 0,
 297                 .virt = (unsigned long)addr,
 298                 .len = 0,
 299                 .opcode = MMIO_UNPROBE
 300         };
 301         struct remap_trace *trace;
 302         struct remap_trace *tmp;
 303         struct remap_trace *found_trace = NULL;
 304
 305         pr_debug("Unmapping %p.\n", addr);
 306
 307         spin_lock_irq(&trace_lock);
 308         if (!is_enabled())
 309                 goto not_enabled;
 310
 311         list_for_each_entry_safe(trace, tmp, &trace_list, list) {
 312                 if ((unsigned long)addr == trace->probe.addr) {
 313                         if (!nommiotrace)
 314                                 unregister_kmmio_probe(&trace->probe);
 315                         list_del(&trace->list);
 316                         found_trace = trace;
 317                         break;
 318                 }
 319         }
 320         map.map_id = (found_trace) ? found_trace->id : -1;
 321         mmio_trace_mapping(&map);
 322
 323 not_enabled:
 324         spin_unlock_irq(&trace_lock);
 325         if (found_trace) {
 326                 synchronize_rcu(); /* unregister_kmmio_probe() requirement */
 327                 kfree(found_trace);
 328         }
 329 }
 330
 331 void mmiotrace_iounmap(volatile void __iomem *addr)
 332 {
 333         might_sleep();
 334         if (is_enabled()) /* recheck and proper locking in *_core() */
 335                 iounmap_trace_core(addr);
 336 }
 337
 338 int mmiotrace_printk(const char *fmt, ...)
 339 {
 340         int ret = 0;
 341         va_list args;
 342         unsigned long flags;
 343         va_start(args, fmt);
 344
 345         spin_lock_irqsave(&trace_lock, flags);
 346         if (is_enabled())
 347                 ret = mmio_trace_printk(fmt, args);
 348         spin_unlock_irqrestore(&trace_lock, flags);
 349
 350         va_end(args);
 351         return ret;
 352 }
 353 EXPORT_SYMBOL(mmiotrace_printk);
 354
 355 static void clear_trace_list(void)
 356 {
 357         struct remap_trace *trace;
 358         struct remap_trace *tmp;
 359
 360         /*
 361          * No locking required, because the caller ensures we are in a
 362          * critical section via mutex, and is_enabled() is false,
 363          * i.e. nothing can traverse or modify this list.
 364          * Caller also ensures is_enabled() cannot change.
 365          */
 366         list_for_each_entry(trace, &trace_list, list) {
 367                 pr_notice("purging non-iounmapped trace @0x%08lx, size 0x%lx.\n",
 368                           trace->probe.addr, trace->probe.len);
 369                 if (!nommiotrace)
 370                         unregister_kmmio_probe(&trace->probe);
 371         }
 372         synchronize_rcu(); /* unregister_kmmio_probe() requirement */
 373
 374         list_for_each_entry_safe(trace, tmp, &trace_list, list) {
 375                 list_del(&trace->list);
 376                 kfree(trace);
 377         }
 378 }
 379
 380 #ifdef CONFIG_HOTPLUG_CPU
 381 static cpumask_var_t downed_cpus;
 382
 383 static void enter_uniprocessor(void)
 384 {
 385         int cpu;
 386         int err;
 387
 388         if (downed_cpus == NULL &&
 389             !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
 390                 pr_notice("Failed to allocate mask\n");
 391                 goto out;
 392         }
 393
 394         get_online_cpus();
 395         cpumask_copy(downed_cpus, cpu_online_mask);
 396         cpumask_clear_cpu(cpumask_first(cpu_online_mask), downed_cpus);
 397         if (num_online_cpus() > 1)
 398                 pr_notice("Disabling non-boot CPUs...\n");
 399         put_online_cpus();
 400
 401         for_each_cpu(cpu, downed_cpus) {
 402                 err = cpu_down(cpu);
 403                 if (!err)
 404                         pr_info("CPU%d is down.\n", cpu);
 405                 else
 406                         pr_err("Error taking CPU%d down: %d\n", cpu, err);
 407         }
 408 out:
 409         if (num_online_cpus() > 1)
 410                 pr_warning("multiple CPUs still online, may miss events.\n");
 411 }
 412
 413 /* __ref because leave_uniprocessor calls cpu_up which is __cpuinit,
 414    but this whole function is ifdefed CONFIG_HOTPLUG_CPU */
 415 static void __ref leave_uniprocessor(void)
 416 {
 417         int cpu;
 418         int err;
 419
 420         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
 421                 return;
 422         pr_notice("Re-enabling CPUs...\n");
 423         for_each_cpu(cpu, downed_cpus) {
 424                 err = cpu_up(cpu);
 425                 if (!err)
 426                         pr_info("enabled CPU%d.\n", cpu);
 427                 else
 428                         pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
 429         }
 430 }
 431
 432 #else /* !CONFIG_HOTPLUG_CPU */
 433 static void enter_uniprocessor(void)
 434 {
 435         if (num_online_cpus() > 1)
 436                 pr_warning("multiple CPUs are online, may miss events. "
 437                            "Suggest booting with maxcpus=1 kernel argument.\n");
 438 }
 439
 440 static void leave_uniprocessor(void)
 441 {
 442 }
 443 #endif
 444
 445 void enable_mmiotrace(void)
 446 {
 447         mutex_lock(&mmiotrace_mutex);
 448         if (is_enabled())
 449                 goto out;
 450
 451         if (nommiotrace)
 452                 pr_info("MMIO tracing disabled.\n");
 453         kmmio_init();
 454         enter_uniprocessor();
 455         spin_lock_irq(&trace_lock);
 456         atomic_inc(&mmiotrace_enabled);
 457         spin_unlock_irq(&trace_lock);
 458         pr_info("enabled.\n");
 459 out:
 460         mutex_unlock(&mmiotrace_mutex);
 461 }
 462
 463 void disable_mmiotrace(void)
 464 {
 465         mutex_lock(&mmiotrace_mutex);
 466         if (!is_enabled())
 467                 goto out;
 468
 469         spin_lock_irq(&trace_lock);
 470         atomic_dec(&mmiotrace_enabled);
 471         BUG_ON(is_enabled());
 472         spin_unlock_irq(&trace_lock);
 473
 474         clear_trace_list(); /* guarantees: no more kmmio callbacks */
 475         leave_uniprocessor();
 476         kmmio_cleanup();
 477         pr_info("disabled.\n");
 478 out:
 479         mutex_unlock(&mmiotrace_mutex);
 480 }