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