root/arch/x86/mm/mmio-mod.c

DEFINITIONS

1. is_enabled
2. print_pte
3. die_kmmio_nesting_error
4. pre
5. post
6. ioremap_trace_core
7. mmiotrace_ioremap
8. iounmap_trace_core
9. mmiotrace_iounmap
10. mmiotrace_printk
11. clear_trace_list
12. enter_uniprocessor
13. leave_uniprocessor
14. enter_uniprocessor
15. leave_uniprocessor
16. enable_mmiotrace
17. disable_mmiotrace

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