kernel/arch/s390/kvm/guestdbg.c

   1 /*
   2  * kvm guest debug support
   3  *
   4  * Copyright IBM Corp. 2014
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License (version 2 only)
   8  * as published by the Free Software Foundation.
   9  *
  10  *    Author(s): David Hildenbrand <dahi@linux.vnet.ibm.com>
  11  */
  12 #include <linux/kvm_host.h>
  13 #include <linux/errno.h>
  14 #include "kvm-s390.h"
  15 #include "gaccess.h"
  16
  17 /*
  18  * Extends the address range given by *start and *stop to include the address
  19  * range starting with estart and the length len. Takes care of overflowing
  20  * intervals and tries to minimize the overall intervall size.
  21  */
  22 static void extend_address_range(u64 *start, u64 *stop, u64 estart, int len)
  23 {
  24         u64 estop;
  25
  26         if (len > 0)
  27                 len--;
  28         else
  29                 len = 0;
  30
  31         estop = estart + len;
  32
  33         /* 0-0 range represents "not set" */
  34         if ((*start == 0) && (*stop == 0)) {
  35                 *start = estart;
  36                 *stop = estop;
  37         } else if (*start <= *stop) {
  38                 /* increase the existing range */
  39                 if (estart < *start)
  40                         *start = estart;
  41                 if (estop > *stop)
  42                         *stop = estop;
  43         } else {
  44                 /* "overflowing" interval, whereby *stop > *start */
  45                 if (estart <= *stop) {
  46                         if (estop > *stop)
  47                                 *stop = estop;
  48                 } else if (estop > *start) {
  49                         if (estart < *start)
  50                                 *start = estart;
  51                 }
  52                 /* minimize the range */
  53                 else if ((estop - *stop) < (*start - estart))
  54                         *stop = estop;
  55                 else
  56                         *start = estart;
  57         }
  58 }
  59
  60 #define MAX_INST_SIZE 6
  61
  62 static void enable_all_hw_bp(struct kvm_vcpu *vcpu)
  63 {
  64         unsigned long start, len;
  65         u64 *cr9 = &vcpu->arch.sie_block->gcr[9];
  66         u64 *cr10 = &vcpu->arch.sie_block->gcr[10];
  67         u64 *cr11 = &vcpu->arch.sie_block->gcr[11];
  68         int i;
  69
  70         if (vcpu->arch.guestdbg.nr_hw_bp <= 0 ||
  71             vcpu->arch.guestdbg.hw_bp_info == NULL)
  72                 return;
  73
  74         /*
  75          * If the guest is not interrested in branching events, we can savely
  76          * limit them to the PER address range.
  77          */
  78         if (!(*cr9 & PER_EVENT_BRANCH))
  79                 *cr9 |= PER_CONTROL_BRANCH_ADDRESS;
  80         *cr9 |= PER_EVENT_IFETCH | PER_EVENT_BRANCH;
  81
  82         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_bp; i++) {
  83                 start = vcpu->arch.guestdbg.hw_bp_info[i].addr;
  84                 len = vcpu->arch.guestdbg.hw_bp_info[i].len;
  85
  86                 /*
  87                  * The instruction in front of the desired bp has to
  88                  * report instruction-fetching events
  89                  */
  90                 if (start < MAX_INST_SIZE) {
  91                         len += start;
  92                         start = 0;
  93                 } else {
  94                         start -= MAX_INST_SIZE;
  95                         len += MAX_INST_SIZE;
  96                 }
  97
  98                 extend_address_range(cr10, cr11, start, len);
  99         }
 100 }
 101
 102 static void enable_all_hw_wp(struct kvm_vcpu *vcpu)
 103 {
 104         unsigned long start, len;
 105         u64 *cr9 = &vcpu->arch.sie_block->gcr[9];
 106         u64 *cr10 = &vcpu->arch.sie_block->gcr[10];
 107         u64 *cr11 = &vcpu->arch.sie_block->gcr[11];
 108         int i;
 109
 110         if (vcpu->arch.guestdbg.nr_hw_wp <= 0 ||
 111             vcpu->arch.guestdbg.hw_wp_info == NULL)
 112                 return;
 113
 114         /* if host uses storage alternation for special address
 115          * spaces, enable all events and give all to the guest */
 116         if (*cr9 & PER_EVENT_STORE && *cr9 & PER_CONTROL_ALTERATION) {
 117                 *cr9 &= ~PER_CONTROL_ALTERATION;
 118                 *cr10 = 0;
 119                 *cr11 = PSW_ADDR_INSN;
 120         } else {
 121                 *cr9 &= ~PER_CONTROL_ALTERATION;
 122                 *cr9 |= PER_EVENT_STORE;
 123
 124                 for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
 125                         start = vcpu->arch.guestdbg.hw_wp_info[i].addr;
 126                         len = vcpu->arch.guestdbg.hw_wp_info[i].len;
 127
 128                         extend_address_range(cr10, cr11, start, len);
 129                 }
 130         }
 131 }
 132
 133 void kvm_s390_backup_guest_per_regs(struct kvm_vcpu *vcpu)
 134 {
 135         vcpu->arch.guestdbg.cr0 = vcpu->arch.sie_block->gcr[0];
 136         vcpu->arch.guestdbg.cr9 = vcpu->arch.sie_block->gcr[9];
 137         vcpu->arch.guestdbg.cr10 = vcpu->arch.sie_block->gcr[10];
 138         vcpu->arch.guestdbg.cr11 = vcpu->arch.sie_block->gcr[11];
 139 }
 140
 141 void kvm_s390_restore_guest_per_regs(struct kvm_vcpu *vcpu)
 142 {
 143         vcpu->arch.sie_block->gcr[0] = vcpu->arch.guestdbg.cr0;
 144         vcpu->arch.sie_block->gcr[9] = vcpu->arch.guestdbg.cr9;
 145         vcpu->arch.sie_block->gcr[10] = vcpu->arch.guestdbg.cr10;
 146         vcpu->arch.sie_block->gcr[11] = vcpu->arch.guestdbg.cr11;
 147 }
 148
 149 void kvm_s390_patch_guest_per_regs(struct kvm_vcpu *vcpu)
 150 {
 151         /*
 152          * TODO: if guest psw has per enabled, otherwise 0s!
 153          * This reduces the amount of reported events.
 154          * Need to intercept all psw changes!
 155          */
 156
 157         if (guestdbg_sstep_enabled(vcpu)) {
 158                 /* disable timer (clock-comparator) interrupts */
 159                 vcpu->arch.sie_block->gcr[0] &= ~0x800ul;
 160                 vcpu->arch.sie_block->gcr[9] |= PER_EVENT_IFETCH;
 161                 vcpu->arch.sie_block->gcr[10] = 0;
 162                 vcpu->arch.sie_block->gcr[11] = PSW_ADDR_INSN;
 163         }
 164
 165         if (guestdbg_hw_bp_enabled(vcpu)) {
 166                 enable_all_hw_bp(vcpu);
 167                 enable_all_hw_wp(vcpu);
 168         }
 169
 170         /* TODO: Instruction-fetching-nullification not allowed for now */
 171         if (vcpu->arch.sie_block->gcr[9] & PER_EVENT_NULLIFICATION)
 172                 vcpu->arch.sie_block->gcr[9] &= ~PER_EVENT_NULLIFICATION;
 173 }
 174
 175 #define MAX_WP_SIZE 100
 176
 177 static int __import_wp_info(struct kvm_vcpu *vcpu,
 178                             struct kvm_hw_breakpoint *bp_data,
 179                             struct kvm_hw_wp_info_arch *wp_info)
 180 {
 181         int ret = 0;
 182         wp_info->len = bp_data->len;
 183         wp_info->addr = bp_data->addr;
 184         wp_info->phys_addr = bp_data->phys_addr;
 185         wp_info->old_data = NULL;
 186
 187         if (wp_info->len < 0 || wp_info->len > MAX_WP_SIZE)
 188                 return -EINVAL;
 189
 190         wp_info->old_data = kmalloc(bp_data->len, GFP_KERNEL);
 191         if (!wp_info->old_data)
 192                 return -ENOMEM;
 193         /* try to backup the original value */
 194         ret = read_guest_abs(vcpu, wp_info->phys_addr, wp_info->old_data,
 195                              wp_info->len);
 196         if (ret) {
 197                 kfree(wp_info->old_data);
 198                 wp_info->old_data = NULL;
 199         }
 200
 201         return ret;
 202 }
 203
 204 #define MAX_BP_COUNT 50
 205
 206 int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
 207                             struct kvm_guest_debug *dbg)
 208 {
 209         int ret = 0, nr_wp = 0, nr_bp = 0, i, size;
 210         struct kvm_hw_breakpoint *bp_data = NULL;
 211         struct kvm_hw_wp_info_arch *wp_info = NULL;
 212         struct kvm_hw_bp_info_arch *bp_info = NULL;
 213
 214         if (dbg->arch.nr_hw_bp <= 0 || !dbg->arch.hw_bp)
 215                 return 0;
 216         else if (dbg->arch.nr_hw_bp > MAX_BP_COUNT)
 217                 return -EINVAL;
 218
 219         size = dbg->arch.nr_hw_bp * sizeof(struct kvm_hw_breakpoint);
 220         bp_data = kmalloc(size, GFP_KERNEL);
 221         if (!bp_data) {
 222                 ret = -ENOMEM;
 223                 goto error;
 224         }
 225
 226         if (copy_from_user(bp_data, dbg->arch.hw_bp, size)) {
 227                 ret = -EFAULT;
 228                 goto error;
 229         }
 230
 231         for (i = 0; i < dbg->arch.nr_hw_bp; i++) {
 232                 switch (bp_data[i].type) {
 233                 case KVM_HW_WP_WRITE:
 234                         nr_wp++;
 235                         break;
 236                 case KVM_HW_BP:
 237                         nr_bp++;
 238                         break;
 239                 default:
 240                         break;
 241                 }
 242         }
 243
 244         size = nr_wp * sizeof(struct kvm_hw_wp_info_arch);
 245         if (size > 0) {
 246                 wp_info = kmalloc(size, GFP_KERNEL);
 247                 if (!wp_info) {
 248                         ret = -ENOMEM;
 249                         goto error;
 250                 }
 251         }
 252         size = nr_bp * sizeof(struct kvm_hw_bp_info_arch);
 253         if (size > 0) {
 254                 bp_info = kmalloc(size, GFP_KERNEL);
 255                 if (!bp_info) {
 256                         ret = -ENOMEM;
 257                         goto error;
 258                 }
 259         }
 260
 261         for (nr_wp = 0, nr_bp = 0, i = 0; i < dbg->arch.nr_hw_bp; i++) {
 262                 switch (bp_data[i].type) {
 263                 case KVM_HW_WP_WRITE:
 264                         ret = __import_wp_info(vcpu, &bp_data[i],
 265                                                &wp_info[nr_wp]);
 266                         if (ret)
 267                                 goto error;
 268                         nr_wp++;
 269                         break;
 270                 case KVM_HW_BP:
 271                         bp_info[nr_bp].len = bp_data[i].len;
 272                         bp_info[nr_bp].addr = bp_data[i].addr;
 273                         nr_bp++;
 274                         break;
 275                 }
 276         }
 277
 278         vcpu->arch.guestdbg.nr_hw_bp = nr_bp;
 279         vcpu->arch.guestdbg.hw_bp_info = bp_info;
 280         vcpu->arch.guestdbg.nr_hw_wp = nr_wp;
 281         vcpu->arch.guestdbg.hw_wp_info = wp_info;
 282         return 0;
 283 error:
 284         kfree(bp_data);
 285         kfree(wp_info);
 286         kfree(bp_info);
 287         return ret;
 288 }
 289
 290 void kvm_s390_clear_bp_data(struct kvm_vcpu *vcpu)
 291 {
 292         int i;
 293         struct kvm_hw_wp_info_arch *hw_wp_info = NULL;
 294
 295         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
 296                 hw_wp_info = &vcpu->arch.guestdbg.hw_wp_info[i];
 297                 kfree(hw_wp_info->old_data);
 298                 hw_wp_info->old_data = NULL;
 299         }
 300         kfree(vcpu->arch.guestdbg.hw_wp_info);
 301         vcpu->arch.guestdbg.hw_wp_info = NULL;
 302
 303         kfree(vcpu->arch.guestdbg.hw_bp_info);
 304         vcpu->arch.guestdbg.hw_bp_info = NULL;
 305
 306         vcpu->arch.guestdbg.nr_hw_wp = 0;
 307         vcpu->arch.guestdbg.nr_hw_bp = 0;
 308 }
 309
 310 static inline int in_addr_range(u64 addr, u64 a, u64 b)
 311 {
 312         if (a <= b)
 313                 return (addr >= a) && (addr <= b);
 314         else
 315                 /* "overflowing" interval */
 316                 return (addr <= a) && (addr >= b);
 317 }
 318
 319 #define end_of_range(bp_info) (bp_info->addr + bp_info->len - 1)
 320
 321 static struct kvm_hw_bp_info_arch *find_hw_bp(struct kvm_vcpu *vcpu,
 322                                               unsigned long addr)
 323 {
 324         struct kvm_hw_bp_info_arch *bp_info = vcpu->arch.guestdbg.hw_bp_info;
 325         int i;
 326
 327         if (vcpu->arch.guestdbg.nr_hw_bp == 0)
 328                 return NULL;
 329
 330         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_bp; i++) {
 331                 /* addr is directly the start or in the range of a bp */
 332                 if (addr == bp_info->addr)
 333                         goto found;
 334                 if (bp_info->len > 0 &&
 335                     in_addr_range(addr, bp_info->addr, end_of_range(bp_info)))
 336                         goto found;
 337
 338                 bp_info++;
 339         }
 340
 341         return NULL;
 342 found:
 343         return bp_info;
 344 }
 345
 346 static struct kvm_hw_wp_info_arch *any_wp_changed(struct kvm_vcpu *vcpu)
 347 {
 348         int i;
 349         struct kvm_hw_wp_info_arch *wp_info = NULL;
 350         void *temp = NULL;
 351
 352         if (vcpu->arch.guestdbg.nr_hw_wp == 0)
 353                 return NULL;
 354
 355         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
 356                 wp_info = &vcpu->arch.guestdbg.hw_wp_info[i];
 357                 if (!wp_info || !wp_info->old_data || wp_info->len <= 0)
 358                         continue;
 359
 360                 temp = kmalloc(wp_info->len, GFP_KERNEL);
 361                 if (!temp)
 362                         continue;
 363
 364                 /* refetch the wp data and compare it to the old value */
 365                 if (!read_guest_abs(vcpu, wp_info->phys_addr, temp,
 366                                     wp_info->len)) {
 367                         if (memcmp(temp, wp_info->old_data, wp_info->len)) {
 368                                 kfree(temp);
 369                                 return wp_info;
 370                         }
 371                 }
 372                 kfree(temp);
 373                 temp = NULL;
 374         }
 375
 376         return NULL;
 377 }
 378
 379 void kvm_s390_prepare_debug_exit(struct kvm_vcpu *vcpu)
 380 {
 381         vcpu->run->exit_reason = KVM_EXIT_DEBUG;
 382         vcpu->guest_debug &= ~KVM_GUESTDBG_EXIT_PENDING;
 383 }
 384
 385 #define per_bp_event(code) \
 386                         (code & (PER_EVENT_IFETCH | PER_EVENT_BRANCH))
 387 #define per_write_wp_event(code) \
 388                         (code & (PER_EVENT_STORE | PER_EVENT_STORE_REAL))
 389
 390 static int debug_exit_required(struct kvm_vcpu *vcpu)
 391 {
 392         u32 perc = (vcpu->arch.sie_block->perc << 24);
 393         struct kvm_debug_exit_arch *debug_exit = &vcpu->run->debug.arch;
 394         struct kvm_hw_wp_info_arch *wp_info = NULL;
 395         struct kvm_hw_bp_info_arch *bp_info = NULL;
 396         unsigned long addr = vcpu->arch.sie_block->gpsw.addr;
 397         unsigned long peraddr = vcpu->arch.sie_block->peraddr;
 398
 399         if (guestdbg_hw_bp_enabled(vcpu)) {
 400                 if (per_write_wp_event(perc) &&
 401                     vcpu->arch.guestdbg.nr_hw_wp > 0) {
 402                         wp_info = any_wp_changed(vcpu);
 403                         if (wp_info) {
 404                                 debug_exit->addr = wp_info->addr;
 405                                 debug_exit->type = KVM_HW_WP_WRITE;
 406                                 goto exit_required;
 407                         }
 408                 }
 409                 if (per_bp_event(perc) &&
 410                          vcpu->arch.guestdbg.nr_hw_bp > 0) {
 411                         bp_info = find_hw_bp(vcpu, addr);
 412                         /* remove duplicate events if PC==PER address */
 413                         if (bp_info && (addr != peraddr)) {
 414                                 debug_exit->addr = addr;
 415                                 debug_exit->type = KVM_HW_BP;
 416                                 vcpu->arch.guestdbg.last_bp = addr;
 417                                 goto exit_required;
 418                         }
 419                         /* breakpoint missed */
 420                         bp_info = find_hw_bp(vcpu, peraddr);
 421                         if (bp_info && vcpu->arch.guestdbg.last_bp != peraddr) {
 422                                 debug_exit->addr = peraddr;
 423                                 debug_exit->type = KVM_HW_BP;
 424                                 goto exit_required;
 425                         }
 426                 }
 427         }
 428         if (guestdbg_sstep_enabled(vcpu) && per_bp_event(perc)) {
 429                 debug_exit->addr = addr;
 430                 debug_exit->type = KVM_SINGLESTEP;
 431                 goto exit_required;
 432         }
 433
 434         return 0;
 435 exit_required:
 436         return 1;
 437 }
 438
 439 #define guest_per_enabled(vcpu) \
 440                              (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PER)
 441
 442 static void filter_guest_per_event(struct kvm_vcpu *vcpu)
 443 {
 444         u32 perc = vcpu->arch.sie_block->perc << 24;
 445         u64 peraddr = vcpu->arch.sie_block->peraddr;
 446         u64 addr = vcpu->arch.sie_block->gpsw.addr;
 447         u64 cr9 = vcpu->arch.sie_block->gcr[9];
 448         u64 cr10 = vcpu->arch.sie_block->gcr[10];
 449         u64 cr11 = vcpu->arch.sie_block->gcr[11];
 450         /* filter all events, demanded by the guest */
 451         u32 guest_perc = perc & cr9 & PER_EVENT_MASK;
 452
 453         if (!guest_per_enabled(vcpu))
 454                 guest_perc = 0;
 455
 456         /* filter "successful-branching" events */
 457         if (guest_perc & PER_EVENT_BRANCH &&
 458             cr9 & PER_CONTROL_BRANCH_ADDRESS &&
 459             !in_addr_range(addr, cr10, cr11))
 460                 guest_perc &= ~PER_EVENT_BRANCH;
 461
 462         /* filter "instruction-fetching" events */
 463         if (guest_perc & PER_EVENT_IFETCH &&
 464             !in_addr_range(peraddr, cr10, cr11))
 465                 guest_perc &= ~PER_EVENT_IFETCH;
 466
 467         /* All other PER events will be given to the guest */
 468         /* TODO: Check alterated address/address space */
 469
 470         vcpu->arch.sie_block->perc = guest_perc >> 24;
 471
 472         if (!guest_perc)
 473                 vcpu->arch.sie_block->iprcc &= ~PGM_PER;
 474 }
 475
 476 void kvm_s390_handle_per_event(struct kvm_vcpu *vcpu)
 477 {
 478         if (debug_exit_required(vcpu))
 479                 vcpu->guest_debug |= KVM_GUESTDBG_EXIT_PENDING;
 480
 481         filter_guest_per_event(vcpu);
 482 }