arch/xtensa/kernel/hw_breakpoint.c

   1 /*
   2  * Xtensa hardware breakpoints/watchpoints handling functions
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (C) 2016 Cadence Design Systems Inc.
   9  */
  10
  11 #include <linux/hw_breakpoint.h>
  12 #include <linux/log2.h>
  13 #include <linux/percpu.h>
  14 #include <linux/perf_event.h>
  15 #include <asm/core.h>
  16
  17 /* Breakpoint currently in use for each IBREAKA. */
  18 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[XCHAL_NUM_IBREAK]);
  19
  20 /* Watchpoint currently in use for each DBREAKA. */
  21 static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[XCHAL_NUM_DBREAK]);
  22
  23 int hw_breakpoint_slots(int type)
  24 {
  25         switch (type) {
  26         case TYPE_INST:
  27                 return XCHAL_NUM_IBREAK;
  28         case TYPE_DATA:
  29                 return XCHAL_NUM_DBREAK;
  30         default:
  31                 pr_warn("unknown slot type: %d\n", type);
  32                 return 0;
  33         }
  34 }
  35
  36 int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
  37 {
  38         unsigned int len;
  39         unsigned long va;
  40
  41         va = hw->address;
  42         len = hw->len;
  43
  44         return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
  45 }
  46
  47 /*
  48  * Construct an arch_hw_breakpoint from a perf_event.
  49  */
  50 int hw_breakpoint_arch_parse(struct perf_event *bp,
  51                              const struct perf_event_attr *attr,
  52                              struct arch_hw_breakpoint *hw)
  53 {
  54         /* Type */
  55         switch (attr->bp_type) {
  56         case HW_BREAKPOINT_X:
  57                 hw->type = XTENSA_BREAKPOINT_EXECUTE;
  58                 break;
  59         case HW_BREAKPOINT_R:
  60                 hw->type = XTENSA_BREAKPOINT_LOAD;
  61                 break;
  62         case HW_BREAKPOINT_W:
  63                 hw->type = XTENSA_BREAKPOINT_STORE;
  64                 break;
  65         case HW_BREAKPOINT_RW:
  66                 hw->type = XTENSA_BREAKPOINT_LOAD | XTENSA_BREAKPOINT_STORE;
  67                 break;
  68         default:
  69                 return -EINVAL;
  70         }
  71
  72         /* Len */
  73         hw->len = attr->bp_len;
  74         if (hw->len < 1 || hw->len > 64 || !is_power_of_2(hw->len))
  75                 return -EINVAL;
  76
  77         /* Address */
  78         hw->address = attr->bp_addr;
  79         if (hw->address & (hw->len - 1))
  80                 return -EINVAL;
  81
  82         return 0;
  83 }
  84
  85 int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
  86                                     unsigned long val, void *data)
  87 {
  88         return NOTIFY_DONE;
  89 }
  90
  91 static void xtensa_wsr(unsigned long v, u8 sr)
  92 {
  93         /* We don't have indexed wsr and creating instruction dynamically
  94          * doesn't seem worth it given how small XCHAL_NUM_IBREAK and
  95          * XCHAL_NUM_DBREAK are. Thus the switch. In case build breaks here
  96          * the switch below needs to be extended.
  97          */
  98         BUILD_BUG_ON(XCHAL_NUM_IBREAK > 2);
  99         BUILD_BUG_ON(XCHAL_NUM_DBREAK > 2);
 100
 101         switch (sr) {
 102 #if XCHAL_NUM_IBREAK > 0
 103         case SREG_IBREAKA + 0:
 104                 xtensa_set_sr(v, SREG_IBREAKA + 0);
 105                 break;
 106 #endif
 107 #if XCHAL_NUM_IBREAK > 1
 108         case SREG_IBREAKA + 1:
 109                 xtensa_set_sr(v, SREG_IBREAKA + 1);
 110                 break;
 111 #endif
 112
 113 #if XCHAL_NUM_DBREAK > 0
 114         case SREG_DBREAKA + 0:
 115                 xtensa_set_sr(v, SREG_DBREAKA + 0);
 116                 break;
 117         case SREG_DBREAKC + 0:
 118                 xtensa_set_sr(v, SREG_DBREAKC + 0);
 119                 break;
 120 #endif
 121 #if XCHAL_NUM_DBREAK > 1
 122         case SREG_DBREAKA + 1:
 123                 xtensa_set_sr(v, SREG_DBREAKA + 1);
 124                 break;
 125
 126         case SREG_DBREAKC + 1:
 127                 xtensa_set_sr(v, SREG_DBREAKC + 1);
 128                 break;
 129 #endif
 130         }
 131 }
 132
 133 static int alloc_slot(struct perf_event **slot, size_t n,
 134                       struct perf_event *bp)
 135 {
 136         size_t i;
 137
 138         for (i = 0; i < n; ++i) {
 139                 if (!slot[i]) {
 140                         slot[i] = bp;
 141                         return i;
 142                 }
 143         }
 144         return -EBUSY;
 145 }
 146
 147 static void set_ibreak_regs(int reg, struct perf_event *bp)
 148 {
 149         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 150         unsigned long ibreakenable;
 151
 152         xtensa_wsr(info->address, SREG_IBREAKA + reg);
 153         ibreakenable = xtensa_get_sr(SREG_IBREAKENABLE);
 154         xtensa_set_sr(ibreakenable | (1 << reg), SREG_IBREAKENABLE);
 155 }
 156
 157 static void set_dbreak_regs(int reg, struct perf_event *bp)
 158 {
 159         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 160         unsigned long dbreakc = DBREAKC_MASK_MASK & -info->len;
 161
 162         if (info->type & XTENSA_BREAKPOINT_LOAD)
 163                 dbreakc |= DBREAKC_LOAD_MASK;
 164         if (info->type & XTENSA_BREAKPOINT_STORE)
 165                 dbreakc |= DBREAKC_STOR_MASK;
 166
 167         xtensa_wsr(info->address, SREG_DBREAKA + reg);
 168         xtensa_wsr(dbreakc, SREG_DBREAKC + reg);
 169 }
 170
 171 int arch_install_hw_breakpoint(struct perf_event *bp)
 172 {
 173         int i;
 174
 175         if (counter_arch_bp(bp)->type == XTENSA_BREAKPOINT_EXECUTE) {
 176                 /* Breakpoint */
 177                 i = alloc_slot(this_cpu_ptr(bp_on_reg), XCHAL_NUM_IBREAK, bp);
 178                 if (i < 0)
 179                         return i;
 180                 set_ibreak_regs(i, bp);
 181
 182         } else {
 183                 /* Watchpoint */
 184                 i = alloc_slot(this_cpu_ptr(wp_on_reg), XCHAL_NUM_DBREAK, bp);
 185                 if (i < 0)
 186                         return i;
 187                 set_dbreak_regs(i, bp);
 188         }
 189         return 0;
 190 }
 191
 192 static int free_slot(struct perf_event **slot, size_t n,
 193                      struct perf_event *bp)
 194 {
 195         size_t i;
 196
 197         for (i = 0; i < n; ++i) {
 198                 if (slot[i] == bp) {
 199                         slot[i] = NULL;
 200                         return i;
 201                 }
 202         }
 203         return -EBUSY;
 204 }
 205
 206 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 207 {
 208         struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 209         int i;
 210
 211         if (info->type == XTENSA_BREAKPOINT_EXECUTE) {
 212                 unsigned long ibreakenable;
 213
 214                 /* Breakpoint */
 215                 i = free_slot(this_cpu_ptr(bp_on_reg), XCHAL_NUM_IBREAK, bp);
 216                 if (i >= 0) {
 217                         ibreakenable = xtensa_get_sr(SREG_IBREAKENABLE);
 218                         xtensa_set_sr(ibreakenable & ~(1 << i),
 219                                       SREG_IBREAKENABLE);
 220                 }
 221         } else {
 222                 /* Watchpoint */
 223                 i = free_slot(this_cpu_ptr(wp_on_reg), XCHAL_NUM_DBREAK, bp);
 224                 if (i >= 0)
 225                         xtensa_wsr(0, SREG_DBREAKC + i);
 226         }
 227 }
 228
 229 void hw_breakpoint_pmu_read(struct perf_event *bp)
 230 {
 231 }
 232
 233 void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
 234 {
 235         int i;
 236         struct thread_struct *t = &tsk->thread;
 237
 238         for (i = 0; i < XCHAL_NUM_IBREAK; ++i) {
 239                 if (t->ptrace_bp[i]) {
 240                         unregister_hw_breakpoint(t->ptrace_bp[i]);
 241                         t->ptrace_bp[i] = NULL;
 242                 }
 243         }
 244         for (i = 0; i < XCHAL_NUM_DBREAK; ++i) {
 245                 if (t->ptrace_wp[i]) {
 246                         unregister_hw_breakpoint(t->ptrace_wp[i]);
 247                         t->ptrace_wp[i] = NULL;
 248                 }
 249         }
 250 }
 251
 252 /*
 253  * Set ptrace breakpoint pointers to zero for this task.
 254  * This is required in order to prevent child processes from unregistering
 255  * breakpoints held by their parent.
 256  */
 257 void clear_ptrace_hw_breakpoint(struct task_struct *tsk)
 258 {
 259         memset(tsk->thread.ptrace_bp, 0, sizeof(tsk->thread.ptrace_bp));
 260         memset(tsk->thread.ptrace_wp, 0, sizeof(tsk->thread.ptrace_wp));
 261 }
 262
 263 void restore_dbreak(void)
 264 {
 265         int i;
 266
 267         for (i = 0; i < XCHAL_NUM_DBREAK; ++i) {
 268                 struct perf_event *bp = this_cpu_ptr(wp_on_reg)[i];
 269
 270                 if (bp)
 271                         set_dbreak_regs(i, bp);
 272         }
 273         clear_thread_flag(TIF_DB_DISABLED);
 274 }
 275
 276 int check_hw_breakpoint(struct pt_regs *regs)
 277 {
 278         if (regs->debugcause & BIT(DEBUGCAUSE_IBREAK_BIT)) {
 279                 int i;
 280                 struct perf_event **bp = this_cpu_ptr(bp_on_reg);
 281
 282                 for (i = 0; i < XCHAL_NUM_IBREAK; ++i) {
 283                         if (bp[i] && !bp[i]->attr.disabled &&
 284                             regs->pc == bp[i]->attr.bp_addr)
 285                                 perf_bp_event(bp[i], regs);
 286                 }
 287                 return 0;
 288         } else if (regs->debugcause & BIT(DEBUGCAUSE_DBREAK_BIT)) {
 289                 struct perf_event **bp = this_cpu_ptr(wp_on_reg);
 290                 int dbnum = (regs->debugcause & DEBUGCAUSE_DBNUM_MASK) >>
 291                         DEBUGCAUSE_DBNUM_SHIFT;
 292
 293                 if (dbnum < XCHAL_NUM_DBREAK && bp[dbnum]) {
 294                         if (user_mode(regs)) {
 295                                 perf_bp_event(bp[dbnum], regs);
 296                         } else {
 297                                 set_thread_flag(TIF_DB_DISABLED);
 298                                 xtensa_wsr(0, SREG_DBREAKC + dbnum);
 299                         }
 300                 } else {
 301                         WARN_ONCE(1,
 302                                   "Wrong/unconfigured DBNUM reported in DEBUGCAUSE: %d\n",
 303                                   dbnum);
 304                 }
 305                 return 0;
 306         }
 307         return -ENOENT;
 308 }