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 #include <asm/hw_breakpoint.h> 17 18 /* Breakpoint currently in use for each IBREAKA. */ 19 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[XCHAL_NUM_IBREAK]); 20 21 /* Watchpoint currently in use for each DBREAKA. */ 22 static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[XCHAL_NUM_DBREAK]); 23 24 int hw_breakpoint_slots(int type) 25 { 26 switch (type) { 27 case TYPE_INST: 28 return XCHAL_NUM_IBREAK; 29 case TYPE_DATA: 30 return XCHAL_NUM_DBREAK; 31 default: 32 pr_warn("unknown slot type: %d\n", type); 33 return 0; 34 } 35 } 36 37 int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw) 38 { 39 unsigned int len; 40 unsigned long va; 41 42 va = hw->address; 43 len = hw->len; 44 45 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE); 46 } 47 48 /* 49 * Construct an arch_hw_breakpoint from a perf_event. 50 */ 51 int hw_breakpoint_arch_parse(struct perf_event *bp, 52 const struct perf_event_attr *attr, 53 struct arch_hw_breakpoint *hw) 54 { 55 /* Type */ 56 switch (attr->bp_type) { 57 case HW_BREAKPOINT_X: 58 hw->type = XTENSA_BREAKPOINT_EXECUTE; 59 break; 60 case HW_BREAKPOINT_R: 61 hw->type = XTENSA_BREAKPOINT_LOAD; 62 break; 63 case HW_BREAKPOINT_W: 64 hw->type = XTENSA_BREAKPOINT_STORE; 65 break; 66 case HW_BREAKPOINT_RW: 67 hw->type = XTENSA_BREAKPOINT_LOAD | XTENSA_BREAKPOINT_STORE; 68 break; 69 default: 70 return -EINVAL; 71 } 72 73 /* Len */ 74 hw->len = attr->bp_len; 75 if (hw->len < 1 || hw->len > 64 || !is_power_of_2(hw->len)) 76 return -EINVAL; 77 78 /* Address */ 79 hw->address = attr->bp_addr; 80 if (hw->address & (hw->len - 1)) 81 return -EINVAL; 82 83 return 0; 84 } 85 86 int hw_breakpoint_exceptions_notify(struct notifier_block *unused, 87 unsigned long val, void *data) 88 { 89 return NOTIFY_DONE; 90 } 91 92 static void xtensa_wsr(unsigned long v, u8 sr) 93 { 94 /* We don't have indexed wsr and creating instruction dynamically 95 * doesn't seem worth it given how small XCHAL_NUM_IBREAK and 96 * XCHAL_NUM_DBREAK are. Thus the switch. In case build breaks here 97 * the switch below needs to be extended. 98 */ 99 BUILD_BUG_ON(XCHAL_NUM_IBREAK > 2); 100 BUILD_BUG_ON(XCHAL_NUM_DBREAK > 2); 101 102 switch (sr) { 103 #if XCHAL_NUM_IBREAK > 0 104 case SREG_IBREAKA + 0: 105 xtensa_set_sr(v, SREG_IBREAKA + 0); 106 break; 107 #endif 108 #if XCHAL_NUM_IBREAK > 1 109 case SREG_IBREAKA + 1: 110 xtensa_set_sr(v, SREG_IBREAKA + 1); 111 break; 112 #endif 113 114 #if XCHAL_NUM_DBREAK > 0 115 case SREG_DBREAKA + 0: 116 xtensa_set_sr(v, SREG_DBREAKA + 0); 117 break; 118 case SREG_DBREAKC + 0: 119 xtensa_set_sr(v, SREG_DBREAKC + 0); 120 break; 121 #endif 122 #if XCHAL_NUM_DBREAK > 1 123 case SREG_DBREAKA + 1: 124 xtensa_set_sr(v, SREG_DBREAKA + 1); 125 break; 126 127 case SREG_DBREAKC + 1: 128 xtensa_set_sr(v, SREG_DBREAKC + 1); 129 break; 130 #endif 131 } 132 } 133 134 static int alloc_slot(struct perf_event **slot, size_t n, 135 struct perf_event *bp) 136 { 137 size_t i; 138 139 for (i = 0; i < n; ++i) { 140 if (!slot[i]) { 141 slot[i] = bp; 142 return i; 143 } 144 } 145 return -EBUSY; 146 } 147 148 static void set_ibreak_regs(int reg, struct perf_event *bp) 149 { 150 struct arch_hw_breakpoint *info = counter_arch_bp(bp); 151 unsigned long ibreakenable; 152 153 xtensa_wsr(info->address, SREG_IBREAKA + reg); 154 ibreakenable = xtensa_get_sr(SREG_IBREAKENABLE); 155 xtensa_set_sr(ibreakenable | (1 << reg), SREG_IBREAKENABLE); 156 } 157 158 static void set_dbreak_regs(int reg, struct perf_event *bp) 159 { 160 struct arch_hw_breakpoint *info = counter_arch_bp(bp); 161 unsigned long dbreakc = DBREAKC_MASK_MASK & -info->len; 162 163 if (info->type & XTENSA_BREAKPOINT_LOAD) 164 dbreakc |= DBREAKC_LOAD_MASK; 165 if (info->type & XTENSA_BREAKPOINT_STORE) 166 dbreakc |= DBREAKC_STOR_MASK; 167 168 xtensa_wsr(info->address, SREG_DBREAKA + reg); 169 xtensa_wsr(dbreakc, SREG_DBREAKC + reg); 170 } 171 172 int arch_install_hw_breakpoint(struct perf_event *bp) 173 { 174 int i; 175 176 if (counter_arch_bp(bp)->type == XTENSA_BREAKPOINT_EXECUTE) { 177 /* Breakpoint */ 178 i = alloc_slot(this_cpu_ptr(bp_on_reg), XCHAL_NUM_IBREAK, bp); 179 if (i < 0) 180 return i; 181 set_ibreak_regs(i, bp); 182 183 } else { 184 /* Watchpoint */ 185 i = alloc_slot(this_cpu_ptr(wp_on_reg), XCHAL_NUM_DBREAK, bp); 186 if (i < 0) 187 return i; 188 set_dbreak_regs(i, bp); 189 } 190 return 0; 191 } 192 193 static int free_slot(struct perf_event **slot, size_t n, 194 struct perf_event *bp) 195 { 196 size_t i; 197 198 for (i = 0; i < n; ++i) { 199 if (slot[i] == bp) { 200 slot[i] = NULL; 201 return i; 202 } 203 } 204 return -EBUSY; 205 } 206 207 void arch_uninstall_hw_breakpoint(struct perf_event *bp) 208 { 209 struct arch_hw_breakpoint *info = counter_arch_bp(bp); 210 int i; 211 212 if (info->type == XTENSA_BREAKPOINT_EXECUTE) { 213 unsigned long ibreakenable; 214 215 /* Breakpoint */ 216 i = free_slot(this_cpu_ptr(bp_on_reg), XCHAL_NUM_IBREAK, bp); 217 if (i >= 0) { 218 ibreakenable = xtensa_get_sr(SREG_IBREAKENABLE); 219 xtensa_set_sr(ibreakenable & ~(1 << i), 220 SREG_IBREAKENABLE); 221 } 222 } else { 223 /* Watchpoint */ 224 i = free_slot(this_cpu_ptr(wp_on_reg), XCHAL_NUM_DBREAK, bp); 225 if (i >= 0) 226 xtensa_wsr(0, SREG_DBREAKC + i); 227 } 228 } 229 230 void hw_breakpoint_pmu_read(struct perf_event *bp) 231 { 232 } 233 234 void flush_ptrace_hw_breakpoint(struct task_struct *tsk) 235 { 236 int i; 237 struct thread_struct *t = &tsk->thread; 238 239 for (i = 0; i < XCHAL_NUM_IBREAK; ++i) { 240 if (t->ptrace_bp[i]) { 241 unregister_hw_breakpoint(t->ptrace_bp[i]); 242 t->ptrace_bp[i] = NULL; 243 } 244 } 245 for (i = 0; i < XCHAL_NUM_DBREAK; ++i) { 246 if (t->ptrace_wp[i]) { 247 unregister_hw_breakpoint(t->ptrace_wp[i]); 248 t->ptrace_wp[i] = NULL; 249 } 250 } 251 } 252 253 /* 254 * Set ptrace breakpoint pointers to zero for this task. 255 * This is required in order to prevent child processes from unregistering 256 * breakpoints held by their parent. 257 */ 258 void clear_ptrace_hw_breakpoint(struct task_struct *tsk) 259 { 260 memset(tsk->thread.ptrace_bp, 0, sizeof(tsk->thread.ptrace_bp)); 261 memset(tsk->thread.ptrace_wp, 0, sizeof(tsk->thread.ptrace_wp)); 262 } 263 264 void restore_dbreak(void) 265 { 266 int i; 267 268 for (i = 0; i < XCHAL_NUM_DBREAK; ++i) { 269 struct perf_event *bp = this_cpu_ptr(wp_on_reg)[i]; 270 271 if (bp) 272 set_dbreak_regs(i, bp); 273 } 274 clear_thread_flag(TIF_DB_DISABLED); 275 } 276 277 int check_hw_breakpoint(struct pt_regs *regs) 278 { 279 if (regs->debugcause & BIT(DEBUGCAUSE_IBREAK_BIT)) { 280 int i; 281 struct perf_event **bp = this_cpu_ptr(bp_on_reg); 282 283 for (i = 0; i < XCHAL_NUM_IBREAK; ++i) { 284 if (bp[i] && !bp[i]->attr.disabled && 285 regs->pc == bp[i]->attr.bp_addr) 286 perf_bp_event(bp[i], regs); 287 } 288 return 0; 289 } else if (regs->debugcause & BIT(DEBUGCAUSE_DBREAK_BIT)) { 290 struct perf_event **bp = this_cpu_ptr(wp_on_reg); 291 int dbnum = (regs->debugcause & DEBUGCAUSE_DBNUM_MASK) >> 292 DEBUGCAUSE_DBNUM_SHIFT; 293 294 if (dbnum < XCHAL_NUM_DBREAK && bp[dbnum]) { 295 if (user_mode(regs)) { 296 perf_bp_event(bp[dbnum], regs); 297 } else { 298 set_thread_flag(TIF_DB_DISABLED); 299 xtensa_wsr(0, SREG_DBREAKC + dbnum); 300 } 301 } else { 302 WARN_ONCE(1, 303 "Wrong/unconfigured DBNUM reported in DEBUGCAUSE: %d\n", 304 dbnum); 305 } 306 return 0; 307 } 308 return -ENOENT; 309 } 310