1 // SPDX-License-Identifier: GPL-2.0+ 2 3 #include <linux/kprobes.h> 4 #include <linux/extable.h> 5 #include <linux/slab.h> 6 #include <linux/stop_machine.h> 7 #include <asm/ptrace.h> 8 #include <linux/uaccess.h> 9 #include <asm/sections.h> 10 #include <asm/cacheflush.h> 11 12 #include "decode-insn.h" 13 14 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; 15 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); 16 17 static void __kprobes 18 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *); 19 20 struct csky_insn_patch { 21 kprobe_opcode_t *addr; 22 u32 opcode; 23 atomic_t cpu_count; 24 }; 25 26 static int __kprobes patch_text_cb(void *priv) 27 { 28 struct csky_insn_patch *param = priv; 29 unsigned int addr = (unsigned int)param->addr; 30 31 if (atomic_inc_return(¶m->cpu_count) == 1) { 32 *(u16 *) addr = cpu_to_le16(param->opcode); 33 dcache_wb_range(addr, addr + 2); 34 atomic_inc(¶m->cpu_count); 35 } else { 36 while (atomic_read(¶m->cpu_count) <= num_online_cpus()) 37 cpu_relax(); 38 } 39 40 icache_inv_range(addr, addr + 2); 41 42 return 0; 43 } 44 45 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode) 46 { 47 struct csky_insn_patch param = { addr, opcode, ATOMIC_INIT(0) }; 48 49 return stop_machine_cpuslocked(patch_text_cb, ¶m, cpu_online_mask); 50 } 51 52 static void __kprobes arch_prepare_ss_slot(struct kprobe *p) 53 { 54 unsigned long offset = is_insn32(p->opcode) ? 4 : 2; 55 56 p->ainsn.api.restore = (unsigned long)p->addr + offset; 57 58 patch_text(p->ainsn.api.insn, p->opcode); 59 } 60 61 static void __kprobes arch_prepare_simulate(struct kprobe *p) 62 { 63 p->ainsn.api.restore = 0; 64 } 65 66 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) 67 { 68 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 69 70 if (p->ainsn.api.handler) 71 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs); 72 73 post_kprobe_handler(kcb, regs); 74 } 75 76 int __kprobes arch_prepare_kprobe(struct kprobe *p) 77 { 78 unsigned long probe_addr = (unsigned long)p->addr; 79 80 if (probe_addr & 0x1) { 81 pr_warn("Address not aligned.\n"); 82 return -EINVAL; 83 } 84 85 /* copy instruction */ 86 p->opcode = le32_to_cpu(*p->addr); 87 88 /* decode instruction */ 89 switch (csky_probe_decode_insn(p->addr, &p->ainsn.api)) { 90 case INSN_REJECTED: /* insn not supported */ 91 return -EINVAL; 92 93 case INSN_GOOD_NO_SLOT: /* insn need simulation */ 94 p->ainsn.api.insn = NULL; 95 break; 96 97 case INSN_GOOD: /* instruction uses slot */ 98 p->ainsn.api.insn = get_insn_slot(); 99 if (!p->ainsn.api.insn) 100 return -ENOMEM; 101 break; 102 } 103 104 /* prepare the instruction */ 105 if (p->ainsn.api.insn) 106 arch_prepare_ss_slot(p); 107 else 108 arch_prepare_simulate(p); 109 110 return 0; 111 } 112 113 /* install breakpoint in text */ 114 void __kprobes arch_arm_kprobe(struct kprobe *p) 115 { 116 patch_text(p->addr, USR_BKPT); 117 } 118 119 /* remove breakpoint from text */ 120 void __kprobes arch_disarm_kprobe(struct kprobe *p) 121 { 122 patch_text(p->addr, p->opcode); 123 } 124 125 void __kprobes arch_remove_kprobe(struct kprobe *p) 126 { 127 } 128 129 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 130 { 131 kcb->prev_kprobe.kp = kprobe_running(); 132 kcb->prev_kprobe.status = kcb->kprobe_status; 133 } 134 135 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 136 { 137 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); 138 kcb->kprobe_status = kcb->prev_kprobe.status; 139 } 140 141 static void __kprobes set_current_kprobe(struct kprobe *p) 142 { 143 __this_cpu_write(current_kprobe, p); 144 } 145 146 /* 147 * Interrupts need to be disabled before single-step mode is set, and not 148 * reenabled until after single-step mode ends. 149 * Without disabling interrupt on local CPU, there is a chance of 150 * interrupt occurrence in the period of exception return and start of 151 * out-of-line single-step, that result in wrongly single stepping 152 * into the interrupt handler. 153 */ 154 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, 155 struct pt_regs *regs) 156 { 157 kcb->saved_sr = regs->sr; 158 regs->sr &= ~BIT(6); 159 } 160 161 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, 162 struct pt_regs *regs) 163 { 164 regs->sr = kcb->saved_sr; 165 } 166 167 static void __kprobes 168 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr, struct kprobe *p) 169 { 170 unsigned long offset = is_insn32(p->opcode) ? 4 : 2; 171 172 kcb->ss_ctx.ss_pending = true; 173 kcb->ss_ctx.match_addr = addr + offset; 174 } 175 176 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb) 177 { 178 kcb->ss_ctx.ss_pending = false; 179 kcb->ss_ctx.match_addr = 0; 180 } 181 182 #define TRACE_MODE_SI BIT(14) 183 #define TRACE_MODE_MASK ~(0x3 << 14) 184 #define TRACE_MODE_RUN 0 185 186 static void __kprobes setup_singlestep(struct kprobe *p, 187 struct pt_regs *regs, 188 struct kprobe_ctlblk *kcb, int reenter) 189 { 190 unsigned long slot; 191 192 if (reenter) { 193 save_previous_kprobe(kcb); 194 set_current_kprobe(p); 195 kcb->kprobe_status = KPROBE_REENTER; 196 } else { 197 kcb->kprobe_status = KPROBE_HIT_SS; 198 } 199 200 if (p->ainsn.api.insn) { 201 /* prepare for single stepping */ 202 slot = (unsigned long)p->ainsn.api.insn; 203 204 set_ss_context(kcb, slot, p); /* mark pending ss */ 205 206 /* IRQs and single stepping do not mix well. */ 207 kprobes_save_local_irqflag(kcb, regs); 208 regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_SI; 209 instruction_pointer_set(regs, slot); 210 } else { 211 /* insn simulation */ 212 arch_simulate_insn(p, regs); 213 } 214 } 215 216 static int __kprobes reenter_kprobe(struct kprobe *p, 217 struct pt_regs *regs, 218 struct kprobe_ctlblk *kcb) 219 { 220 switch (kcb->kprobe_status) { 221 case KPROBE_HIT_SSDONE: 222 case KPROBE_HIT_ACTIVE: 223 kprobes_inc_nmissed_count(p); 224 setup_singlestep(p, regs, kcb, 1); 225 break; 226 case KPROBE_HIT_SS: 227 case KPROBE_REENTER: 228 pr_warn("Unrecoverable kprobe detected.\n"); 229 dump_kprobe(p); 230 BUG(); 231 break; 232 default: 233 WARN_ON(1); 234 return 0; 235 } 236 237 return 1; 238 } 239 240 static void __kprobes 241 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs) 242 { 243 struct kprobe *cur = kprobe_running(); 244 245 if (!cur) 246 return; 247 248 /* return addr restore if non-branching insn */ 249 if (cur->ainsn.api.restore != 0) 250 regs->pc = cur->ainsn.api.restore; 251 252 /* restore back original saved kprobe variables and continue */ 253 if (kcb->kprobe_status == KPROBE_REENTER) { 254 restore_previous_kprobe(kcb); 255 return; 256 } 257 258 /* call post handler */ 259 kcb->kprobe_status = KPROBE_HIT_SSDONE; 260 if (cur->post_handler) { 261 /* post_handler can hit breakpoint and single step 262 * again, so we enable D-flag for recursive exception. 263 */ 264 cur->post_handler(cur, regs, 0); 265 } 266 267 reset_current_kprobe(); 268 } 269 270 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr) 271 { 272 struct kprobe *cur = kprobe_running(); 273 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 274 275 switch (kcb->kprobe_status) { 276 case KPROBE_HIT_SS: 277 case KPROBE_REENTER: 278 /* 279 * We are here because the instruction being single 280 * stepped caused a page fault. We reset the current 281 * kprobe and the ip points back to the probe address 282 * and allow the page fault handler to continue as a 283 * normal page fault. 284 */ 285 regs->pc = (unsigned long) cur->addr; 286 if (!instruction_pointer(regs)) 287 BUG(); 288 289 if (kcb->kprobe_status == KPROBE_REENTER) 290 restore_previous_kprobe(kcb); 291 else 292 reset_current_kprobe(); 293 294 break; 295 case KPROBE_HIT_ACTIVE: 296 case KPROBE_HIT_SSDONE: 297 /* 298 * We increment the nmissed count for accounting, 299 * we can also use npre/npostfault count for accounting 300 * these specific fault cases. 301 */ 302 kprobes_inc_nmissed_count(cur); 303 304 /* 305 * We come here because instructions in the pre/post 306 * handler caused the page_fault, this could happen 307 * if handler tries to access user space by 308 * copy_from_user(), get_user() etc. Let the 309 * user-specified handler try to fix it first. 310 */ 311 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) 312 return 1; 313 314 /* 315 * In case the user-specified fault handler returned 316 * zero, try to fix up. 317 */ 318 if (fixup_exception(regs)) 319 return 1; 320 } 321 return 0; 322 } 323 324 int __kprobes 325 kprobe_breakpoint_handler(struct pt_regs *regs) 326 { 327 struct kprobe *p, *cur_kprobe; 328 struct kprobe_ctlblk *kcb; 329 unsigned long addr = instruction_pointer(regs); 330 331 kcb = get_kprobe_ctlblk(); 332 cur_kprobe = kprobe_running(); 333 334 p = get_kprobe((kprobe_opcode_t *) addr); 335 336 if (p) { 337 if (cur_kprobe) { 338 if (reenter_kprobe(p, regs, kcb)) 339 return 1; 340 } else { 341 /* Probe hit */ 342 set_current_kprobe(p); 343 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 344 345 /* 346 * If we have no pre-handler or it returned 0, we 347 * continue with normal processing. If we have a 348 * pre-handler and it returned non-zero, it will 349 * modify the execution path and no need to single 350 * stepping. Let's just reset current kprobe and exit. 351 * 352 * pre_handler can hit a breakpoint and can step thru 353 * before return. 354 */ 355 if (!p->pre_handler || !p->pre_handler(p, regs)) 356 setup_singlestep(p, regs, kcb, 0); 357 else 358 reset_current_kprobe(); 359 } 360 return 1; 361 } 362 363 /* 364 * The breakpoint instruction was removed right 365 * after we hit it. Another cpu has removed 366 * either a probepoint or a debugger breakpoint 367 * at this address. In either case, no further 368 * handling of this interrupt is appropriate. 369 * Return back to original instruction, and continue. 370 */ 371 return 0; 372 } 373 374 int __kprobes 375 kprobe_single_step_handler(struct pt_regs *regs) 376 { 377 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 378 379 if ((kcb->ss_ctx.ss_pending) 380 && (kcb->ss_ctx.match_addr == instruction_pointer(regs))) { 381 clear_ss_context(kcb); /* clear pending ss */ 382 383 kprobes_restore_local_irqflag(kcb, regs); 384 regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_RUN; 385 386 post_kprobe_handler(kcb, regs); 387 return 1; 388 } 389 return 0; 390 } 391 392 /* 393 * Provide a blacklist of symbols identifying ranges which cannot be kprobed. 394 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist). 395 */ 396 int __init arch_populate_kprobe_blacklist(void) 397 { 398 int ret; 399 400 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, 401 (unsigned long)__irqentry_text_end); 402 return ret; 403 } 404 405 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) 406 { 407 return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL); 408 } 409 410 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 411 struct pt_regs *regs) 412 { 413 ri->ret_addr = (kprobe_opcode_t *)regs->lr; 414 ri->fp = NULL; 415 regs->lr = (unsigned long) &kretprobe_trampoline; 416 } 417 418 int __kprobes arch_trampoline_kprobe(struct kprobe *p) 419 { 420 return 0; 421 } 422 423 int __init arch_init_kprobes(void) 424 { 425 return 0; 426 } 427