1 // SPDX-License-Identifier: GPL-2.0+ 2 3 #define pr_fmt(fmt) "kprobes: " fmt 4 5 #include <linux/kprobes.h> 6 #include <linux/extable.h> 7 #include <linux/slab.h> 8 #include <linux/stop_machine.h> 9 #include <asm/ptrace.h> 10 #include <linux/uaccess.h> 11 #include <asm/sections.h> 12 #include <asm/cacheflush.h> 13 #include <asm/bug.h> 14 #include <asm/patch.h> 15 16 #include "decode-insn.h" 17 18 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; 19 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); 20 21 static void __kprobes 22 post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *); 23 24 static void __kprobes arch_prepare_ss_slot(struct kprobe *p) 25 { 26 u32 insn = __BUG_INSN_32; 27 unsigned long offset = GET_INSN_LENGTH(p->opcode); 28 29 p->ainsn.api.restore = (unsigned long)p->addr + offset; 30 31 patch_text_nosync(p->ainsn.api.insn, &p->opcode, 1); 32 patch_text_nosync(p->ainsn.api.insn + offset, &insn, 1); 33 } 34 35 static void __kprobes arch_prepare_simulate(struct kprobe *p) 36 { 37 p->ainsn.api.restore = 0; 38 } 39 40 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) 41 { 42 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 43 44 if (p->ainsn.api.handler) 45 p->ainsn.api.handler((u32)p->opcode, 46 (unsigned long)p->addr, regs); 47 48 post_kprobe_handler(p, kcb, regs); 49 } 50 51 static bool __kprobes arch_check_kprobe(struct kprobe *p) 52 { 53 unsigned long tmp = (unsigned long)p->addr - p->offset; 54 unsigned long addr = (unsigned long)p->addr; 55 56 while (tmp <= addr) { 57 if (tmp == addr) 58 return true; 59 60 tmp += GET_INSN_LENGTH(*(u16 *)tmp); 61 } 62 63 return false; 64 } 65 66 int __kprobes arch_prepare_kprobe(struct kprobe *p) 67 { 68 u16 *insn = (u16 *)p->addr; 69 70 if ((unsigned long)insn & 0x1) 71 return -EILSEQ; 72 73 if (!arch_check_kprobe(p)) 74 return -EILSEQ; 75 76 /* copy instruction */ 77 p->opcode = (kprobe_opcode_t)(*insn++); 78 if (GET_INSN_LENGTH(p->opcode) == 4) 79 p->opcode |= (kprobe_opcode_t)(*insn) << 16; 80 81 /* decode instruction */ 82 switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) { 83 case INSN_REJECTED: /* insn not supported */ 84 return -EINVAL; 85 86 case INSN_GOOD_NO_SLOT: /* insn need simulation */ 87 p->ainsn.api.insn = NULL; 88 break; 89 90 case INSN_GOOD: /* instruction uses slot */ 91 p->ainsn.api.insn = get_insn_slot(); 92 if (!p->ainsn.api.insn) 93 return -ENOMEM; 94 break; 95 } 96 97 /* prepare the instruction */ 98 if (p->ainsn.api.insn) 99 arch_prepare_ss_slot(p); 100 else 101 arch_prepare_simulate(p); 102 103 return 0; 104 } 105 106 #ifdef CONFIG_MMU 107 void *alloc_insn_page(void) 108 { 109 return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, 110 GFP_KERNEL, PAGE_KERNEL_READ_EXEC, 111 VM_FLUSH_RESET_PERMS, NUMA_NO_NODE, 112 __builtin_return_address(0)); 113 } 114 #endif 115 116 /* install breakpoint in text */ 117 void __kprobes arch_arm_kprobe(struct kprobe *p) 118 { 119 u32 insn = (p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32 ? 120 __BUG_INSN_32 : __BUG_INSN_16; 121 122 patch_text(p->addr, &insn, 1); 123 } 124 125 /* remove breakpoint from text */ 126 void __kprobes arch_disarm_kprobe(struct kprobe *p) 127 { 128 patch_text(p->addr, &p->opcode, 1); 129 } 130 131 void __kprobes arch_remove_kprobe(struct kprobe *p) 132 { 133 } 134 135 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 136 { 137 kcb->prev_kprobe.kp = kprobe_running(); 138 kcb->prev_kprobe.status = kcb->kprobe_status; 139 } 140 141 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 142 { 143 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); 144 kcb->kprobe_status = kcb->prev_kprobe.status; 145 } 146 147 static void __kprobes set_current_kprobe(struct kprobe *p) 148 { 149 __this_cpu_write(current_kprobe, p); 150 } 151 152 /* 153 * Interrupts need to be disabled before single-step mode is set, and not 154 * reenabled until after single-step mode ends. 155 * Without disabling interrupt on local CPU, there is a chance of 156 * interrupt occurrence in the period of exception return and start of 157 * out-of-line single-step, that result in wrongly single stepping 158 * into the interrupt handler. 159 */ 160 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, 161 struct pt_regs *regs) 162 { 163 kcb->saved_status = regs->status; 164 regs->status &= ~SR_SPIE; 165 } 166 167 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, 168 struct pt_regs *regs) 169 { 170 regs->status = kcb->saved_status; 171 } 172 173 static void __kprobes setup_singlestep(struct kprobe *p, 174 struct pt_regs *regs, 175 struct kprobe_ctlblk *kcb, int reenter) 176 { 177 unsigned long slot; 178 179 if (reenter) { 180 save_previous_kprobe(kcb); 181 set_current_kprobe(p); 182 kcb->kprobe_status = KPROBE_REENTER; 183 } else { 184 kcb->kprobe_status = KPROBE_HIT_SS; 185 } 186 187 if (p->ainsn.api.insn) { 188 /* prepare for single stepping */ 189 slot = (unsigned long)p->ainsn.api.insn; 190 191 /* IRQs and single stepping do not mix well. */ 192 kprobes_save_local_irqflag(kcb, regs); 193 194 instruction_pointer_set(regs, slot); 195 } else { 196 /* insn simulation */ 197 arch_simulate_insn(p, regs); 198 } 199 } 200 201 static int __kprobes reenter_kprobe(struct kprobe *p, 202 struct pt_regs *regs, 203 struct kprobe_ctlblk *kcb) 204 { 205 switch (kcb->kprobe_status) { 206 case KPROBE_HIT_SSDONE: 207 case KPROBE_HIT_ACTIVE: 208 kprobes_inc_nmissed_count(p); 209 setup_singlestep(p, regs, kcb, 1); 210 break; 211 case KPROBE_HIT_SS: 212 case KPROBE_REENTER: 213 pr_warn("Failed to recover from reentered kprobes.\n"); 214 dump_kprobe(p); 215 BUG(); 216 break; 217 default: 218 WARN_ON(1); 219 return 0; 220 } 221 222 return 1; 223 } 224 225 static void __kprobes 226 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs) 227 { 228 /* return addr restore if non-branching insn */ 229 if (cur->ainsn.api.restore != 0) 230 regs->epc = cur->ainsn.api.restore; 231 232 /* restore back original saved kprobe variables and continue */ 233 if (kcb->kprobe_status == KPROBE_REENTER) { 234 restore_previous_kprobe(kcb); 235 return; 236 } 237 238 /* call post handler */ 239 kcb->kprobe_status = KPROBE_HIT_SSDONE; 240 if (cur->post_handler) { 241 /* post_handler can hit breakpoint and single step 242 * again, so we enable D-flag for recursive exception. 243 */ 244 cur->post_handler(cur, regs, 0); 245 } 246 247 reset_current_kprobe(); 248 } 249 250 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr) 251 { 252 struct kprobe *cur = kprobe_running(); 253 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 254 255 switch (kcb->kprobe_status) { 256 case KPROBE_HIT_SS: 257 case KPROBE_REENTER: 258 /* 259 * We are here because the instruction being single 260 * stepped caused a page fault. We reset the current 261 * kprobe and the ip points back to the probe address 262 * and allow the page fault handler to continue as a 263 * normal page fault. 264 */ 265 regs->epc = (unsigned long) cur->addr; 266 BUG_ON(!instruction_pointer(regs)); 267 268 if (kcb->kprobe_status == KPROBE_REENTER) 269 restore_previous_kprobe(kcb); 270 else { 271 kprobes_restore_local_irqflag(kcb, regs); 272 reset_current_kprobe(); 273 } 274 275 break; 276 case KPROBE_HIT_ACTIVE: 277 case KPROBE_HIT_SSDONE: 278 /* 279 * In case the user-specified fault handler returned 280 * zero, try to fix up. 281 */ 282 if (fixup_exception(regs)) 283 return 1; 284 } 285 return 0; 286 } 287 288 bool __kprobes 289 kprobe_breakpoint_handler(struct pt_regs *regs) 290 { 291 struct kprobe *p, *cur_kprobe; 292 struct kprobe_ctlblk *kcb; 293 unsigned long addr = instruction_pointer(regs); 294 295 kcb = get_kprobe_ctlblk(); 296 cur_kprobe = kprobe_running(); 297 298 p = get_kprobe((kprobe_opcode_t *) addr); 299 300 if (p) { 301 if (cur_kprobe) { 302 if (reenter_kprobe(p, regs, kcb)) 303 return true; 304 } else { 305 /* Probe hit */ 306 set_current_kprobe(p); 307 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 308 309 /* 310 * If we have no pre-handler or it returned 0, we 311 * continue with normal processing. If we have a 312 * pre-handler and it returned non-zero, it will 313 * modify the execution path and no need to single 314 * stepping. Let's just reset current kprobe and exit. 315 * 316 * pre_handler can hit a breakpoint and can step thru 317 * before return. 318 */ 319 if (!p->pre_handler || !p->pre_handler(p, regs)) 320 setup_singlestep(p, regs, kcb, 0); 321 else 322 reset_current_kprobe(); 323 } 324 return true; 325 } 326 327 /* 328 * The breakpoint instruction was removed right 329 * after we hit it. Another cpu has removed 330 * either a probepoint or a debugger breakpoint 331 * at this address. In either case, no further 332 * handling of this interrupt is appropriate. 333 * Return back to original instruction, and continue. 334 */ 335 return false; 336 } 337 338 bool __kprobes 339 kprobe_single_step_handler(struct pt_regs *regs) 340 { 341 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 342 unsigned long addr = instruction_pointer(regs); 343 struct kprobe *cur = kprobe_running(); 344 345 if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && 346 ((unsigned long)&cur->ainsn.api.insn[0] + GET_INSN_LENGTH(cur->opcode) == addr)) { 347 kprobes_restore_local_irqflag(kcb, regs); 348 post_kprobe_handler(cur, kcb, regs); 349 return true; 350 } 351 /* not ours, kprobes should ignore it */ 352 return false; 353 } 354 355 /* 356 * Provide a blacklist of symbols identifying ranges which cannot be kprobed. 357 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist). 358 */ 359 int __init arch_populate_kprobe_blacklist(void) 360 { 361 int ret; 362 363 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, 364 (unsigned long)__irqentry_text_end); 365 return ret; 366 } 367 368 int __kprobes arch_trampoline_kprobe(struct kprobe *p) 369 { 370 return 0; 371 } 372 373 int __init arch_init_kprobes(void) 374 { 375 return 0; 376 } 377