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(p->ainsn.api.insn, &p->opcode, 1); 32 patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset), 33 &insn, 1); 34 } 35 36 static void __kprobes arch_prepare_simulate(struct kprobe *p) 37 { 38 p->ainsn.api.restore = 0; 39 } 40 41 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) 42 { 43 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 44 45 if (p->ainsn.api.handler) 46 p->ainsn.api.handler((u32)p->opcode, 47 (unsigned long)p->addr, regs); 48 49 post_kprobe_handler(p, kcb, regs); 50 } 51 52 static bool __kprobes arch_check_kprobe(struct kprobe *p) 53 { 54 unsigned long tmp = (unsigned long)p->addr - p->offset; 55 unsigned long addr = (unsigned long)p->addr; 56 57 while (tmp <= addr) { 58 if (tmp == addr) 59 return true; 60 61 tmp += GET_INSN_LENGTH(*(u16 *)tmp); 62 } 63 64 return false; 65 } 66 67 int __kprobes arch_prepare_kprobe(struct kprobe *p) 68 { 69 u16 *insn = (u16 *)p->addr; 70 71 if ((unsigned long)insn & 0x1) 72 return -EILSEQ; 73 74 if (!arch_check_kprobe(p)) 75 return -EILSEQ; 76 77 /* copy instruction */ 78 p->opcode = (kprobe_opcode_t)(*insn++); 79 if (GET_INSN_LENGTH(p->opcode) == 4) 80 p->opcode |= (kprobe_opcode_t)(*insn) << 16; 81 82 /* decode instruction */ 83 switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) { 84 case INSN_REJECTED: /* insn not supported */ 85 return -EINVAL; 86 87 case INSN_GOOD_NO_SLOT: /* insn need simulation */ 88 p->ainsn.api.insn = NULL; 89 break; 90 91 case INSN_GOOD: /* instruction uses slot */ 92 p->ainsn.api.insn = get_insn_slot(); 93 if (!p->ainsn.api.insn) 94 return -ENOMEM; 95 break; 96 } 97 98 /* prepare the instruction */ 99 if (p->ainsn.api.insn) 100 arch_prepare_ss_slot(p); 101 else 102 arch_prepare_simulate(p); 103 104 return 0; 105 } 106 107 #ifdef CONFIG_MMU 108 void *alloc_insn_page(void) 109 { 110 return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, 111 GFP_KERNEL, PAGE_KERNEL_READ_EXEC, 112 VM_FLUSH_RESET_PERMS, NUMA_NO_NODE, 113 __builtin_return_address(0)); 114 } 115 #endif 116 117 /* install breakpoint in text */ 118 void __kprobes arch_arm_kprobe(struct kprobe *p) 119 { 120 u32 insn = (p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32 ? 121 __BUG_INSN_32 : __BUG_INSN_16; 122 123 patch_text(p->addr, &insn, 1); 124 } 125 126 /* remove breakpoint from text */ 127 void __kprobes arch_disarm_kprobe(struct kprobe *p) 128 { 129 patch_text(p->addr, &p->opcode, 1); 130 } 131 132 void __kprobes arch_remove_kprobe(struct kprobe *p) 133 { 134 } 135 136 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 137 { 138 kcb->prev_kprobe.kp = kprobe_running(); 139 kcb->prev_kprobe.status = kcb->kprobe_status; 140 } 141 142 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 143 { 144 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); 145 kcb->kprobe_status = kcb->prev_kprobe.status; 146 } 147 148 static void __kprobes set_current_kprobe(struct kprobe *p) 149 { 150 __this_cpu_write(current_kprobe, p); 151 } 152 153 /* 154 * Interrupts need to be disabled before single-step mode is set, and not 155 * reenabled until after single-step mode ends. 156 * Without disabling interrupt on local CPU, there is a chance of 157 * interrupt occurrence in the period of exception return and start of 158 * out-of-line single-step, that result in wrongly single stepping 159 * into the interrupt handler. 160 */ 161 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, 162 struct pt_regs *regs) 163 { 164 kcb->saved_status = regs->status; 165 regs->status &= ~SR_SPIE; 166 } 167 168 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, 169 struct pt_regs *regs) 170 { 171 regs->status = kcb->saved_status; 172 } 173 174 static void __kprobes setup_singlestep(struct kprobe *p, 175 struct pt_regs *regs, 176 struct kprobe_ctlblk *kcb, int reenter) 177 { 178 unsigned long slot; 179 180 if (reenter) { 181 save_previous_kprobe(kcb); 182 set_current_kprobe(p); 183 kcb->kprobe_status = KPROBE_REENTER; 184 } else { 185 kcb->kprobe_status = KPROBE_HIT_SS; 186 } 187 188 if (p->ainsn.api.insn) { 189 /* prepare for single stepping */ 190 slot = (unsigned long)p->ainsn.api.insn; 191 192 /* IRQs and single stepping do not mix well. */ 193 kprobes_save_local_irqflag(kcb, regs); 194 195 instruction_pointer_set(regs, slot); 196 } else { 197 /* insn simulation */ 198 arch_simulate_insn(p, regs); 199 } 200 } 201 202 static int __kprobes reenter_kprobe(struct kprobe *p, 203 struct pt_regs *regs, 204 struct kprobe_ctlblk *kcb) 205 { 206 switch (kcb->kprobe_status) { 207 case KPROBE_HIT_SSDONE: 208 case KPROBE_HIT_ACTIVE: 209 kprobes_inc_nmissed_count(p); 210 setup_singlestep(p, regs, kcb, 1); 211 break; 212 case KPROBE_HIT_SS: 213 case KPROBE_REENTER: 214 pr_warn("Failed to recover from reentered kprobes.\n"); 215 dump_kprobe(p); 216 BUG(); 217 break; 218 default: 219 WARN_ON(1); 220 return 0; 221 } 222 223 return 1; 224 } 225 226 static void __kprobes 227 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs) 228 { 229 /* return addr restore if non-branching insn */ 230 if (cur->ainsn.api.restore != 0) 231 regs->epc = cur->ainsn.api.restore; 232 233 /* restore back original saved kprobe variables and continue */ 234 if (kcb->kprobe_status == KPROBE_REENTER) { 235 restore_previous_kprobe(kcb); 236 return; 237 } 238 239 /* call post handler */ 240 kcb->kprobe_status = KPROBE_HIT_SSDONE; 241 if (cur->post_handler) { 242 /* post_handler can hit breakpoint and single step 243 * again, so we enable D-flag for recursive exception. 244 */ 245 cur->post_handler(cur, regs, 0); 246 } 247 248 reset_current_kprobe(); 249 } 250 251 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr) 252 { 253 struct kprobe *cur = kprobe_running(); 254 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 255 256 switch (kcb->kprobe_status) { 257 case KPROBE_HIT_SS: 258 case KPROBE_REENTER: 259 /* 260 * We are here because the instruction being single 261 * stepped caused a page fault. We reset the current 262 * kprobe and the ip points back to the probe address 263 * and allow the page fault handler to continue as a 264 * normal page fault. 265 */ 266 regs->epc = (unsigned long) cur->addr; 267 BUG_ON(!instruction_pointer(regs)); 268 269 if (kcb->kprobe_status == KPROBE_REENTER) 270 restore_previous_kprobe(kcb); 271 else { 272 kprobes_restore_local_irqflag(kcb, regs); 273 reset_current_kprobe(); 274 } 275 276 break; 277 case KPROBE_HIT_ACTIVE: 278 case KPROBE_HIT_SSDONE: 279 /* 280 * In case the user-specified fault handler returned 281 * zero, try to fix up. 282 */ 283 if (fixup_exception(regs)) 284 return 1; 285 } 286 return 0; 287 } 288 289 bool __kprobes 290 kprobe_breakpoint_handler(struct pt_regs *regs) 291 { 292 struct kprobe *p, *cur_kprobe; 293 struct kprobe_ctlblk *kcb; 294 unsigned long addr = instruction_pointer(regs); 295 296 kcb = get_kprobe_ctlblk(); 297 cur_kprobe = kprobe_running(); 298 299 p = get_kprobe((kprobe_opcode_t *) addr); 300 301 if (p) { 302 if (cur_kprobe) { 303 if (reenter_kprobe(p, regs, kcb)) 304 return true; 305 } else { 306 /* Probe hit */ 307 set_current_kprobe(p); 308 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 309 310 /* 311 * If we have no pre-handler or it returned 0, we 312 * continue with normal processing. If we have a 313 * pre-handler and it returned non-zero, it will 314 * modify the execution path and no need to single 315 * stepping. Let's just reset current kprobe and exit. 316 * 317 * pre_handler can hit a breakpoint and can step thru 318 * before return. 319 */ 320 if (!p->pre_handler || !p->pre_handler(p, regs)) 321 setup_singlestep(p, regs, kcb, 0); 322 else 323 reset_current_kprobe(); 324 } 325 return true; 326 } 327 328 /* 329 * The breakpoint instruction was removed right 330 * after we hit it. Another cpu has removed 331 * either a probepoint or a debugger breakpoint 332 * at this address. In either case, no further 333 * handling of this interrupt is appropriate. 334 * Return back to original instruction, and continue. 335 */ 336 return false; 337 } 338 339 bool __kprobes 340 kprobe_single_step_handler(struct pt_regs *regs) 341 { 342 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 343 unsigned long addr = instruction_pointer(regs); 344 struct kprobe *cur = kprobe_running(); 345 346 if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && 347 ((unsigned long)&cur->ainsn.api.insn[0] + GET_INSN_LENGTH(cur->opcode) == addr)) { 348 kprobes_restore_local_irqflag(kcb, regs); 349 post_kprobe_handler(cur, kcb, regs); 350 return true; 351 } 352 /* not ours, kprobes should ignore it */ 353 return false; 354 } 355 356 /* 357 * Provide a blacklist of symbols identifying ranges which cannot be kprobed. 358 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist). 359 */ 360 int __init arch_populate_kprobe_blacklist(void) 361 { 362 int ret; 363 364 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, 365 (unsigned long)__irqentry_text_end); 366 return ret; 367 } 368 369 int __kprobes arch_trampoline_kprobe(struct kprobe *p) 370 { 371 return 0; 372 } 373 374 int __init arch_init_kprobes(void) 375 { 376 return 0; 377 } 378