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