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