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