1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Code for Kernel probes Jump optimization. 4 * 5 * Copyright 2017, Anju T, IBM Corp. 6 */ 7 8 #include <linux/kprobes.h> 9 #include <linux/jump_label.h> 10 #include <linux/types.h> 11 #include <linux/slab.h> 12 #include <linux/list.h> 13 #include <asm/kprobes.h> 14 #include <asm/ptrace.h> 15 #include <asm/cacheflush.h> 16 #include <asm/code-patching.h> 17 #include <asm/sstep.h> 18 #include <asm/ppc-opcode.h> 19 #include <asm/inst.h> 20 21 #define TMPL_CALL_HDLR_IDX (optprobe_template_call_handler - optprobe_template_entry) 22 #define TMPL_EMULATE_IDX (optprobe_template_call_emulate - optprobe_template_entry) 23 #define TMPL_RET_IDX (optprobe_template_ret - optprobe_template_entry) 24 #define TMPL_OP_IDX (optprobe_template_op_address - optprobe_template_entry) 25 #define TMPL_INSN_IDX (optprobe_template_insn - optprobe_template_entry) 26 #define TMPL_END_IDX (optprobe_template_end - optprobe_template_entry) 27 28 static bool insn_page_in_use; 29 30 void *alloc_optinsn_page(void) 31 { 32 if (insn_page_in_use) 33 return NULL; 34 insn_page_in_use = true; 35 return &optinsn_slot; 36 } 37 38 void free_optinsn_page(void *page) 39 { 40 insn_page_in_use = false; 41 } 42 43 /* 44 * Check if we can optimize this probe. Returns NIP post-emulation if this can 45 * be optimized and 0 otherwise. 46 */ 47 static unsigned long can_optimize(struct kprobe *p) 48 { 49 struct pt_regs regs; 50 struct instruction_op op; 51 unsigned long nip = 0; 52 unsigned long addr = (unsigned long)p->addr; 53 54 /* 55 * kprobe placed for kretprobe during boot time 56 * has a 'nop' instruction, which can be emulated. 57 * So further checks can be skipped. 58 */ 59 if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline) 60 return addr + sizeof(kprobe_opcode_t); 61 62 /* 63 * We only support optimizing kernel addresses, but not 64 * module addresses. 65 * 66 * FIXME: Optimize kprobes placed in module addresses. 67 */ 68 if (!is_kernel_addr(addr)) 69 return 0; 70 71 memset(®s, 0, sizeof(struct pt_regs)); 72 regs.nip = addr; 73 regs.trap = 0x0; 74 regs.msr = MSR_KERNEL; 75 76 /* 77 * Kprobe placed in conditional branch instructions are 78 * not optimized, as we can't predict the nip prior with 79 * dummy pt_regs and can not ensure that the return branch 80 * from detour buffer falls in the range of address (i.e 32MB). 81 * A branch back from trampoline is set up in the detour buffer 82 * to the nip returned by the analyse_instr() here. 83 * 84 * Ensure that the instruction is not a conditional branch, 85 * and that can be emulated. 86 */ 87 if (!is_conditional_branch(ppc_inst_read(p->ainsn.insn)) && 88 analyse_instr(&op, ®s, ppc_inst_read(p->ainsn.insn)) == 1) { 89 emulate_update_regs(®s, &op); 90 nip = regs.nip; 91 } 92 93 return nip; 94 } 95 96 static void optimized_callback(struct optimized_kprobe *op, 97 struct pt_regs *regs) 98 { 99 /* This is possible if op is under delayed unoptimizing */ 100 if (kprobe_disabled(&op->kp)) 101 return; 102 103 preempt_disable(); 104 105 if (kprobe_running()) { 106 kprobes_inc_nmissed_count(&op->kp); 107 } else { 108 __this_cpu_write(current_kprobe, &op->kp); 109 regs_set_return_ip(regs, (unsigned long)op->kp.addr); 110 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; 111 opt_pre_handler(&op->kp, regs); 112 __this_cpu_write(current_kprobe, NULL); 113 } 114 115 preempt_enable(); 116 } 117 NOKPROBE_SYMBOL(optimized_callback); 118 119 void arch_remove_optimized_kprobe(struct optimized_kprobe *op) 120 { 121 if (op->optinsn.insn) { 122 free_optinsn_slot(op->optinsn.insn, 1); 123 op->optinsn.insn = NULL; 124 } 125 } 126 127 static void patch_imm32_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr) 128 { 129 patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HI(val)))); 130 patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val)))); 131 } 132 133 /* 134 * Generate instructions to load provided immediate 64-bit value 135 * to register 'reg' and patch these instructions at 'addr'. 136 */ 137 static void patch_imm64_load_insns(unsigned long long val, int reg, kprobe_opcode_t *addr) 138 { 139 patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HIGHEST(val)))); 140 patch_instruction(addr++, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_HIGHER(val)))); 141 patch_instruction(addr++, ppc_inst(PPC_RAW_SLDI(reg, reg, 32))); 142 patch_instruction(addr++, ppc_inst(PPC_RAW_ORIS(reg, reg, PPC_HI(val)))); 143 patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val)))); 144 } 145 146 static void patch_imm_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr) 147 { 148 if (IS_ENABLED(CONFIG_PPC64)) 149 patch_imm64_load_insns(val, reg, addr); 150 else 151 patch_imm32_load_insns(val, reg, addr); 152 } 153 154 int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p) 155 { 156 ppc_inst_t branch_op_callback, branch_emulate_step, temp; 157 unsigned long op_callback_addr, emulate_step_addr; 158 kprobe_opcode_t *buff; 159 long b_offset; 160 unsigned long nip, size; 161 int rc, i; 162 163 nip = can_optimize(p); 164 if (!nip) 165 return -EILSEQ; 166 167 /* Allocate instruction slot for detour buffer */ 168 buff = get_optinsn_slot(); 169 if (!buff) 170 return -ENOMEM; 171 172 /* 173 * OPTPROBE uses 'b' instruction to branch to optinsn.insn. 174 * 175 * The target address has to be relatively nearby, to permit use 176 * of branch instruction in powerpc, because the address is specified 177 * in an immediate field in the instruction opcode itself, ie 24 bits 178 * in the opcode specify the address. Therefore the address should 179 * be within 32MB on either side of the current instruction. 180 */ 181 b_offset = (unsigned long)buff - (unsigned long)p->addr; 182 if (!is_offset_in_branch_range(b_offset)) 183 goto error; 184 185 /* Check if the return address is also within 32MB range */ 186 b_offset = (unsigned long)(buff + TMPL_RET_IDX) - nip; 187 if (!is_offset_in_branch_range(b_offset)) 188 goto error; 189 190 /* Setup template */ 191 /* We can optimize this via patch_instruction_window later */ 192 size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int); 193 pr_devel("Copying template to %p, size %lu\n", buff, size); 194 for (i = 0; i < size; i++) { 195 rc = patch_instruction(buff + i, ppc_inst(*(optprobe_template_entry + i))); 196 if (rc < 0) 197 goto error; 198 } 199 200 /* 201 * Fixup the template with instructions to: 202 * 1. load the address of the actual probepoint 203 */ 204 patch_imm_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX); 205 206 /* 207 * 2. branch to optimized_callback() and emulate_step() 208 */ 209 op_callback_addr = ppc_kallsyms_lookup_name("optimized_callback"); 210 emulate_step_addr = ppc_kallsyms_lookup_name("emulate_step"); 211 if (!op_callback_addr || !emulate_step_addr) { 212 WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n"); 213 goto error; 214 } 215 216 rc = create_branch(&branch_op_callback, buff + TMPL_CALL_HDLR_IDX, 217 op_callback_addr, BRANCH_SET_LINK); 218 219 rc |= create_branch(&branch_emulate_step, buff + TMPL_EMULATE_IDX, 220 emulate_step_addr, BRANCH_SET_LINK); 221 222 if (rc) 223 goto error; 224 225 patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback); 226 patch_instruction(buff + TMPL_EMULATE_IDX, branch_emulate_step); 227 228 /* 229 * 3. load instruction to be emulated into relevant register, and 230 */ 231 temp = ppc_inst_read(p->ainsn.insn); 232 patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX); 233 234 /* 235 * 4. branch back from trampoline 236 */ 237 patch_branch(buff + TMPL_RET_IDX, nip, 0); 238 239 flush_icache_range((unsigned long)buff, (unsigned long)(&buff[TMPL_END_IDX])); 240 241 op->optinsn.insn = buff; 242 243 return 0; 244 245 error: 246 free_optinsn_slot(buff, 0); 247 return -ERANGE; 248 249 } 250 251 int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) 252 { 253 return optinsn->insn != NULL; 254 } 255 256 /* 257 * On powerpc, Optprobes always replaces one instruction (4 bytes 258 * aligned and 4 bytes long). It is impossible to encounter another 259 * kprobe in this address range. So always return 0. 260 */ 261 int arch_check_optimized_kprobe(struct optimized_kprobe *op) 262 { 263 return 0; 264 } 265 266 void arch_optimize_kprobes(struct list_head *oplist) 267 { 268 ppc_inst_t instr; 269 struct optimized_kprobe *op; 270 struct optimized_kprobe *tmp; 271 272 list_for_each_entry_safe(op, tmp, oplist, list) { 273 /* 274 * Backup instructions which will be replaced 275 * by jump address 276 */ 277 memcpy(op->optinsn.copied_insn, op->kp.addr, RELATIVEJUMP_SIZE); 278 create_branch(&instr, op->kp.addr, (unsigned long)op->optinsn.insn, 0); 279 patch_instruction(op->kp.addr, instr); 280 list_del_init(&op->list); 281 } 282 } 283 284 void arch_unoptimize_kprobe(struct optimized_kprobe *op) 285 { 286 arch_arm_kprobe(&op->kp); 287 } 288 289 void arch_unoptimize_kprobes(struct list_head *oplist, struct list_head *done_list) 290 { 291 struct optimized_kprobe *op; 292 struct optimized_kprobe *tmp; 293 294 list_for_each_entry_safe(op, tmp, oplist, list) { 295 arch_unoptimize_kprobe(op); 296 list_move(&op->list, done_list); 297 } 298 } 299 300 int arch_within_optimized_kprobe(struct optimized_kprobe *op, kprobe_opcode_t *addr) 301 { 302 return (op->kp.addr <= addr && 303 op->kp.addr + (RELATIVEJUMP_SIZE / sizeof(kprobe_opcode_t)) > addr); 304 } 305