| /* |
| * Code for Kernel probes Jump optimization. |
| * |
| * Copyright 2017, Anju T, IBM Corp. |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version |
| * 2 of the License, or (at your option) any later version. |
| */ |
| |
| #include <linux/kprobes.h> |
| #include <linux/jump_label.h> |
| #include <linux/types.h> |
| #include <linux/slab.h> |
| #include <linux/list.h> |
| #include <asm/kprobes.h> |
| #include <asm/ptrace.h> |
| #include <asm/cacheflush.h> |
| #include <asm/code-patching.h> |
| #include <asm/sstep.h> |
| #include <asm/ppc-opcode.h> |
| |
| #define TMPL_CALL_HDLR_IDX \ |
| (optprobe_template_call_handler - optprobe_template_entry) |
| #define TMPL_EMULATE_IDX \ |
| (optprobe_template_call_emulate - optprobe_template_entry) |
| #define TMPL_RET_IDX \ |
| (optprobe_template_ret - optprobe_template_entry) |
| #define TMPL_OP_IDX \ |
| (optprobe_template_op_address - optprobe_template_entry) |
| #define TMPL_INSN_IDX \ |
| (optprobe_template_insn - optprobe_template_entry) |
| #define TMPL_END_IDX \ |
| (optprobe_template_end - optprobe_template_entry) |
| |
| DEFINE_INSN_CACHE_OPS(ppc_optinsn); |
| |
| static bool insn_page_in_use; |
| |
| static void *__ppc_alloc_insn_page(void) |
| { |
| if (insn_page_in_use) |
| return NULL; |
| insn_page_in_use = true; |
| return &optinsn_slot; |
| } |
| |
| static void __ppc_free_insn_page(void *page __maybe_unused) |
| { |
| insn_page_in_use = false; |
| } |
| |
| struct kprobe_insn_cache kprobe_ppc_optinsn_slots = { |
| .mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex), |
| .pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages), |
| /* insn_size initialized later */ |
| .alloc = __ppc_alloc_insn_page, |
| .free = __ppc_free_insn_page, |
| .nr_garbage = 0, |
| }; |
| |
| /* |
| * Check if we can optimize this probe. Returns NIP post-emulation if this can |
| * be optimized and 0 otherwise. |
| */ |
| static unsigned long can_optimize(struct kprobe *p) |
| { |
| struct pt_regs regs; |
| struct instruction_op op; |
| unsigned long nip = 0; |
| |
| /* |
| * kprobe placed for kretprobe during boot time |
| * has a 'nop' instruction, which can be emulated. |
| * So further checks can be skipped. |
| */ |
| if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) |
| return (unsigned long)p->addr + sizeof(kprobe_opcode_t); |
| |
| /* |
| * We only support optimizing kernel addresses, but not |
| * module addresses. |
| * |
| * FIXME: Optimize kprobes placed in module addresses. |
| */ |
| if (!is_kernel_addr((unsigned long)p->addr)) |
| return 0; |
| |
| memset(®s, 0, sizeof(struct pt_regs)); |
| regs.nip = (unsigned long)p->addr; |
| regs.trap = 0x0; |
| regs.msr = MSR_KERNEL; |
| |
| /* |
| * Kprobe placed in conditional branch instructions are |
| * not optimized, as we can't predict the nip prior with |
| * dummy pt_regs and can not ensure that the return branch |
| * from detour buffer falls in the range of address (i.e 32MB). |
| * A branch back from trampoline is set up in the detour buffer |
| * to the nip returned by the analyse_instr() here. |
| * |
| * Ensure that the instruction is not a conditional branch, |
| * and that can be emulated. |
| */ |
| if (!is_conditional_branch(*p->ainsn.insn) && |
| analyse_instr(&op, ®s, *p->ainsn.insn)) |
| nip = regs.nip; |
| |
| return nip; |
| } |
| |
| static void optimized_callback(struct optimized_kprobe *op, |
| struct pt_regs *regs) |
| { |
| struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
| unsigned long flags; |
| |
| /* This is possible if op is under delayed unoptimizing */ |
| if (kprobe_disabled(&op->kp)) |
| return; |
| |
| local_irq_save(flags); |
| hard_irq_disable(); |
| |
| if (kprobe_running()) { |
| kprobes_inc_nmissed_count(&op->kp); |
| } else { |
| __this_cpu_write(current_kprobe, &op->kp); |
| regs->nip = (unsigned long)op->kp.addr; |
| kcb->kprobe_status = KPROBE_HIT_ACTIVE; |
| opt_pre_handler(&op->kp, regs); |
| __this_cpu_write(current_kprobe, NULL); |
| } |
| |
| /* |
| * No need for an explicit __hard_irq_enable() here. |
| * local_irq_restore() will re-enable interrupts, |
| * if they were hard disabled. |
| */ |
| local_irq_restore(flags); |
| } |
| NOKPROBE_SYMBOL(optimized_callback); |
| |
| void arch_remove_optimized_kprobe(struct optimized_kprobe *op) |
| { |
| if (op->optinsn.insn) { |
| free_ppc_optinsn_slot(op->optinsn.insn, 1); |
| op->optinsn.insn = NULL; |
| } |
| } |
| |
| /* |
| * emulate_step() requires insn to be emulated as |
| * second parameter. Load register 'r4' with the |
| * instruction. |
| */ |
| void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr) |
| { |
| /* addis r4,0,(insn)@h */ |
| *addr++ = PPC_INST_ADDIS | ___PPC_RT(4) | |
| ((val >> 16) & 0xffff); |
| |
| /* ori r4,r4,(insn)@l */ |
| *addr = PPC_INST_ORI | ___PPC_RA(4) | ___PPC_RS(4) | |
| (val & 0xffff); |
| } |
| |
| /* |
| * Generate instructions to load provided immediate 64-bit value |
| * to register 'r3' and patch these instructions at 'addr'. |
| */ |
| void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr) |
| { |
| /* lis r3,(op)@highest */ |
| *addr++ = PPC_INST_ADDIS | ___PPC_RT(3) | |
| ((val >> 48) & 0xffff); |
| |
| /* ori r3,r3,(op)@higher */ |
| *addr++ = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) | |
| ((val >> 32) & 0xffff); |
| |
| /* rldicr r3,r3,32,31 */ |
| *addr++ = PPC_INST_RLDICR | ___PPC_RA(3) | ___PPC_RS(3) | |
| __PPC_SH64(32) | __PPC_ME64(31); |
| |
| /* oris r3,r3,(op)@h */ |
| *addr++ = PPC_INST_ORIS | ___PPC_RA(3) | ___PPC_RS(3) | |
| ((val >> 16) & 0xffff); |
| |
| /* ori r3,r3,(op)@l */ |
| *addr = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) | |
| (val & 0xffff); |
| } |
| |
| int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p) |
| { |
| kprobe_opcode_t *buff, branch_op_callback, branch_emulate_step; |
| kprobe_opcode_t *op_callback_addr, *emulate_step_addr; |
| long b_offset; |
| unsigned long nip; |
| |
| kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE; |
| |
| nip = can_optimize(p); |
| if (!nip) |
| return -EILSEQ; |
| |
| /* Allocate instruction slot for detour buffer */ |
| buff = get_ppc_optinsn_slot(); |
| if (!buff) |
| return -ENOMEM; |
| |
| /* |
| * OPTPROBE uses 'b' instruction to branch to optinsn.insn. |
| * |
| * The target address has to be relatively nearby, to permit use |
| * of branch instruction in powerpc, because the address is specified |
| * in an immediate field in the instruction opcode itself, ie 24 bits |
| * in the opcode specify the address. Therefore the address should |
| * be within 32MB on either side of the current instruction. |
| */ |
| b_offset = (unsigned long)buff - (unsigned long)p->addr; |
| if (!is_offset_in_branch_range(b_offset)) |
| goto error; |
| |
| /* Check if the return address is also within 32MB range */ |
| b_offset = (unsigned long)(buff + TMPL_RET_IDX) - |
| (unsigned long)nip; |
| if (!is_offset_in_branch_range(b_offset)) |
| goto error; |
| |
| /* Setup template */ |
| memcpy(buff, optprobe_template_entry, |
| TMPL_END_IDX * sizeof(kprobe_opcode_t)); |
| |
| /* |
| * Fixup the template with instructions to: |
| * 1. load the address of the actual probepoint |
| */ |
| patch_imm64_load_insns((unsigned long)op, buff + TMPL_OP_IDX); |
| |
| /* |
| * 2. branch to optimized_callback() and emulate_step() |
| */ |
| op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback"); |
| emulate_step_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("emulate_step"); |
| if (!op_callback_addr || !emulate_step_addr) { |
| WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n"); |
| goto error; |
| } |
| |
| branch_op_callback = create_branch((unsigned int *)buff + TMPL_CALL_HDLR_IDX, |
| (unsigned long)op_callback_addr, |
| BRANCH_SET_LINK); |
| |
| branch_emulate_step = create_branch((unsigned int *)buff + TMPL_EMULATE_IDX, |
| (unsigned long)emulate_step_addr, |
| BRANCH_SET_LINK); |
| |
| if (!branch_op_callback || !branch_emulate_step) |
| goto error; |
| |
| buff[TMPL_CALL_HDLR_IDX] = branch_op_callback; |
| buff[TMPL_EMULATE_IDX] = branch_emulate_step; |
| |
| /* |
| * 3. load instruction to be emulated into relevant register, and |
| */ |
| patch_imm32_load_insns(*p->ainsn.insn, buff + TMPL_INSN_IDX); |
| |
| /* |
| * 4. branch back from trampoline |
| */ |
| buff[TMPL_RET_IDX] = create_branch((unsigned int *)buff + TMPL_RET_IDX, |
| (unsigned long)nip, 0); |
| |
| flush_icache_range((unsigned long)buff, |
| (unsigned long)(&buff[TMPL_END_IDX])); |
| |
| op->optinsn.insn = buff; |
| |
| return 0; |
| |
| error: |
| free_ppc_optinsn_slot(buff, 0); |
| return -ERANGE; |
| |
| } |
| |
| int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) |
| { |
| return optinsn->insn != NULL; |
| } |
| |
| /* |
| * On powerpc, Optprobes always replaces one instruction (4 bytes |
| * aligned and 4 bytes long). It is impossible to encounter another |
| * kprobe in this address range. So always return 0. |
| */ |
| int arch_check_optimized_kprobe(struct optimized_kprobe *op) |
| { |
| return 0; |
| } |
| |
| void arch_optimize_kprobes(struct list_head *oplist) |
| { |
| struct optimized_kprobe *op; |
| struct optimized_kprobe *tmp; |
| |
| list_for_each_entry_safe(op, tmp, oplist, list) { |
| /* |
| * Backup instructions which will be replaced |
| * by jump address |
| */ |
| memcpy(op->optinsn.copied_insn, op->kp.addr, |
| RELATIVEJUMP_SIZE); |
| patch_instruction(op->kp.addr, |
| create_branch((unsigned int *)op->kp.addr, |
| (unsigned long)op->optinsn.insn, 0)); |
| list_del_init(&op->list); |
| } |
| } |
| |
| void arch_unoptimize_kprobe(struct optimized_kprobe *op) |
| { |
| arch_arm_kprobe(&op->kp); |
| } |
| |
| void arch_unoptimize_kprobes(struct list_head *oplist, |
| struct list_head *done_list) |
| { |
| struct optimized_kprobe *op; |
| struct optimized_kprobe *tmp; |
| |
| list_for_each_entry_safe(op, tmp, oplist, list) { |
| arch_unoptimize_kprobe(op); |
| list_move(&op->list, done_list); |
| } |
| } |
| |
| int arch_within_optimized_kprobe(struct optimized_kprobe *op, |
| unsigned long addr) |
| { |
| return ((unsigned long)op->kp.addr <= addr && |
| (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr); |
| } |