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308 lines
8.6 KiB
308 lines
8.6 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Code for Kernel probes Jump optimization. |
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* |
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* Copyright 2017, Anju T, IBM Corp. |
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*/ |
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#include <linux/kprobes.h> |
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#include <linux/jump_label.h> |
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#include <linux/types.h> |
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#include <linux/slab.h> |
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#include <linux/list.h> |
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#include <asm/kprobes.h> |
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#include <asm/ptrace.h> |
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#include <asm/cacheflush.h> |
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#include <asm/code-patching.h> |
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#include <asm/sstep.h> |
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#include <asm/ppc-opcode.h> |
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#include <asm/inst.h> |
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#define TMPL_CALL_HDLR_IDX (optprobe_template_call_handler - optprobe_template_entry) |
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#define TMPL_EMULATE_IDX (optprobe_template_call_emulate - optprobe_template_entry) |
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#define TMPL_RET_IDX (optprobe_template_ret - optprobe_template_entry) |
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#define TMPL_OP_IDX (optprobe_template_op_address - optprobe_template_entry) |
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#define TMPL_INSN_IDX (optprobe_template_insn - optprobe_template_entry) |
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#define TMPL_END_IDX (optprobe_template_end - optprobe_template_entry) |
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static bool insn_page_in_use; |
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void *alloc_optinsn_page(void) |
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{ |
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if (insn_page_in_use) |
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return NULL; |
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insn_page_in_use = true; |
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return &optinsn_slot; |
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} |
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void free_optinsn_page(void *page) |
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{ |
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insn_page_in_use = false; |
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} |
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/* |
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* Check if we can optimize this probe. Returns NIP post-emulation if this can |
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* be optimized and 0 otherwise. |
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*/ |
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static unsigned long can_optimize(struct kprobe *p) |
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{ |
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struct pt_regs regs; |
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struct instruction_op op; |
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unsigned long nip = 0; |
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unsigned long addr = (unsigned long)p->addr; |
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/* |
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* kprobe placed for kretprobe during boot time |
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* has a 'nop' instruction, which can be emulated. |
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* So further checks can be skipped. |
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*/ |
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if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) |
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return addr + sizeof(kprobe_opcode_t); |
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/* |
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* We only support optimizing kernel addresses, but not |
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* module addresses. |
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* |
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* FIXME: Optimize kprobes placed in module addresses. |
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*/ |
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if (!is_kernel_addr(addr)) |
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return 0; |
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memset(®s, 0, sizeof(struct pt_regs)); |
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regs.nip = addr; |
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regs.trap = 0x0; |
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regs.msr = MSR_KERNEL; |
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/* |
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* Kprobe placed in conditional branch instructions are |
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* not optimized, as we can't predict the nip prior with |
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* dummy pt_regs and can not ensure that the return branch |
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* from detour buffer falls in the range of address (i.e 32MB). |
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* A branch back from trampoline is set up in the detour buffer |
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* to the nip returned by the analyse_instr() here. |
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* |
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* Ensure that the instruction is not a conditional branch, |
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* and that can be emulated. |
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*/ |
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if (!is_conditional_branch(ppc_inst_read(p->ainsn.insn)) && |
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analyse_instr(&op, ®s, ppc_inst_read(p->ainsn.insn)) == 1) { |
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emulate_update_regs(®s, &op); |
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nip = regs.nip; |
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} |
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return nip; |
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} |
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static void optimized_callback(struct optimized_kprobe *op, |
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struct pt_regs *regs) |
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{ |
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/* This is possible if op is under delayed unoptimizing */ |
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if (kprobe_disabled(&op->kp)) |
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return; |
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preempt_disable(); |
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if (kprobe_running()) { |
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kprobes_inc_nmissed_count(&op->kp); |
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} else { |
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__this_cpu_write(current_kprobe, &op->kp); |
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regs_set_return_ip(regs, (unsigned long)op->kp.addr); |
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get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; |
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opt_pre_handler(&op->kp, regs); |
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__this_cpu_write(current_kprobe, NULL); |
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} |
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preempt_enable_no_resched(); |
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} |
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NOKPROBE_SYMBOL(optimized_callback); |
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void arch_remove_optimized_kprobe(struct optimized_kprobe *op) |
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{ |
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if (op->optinsn.insn) { |
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free_optinsn_slot(op->optinsn.insn, 1); |
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op->optinsn.insn = NULL; |
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} |
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} |
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static void patch_imm32_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr) |
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{ |
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patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HI(val)))); |
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patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val)))); |
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} |
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/* |
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* Generate instructions to load provided immediate 64-bit value |
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* to register 'reg' and patch these instructions at 'addr'. |
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*/ |
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static void patch_imm64_load_insns(unsigned long long val, int reg, kprobe_opcode_t *addr) |
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{ |
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patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HIGHEST(val)))); |
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patch_instruction(addr++, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_HIGHER(val)))); |
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patch_instruction(addr++, ppc_inst(PPC_RAW_SLDI(reg, reg, 32))); |
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patch_instruction(addr++, ppc_inst(PPC_RAW_ORIS(reg, reg, PPC_HI(val)))); |
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patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val)))); |
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} |
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static void patch_imm_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr) |
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{ |
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if (IS_ENABLED(CONFIG_PPC64)) |
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patch_imm64_load_insns(val, reg, addr); |
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else |
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patch_imm32_load_insns(val, reg, addr); |
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} |
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int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p) |
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{ |
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struct ppc_inst branch_op_callback, branch_emulate_step, temp; |
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unsigned long op_callback_addr, emulate_step_addr; |
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kprobe_opcode_t *buff; |
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long b_offset; |
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unsigned long nip, size; |
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int rc, i; |
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nip = can_optimize(p); |
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if (!nip) |
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return -EILSEQ; |
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/* Allocate instruction slot for detour buffer */ |
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buff = get_optinsn_slot(); |
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if (!buff) |
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return -ENOMEM; |
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/* |
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* OPTPROBE uses 'b' instruction to branch to optinsn.insn. |
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* |
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* The target address has to be relatively nearby, to permit use |
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* of branch instruction in powerpc, because the address is specified |
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* in an immediate field in the instruction opcode itself, ie 24 bits |
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* in the opcode specify the address. Therefore the address should |
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* be within 32MB on either side of the current instruction. |
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*/ |
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b_offset = (unsigned long)buff - (unsigned long)p->addr; |
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if (!is_offset_in_branch_range(b_offset)) |
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goto error; |
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/* Check if the return address is also within 32MB range */ |
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b_offset = (unsigned long)(buff + TMPL_RET_IDX) - nip; |
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if (!is_offset_in_branch_range(b_offset)) |
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goto error; |
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/* Setup template */ |
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/* We can optimize this via patch_instruction_window later */ |
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size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int); |
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pr_devel("Copying template to %p, size %lu\n", buff, size); |
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for (i = 0; i < size; i++) { |
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rc = patch_instruction(buff + i, ppc_inst(*(optprobe_template_entry + i))); |
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if (rc < 0) |
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goto error; |
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} |
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/* |
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* Fixup the template with instructions to: |
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* 1. load the address of the actual probepoint |
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*/ |
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patch_imm_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX); |
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/* |
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* 2. branch to optimized_callback() and emulate_step() |
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*/ |
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op_callback_addr = ppc_kallsyms_lookup_name("optimized_callback"); |
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emulate_step_addr = ppc_kallsyms_lookup_name("emulate_step"); |
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if (!op_callback_addr || !emulate_step_addr) { |
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WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n"); |
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goto error; |
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} |
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rc = create_branch(&branch_op_callback, buff + TMPL_CALL_HDLR_IDX, |
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op_callback_addr, BRANCH_SET_LINK); |
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rc |= create_branch(&branch_emulate_step, buff + TMPL_EMULATE_IDX, |
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emulate_step_addr, BRANCH_SET_LINK); |
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if (rc) |
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goto error; |
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patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback); |
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patch_instruction(buff + TMPL_EMULATE_IDX, branch_emulate_step); |
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/* |
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* 3. load instruction to be emulated into relevant register, and |
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*/ |
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if (IS_ENABLED(CONFIG_PPC64)) { |
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temp = ppc_inst_read(p->ainsn.insn); |
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patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX); |
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} else { |
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patch_imm_load_insns((unsigned long)p->ainsn.insn, 4, buff + TMPL_INSN_IDX); |
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} |
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/* |
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* 4. branch back from trampoline |
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*/ |
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patch_branch(buff + TMPL_RET_IDX, nip, 0); |
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flush_icache_range((unsigned long)buff, (unsigned long)(&buff[TMPL_END_IDX])); |
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op->optinsn.insn = buff; |
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return 0; |
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error: |
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free_optinsn_slot(buff, 0); |
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return -ERANGE; |
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} |
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int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) |
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{ |
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return optinsn->insn != NULL; |
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} |
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/* |
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* On powerpc, Optprobes always replaces one instruction (4 bytes |
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* aligned and 4 bytes long). It is impossible to encounter another |
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* kprobe in this address range. So always return 0. |
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*/ |
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int arch_check_optimized_kprobe(struct optimized_kprobe *op) |
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{ |
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return 0; |
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} |
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void arch_optimize_kprobes(struct list_head *oplist) |
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{ |
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struct ppc_inst instr; |
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struct optimized_kprobe *op; |
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struct optimized_kprobe *tmp; |
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list_for_each_entry_safe(op, tmp, oplist, list) { |
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/* |
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* Backup instructions which will be replaced |
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* by jump address |
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*/ |
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memcpy(op->optinsn.copied_insn, op->kp.addr, RELATIVEJUMP_SIZE); |
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create_branch(&instr, op->kp.addr, (unsigned long)op->optinsn.insn, 0); |
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patch_instruction(op->kp.addr, instr); |
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list_del_init(&op->list); |
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} |
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} |
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void arch_unoptimize_kprobe(struct optimized_kprobe *op) |
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{ |
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arch_arm_kprobe(&op->kp); |
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} |
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void arch_unoptimize_kprobes(struct list_head *oplist, struct list_head *done_list) |
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{ |
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struct optimized_kprobe *op; |
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struct optimized_kprobe *tmp; |
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list_for_each_entry_safe(op, tmp, oplist, list) { |
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arch_unoptimize_kprobe(op); |
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list_move(&op->list, done_list); |
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} |
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} |
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int arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr) |
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{ |
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return ((unsigned long)op->kp.addr <= addr && |
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(unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr); |
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}
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