/* * arch/arm64/kernel/probes/kprobes.c * * Kprobes support for ARM64 * * Copyright (C) 2013 Linaro Limited. * Author: Sandeepa Prabhu * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "decode-insn.h" DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); static void __kprobes post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *); static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode) { void *addrs[1]; u32 insns[1]; addrs[0] = addr; insns[0] = opcode; return aarch64_insn_patch_text(addrs, insns, 1); } static void __kprobes arch_prepare_ss_slot(struct kprobe *p) { /* prepare insn slot */ patch_text(p->ainsn.api.insn, p->opcode); flush_icache_range((uintptr_t) (p->ainsn.api.insn), (uintptr_t) (p->ainsn.api.insn) + MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); /* * Needs restoring of return address after stepping xol. */ p->ainsn.api.restore = (unsigned long) p->addr + sizeof(kprobe_opcode_t); } static void __kprobes arch_prepare_simulate(struct kprobe *p) { /* This instructions is not executed xol. No need to adjust the PC */ p->ainsn.api.restore = 0; } static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); if (p->ainsn.api.handler) p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs); /* single step simulated, now go for post processing */ post_kprobe_handler(kcb, regs); } int __kprobes arch_prepare_kprobe(struct kprobe *p) { unsigned long probe_addr = (unsigned long)p->addr; extern char __start_rodata[]; extern char __end_rodata[]; if (probe_addr & 0x3) return -EINVAL; /* copy instruction */ p->opcode = le32_to_cpu(*p->addr); if (in_exception_text(probe_addr)) return -EINVAL; if (probe_addr >= (unsigned long) __start_rodata && probe_addr <= (unsigned long) __end_rodata) return -EINVAL; /* decode instruction */ switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) { case INSN_REJECTED: /* insn not supported */ return -EINVAL; case INSN_GOOD_NO_SLOT: /* insn need simulation */ p->ainsn.api.insn = NULL; break; case INSN_GOOD: /* instruction uses slot */ p->ainsn.api.insn = get_insn_slot(); if (!p->ainsn.api.insn) return -ENOMEM; break; }; /* prepare the instruction */ if (p->ainsn.api.insn) arch_prepare_ss_slot(p); else arch_prepare_simulate(p); return 0; } void *alloc_insn_page(void) { void *page; page = vmalloc_exec(PAGE_SIZE); if (page) set_memory_ro((unsigned long)page, 1); return page; } /* arm kprobe: install breakpoint in text */ void __kprobes arch_arm_kprobe(struct kprobe *p) { patch_text(p->addr, BRK64_OPCODE_KPROBES); } /* disarm kprobe: remove breakpoint from text */ void __kprobes arch_disarm_kprobe(struct kprobe *p) { patch_text(p->addr, p->opcode); } void __kprobes arch_remove_kprobe(struct kprobe *p) { if (p->ainsn.api.insn) { free_insn_slot(p->ainsn.api.insn, 0); p->ainsn.api.insn = NULL; } } static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; } static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); kcb->kprobe_status = kcb->prev_kprobe.status; } static void __kprobes set_current_kprobe(struct kprobe *p) { __this_cpu_write(current_kprobe, p); } /* * When PSTATE.D is set (masked), then software step exceptions can not be * generated. * SPSR's D bit shows the value of PSTATE.D immediately before the * exception was taken. PSTATE.D is set while entering into any exception * mode, however software clears it for any normal (none-debug-exception) * mode in the exception entry. Therefore, when we are entering into kprobe * breakpoint handler from any normal mode then SPSR.D bit is already * cleared, however it is set when we are entering from any debug exception * mode. * Since we always need to generate single step exception after a kprobe * breakpoint exception therefore we need to clear it unconditionally, when * we become sure that the current breakpoint exception is for kprobe. */ static void __kprobes spsr_set_debug_flag(struct pt_regs *regs, int mask) { unsigned long spsr = regs->pstate; if (mask) spsr |= PSR_D_BIT; else spsr &= ~PSR_D_BIT; regs->pstate = spsr; } /* * Interrupts need to be disabled before single-step mode is set, and not * reenabled until after single-step mode ends. * Without disabling interrupt on local CPU, there is a chance of * interrupt occurrence in the period of exception return and start of * out-of-line single-step, that result in wrongly single stepping * into the interrupt handler. */ static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, struct pt_regs *regs) { kcb->saved_irqflag = regs->pstate; regs->pstate |= PSR_I_BIT; } static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, struct pt_regs *regs) { if (kcb->saved_irqflag & PSR_I_BIT) regs->pstate |= PSR_I_BIT; else regs->pstate &= ~PSR_I_BIT; } static void __kprobes set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr) { kcb->ss_ctx.ss_pending = true; kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t); } static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb) { kcb->ss_ctx.ss_pending = false; kcb->ss_ctx.match_addr = 0; } static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb, int reenter) { unsigned long slot; if (reenter) { save_previous_kprobe(kcb); set_current_kprobe(p); kcb->kprobe_status = KPROBE_REENTER; } else { kcb->kprobe_status = KPROBE_HIT_SS; } if (p->ainsn.api.insn) { /* prepare for single stepping */ slot = (unsigned long)p->ainsn.api.insn; set_ss_context(kcb, slot); /* mark pending ss */ spsr_set_debug_flag(regs, 0); /* IRQs and single stepping do not mix well. */ kprobes_save_local_irqflag(kcb, regs); kernel_enable_single_step(regs); instruction_pointer_set(regs, slot); } else { /* insn simulation */ arch_simulate_insn(p, regs); } } static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { switch (kcb->kprobe_status) { case KPROBE_HIT_SSDONE: case KPROBE_HIT_ACTIVE: kprobes_inc_nmissed_count(p); setup_singlestep(p, regs, kcb, 1); break; case KPROBE_HIT_SS: case KPROBE_REENTER: pr_warn("Unrecoverable kprobe detected.\n"); dump_kprobe(p); BUG(); break; default: WARN_ON(1); return 0; } return 1; } static void __kprobes post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs) { struct kprobe *cur = kprobe_running(); if (!cur) return; /* return addr restore if non-branching insn */ if (cur->ainsn.api.restore != 0) instruction_pointer_set(regs, cur->ainsn.api.restore); /* restore back original saved kprobe variables and continue */ if (kcb->kprobe_status == KPROBE_REENTER) { restore_previous_kprobe(kcb); return; } /* call post handler */ kcb->kprobe_status = KPROBE_HIT_SSDONE; if (cur->post_handler) { /* post_handler can hit breakpoint and single step * again, so we enable D-flag for recursive exception. */ cur->post_handler(cur, regs, 0); } reset_current_kprobe(); } int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); switch (kcb->kprobe_status) { case KPROBE_HIT_SS: case KPROBE_REENTER: /* * We are here because the instruction being single * stepped caused a page fault. We reset the current * kprobe and the ip points back to the probe address * and allow the page fault handler to continue as a * normal page fault. */ instruction_pointer_set(regs, (unsigned long) cur->addr); if (!instruction_pointer(regs)) BUG(); kernel_disable_single_step(); if (kcb->kprobe_status == KPROBE_REENTER) restore_previous_kprobe(kcb); else reset_current_kprobe(); break; case KPROBE_HIT_ACTIVE: case KPROBE_HIT_SSDONE: /* * We increment the nmissed count for accounting, * we can also use npre/npostfault count for accounting * these specific fault cases. */ kprobes_inc_nmissed_count(cur); /* * We come here because instructions in the pre/post * handler caused the page_fault, this could happen * if handler tries to access user space by * copy_from_user(), get_user() etc. Let the * user-specified handler try to fix it first. */ if (cur->fault_handler && cur->fault_handler(cur, regs, fsr)) return 1; /* * In case the user-specified fault handler returned * zero, try to fix up. */ if (fixup_exception(regs)) return 1; } return 0; } static void __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p, *cur_kprobe; struct kprobe_ctlblk *kcb; unsigned long addr = instruction_pointer(regs); kcb = get_kprobe_ctlblk(); cur_kprobe = kprobe_running(); p = get_kprobe((kprobe_opcode_t *) addr); if (p) { if (cur_kprobe) { if (reenter_kprobe(p, regs, kcb)) return; } else { /* Probe hit */ set_current_kprobe(p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; /* * If we have no pre-handler or it returned 0, we * continue with normal processing. If we have a * pre-handler and it returned non-zero, it prepped * for calling the break_handler below on re-entry, * so get out doing nothing more here. * * pre_handler can hit a breakpoint and can step thru * before return, keep PSTATE D-flag enabled until * pre_handler return back. */ if (!p->pre_handler || !p->pre_handler(p, regs)) { setup_singlestep(p, regs, kcb, 0); return; } } } else if ((le32_to_cpu(*(kprobe_opcode_t *) addr) == BRK64_OPCODE_KPROBES) && cur_kprobe) { /* We probably hit a jprobe. Call its break handler. */ if (cur_kprobe->break_handler && cur_kprobe->break_handler(cur_kprobe, regs)) { setup_singlestep(cur_kprobe, regs, kcb, 0); return; } } /* * The breakpoint instruction was removed right * after we hit it. Another cpu has removed * either a probepoint or a debugger breakpoint * at this address. In either case, no further * handling of this interrupt is appropriate. * Return back to original instruction, and continue. */ } static int __kprobes kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr) { if ((kcb->ss_ctx.ss_pending) && (kcb->ss_ctx.match_addr == addr)) { clear_ss_context(kcb); /* clear pending ss */ return DBG_HOOK_HANDLED; } /* not ours, kprobes should ignore it */ return DBG_HOOK_ERROR; } int __kprobes kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); int retval; if (user_mode(regs)) return DBG_HOOK_ERROR; /* return error if this is not our step */ retval = kprobe_ss_hit(kcb, instruction_pointer(regs)); if (retval == DBG_HOOK_HANDLED) { kprobes_restore_local_irqflag(kcb, regs); kernel_disable_single_step(); post_kprobe_handler(kcb, regs); } return retval; } int __kprobes kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr) { if (user_mode(regs)) return DBG_HOOK_ERROR; kprobe_handler(regs); return DBG_HOOK_HANDLED; } int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct jprobe *jp = container_of(p, struct jprobe, kp); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); kcb->jprobe_saved_regs = *regs; /* * Since we can't be sure where in the stack frame "stacked" * pass-by-value arguments are stored we just don't try to * duplicate any of the stack. Do not use jprobes on functions that * use more than 64 bytes (after padding each to an 8 byte boundary) * of arguments, or pass individual arguments larger than 16 bytes. */ instruction_pointer_set(regs, (unsigned long) jp->entry); preempt_disable(); pause_graph_tracing(); return 1; } void __kprobes jprobe_return(void) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); /* * Jprobe handler return by entering break exception, * encoded same as kprobe, but with following conditions * -a special PC to identify it from the other kprobes. * -restore stack addr to original saved pt_regs */ asm volatile(" mov sp, %0 \n" "jprobe_return_break: brk %1 \n" : : "r" (kcb->jprobe_saved_regs.sp), "I" (BRK64_ESR_KPROBES) : "memory"); unreachable(); } int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); long stack_addr = kcb->jprobe_saved_regs.sp; long orig_sp = kernel_stack_pointer(regs); struct jprobe *jp = container_of(p, struct jprobe, kp); extern const char jprobe_return_break[]; if (instruction_pointer(regs) != (u64) jprobe_return_break) return 0; if (orig_sp != stack_addr) { struct pt_regs *saved_regs = (struct pt_regs *)kcb->jprobe_saved_regs.sp; pr_err("current sp %lx does not match saved sp %lx\n", orig_sp, stack_addr); pr_err("Saved registers for jprobe %p\n", jp); __show_regs(saved_regs); pr_err("Current registers\n"); __show_regs(regs); BUG(); } unpause_graph_tracing(); *regs = kcb->jprobe_saved_regs; preempt_enable_no_resched(); return 1; } bool arch_within_kprobe_blacklist(unsigned long addr) { if ((addr >= (unsigned long)__kprobes_text_start && addr < (unsigned long)__kprobes_text_end) || (addr >= (unsigned long)__entry_text_start && addr < (unsigned long)__entry_text_end) || (addr >= (unsigned long)__idmap_text_start && addr < (unsigned long)__idmap_text_end) || (addr >= (unsigned long)__hyp_text_start && addr < (unsigned long)__hyp_text_end) || !!search_exception_tables(addr)) return true; if (!is_kernel_in_hyp_mode()) { if ((addr >= (unsigned long)__hyp_idmap_text_start && addr < (unsigned long)__hyp_idmap_text_end)) return true; } return false; } void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) { struct kretprobe_instance *ri = NULL; struct hlist_head *head, empty_rp; struct hlist_node *tmp; unsigned long flags, orig_ret_address = 0; unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; kprobe_opcode_t *correct_ret_addr = NULL; INIT_HLIST_HEAD(&empty_rp); kretprobe_hash_lock(current, &head, &flags); /* * It is possible to have multiple instances associated with a given * task either because multiple functions in the call path have * return probes installed on them, and/or more than one * return probe was registered for a target function. * * We can handle this because: * - instances are always pushed into the head of the list * - when multiple return probes are registered for the same * function, the (chronologically) first instance's ret_addr * will be the real return address, and all the rest will * point to kretprobe_trampoline. */ hlist_for_each_entry_safe(ri, tmp, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; orig_ret_address = (unsigned long)ri->ret_addr; if (orig_ret_address != trampoline_address) /* * This is the real return address. Any other * instances associated with this task are for * other calls deeper on the call stack */ break; } kretprobe_assert(ri, orig_ret_address, trampoline_address); correct_ret_addr = ri->ret_addr; hlist_for_each_entry_safe(ri, tmp, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; orig_ret_address = (unsigned long)ri->ret_addr; if (ri->rp && ri->rp->handler) { __this_cpu_write(current_kprobe, &ri->rp->kp); get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; ri->ret_addr = correct_ret_addr; ri->rp->handler(ri, regs); __this_cpu_write(current_kprobe, NULL); } recycle_rp_inst(ri, &empty_rp); if (orig_ret_address != trampoline_address) /* * This is the real return address. Any other * instances associated with this task are for * other calls deeper on the call stack */ break; } kretprobe_hash_unlock(current, &flags); hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } return (void *)orig_ret_address; } void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { ri->ret_addr = (kprobe_opcode_t *)regs->regs[30]; /* replace return addr (x30) with trampoline */ regs->regs[30] = (long)&kretprobe_trampoline; } int __kprobes arch_trampoline_kprobe(struct kprobe *p) { return 0; } int __init arch_init_kprobes(void) { return 0; }