diff options
Diffstat (limited to 'arch/mips/kernel/kprobes.c')
| -rw-r--r-- | arch/mips/kernel/kprobes.c | 518 |
1 files changed, 518 insertions, 0 deletions
diff --git a/arch/mips/kernel/kprobes.c b/arch/mips/kernel/kprobes.c new file mode 100644 index 000000000..54dfba8fa --- /dev/null +++ b/arch/mips/kernel/kprobes.c @@ -0,0 +1,518 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Kernel Probes (KProbes) + * arch/mips/kernel/kprobes.c + * + * Copyright 2006 Sony Corp. + * Copyright 2010 Cavium Networks + * + * Some portions copied from the powerpc version. + * + * Copyright (C) IBM Corporation, 2002, 2004 + */ + +#include <linux/kprobes.h> +#include <linux/preempt.h> +#include <linux/uaccess.h> +#include <linux/kdebug.h> +#include <linux/slab.h> + +#include <asm/ptrace.h> +#include <asm/branch.h> +#include <asm/break.h> + +#include "probes-common.h" + +static const union mips_instruction breakpoint_insn = { + .b_format = { + .opcode = spec_op, + .code = BRK_KPROBE_BP, + .func = break_op + } +}; + +static const union mips_instruction breakpoint2_insn = { + .b_format = { + .opcode = spec_op, + .code = BRK_KPROBE_SSTEPBP, + .func = break_op + } +}; + +DEFINE_PER_CPU(struct kprobe *, current_kprobe); +DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); + +static int __kprobes insn_has_delayslot(union mips_instruction insn) +{ + return __insn_has_delay_slot(insn); +} + +/* + * insn_has_ll_or_sc function checks whether instruction is ll or sc + * one; putting breakpoint on top of atomic ll/sc pair is bad idea; + * so we need to prevent it and refuse kprobes insertion for such + * instructions; cannot do much about breakpoint in the middle of + * ll/sc pair; it is upto user to avoid those places + */ +static int __kprobes insn_has_ll_or_sc(union mips_instruction insn) +{ + int ret = 0; + + switch (insn.i_format.opcode) { + case ll_op: + case lld_op: + case sc_op: + case scd_op: + ret = 1; + break; + default: + break; + } + return ret; +} + +int __kprobes arch_prepare_kprobe(struct kprobe *p) +{ + union mips_instruction insn; + union mips_instruction prev_insn; + int ret = 0; + + insn = p->addr[0]; + + if (insn_has_ll_or_sc(insn)) { + pr_notice("Kprobes for ll and sc instructions are not" + "supported\n"); + ret = -EINVAL; + goto out; + } + + if (copy_from_kernel_nofault(&prev_insn, p->addr - 1, + sizeof(mips_instruction)) == 0 && + insn_has_delayslot(prev_insn)) { + pr_notice("Kprobes for branch delayslot are not supported\n"); + ret = -EINVAL; + goto out; + } + + if (__insn_is_compact_branch(insn)) { + pr_notice("Kprobes for compact branches are not supported\n"); + ret = -EINVAL; + goto out; + } + + /* insn: must be on special executable page on mips. */ + p->ainsn.insn = get_insn_slot(); + if (!p->ainsn.insn) { + ret = -ENOMEM; + goto out; + } + + /* + * In the kprobe->ainsn.insn[] array we store the original + * instruction at index zero and a break trap instruction at + * index one. + * + * On MIPS arch if the instruction at probed address is a + * branch instruction, we need to execute the instruction at + * Branch Delayslot (BD) at the time of probe hit. As MIPS also + * doesn't have single stepping support, the BD instruction can + * not be executed in-line and it would be executed on SSOL slot + * using a normal breakpoint instruction in the next slot. + * So, read the instruction and save it for later execution. + */ + if (insn_has_delayslot(insn)) + memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t)); + else + memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t)); + + p->ainsn.insn[1] = breakpoint2_insn; + p->opcode = *p->addr; + +out: + return ret; +} + +void __kprobes arch_arm_kprobe(struct kprobe *p) +{ + *p->addr = breakpoint_insn; + flush_insn_slot(p); +} + +void __kprobes arch_disarm_kprobe(struct kprobe *p) +{ + *p->addr = p->opcode; + flush_insn_slot(p); +} + +void __kprobes arch_remove_kprobe(struct kprobe *p) +{ + if (p->ainsn.insn) { + free_insn_slot(p->ainsn.insn, 0); + p->ainsn.insn = NULL; + } +} + +static void save_previous_kprobe(struct kprobe_ctlblk *kcb) +{ + kcb->prev_kprobe.kp = kprobe_running(); + kcb->prev_kprobe.status = kcb->kprobe_status; + kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR; + kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR; + kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc; +} + +static void restore_previous_kprobe(struct kprobe_ctlblk *kcb) +{ + __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); + kcb->kprobe_status = kcb->prev_kprobe.status; + kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR; + kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR; + kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc; +} + +static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs, + struct kprobe_ctlblk *kcb) +{ + __this_cpu_write(current_kprobe, p); + kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE); + kcb->kprobe_saved_epc = regs->cp0_epc; +} + +/** + * evaluate_branch_instrucion - + * + * Evaluate the branch instruction at probed address during probe hit. The + * result of evaluation would be the updated epc. The insturction in delayslot + * would actually be single stepped using a normal breakpoint) on SSOL slot. + * + * The result is also saved in the kprobe control block for later use, + * in case we need to execute the delayslot instruction. The latter will be + * false for NOP instruction in dealyslot and the branch-likely instructions + * when the branch is taken. And for those cases we set a flag as + * SKIP_DELAYSLOT in the kprobe control block + */ +static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs, + struct kprobe_ctlblk *kcb) +{ + union mips_instruction insn = p->opcode; + long epc; + int ret = 0; + + epc = regs->cp0_epc; + if (epc & 3) + goto unaligned; + + if (p->ainsn.insn->word == 0) + kcb->flags |= SKIP_DELAYSLOT; + else + kcb->flags &= ~SKIP_DELAYSLOT; + + ret = __compute_return_epc_for_insn(regs, insn); + if (ret < 0) + return ret; + + if (ret == BRANCH_LIKELY_TAKEN) + kcb->flags |= SKIP_DELAYSLOT; + + kcb->target_epc = regs->cp0_epc; + + return 0; + +unaligned: + pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm); + force_sig(SIGBUS); + return -EFAULT; + +} + +static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs, + struct kprobe_ctlblk *kcb) +{ + int ret = 0; + + regs->cp0_status &= ~ST0_IE; + + /* single step inline if the instruction is a break */ + if (p->opcode.word == breakpoint_insn.word || + p->opcode.word == breakpoint2_insn.word) + regs->cp0_epc = (unsigned long)p->addr; + else if (insn_has_delayslot(p->opcode)) { + ret = evaluate_branch_instruction(p, regs, kcb); + if (ret < 0) { + pr_notice("Kprobes: Error in evaluating branch\n"); + return; + } + } + regs->cp0_epc = (unsigned long)&p->ainsn.insn[0]; +} + +/* + * Called after single-stepping. p->addr is the address of the + * instruction whose first byte has been replaced by the "break 0" + * instruction. To avoid the SMP problems that can occur when we + * temporarily put back the original opcode to single-step, we + * single-stepped a copy of the instruction. The address of this + * copy is p->ainsn.insn. + * + * This function prepares to return from the post-single-step + * breakpoint trap. In case of branch instructions, the target + * epc to be restored. + */ +static void __kprobes resume_execution(struct kprobe *p, + struct pt_regs *regs, + struct kprobe_ctlblk *kcb) +{ + if (insn_has_delayslot(p->opcode)) + regs->cp0_epc = kcb->target_epc; + else { + unsigned long orig_epc = kcb->kprobe_saved_epc; + regs->cp0_epc = orig_epc + 4; + } +} + +static int __kprobes kprobe_handler(struct pt_regs *regs) +{ + struct kprobe *p; + int ret = 0; + kprobe_opcode_t *addr; + struct kprobe_ctlblk *kcb; + + addr = (kprobe_opcode_t *) regs->cp0_epc; + + /* + * We don't want to be preempted for the entire + * duration of kprobe processing + */ + preempt_disable(); + kcb = get_kprobe_ctlblk(); + + /* Check we're not actually recursing */ + if (kprobe_running()) { + p = get_kprobe(addr); + if (p) { + if (kcb->kprobe_status == KPROBE_HIT_SS && + p->ainsn.insn->word == breakpoint_insn.word) { + regs->cp0_status &= ~ST0_IE; + regs->cp0_status |= kcb->kprobe_saved_SR; + goto no_kprobe; + } + /* + * We have reentered the kprobe_handler(), since + * another probe was hit while within the handler. + * We here save the original kprobes variables and + * just single step on the instruction of the new probe + * without calling any user handlers. + */ + save_previous_kprobe(kcb); + set_current_kprobe(p, regs, kcb); + kprobes_inc_nmissed_count(p); + prepare_singlestep(p, regs, kcb); + kcb->kprobe_status = KPROBE_REENTER; + if (kcb->flags & SKIP_DELAYSLOT) { + resume_execution(p, regs, kcb); + restore_previous_kprobe(kcb); + preempt_enable_no_resched(); + } + return 1; + } else if (addr->word != breakpoint_insn.word) { + /* + * The breakpoint instruction was removed by + * another cpu right after we hit, no further + * handling of this interrupt is appropriate + */ + ret = 1; + } + goto no_kprobe; + } + + p = get_kprobe(addr); + if (!p) { + if (addr->word != breakpoint_insn.word) { + /* + * 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. + */ + ret = 1; + } + /* Not one of ours: let kernel handle it */ + goto no_kprobe; + } + + set_current_kprobe(p, regs, kcb); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + + if (p->pre_handler && p->pre_handler(p, regs)) { + /* handler has already set things up, so skip ss setup */ + reset_current_kprobe(); + preempt_enable_no_resched(); + return 1; + } + + prepare_singlestep(p, regs, kcb); + if (kcb->flags & SKIP_DELAYSLOT) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + if (p->post_handler) + p->post_handler(p, regs, 0); + resume_execution(p, regs, kcb); + preempt_enable_no_resched(); + } else + kcb->kprobe_status = KPROBE_HIT_SS; + + return 1; + +no_kprobe: + preempt_enable_no_resched(); + return ret; + +} + +static inline int post_kprobe_handler(struct pt_regs *regs) +{ + struct kprobe *cur = kprobe_running(); + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + if (!cur) + return 0; + + if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + cur->post_handler(cur, regs, 0); + } + + resume_execution(cur, regs, kcb); + + regs->cp0_status |= kcb->kprobe_saved_SR; + + /* Restore back the original saved kprobes variables and continue. */ + if (kcb->kprobe_status == KPROBE_REENTER) { + restore_previous_kprobe(kcb); + goto out; + } + reset_current_kprobe(); +out: + preempt_enable_no_resched(); + + return 1; +} + +int kprobe_fault_handler(struct pt_regs *regs, int trapnr) +{ + struct kprobe *cur = kprobe_running(); + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) + return 1; + + if (kcb->kprobe_status & KPROBE_HIT_SS) { + resume_execution(cur, regs, kcb); + regs->cp0_status |= kcb->kprobe_old_SR; + + reset_current_kprobe(); + preempt_enable_no_resched(); + } + return 0; +} + +/* + * Wrapper routine for handling exceptions. + */ +int __kprobes kprobe_exceptions_notify(struct notifier_block *self, + unsigned long val, void *data) +{ + + struct die_args *args = (struct die_args *)data; + int ret = NOTIFY_DONE; + + switch (val) { + case DIE_BREAK: + if (kprobe_handler(args->regs)) + ret = NOTIFY_STOP; + break; + case DIE_SSTEPBP: + if (post_kprobe_handler(args->regs)) + ret = NOTIFY_STOP; + break; + + case DIE_PAGE_FAULT: + /* kprobe_running() needs smp_processor_id() */ + preempt_disable(); + + if (kprobe_running() + && kprobe_fault_handler(args->regs, args->trapnr)) + ret = NOTIFY_STOP; + preempt_enable(); + break; + default: + break; + } + return ret; +} + +/* + * Function return probe trampoline: + * - init_kprobes() establishes a probepoint here + * - When the probed function returns, this probe causes the + * handlers to fire + */ +static void __used kretprobe_trampoline_holder(void) +{ + asm volatile( + ".set push\n\t" + /* Keep the assembler from reordering and placing JR here. */ + ".set noreorder\n\t" + "nop\n\t" + ".global kretprobe_trampoline\n" + "kretprobe_trampoline:\n\t" + "nop\n\t" + ".set pop" + : : : "memory"); +} + +void kretprobe_trampoline(void); + +void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, + struct pt_regs *regs) +{ + ri->ret_addr = (kprobe_opcode_t *) regs->regs[31]; + ri->fp = NULL; + + /* Replace the return addr with trampoline addr */ + regs->regs[31] = (unsigned long)kretprobe_trampoline; +} + +/* + * Called when the probe at kretprobe trampoline is hit + */ +static int __kprobes trampoline_probe_handler(struct kprobe *p, + struct pt_regs *regs) +{ + instruction_pointer(regs) = __kretprobe_trampoline_handler(regs, + kretprobe_trampoline, NULL); + /* + * By returning a non-zero value, we are telling + * kprobe_handler() that we don't want the post_handler + * to run (and have re-enabled preemption) + */ + return 1; +} + +int __kprobes arch_trampoline_kprobe(struct kprobe *p) +{ + if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline) + return 1; + + return 0; +} + +static struct kprobe trampoline_p = { + .addr = (kprobe_opcode_t *)kretprobe_trampoline, + .pre_handler = trampoline_probe_handler +}; + +int __init arch_init_kprobes(void) +{ + return register_kprobe(&trampoline_p); +} |