/* * Kernel Probes (KProbes) * * 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. * * 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. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Copyright (C) IBM Corporation, 2002, 2006 * * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com> */ #include <linux/kprobes.h> #include <linux/ptrace.h> #include <linux/preempt.h> #include <linux/stop_machine.h> #include <linux/kdebug.h> #include <asm/cacheflush.h> #include <asm/sections.h> #include <asm/uaccess.h> #include <linux/module.h> DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); int __kprobes arch_prepare_kprobe(struct kprobe *p) { /* Make sure the probe isn't going on a difficult instruction */ if (is_prohibited_opcode((kprobe_opcode_t *) p->addr)) return -EINVAL; if ((unsigned long)p->addr & 0x01) { printk("Attempt to register kprobe at an unaligned address\n"); return -EINVAL; } /* Use the get_insn_slot() facility for correctness */ if (!(p->ainsn.insn = get_insn_slot())) return -ENOMEM; memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); get_instruction_type(&p->ainsn); p->opcode = *p->addr; return 0; } int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction) { switch (*(__u8 *) instruction) { case 0x0c: /* bassm */ case 0x0b: /* bsm */ case 0x83: /* diag */ case 0x44: /* ex */ return -EINVAL; } switch (*(__u16 *) instruction) { case 0x0101: /* pr */ case 0xb25a: /* bsa */ case 0xb240: /* bakr */ case 0xb258: /* bsg */ case 0xb218: /* pc */ case 0xb228: /* pt */ return -EINVAL; } return 0; } void __kprobes get_instruction_type(struct arch_specific_insn *ainsn) { /* default fixup method */ ainsn->fixup = FIXUP_PSW_NORMAL; /* save r1 operand */ ainsn->reg = (*ainsn->insn & 0xf0) >> 4; /* save the instruction length (pop 5-5) in bytes */ switch (*(__u8 *) (ainsn->insn) >> 6) { case 0: ainsn->ilen = 2; break; case 1: case 2: ainsn->ilen = 4; break; case 3: ainsn->ilen = 6; break; } switch (*(__u8 *) ainsn->insn) { case 0x05: /* balr */ case 0x0d: /* basr */ ainsn->fixup = FIXUP_RETURN_REGISTER; /* if r2 = 0, no branch will be taken */ if ((*ainsn->insn & 0x0f) == 0) ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN; break; case 0x06: /* bctr */ case 0x07: /* bcr */ ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN; break; case 0x45: /* bal */ case 0x4d: /* bas */ ainsn->fixup = FIXUP_RETURN_REGISTER; break; case 0x47: /* bc */ case 0x46: /* bct */ case 0x86: /* bxh */ case 0x87: /* bxle */ ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN; break; case 0x82: /* lpsw */ ainsn->fixup = FIXUP_NOT_REQUIRED; break; case 0xb2: /* lpswe */ if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) { ainsn->fixup = FIXUP_NOT_REQUIRED; } break; case 0xa7: /* bras */ if ((*ainsn->insn & 0x0f) == 0x05) { ainsn->fixup |= FIXUP_RETURN_REGISTER; } break; case 0xc0: if ((*ainsn->insn & 0x0f) == 0x00 /* larl */ || (*ainsn->insn & 0x0f) == 0x05) /* brasl */ ainsn->fixup |= FIXUP_RETURN_REGISTER; break; case 0xeb: if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 || /* bxhg */ *(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */ ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN; } break; case 0xe3: /* bctg */ if (*(((__u8 *) ainsn->insn) + 5) == 0x46) { ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN; } break; } } static int __kprobes swap_instruction(void *aref) { struct ins_replace_args *args = aref; u32 *addr; u32 instr; int err = -EFAULT; /* * Text segment is read-only, hence we use stura to bypass dynamic * address translation to exchange the instruction. Since stura * always operates on four bytes, but we only want to exchange two * bytes do some calculations to get things right. In addition we * shall not cross any page boundaries (vmalloc area!) when writing * the new instruction. */ addr = (u32 *)((unsigned long)args->ptr & -4UL); if ((unsigned long)args->ptr & 2) instr = ((*addr) & 0xffff0000) | args->new; else instr = ((*addr) & 0x0000ffff) | args->new << 16; asm volatile( " lra %1,0(%1)\n" "0: stura %2,%1\n" "1: la %0,0\n" "2:\n" EX_TABLE(0b,2b) : "+d" (err) : "a" (addr), "d" (instr) : "memory", "cc"); return err; } void __kprobes arch_arm_kprobe(struct kprobe *p) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long status = kcb->kprobe_status; struct ins_replace_args args; args.ptr = p->addr; args.old = p->opcode; args.new = BREAKPOINT_INSTRUCTION; kcb->kprobe_status = KPROBE_SWAP_INST; stop_machine_run(swap_instruction, &args, NR_CPUS); kcb->kprobe_status = status; } void __kprobes arch_disarm_kprobe(struct kprobe *p) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long status = kcb->kprobe_status; struct ins_replace_args args; args.ptr = p->addr; args.old = BREAKPOINT_INSTRUCTION; args.new = p->opcode; kcb->kprobe_status = KPROBE_SWAP_INST; stop_machine_run(swap_instruction, &args, NR_CPUS); kcb->kprobe_status = status; } void __kprobes arch_remove_kprobe(struct kprobe *p) { mutex_lock(&kprobe_mutex); free_insn_slot(p->ainsn.insn, 0); mutex_unlock(&kprobe_mutex); } static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) { per_cr_bits kprobe_per_regs[1]; memset(kprobe_per_regs, 0, sizeof(per_cr_bits)); regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE; /* Set up the per control reg info, will pass to lctl */ kprobe_per_regs[0].em_instruction_fetch = 1; kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn; kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1; /* Set the PER control regs, turns on single step for this address */ __ctl_load(kprobe_per_regs, 9, 11); regs->psw.mask |= PSW_MASK_PER; regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK); } static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask; memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl, sizeof(kcb->kprobe_saved_ctl)); } static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; kcb->kprobe_status = kcb->prev_kprobe.status; kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask; memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl, sizeof(kcb->kprobe_saved_ctl)); } static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = p; /* Save the interrupt and per flags */ kcb->kprobe_saved_imask = regs->psw.mask & (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK); /* Save the control regs that govern PER */ __ctl_store(kcb->kprobe_saved_ctl, 9, 11); } /* Called with kretprobe_lock held */ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14]; /* Replace the return addr with trampoline addr */ regs->gprs[14] = (unsigned long)&kretprobe_trampoline; } static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p; int ret = 0; unsigned long *addr = (unsigned long *) ((regs->psw.addr & PSW_ADDR_INSN) - 2); struct kprobe_ctlblk *kcb; /* * 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 == BREAKPOINT_INSTRUCTION) { regs->psw.mask &= ~PSW_MASK_PER; regs->psw.mask |= kcb->kprobe_saved_imask; 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->kprobe_status = KPROBE_REENTER; return 1; } else { p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe; } } goto no_kprobe; } p = get_kprobe(addr); if (!p) /* * No kprobe at this address. The fault has not been * caused by a kprobe breakpoint. The race of breakpoint * vs. kprobe remove does not exist because on s390 we * use stop_machine_run to arm/disarm the breakpoints. */ goto no_kprobe; kcb->kprobe_status = KPROBE_HIT_ACTIVE; set_current_kprobe(p, regs, kcb); if (p->pre_handler && p->pre_handler(p, regs)) /* handler has already set things up, so skip ss setup */ return 1; ss_probe: prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; return 1; no_kprobe: preempt_enable_no_resched(); return ret; } /* * Function return probe trampoline: * - init_kprobes() establishes a probepoint here * - When the probed function returns, this probe * causes the handlers to fire */ void kretprobe_trampoline_holder(void) { asm volatile(".global kretprobe_trampoline\n" "kretprobe_trampoline: bcr 0,0\n"); } /* * Called when the probe at kretprobe trampoline is hit */ static int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) { struct kretprobe_instance *ri = NULL; struct hlist_head *head, empty_rp; struct hlist_node *node, *tmp; unsigned long flags, orig_ret_address = 0; unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; INIT_HLIST_HEAD(&empty_rp); spin_lock_irqsave(&kretprobe_lock, flags); head = kretprobe_inst_table_head(current); /* * It is possible to have multiple instances associated with a given * task either because an multiple functions in the call path * have a return probe installed on them, and/or more then one return * return probe was registered for a target function. * * We can handle this because: * - instances are always inserted at the head of the list * - when multiple return probes are registered for the same * function, the first instance's ret_addr will point to the * real return address, and all the rest will point to * kretprobe_trampoline */ hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; if (ri->rp && ri->rp->handler) ri->rp->handler(ri, regs); orig_ret_address = (unsigned long)ri->ret_addr; 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_assert(ri, orig_ret_address, trampoline_address); regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE; reset_current_kprobe(); spin_unlock_irqrestore(&kretprobe_lock, flags); preempt_enable_no_resched(); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } /* * 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; } /* * Called after single-stepping. p->addr is the address of the * instruction whose first byte has been replaced by the "breakpoint" * 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. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); regs->psw.addr &= PSW_ADDR_INSN; if (p->ainsn.fixup & FIXUP_PSW_NORMAL) regs->psw.addr = (unsigned long)p->addr + ((unsigned long)regs->psw.addr - (unsigned long)p->ainsn.insn); if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN) if ((unsigned long)regs->psw.addr - (unsigned long)p->ainsn.insn == p->ainsn.ilen) regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen; if (p->ainsn.fixup & FIXUP_RETURN_REGISTER) regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr + (regs->gprs[p->ainsn.reg] - (unsigned long)p->ainsn.insn)) | PSW_ADDR_AMODE; regs->psw.addr |= PSW_ADDR_AMODE; /* turn off PER mode */ regs->psw.mask &= ~PSW_MASK_PER; /* Restore the original per control regs */ __ctl_load(kcb->kprobe_saved_ctl, 9, 11); regs->psw.mask |= kcb->kprobe_saved_imask; } static int __kprobes 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); /*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(); /* * if somebody else is singlestepping across a probe point, psw mask * will have PER set, in which case, continue the remaining processing * of do_single_step, as if this is not a probe hit. */ if (regs->psw.mask & PSW_MASK_PER) { return 0; } return 1; } int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); const struct exception_table_entry *entry; switch(kcb->kprobe_status) { case KPROBE_SWAP_INST: /* We are here because the instruction replacement failed */ return 0; 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 nip points back to the probe address * and allow the page fault handler to continue as a * normal page fault. */ regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE; regs->psw.mask &= ~PSW_MASK_PER; regs->psw.mask |= kcb->kprobe_saved_imask; if (kcb->kprobe_status == KPROBE_REENTER) restore_previous_kprobe(kcb); else reset_current_kprobe(); preempt_enable_no_resched(); break; case KPROBE_HIT_ACTIVE: case KPROBE_HIT_SSDONE: /* * We increment the nmissed count for accounting, * we can also use npre/npostfault count for accouting * 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, trapnr)) return 1; /* * In case the user-specified fault handler returned * zero, try to fix up. */ entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN); if (entry) { regs->psw.addr = entry->fixup | PSW_ADDR_AMODE; return 1; } /* * fixup_exception() could not handle it, * Let do_page_fault() fix it. */ break; default: break; } return 0; } /* * Wrapper routine to 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_BPT: if (kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_SSTEP: if (post_kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_TRAP: /* 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; } int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct jprobe *jp = container_of(p, struct jprobe, kp); unsigned long addr; struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs)); /* setup return addr to the jprobe handler routine */ regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE; /* r14 is the function return address */ kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14]; /* r15 is the stack pointer */ kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15]; addr = (unsigned long)kcb->jprobe_saved_r15; memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr)); return 1; } void __kprobes jprobe_return(void) { asm volatile(".word 0x0002"); } void __kprobes jprobe_return_end(void) { asm volatile("bcr 0,0"); } int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15); /* Put the regs back */ memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); /* put the stack back */ memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack, MIN_STACK_SIZE(stack_addr)); preempt_enable_no_resched(); return 1; } 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); } int __kprobes arch_trampoline_kprobe(struct kprobe *p) { if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline) return 1; return 0; }