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Diffstat (limited to 'arch/s390/kernel/kprobes.c')
| -rw-r--r-- | arch/s390/kernel/kprobes.c | 671 |
1 files changed, 671 insertions, 0 deletions
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c new file mode 100644 index 00000000..64b761ae --- /dev/null +++ b/arch/s390/kernel/kprobes.c @@ -0,0 +1,671 @@ +/* + * 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 <linux/uaccess.h> +#include <asm/cacheflush.h> +#include <asm/sections.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/hardirq.h> + +DEFINE_PER_CPU(struct kprobe *, current_kprobe); +DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); + +struct kretprobe_blackpoint kretprobe_blacklist[] = { }; + +static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn) +{ + switch (insn[0] >> 8) { + case 0x0c: /* bassm */ + case 0x0b: /* bsm */ + case 0x83: /* diag */ + case 0x44: /* ex */ + case 0xac: /* stnsm */ + case 0xad: /* stosm */ + return -EINVAL; + } + switch (insn[0]) { + case 0x0101: /* pr */ + case 0xb25a: /* bsa */ + case 0xb240: /* bakr */ + case 0xb258: /* bsg */ + case 0xb218: /* pc */ + case 0xb228: /* pt */ + case 0xb98d: /* epsw */ + return -EINVAL; + } + return 0; +} + +static int __kprobes get_fixup_type(kprobe_opcode_t *insn) +{ + /* default fixup method */ + int fixup = FIXUP_PSW_NORMAL; + + switch (insn[0] >> 8) { + case 0x05: /* balr */ + case 0x0d: /* basr */ + fixup = FIXUP_RETURN_REGISTER; + /* if r2 = 0, no branch will be taken */ + if ((insn[0] & 0x0f) == 0) + fixup |= FIXUP_BRANCH_NOT_TAKEN; + break; + case 0x06: /* bctr */ + case 0x07: /* bcr */ + fixup = FIXUP_BRANCH_NOT_TAKEN; + break; + case 0x45: /* bal */ + case 0x4d: /* bas */ + fixup = FIXUP_RETURN_REGISTER; + break; + case 0x47: /* bc */ + case 0x46: /* bct */ + case 0x86: /* bxh */ + case 0x87: /* bxle */ + fixup = FIXUP_BRANCH_NOT_TAKEN; + break; + case 0x82: /* lpsw */ + fixup = FIXUP_NOT_REQUIRED; + break; + case 0xb2: /* lpswe */ + if ((insn[0] & 0xff) == 0xb2) + fixup = FIXUP_NOT_REQUIRED; + break; + case 0xa7: /* bras */ + if ((insn[0] & 0x0f) == 0x05) + fixup |= FIXUP_RETURN_REGISTER; + break; + case 0xc0: + if ((insn[0] & 0x0f) == 0x00 || /* larl */ + (insn[0] & 0x0f) == 0x05) /* brasl */ + fixup |= FIXUP_RETURN_REGISTER; + break; + case 0xeb: + if ((insn[2] & 0xff) == 0x44 || /* bxhg */ + (insn[2] & 0xff) == 0x45) /* bxleg */ + fixup = FIXUP_BRANCH_NOT_TAKEN; + break; + case 0xe3: /* bctg */ + if ((insn[2] & 0xff) == 0x46) + fixup = FIXUP_BRANCH_NOT_TAKEN; + break; + } + return fixup; +} + +int __kprobes arch_prepare_kprobe(struct kprobe *p) +{ + if ((unsigned long) p->addr & 0x01) + return -EINVAL; + + /* Make sure the probe isn't going on a difficult instruction */ + if (is_prohibited_opcode(p->addr)) + return -EINVAL; + + p->opcode = *p->addr; + memcpy(p->ainsn.insn, p->addr, ((p->opcode >> 14) + 3) & -2); + + return 0; +} + +struct ins_replace_args { + kprobe_opcode_t *ptr; + kprobe_opcode_t opcode; +}; + +static int __kprobes swap_instruction(void *aref) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + unsigned long status = kcb->kprobe_status; + struct ins_replace_args *args = aref; + + kcb->kprobe_status = KPROBE_SWAP_INST; + probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode)); + kcb->kprobe_status = status; + return 0; +} + +void __kprobes arch_arm_kprobe(struct kprobe *p) +{ + struct ins_replace_args args; + + args.ptr = p->addr; + args.opcode = BREAKPOINT_INSTRUCTION; + stop_machine(swap_instruction, &args, NULL); +} + +void __kprobes arch_disarm_kprobe(struct kprobe *p) +{ + struct ins_replace_args args; + + args.ptr = p->addr; + args.opcode = p->opcode; + stop_machine(swap_instruction, &args, NULL); +} + +void __kprobes arch_remove_kprobe(struct kprobe *p) +{ +} + +static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb, + struct pt_regs *regs, + unsigned long ip) +{ + struct per_regs per_kprobe; + + /* Set up the PER control registers %cr9-%cr11 */ + per_kprobe.control = PER_EVENT_IFETCH; + per_kprobe.start = ip; + per_kprobe.end = ip; + + /* Save control regs and psw mask */ + __ctl_store(kcb->kprobe_saved_ctl, 9, 11); + kcb->kprobe_saved_imask = regs->psw.mask & + (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT); + + /* Set PER control regs, turns on single step for the given address */ + __ctl_load(per_kprobe, 9, 11); + regs->psw.mask |= PSW_MASK_PER; + regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT); + regs->psw.addr = ip | PSW_ADDR_AMODE; +} + +static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb, + struct pt_regs *regs, + unsigned long ip) +{ + /* Restore control regs and psw mask, set new psw address */ + __ctl_load(kcb->kprobe_saved_ctl, 9, 11); + regs->psw.mask &= ~PSW_MASK_PER; + regs->psw.mask |= kcb->kprobe_saved_imask; + regs->psw.addr = ip | PSW_ADDR_AMODE; +} + +/* + * Activate a kprobe by storing its pointer to current_kprobe. The + * previous kprobe is stored in kcb->prev_kprobe. A stack of up to + * two kprobes can be active, see KPROBE_REENTER. + */ +static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p) +{ + kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe); + kcb->prev_kprobe.status = kcb->kprobe_status; + __get_cpu_var(current_kprobe) = p; +} + +/* + * Deactivate a kprobe by backing up to the previous state. If the + * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL, + * for any other state prev_kprobe.kp will be NULL. + */ +static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb) +{ + __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; + kcb->kprobe_status = kcb->prev_kprobe.status; +} + +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 void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb, + struct kprobe *p) +{ + switch (kcb->kprobe_status) { + case KPROBE_HIT_SSDONE: + case KPROBE_HIT_ACTIVE: + kprobes_inc_nmissed_count(p); + break; + case KPROBE_HIT_SS: + case KPROBE_REENTER: + default: + /* + * A kprobe on the code path to single step an instruction + * is a BUG. The code path resides in the .kprobes.text + * section and is executed with interrupts disabled. + */ + printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr); + dump_kprobe(p); + BUG(); + } +} + +static int __kprobes kprobe_handler(struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb; + struct kprobe *p; + + /* + * We want to disable preemption for the entire duration of kprobe + * processing. That includes the calls to the pre/post handlers + * and single stepping the kprobe instruction. + */ + preempt_disable(); + kcb = get_kprobe_ctlblk(); + p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2)); + + if (p) { + if (kprobe_running()) { + /* + * We have hit a kprobe while another is still + * active. This can happen in the pre and post + * handler. Single step the instruction of the + * new probe but do not call any handler function + * of this secondary kprobe. + * push_kprobe and pop_kprobe saves and restores + * the currently active kprobe. + */ + kprobe_reenter_check(kcb, p); + push_kprobe(kcb, p); + kcb->kprobe_status = KPROBE_REENTER; + } else { + /* + * If we have no pre-handler or it returned 0, we + * continue with single stepping. If we have a + * pre-handler and it returned non-zero, it prepped + * for calling the break_handler below on re-entry + * for jprobe processing, so get out doing nothing + * more here. + */ + push_kprobe(kcb, p); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + if (p->pre_handler && p->pre_handler(p, regs)) + return 1; + kcb->kprobe_status = KPROBE_HIT_SS; + } + enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn); + return 1; + } else if (kprobe_running()) { + p = __get_cpu_var(current_kprobe); + if (p->break_handler && p->break_handler(p, regs)) { + /* + * Continuation after the jprobe completed and + * caused the jprobe_return trap. The jprobe + * break_handler "returns" to the original + * function that still has the kprobe breakpoint + * installed. We continue with single stepping. + */ + kcb->kprobe_status = KPROBE_HIT_SS; + enable_singlestep(kcb, regs, + (unsigned long) p->ainsn.insn); + return 1; + } /* else: + * No kprobe at this address and the current kprobe + * has no break handler (no jprobe!). The kernel just + * exploded, let the standard trap handler pick up the + * pieces. + */ + } /* else: + * No kprobe at this address and no active kprobe. The trap has + * not been caused by a kprobe breakpoint. The race of breakpoint + * vs. kprobe remove does not exist because on s390 as we use + * stop_machine to arm/disarm the breakpoints. + */ + preempt_enable_no_resched(); + return 0; +} + +/* + * 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(".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; + struct hlist_head *head, empty_rp; + struct hlist_node *node, *tmp; + unsigned long flags, orig_ret_address; + unsigned long trampoline_address; + kprobe_opcode_t *correct_ret_addr; + + 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 an multiple functions in the call path + * have a return probe installed on them, and/or more than 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 + */ + ri = NULL; + orig_ret_address = 0; + correct_ret_addr = NULL; + trampoline_address = (unsigned long) &kretprobe_trampoline; + hlist_for_each_entry_safe(ri, node, 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, node, 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) { + ri->ret_addr = correct_ret_addr; + ri->rp->handler(ri, regs); + } + + 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; + } + + regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE; + + pop_kprobe(get_kprobe_ctlblk()); + kretprobe_hash_unlock(current, &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(); + unsigned long ip = regs->psw.addr & PSW_ADDR_INSN; + int fixup = get_fixup_type(p->ainsn.insn); + + if (fixup & FIXUP_PSW_NORMAL) + ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn; + + if (fixup & FIXUP_BRANCH_NOT_TAKEN) { + int ilen = ((p->ainsn.insn[0] >> 14) + 3) & -2; + if (ip - (unsigned long) p->ainsn.insn == ilen) + ip = (unsigned long) p->addr + ilen; + } + + if (fixup & FIXUP_RETURN_REGISTER) { + int reg = (p->ainsn.insn[0] & 0xf0) >> 4; + regs->gprs[reg] += (unsigned long) p->addr - + (unsigned long) p->ainsn.insn; + } + + disable_singlestep(kcb, regs, ip); +} + +static int __kprobes post_kprobe_handler(struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + struct kprobe *p = kprobe_running(); + + if (!p) + return 0; + + if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + p->post_handler(p, regs, 0); + } + + resume_execution(p, regs); + pop_kprobe(kcb); + 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; +} + +static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + struct kprobe *p = kprobe_running(); + 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. + */ + disable_singlestep(kcb, regs, (unsigned long) p->addr); + pop_kprobe(kcb); + 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(p); + + /* + * 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 (p->fault_handler && p->fault_handler(p, 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; +} + +int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) +{ + int ret; + + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_disable(); + ret = kprobe_trap_handler(regs, trapnr); + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_restore(regs->psw.mask & ~PSW_MASK_PER); + return ret; +} + +/* + * 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; + struct pt_regs *regs = args->regs; + int ret = NOTIFY_DONE; + + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_disable(); + + switch (val) { + case DIE_BPT: + if (kprobe_handler(regs)) + ret = NOTIFY_STOP; + break; + case DIE_SSTEP: + if (post_kprobe_handler(regs)) + ret = NOTIFY_STOP; + break; + case DIE_TRAP: + if (!preemptible() && kprobe_running() && + kprobe_trap_handler(regs, args->trapnr)) + ret = NOTIFY_STOP; + break; + default: + break; + } + + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_restore(regs->psw.mask & ~PSW_MASK_PER); + + return ret; +} + +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(); + unsigned long stack; + + 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; + regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT); + + /* r15 is the stack pointer */ + stack = (unsigned long) regs->gprs[15]; + + memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack)); + return 1; +} + +void __kprobes jprobe_return(void) +{ + asm volatile(".word 0x0002"); +} + +static void __used __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; + + stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15]; + + /* Put the regs back */ + memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); + /* put the stack back */ + memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack)); + preempt_enable_no_resched(); + return 1; +} + +static struct kprobe trampoline = { + .addr = (kprobe_opcode_t *) &kretprobe_trampoline, + .pre_handler = trampoline_probe_handler +}; + +int __init arch_init_kprobes(void) +{ + return register_kprobe(&trampoline); +} + +int __kprobes arch_trampoline_kprobe(struct kprobe *p) +{ + return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline; +} |