/*
* 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;
}
