blob: f0cf20d4b3c58070159b9a64b250ec4af12add53 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0+
/*
* Kernel Probes (KProbes)
*
* Copyright IBM Corp. 2002, 2006
*
* s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
*/
#define pr_fmt(fmt) "kprobes: " fmt
#include <linux/moduleloader.h>
#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 <linux/extable.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/hardirq.h>
#include <linux/ftrace.h>
#include <asm/set_memory.h>
#include <asm/sections.h>
#include <asm/dis.h>
#include "kprobes.h"
#include "entry.h"
DEFINE_PER_CPU(struct kprobe *, current_kprobe);
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
struct kretprobe_blackpoint kretprobe_blacklist[] = { };
static int insn_page_in_use;
void *alloc_insn_page(void)
{
void *page;
page = module_alloc(PAGE_SIZE);
if (!page)
return NULL;
set_memory_rox((unsigned long)page, 1);
return page;
}
static void *alloc_s390_insn_page(void)
{
if (xchg(&insn_page_in_use, 1) == 1)
return NULL;
return &kprobes_insn_page;
}
static void free_s390_insn_page(void *page)
{
xchg(&insn_page_in_use, 0);
}
struct kprobe_insn_cache kprobe_s390_insn_slots = {
.mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
.alloc = alloc_s390_insn_page,
.free = free_s390_insn_page,
.pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
.insn_size = MAX_INSN_SIZE,
};
static void copy_instruction(struct kprobe *p)
{
kprobe_opcode_t insn[MAX_INSN_SIZE];
s64 disp, new_disp;
u64 addr, new_addr;
unsigned int len;
len = insn_length(*p->addr >> 8);
memcpy(&insn, p->addr, len);
p->opcode = insn[0];
if (probe_is_insn_relative_long(&insn[0])) {
/*
* For pc-relative instructions in RIL-b or RIL-c format patch
* the RI2 displacement field. We have already made sure that
* the insn slot for the patched instruction is within the same
* 2GB area as the original instruction (either kernel image or
* module area). Therefore the new displacement will always fit.
*/
disp = *(s32 *)&insn[1];
addr = (u64)(unsigned long)p->addr;
new_addr = (u64)(unsigned long)p->ainsn.insn;
new_disp = ((addr + (disp * 2)) - new_addr) / 2;
*(s32 *)&insn[1] = new_disp;
}
s390_kernel_write(p->ainsn.insn, &insn, len);
}
NOKPROBE_SYMBOL(copy_instruction);
static int s390_get_insn_slot(struct kprobe *p)
{
/*
* Get an insn slot that is within the same 2GB area like the original
* instruction. That way instructions with a 32bit signed displacement
* field can be patched and executed within the insn slot.
*/
p->ainsn.insn = NULL;
if (is_kernel((unsigned long)p->addr))
p->ainsn.insn = get_s390_insn_slot();
else if (is_module_addr(p->addr))
p->ainsn.insn = get_insn_slot();
return p->ainsn.insn ? 0 : -ENOMEM;
}
NOKPROBE_SYMBOL(s390_get_insn_slot);
static void s390_free_insn_slot(struct kprobe *p)
{
if (!p->ainsn.insn)
return;
if (is_kernel((unsigned long)p->addr))
free_s390_insn_slot(p->ainsn.insn, 0);
else
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
NOKPROBE_SYMBOL(s390_free_insn_slot);
/* Check if paddr is at an instruction boundary */
static bool can_probe(unsigned long paddr)
{
unsigned long addr, offset = 0;
kprobe_opcode_t insn;
struct kprobe *kp;
if (paddr & 0x01)
return false;
if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
return false;
/* Decode instructions */
addr = paddr - offset;
while (addr < paddr) {
if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
return false;
if (insn >> 8 == 0) {
if (insn != BREAKPOINT_INSTRUCTION) {
/*
* Note that QEMU inserts opcode 0x0000 to implement
* software breakpoints for guests. Since the size of
* the original instruction is unknown, stop following
* instructions and prevent setting a kprobe.
*/
return false;
}
/*
* Check if the instruction has been modified by another
* kprobe, in which case the original instruction is
* decoded.
*/
kp = get_kprobe((void *)addr);
if (!kp) {
/* not a kprobe */
return false;
}
insn = kp->opcode;
}
addr += insn_length(insn >> 8);
}
return addr == paddr;
}
int arch_prepare_kprobe(struct kprobe *p)
{
if (!can_probe((unsigned long)p->addr))
return -EINVAL;
/* Make sure the probe isn't going on a difficult instruction */
if (probe_is_prohibited_opcode(p->addr))
return -EINVAL;
if (s390_get_insn_slot(p))
return -ENOMEM;
copy_instruction(p);
return 0;
}
NOKPROBE_SYMBOL(arch_prepare_kprobe);
struct swap_insn_args {
struct kprobe *p;
unsigned int arm_kprobe : 1;
};
static int swap_instruction(void *data)
{
struct swap_insn_args *args = data;
struct kprobe *p = args->p;
u16 opc;
opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
s390_kernel_write(p->addr, &opc, sizeof(opc));
return 0;
}
NOKPROBE_SYMBOL(swap_instruction);
void arch_arm_kprobe(struct kprobe *p)
{
struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
stop_machine_cpuslocked(swap_instruction, &args, NULL);
}
NOKPROBE_SYMBOL(arch_arm_kprobe);
void arch_disarm_kprobe(struct kprobe *p)
{
struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
stop_machine_cpuslocked(swap_instruction, &args, NULL);
}
NOKPROBE_SYMBOL(arch_disarm_kprobe);
void arch_remove_kprobe(struct kprobe *p)
{
s390_free_insn_slot(p);
}
NOKPROBE_SYMBOL(arch_remove_kprobe);
static void enable_singlestep(struct kprobe_ctlblk *kcb,
struct pt_regs *regs,
unsigned long ip)
{
union {
struct ctlreg regs[3];
struct {
struct ctlreg control;
struct ctlreg start;
struct ctlreg end;
};
} per_kprobe;
/* Set up the PER control registers %cr9-%cr11 */
per_kprobe.control.val = PER_EVENT_IFETCH;
per_kprobe.start.val = ip;
per_kprobe.end.val = ip;
/* Save control regs and psw mask */
__local_ctl_store(9, 11, kcb->kprobe_saved_ctl);
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 */
__local_ctl_load(9, 11, per_kprobe.regs);
regs->psw.mask |= PSW_MASK_PER;
regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
regs->psw.addr = ip;
}
NOKPROBE_SYMBOL(enable_singlestep);
static void disable_singlestep(struct kprobe_ctlblk *kcb,
struct pt_regs *regs,
unsigned long ip)
{
/* Restore control regs and psw mask, set new psw address */
__local_ctl_load(9, 11, kcb->kprobe_saved_ctl);
regs->psw.mask &= ~PSW_MASK_PER;
regs->psw.mask |= kcb->kprobe_saved_imask;
regs->psw.addr = ip;
}
NOKPROBE_SYMBOL(disable_singlestep);
/*
* 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 push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
{
kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
kcb->prev_kprobe.status = kcb->kprobe_status;
__this_cpu_write(current_kprobe, p);
}
NOKPROBE_SYMBOL(push_kprobe);
/*
* 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 pop_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
kcb->prev_kprobe.kp = NULL;
}
NOKPROBE_SYMBOL(pop_kprobe);
static void 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.
*/
pr_err("Failed to recover from reentered kprobes.\n");
dump_kprobe(p);
BUG();
}
}
NOKPROBE_SYMBOL(kprobe_reenter_check);
static int 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 - 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 changing execution path, 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)) {
pop_kprobe(kcb);
preempt_enable_no_resched();
return 1;
}
kcb->kprobe_status = KPROBE_HIT_SS;
}
enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
return 1;
} /* 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;
}
NOKPROBE_SYMBOL(kprobe_handler);
/*
* 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 resume_execution(struct kprobe *p, struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
unsigned long ip = regs->psw.addr;
int fixup = probe_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 = insn_length(p->ainsn.insn[0] >> 8);
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);
}
NOKPROBE_SYMBOL(resume_execution);
static int post_kprobe_handler(struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe *p = kprobe_running();
if (!p)
return 0;
resume_execution(p, regs);
if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0);
}
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;
}
NOKPROBE_SYMBOL(post_kprobe_handler);
static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe *p = kprobe_running();
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 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:
/*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
if (fixup_exception(regs))
return 1;
/*
* fixup_exception() could not handle it,
* Let do_page_fault() fix it.
*/
break;
default:
break;
}
return 0;
}
NOKPROBE_SYMBOL(kprobe_trap_handler);
int 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;
}
NOKPROBE_SYMBOL(kprobe_fault_handler);
/*
* Wrapper routine to for handling exceptions.
*/
int 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;
}
NOKPROBE_SYMBOL(kprobe_exceptions_notify);
int __init arch_init_kprobes(void)
{
return 0;
}
int arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}
NOKPROBE_SYMBOL(arch_trampoline_kprobe);