// 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>
*/
#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>
DEFINE_PER_CPU(struct kprobe *, current_kprobe);
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
struct kretprobe_blackpoint kretprobe_blacklist[] = { };
DEFINE_INSN_CACHE_OPS(s390_insn);
static int insn_page_in_use;
static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE);
static void *alloc_s390_insn_page(void)
{
if (xchg(&insn_page_in_use, 1) == 1)
return NULL;
set_memory_x((unsigned long) &insn_page, 1);
return &insn_page;
}
static void free_s390_insn_page(void *page)
{
set_memory_nx((unsigned long) page, 1);
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)
{
unsigned long ip = (unsigned long) p->addr;
s64 disp, new_disp;
u64 addr, new_addr;
if (ftrace_location(ip) == ip) {
/*
* If kprobes patches the instruction that is morphed by
* ftrace make sure that kprobes always sees the branch
* "jg .+24" that skips the mcount block or the "brcl 0,0"
* in case of hotpatch.
*/
ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
p->ainsn.is_ftrace_insn = 1;
} else
memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
p->opcode = p->ainsn.insn[0];
if (!probe_is_insn_relative_long(p->ainsn.insn))
return;
/*
* 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 *)&p->ainsn.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 *)&p->ainsn.insn[1] = new_disp;
}
NOKPROBE_SYMBOL(copy_instruction);
static inline int is_kernel_addr(void *addr)
{
return addr < (void *)_end;
}
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_addr(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_addr(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);
int 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 (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);
int arch_check_ftrace_location(struct kprobe *p)
{
return 0;
}
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 ftrace_insn new_insn, *insn;
struct kprobe *p = args->p;
size_t len;
new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
len = sizeof(new_insn.opc);
if (!p->ainsn.is_ftrace_insn)
goto skip_ftrace;
len = sizeof(new_insn);
insn = (struct ftrace_insn *) p->addr;
if (args->arm_kprobe) {
if (is_ftrace_nop(insn))
new_insn.disp = KPROBE_ON_FTRACE_NOP;
else
new_insn.disp = KPROBE_ON_FTRACE_CALL;
} else {
ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
if (insn->disp == KPROBE_ON_FTRACE_NOP)
ftrace_generate_nop_insn(&new_insn);
}
skip_ftrace:
s390_kernel_write(p->addr, &new_insn, len);
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)
{
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;
}
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 */
__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;
}
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;
}
NOKPROBE_SYMBOL(pop_kprobe);
void 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;
}
NOKPROBE_SYMBOL(arch_prepare_kretprobe);
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("Invalid kprobe detected.\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);
/*
* 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 trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
struct kretprobe_instance *ri;
struct hlist_head *head, empty_rp;
struct hlist_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, 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, 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;
kretprobe_hash_unlock(current, &flags);
hlist_for_each_entry_safe(ri, 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;
}
NOKPROBE_SYMBOL(trampoline_probe_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);
/* Check if the kprobes location is an enabled ftrace caller */
if (p->ainsn.is_ftrace_insn) {
struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
struct ftrace_insn call_insn;
ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
/*
* A kprobe on an enabled ftrace call site actually single
* stepped an unconditional branch (ftrace nop equivalent).
* Now we need to fixup things and pretend that a brasl r0,...
* was executed instead.
*/
if (insn->disp == KPROBE_ON_FTRACE_CALL) {
ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
regs->gprs[0] = (unsigned long)p->addr + sizeof(*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;
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;
}
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();
const struct exception_table_entry *entry;
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:
/*
* We increment the nmissed count for accounting,
* we can also use npre/npostfault count for accounting
* 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 = s390_search_extables(regs->psw.addr);
if (entry) {
regs->psw.addr = extable_fixup(entry);
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);
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 arch_trampoline_kprobe(struct kprobe *p)
{
return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
}
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
