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// SPDX-License-Identifier: GPL-2.0
/*
* arch/parisc/kernel/kprobes.c
*
* PA-RISC kprobes implementation
*
* Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
* Copyright (c) 2022 Helge Deller <deller@gmx.de>
*/
#include <linux/types.h>
#include <linux/kprobes.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <asm/patch.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)
{
if ((unsigned long)p->addr & 3UL)
return -EINVAL;
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
return -ENOMEM;
/*
* Set up new instructions. Second break instruction will
* trigger call of parisc_kprobe_ss_handler().
*/
p->opcode = *p->addr;
p->ainsn.insn[0] = p->opcode;
p->ainsn.insn[1] = PARISC_KPROBES_BREAK_INSN2;
flush_insn_slot(p);
return 0;
}
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
if (!p->ainsn.insn)
return;
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
patch_text(p->addr, PARISC_KPROBES_BREAK_INSN);
}
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
patch_text(p->addr, p->opcode);
}
static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
}
static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
}
static inline void __kprobes set_current_kprobe(struct kprobe *p)
{
__this_cpu_write(current_kprobe, p);
}
static void __kprobes setup_singlestep(struct kprobe *p,
struct kprobe_ctlblk *kcb, struct pt_regs *regs)
{
kcb->iaoq[0] = regs->iaoq[0];
kcb->iaoq[1] = regs->iaoq[1];
instruction_pointer_set(regs, (unsigned long)p->ainsn.insn);
}
int __kprobes parisc_kprobe_break_handler(struct pt_regs *regs)
{
struct kprobe *p;
struct kprobe_ctlblk *kcb;
preempt_disable();
kcb = get_kprobe_ctlblk();
p = get_kprobe((unsigned long *)regs->iaoq[0]);
if (!p) {
preempt_enable_no_resched();
return 0;
}
if (kprobe_running()) {
/*
* We have reentered the kprobe_handler, since another kprobe
* was hit while within the handler, we save the original
* kprobes and single step on the instruction of the new probe
* without calling any user handlers to avoid recursive
* kprobes.
*/
save_previous_kprobe(kcb);
set_current_kprobe(p);
kprobes_inc_nmissed_count(p);
setup_singlestep(p, kcb, regs);
kcb->kprobe_status = KPROBE_REENTER;
return 1;
}
set_current_kprobe(p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
/* If we have no pre-handler or it returned 0, we continue with
* normal processing. If we have a pre-handler and it returned
* non-zero - which means user handler setup registers to exit
* to another instruction, we must skip the single stepping.
*/
if (!p->pre_handler || !p->pre_handler(p, regs)) {
setup_singlestep(p, kcb, regs);
kcb->kprobe_status = KPROBE_HIT_SS;
} else {
reset_current_kprobe();
preempt_enable_no_resched();
}
return 1;
}
int __kprobes parisc_kprobe_ss_handler(struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe *p = kprobe_running();
if (!p)
return 0;
if (regs->iaoq[0] != (unsigned long)p->ainsn.insn+4)
return 0;
/* restore back original saved kprobe variables and continue */
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
return 1;
}
/* for absolute branch instructions we can copy iaoq_b. for relative
* branch instructions we need to calculate the new address based on the
* difference between iaoq_f and iaoq_b. We cannot use iaoq_b without
* modifications because it's based on our ainsn.insn address.
*/
if (p->post_handler)
p->post_handler(p, regs, 0);
switch (regs->iir >> 26) {
case 0x38: /* BE */
case 0x39: /* BE,L */
case 0x3a: /* BV */
case 0x3b: /* BVE */
/* for absolute branches, regs->iaoq[1] has already the right
* address
*/
regs->iaoq[0] = kcb->iaoq[1];
break;
default:
regs->iaoq[0] = kcb->iaoq[1];
regs->iaoq[1] = regs->iaoq[0] + 4;
break;
}
kcb->kprobe_status = KPROBE_HIT_SSDONE;
reset_current_kprobe();
return 1;
}
void __kretprobe_trampoline(void)
{
asm volatile("nop");
asm volatile("nop");
}
static int __kprobes trampoline_probe_handler(struct kprobe *p,
struct pt_regs *regs);
static struct kprobe trampoline_p = {
.pre_handler = trampoline_probe_handler
};
static int __kprobes trampoline_probe_handler(struct kprobe *p,
struct pt_regs *regs)
{
__kretprobe_trampoline_handler(regs, NULL);
return 1;
}
void arch_kretprobe_fixup_return(struct pt_regs *regs,
kprobe_opcode_t *correct_ret_addr)
{
regs->gr[2] = (unsigned long)correct_ret_addr;
}
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
ri->ret_addr = (kprobe_opcode_t *)regs->gr[2];
ri->fp = NULL;
/* Replace the return addr with trampoline addr. */
regs->gr[2] = (unsigned long)trampoline_p.addr;
}
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
return p->addr == trampoline_p.addr;
}
int __init arch_init_kprobes(void)
{
trampoline_p.addr = (kprobe_opcode_t *)
dereference_function_descriptor(__kretprobe_trampoline);
return register_kprobe(&trampoline_p);
}
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