1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * arch/parisc/kernel/kprobes.c
  4 *
  5 * PA-RISC kprobes implementation
  6 *
  7 * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
  8 */
  9
 10#include <linux/types.h>
 11#include <linux/kprobes.h>
 12#include <linux/slab.h>
 13#include <asm/cacheflush.h>
 14#include <asm/patch.h>
 15
 16DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 17DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 18
 19int __kprobes arch_prepare_kprobe(struct kprobe *p)
 20{
 21	if ((unsigned long)p->addr & 3UL)
 22		return -EINVAL;
 23
 24	p->ainsn.insn = get_insn_slot();
 25	if (!p->ainsn.insn)
 26		return -ENOMEM;
 27
 28	memcpy(p->ainsn.insn, p->addr,
 29		MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
 30	p->opcode = *p->addr;
 31	flush_insn_slot(p);
 32	return 0;
 33}
 34
 35void __kprobes arch_remove_kprobe(struct kprobe *p)
 36{
 37	if (!p->ainsn.insn)
 38		return;
 39
 40	free_insn_slot(p->ainsn.insn, 0);
 41	p->ainsn.insn = NULL;
 42}
 43
 44void __kprobes arch_arm_kprobe(struct kprobe *p)
 45{
 46	patch_text(p->addr, PARISC_KPROBES_BREAK_INSN);
 47}
 48
 49void __kprobes arch_disarm_kprobe(struct kprobe *p)
 50{
 51	patch_text(p->addr, p->opcode);
 52}
 53
 54static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 55{
 56	kcb->prev_kprobe.kp = kprobe_running();
 57	kcb->prev_kprobe.status = kcb->kprobe_status;
 58}
 59
 60static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 61{
 62	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 63	kcb->kprobe_status = kcb->prev_kprobe.status;
 64}
 65
 66static inline void __kprobes set_current_kprobe(struct kprobe *p)
 67{
 68	__this_cpu_write(current_kprobe, p);
 69}
 70
 71static void __kprobes setup_singlestep(struct kprobe *p,
 72		struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 73{
 74	kcb->iaoq[0] = regs->iaoq[0];
 75	kcb->iaoq[1] = regs->iaoq[1];
 76	regs->iaoq[0] = (unsigned long)p->ainsn.insn;
 77	mtctl(0, 0);
 78	regs->gr[0] |= PSW_R;
 79}
 80
 81int __kprobes parisc_kprobe_break_handler(struct pt_regs *regs)
 82{
 83	struct kprobe *p;
 84	struct kprobe_ctlblk *kcb;
 85
 86	preempt_disable();
 87
 88	kcb = get_kprobe_ctlblk();
 89	p = get_kprobe((unsigned long *)regs->iaoq[0]);
 90
 91	if (!p) {
 92		preempt_enable_no_resched();
 93		return 0;
 94	}
 95
 96	if (kprobe_running()) {
 97		/*
 98		 * We have reentered the kprobe_handler, since another kprobe
 99		 * was hit while within the handler, we save the original
100		 * kprobes and single step on the instruction of the new probe
101		 * without calling any user handlers to avoid recursive
102		 * kprobes.
103		 */
104		save_previous_kprobe(kcb);
105		set_current_kprobe(p);
106		kprobes_inc_nmissed_count(p);
107		setup_singlestep(p, kcb, regs);
108		kcb->kprobe_status = KPROBE_REENTER;
109		return 1;
110	}
111
112	set_current_kprobe(p);
113	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
114
115	/* If we have no pre-handler or it returned 0, we continue with
116	 * normal processing. If we have a pre-handler and it returned
117	 * non-zero - which means user handler setup registers to exit
118	 * to another instruction, we must skip the single stepping.
119	 */
120
121	if (!p->pre_handler || !p->pre_handler(p, regs)) {
122		setup_singlestep(p, kcb, regs);
123		kcb->kprobe_status = KPROBE_HIT_SS;
124	} else {
125		reset_current_kprobe();
126		preempt_enable_no_resched();
127	}
128	return 1;
129}
130
131int __kprobes parisc_kprobe_ss_handler(struct pt_regs *regs)
132{
133	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
134	struct kprobe *p = kprobe_running();
135
136	if (!p)
137		return 0;
138
139	if (regs->iaoq[0] != (unsigned long)p->ainsn.insn+4)
140		return 0;
141
142	/* restore back original saved kprobe variables and continue */
143	if (kcb->kprobe_status == KPROBE_REENTER) {
144		restore_previous_kprobe(kcb);
145		return 1;
146	}
147
148	/* for absolute branch instructions we can copy iaoq_b. for relative
149	 * branch instructions we need to calculate the new address based on the
150	 * difference between iaoq_f and iaoq_b. We cannot use iaoq_b without
151	 * modificationt because it's based on our ainsn.insn address.
152	 */
153
154	if (p->post_handler)
155		p->post_handler(p, regs, 0);
156
157	switch (regs->iir >> 26) {
158	case 0x38: /* BE */
159	case 0x39: /* BE,L */
160	case 0x3a: /* BV */
161	case 0x3b: /* BVE */
162		/* for absolute branches, regs->iaoq[1] has already the right
163		 * address
164		 */
165		regs->iaoq[0] = kcb->iaoq[1];
166		break;
167	default:
168		regs->iaoq[1] = kcb->iaoq[0];
169		regs->iaoq[1] += (regs->iaoq[1] - regs->iaoq[0]) + 4;
170		regs->iaoq[0] = kcb->iaoq[1];
171		break;
172	}
173	kcb->kprobe_status = KPROBE_HIT_SSDONE;
174	reset_current_kprobe();
175	return 1;
176}
177
178static inline void kretprobe_trampoline(void)
179{
180	asm volatile("nop");
181	asm volatile("nop");
182}
183
184static int __kprobes trampoline_probe_handler(struct kprobe *p,
185					      struct pt_regs *regs);
186
187static struct kprobe trampoline_p = {
188	.pre_handler = trampoline_probe_handler
189};
190
191static int __kprobes trampoline_probe_handler(struct kprobe *p,
192					      struct pt_regs *regs)
193{
194	unsigned long orig_ret_address;
195
196	orig_ret_address = __kretprobe_trampoline_handler(regs, trampoline_p.addr, NULL);
197	instruction_pointer_set(regs, orig_ret_address);
198
199	return 1;
200}
201
202void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
203				      struct pt_regs *regs)
204{
205	ri->ret_addr = (kprobe_opcode_t *)regs->gr[2];
206	ri->fp = NULL;
207
208	/* Replace the return addr with trampoline addr. */
209	regs->gr[2] = (unsigned long)trampoline_p.addr;
210}
211
212int __kprobes arch_trampoline_kprobe(struct kprobe *p)
213{
214	return p->addr == trampoline_p.addr;
215}
216
217int __init arch_init_kprobes(void)
218{
219	trampoline_p.addr = (kprobe_opcode_t *)
220		dereference_function_descriptor(kretprobe_trampoline);
221	return register_kprobe(&trampoline_p);
222}