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 * Copyright (c) 2022 Helge Deller <deller@gmx.de>
9 */
10
11#include <linux/types.h>
12#include <linux/kprobes.h>
13#include <linux/slab.h>
14#include <asm/cacheflush.h>
15#include <asm/patch.h>
16
17DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
18DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
19
20int __kprobes arch_prepare_kprobe(struct kprobe *p)
21{
22	if ((unsigned long)p->addr & 3UL)
23		return -EINVAL;
24
25	p->ainsn.insn = get_insn_slot();
26	if (!p->ainsn.insn)
27		return -ENOMEM;
28
29	/*
30	 * Set up new instructions. Second break instruction will
31	 * trigger call of parisc_kprobe_ss_handler().
32	 */
33	p->opcode = *p->addr;
34	p->ainsn.insn[0] = p->opcode;
35	p->ainsn.insn[1] = PARISC_KPROBES_BREAK_INSN2;
36
37	flush_insn_slot(p);
38	return 0;
39}
40
41void __kprobes arch_remove_kprobe(struct kprobe *p)
42{
43	if (!p->ainsn.insn)
44		return;
45
46	free_insn_slot(p->ainsn.insn, 0);
47	p->ainsn.insn = NULL;
48}
49
50void __kprobes arch_arm_kprobe(struct kprobe *p)
51{
52	patch_text(p->addr, PARISC_KPROBES_BREAK_INSN);
53}
54
55void __kprobes arch_disarm_kprobe(struct kprobe *p)
56{
57	patch_text(p->addr, p->opcode);
58}
59
60static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
61{
62	kcb->prev_kprobe.kp = kprobe_running();
63	kcb->prev_kprobe.status = kcb->kprobe_status;
64}
65
66static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
67{
68	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
69	kcb->kprobe_status = kcb->prev_kprobe.status;
70}
71
72static inline void __kprobes set_current_kprobe(struct kprobe *p)
73{
74	__this_cpu_write(current_kprobe, p);
75}
76
77static void __kprobes setup_singlestep(struct kprobe *p,
78		struct kprobe_ctlblk *kcb, struct pt_regs *regs)
79{
80	kcb->iaoq[0] = regs->iaoq[0];
81	kcb->iaoq[1] = regs->iaoq[1];
82	instruction_pointer_set(regs, (unsigned long)p->ainsn.insn);
83}
84
85int __kprobes parisc_kprobe_break_handler(struct pt_regs *regs)
86{
87	struct kprobe *p;
88	struct kprobe_ctlblk *kcb;
89
90	preempt_disable();
91
92	kcb = get_kprobe_ctlblk();
93	p = get_kprobe((unsigned long *)regs->iaoq[0]);
94
95	if (!p) {
96		preempt_enable_no_resched();
97		return 0;
98	}
99
100	if (kprobe_running()) {
101		/*
102		 * We have reentered the kprobe_handler, since another kprobe
103		 * was hit while within the handler, we save the original
104		 * kprobes and single step on the instruction of the new probe
105		 * without calling any user handlers to avoid recursive
106		 * kprobes.
107		 */
108		save_previous_kprobe(kcb);
109		set_current_kprobe(p);
110		kprobes_inc_nmissed_count(p);
111		setup_singlestep(p, kcb, regs);
112		kcb->kprobe_status = KPROBE_REENTER;
113		return 1;
114	}
115
116	set_current_kprobe(p);
117	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
118
119	/* If we have no pre-handler or it returned 0, we continue with
120	 * normal processing. If we have a pre-handler and it returned
121	 * non-zero - which means user handler setup registers to exit
122	 * to another instruction, we must skip the single stepping.
123	 */
124
125	if (!p->pre_handler || !p->pre_handler(p, regs)) {
126		setup_singlestep(p, kcb, regs);
127		kcb->kprobe_status = KPROBE_HIT_SS;
128	} else {
129		reset_current_kprobe();
130		preempt_enable_no_resched();
131	}
132	return 1;
133}
134
135int __kprobes parisc_kprobe_ss_handler(struct pt_regs *regs)
136{
137	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
138	struct kprobe *p = kprobe_running();
139
140	if (!p)
141		return 0;
142
143	if (regs->iaoq[0] != (unsigned long)p->ainsn.insn+4)
144		return 0;
145
146	/* restore back original saved kprobe variables and continue */
147	if (kcb->kprobe_status == KPROBE_REENTER) {
148		restore_previous_kprobe(kcb);
149		return 1;
150	}
151
152	/* for absolute branch instructions we can copy iaoq_b. for relative
153	 * branch instructions we need to calculate the new address based on the
154	 * difference between iaoq_f and iaoq_b. We cannot use iaoq_b without
155	 * modifications because it's based on our ainsn.insn address.
156	 */
157
158	if (p->post_handler)
159		p->post_handler(p, regs, 0);
160
161	switch (regs->iir >> 26) {
162	case 0x38: /* BE */
163	case 0x39: /* BE,L */
164	case 0x3a: /* BV */
165	case 0x3b: /* BVE */
166		/* for absolute branches, regs->iaoq[1] has already the right
167		 * address
168		 */
169		regs->iaoq[0] = kcb->iaoq[1];
170		break;
171	default:
172		regs->iaoq[0] = kcb->iaoq[1];
173		regs->iaoq[1] = regs->iaoq[0] + 4;
174		break;
175	}
176	kcb->kprobe_status = KPROBE_HIT_SSDONE;
177	reset_current_kprobe();
178	return 1;
179}
180
181void __kretprobe_trampoline(void)
182{
183	asm volatile("nop");
184	asm volatile("nop");
185}
186
187static int __kprobes trampoline_probe_handler(struct kprobe *p,
188					      struct pt_regs *regs);
189
190static struct kprobe trampoline_p = {
191	.pre_handler = trampoline_probe_handler
192};
193
194static int __kprobes trampoline_probe_handler(struct kprobe *p,
195					      struct pt_regs *regs)
196{
197	__kretprobe_trampoline_handler(regs, NULL);
198
199	return 1;
200}
201
202void arch_kretprobe_fixup_return(struct pt_regs *regs,
203				 kprobe_opcode_t *correct_ret_addr)
204{
205	regs->gr[2] = (unsigned long)correct_ret_addr;
206}
207
208void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
209				      struct pt_regs *regs)
210{
211	ri->ret_addr = (kprobe_opcode_t *)regs->gr[2];
212	ri->fp = NULL;
213
214	/* Replace the return addr with trampoline addr. */
215	regs->gr[2] = (unsigned long)trampoline_p.addr;
216}
217
218int __kprobes arch_trampoline_kprobe(struct kprobe *p)
219{
220	return p->addr == trampoline_p.addr;
221}
222
223int __init arch_init_kprobes(void)
224{
225	trampoline_p.addr = (kprobe_opcode_t *)
226		dereference_function_descriptor(__kretprobe_trampoline);
227	return register_kprobe(&trampoline_p);
228}
229