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
17 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
18 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
19
20 int __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
41 void __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
50 void __kprobes arch_arm_kprobe(struct kprobe *p)
51 {
52 patch_text(p->addr, PARISC_KPROBES_BREAK_INSN);
53 }
54
55 void __kprobes arch_disarm_kprobe(struct kprobe *p)
56 {
57 patch_text(p->addr, p->opcode);
58 }
59
60 static 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
66 static 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
72 static inline void __kprobes set_current_kprobe(struct kprobe *p)
73 {
74 __this_cpu_write(current_kprobe, p);
75 }
76
77 static 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
85 int __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
135 int __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
181 void __kretprobe_trampoline(void)
182 {
183 asm volatile("nop");
184 asm volatile("nop");
185 }
186
187 static int __kprobes trampoline_probe_handler(struct kprobe *p,
188 struct pt_regs *regs);
189
190 static struct kprobe trampoline_p = {
191 .pre_handler = trampoline_probe_handler
192 };
193
194 static 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
202 void 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
208 void __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
218 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
219 {
220 return p->addr == trampoline_p.addr;
221 }
222
223 int __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
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