1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/kdebug.h>
  3#include <linux/kprobes.h>
  4#include <linux/preempt.h>
  5#include <asm/break.h>
  6
  7#define KPROBE_BP_INSN		larch_insn_gen_break(BRK_KPROBE_BP)
  8#define KPROBE_SSTEPBP_INSN	larch_insn_gen_break(BRK_KPROBE_SSTEPBP)
  9
 10DEFINE_PER_CPU(struct kprobe *, current_kprobe);
 11DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 12
 13static void arch_prepare_ss_slot(struct kprobe *p)
 14{
 15	p->ainsn.insn[0] = *p->addr;
 16	p->ainsn.insn[1] = KPROBE_SSTEPBP_INSN;
 17	p->ainsn.restore = (unsigned long)p->addr + LOONGARCH_INSN_SIZE;
 18}
 19NOKPROBE_SYMBOL(arch_prepare_ss_slot);
 20
 21static void arch_prepare_simulate(struct kprobe *p)
 22{
 23	p->ainsn.restore = 0;
 24}
 25NOKPROBE_SYMBOL(arch_prepare_simulate);
 26
 27int arch_prepare_kprobe(struct kprobe *p)
 28{
 29	union loongarch_instruction insn;
 30
 31	if ((unsigned long)p->addr & 0x3)
 32		return -EILSEQ;
 33
 34	/* copy instruction */
 35	p->opcode = *p->addr;
 36	insn.word = p->opcode;
 37
 38	/* decode instruction */
 39	if (insns_not_supported(insn))
 40		return -EINVAL;
 41
 42	if (insns_need_simulation(insn)) {
 43		p->ainsn.insn = NULL;
 44	} else {
 45		p->ainsn.insn = get_insn_slot();
 46		if (!p->ainsn.insn)
 47			return -ENOMEM;
 48	}
 49
 50	/* prepare the instruction */
 51	if (p->ainsn.insn)
 52		arch_prepare_ss_slot(p);
 53	else
 54		arch_prepare_simulate(p);
 55
 56	return 0;
 57}
 58NOKPROBE_SYMBOL(arch_prepare_kprobe);
 59
 60/* Install breakpoint in text */
 61void arch_arm_kprobe(struct kprobe *p)
 62{
 63	*p->addr = KPROBE_BP_INSN;
 64	flush_insn_slot(p);
 65}
 66NOKPROBE_SYMBOL(arch_arm_kprobe);
 67
 68/* Remove breakpoint from text */
 69void arch_disarm_kprobe(struct kprobe *p)
 70{
 71	*p->addr = p->opcode;
 72	flush_insn_slot(p);
 73}
 74NOKPROBE_SYMBOL(arch_disarm_kprobe);
 75
 76void arch_remove_kprobe(struct kprobe *p)
 77{
 78	if (p->ainsn.insn) {
 79		free_insn_slot(p->ainsn.insn, 0);
 80		p->ainsn.insn = NULL;
 81	}
 82}
 83NOKPROBE_SYMBOL(arch_remove_kprobe);
 84
 85static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
 86{
 87	kcb->prev_kprobe.kp = kprobe_running();
 88	kcb->prev_kprobe.status = kcb->kprobe_status;
 89}
 90NOKPROBE_SYMBOL(save_previous_kprobe);
 91
 92static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 93{
 94	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 95	kcb->kprobe_status = kcb->prev_kprobe.status;
 96}
 97NOKPROBE_SYMBOL(restore_previous_kprobe);
 98
 99static void set_current_kprobe(struct kprobe *p)
100{
101	__this_cpu_write(current_kprobe, p);
102}
103NOKPROBE_SYMBOL(set_current_kprobe);
104
105/*
106 * Interrupts need to be disabled before single-step mode is set,
107 * and not reenabled until after single-step mode ends.
108 * Without disabling interrupt on local CPU, there is a chance of
109 * interrupt occurrence in the period of exception return and start
110 * of out-of-line single-step, that result in wrongly single stepping
111 * into the interrupt handler.
112 */
113static void save_local_irqflag(struct kprobe_ctlblk *kcb,
114			       struct pt_regs *regs)
115{
116	kcb->saved_status = regs->csr_prmd;
117	regs->csr_prmd &= ~CSR_PRMD_PIE;
118}
119NOKPROBE_SYMBOL(save_local_irqflag);
120
121static void restore_local_irqflag(struct kprobe_ctlblk *kcb,
122				  struct pt_regs *regs)
123{
124	regs->csr_prmd = kcb->saved_status;
125}
126NOKPROBE_SYMBOL(restore_local_irqflag);
127
128static void post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb,
129				struct pt_regs *regs)
130{
131	/* return addr restore if non-branching insn */
132	if (cur->ainsn.restore != 0)
133		instruction_pointer_set(regs, cur->ainsn.restore);
134
135	/* restore back original saved kprobe variables and continue */
136	if (kcb->kprobe_status == KPROBE_REENTER) {
137		restore_previous_kprobe(kcb);
138		preempt_enable_no_resched();
139		return;
140	}
141
142	/*
143	 * update the kcb status even if the cur->post_handler is
144	 * not set because reset_curent_kprobe() doesn't update kcb.
145	 */
146	kcb->kprobe_status = KPROBE_HIT_SSDONE;
147	if (cur->post_handler)
148		cur->post_handler(cur, regs, 0);
149
150	reset_current_kprobe();
151	preempt_enable_no_resched();
152}
153NOKPROBE_SYMBOL(post_kprobe_handler);
154
155static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
156			     struct kprobe_ctlblk *kcb, int reenter)
157{
158	union loongarch_instruction insn;
159
160	if (reenter) {
161		save_previous_kprobe(kcb);
162		set_current_kprobe(p);
163		kcb->kprobe_status = KPROBE_REENTER;
164	} else {
165		kcb->kprobe_status = KPROBE_HIT_SS;
166	}
167
168	if (p->ainsn.insn) {
169		/* IRQs and single stepping do not mix well */
170		save_local_irqflag(kcb, regs);
171		/* set ip register to prepare for single stepping */
172		regs->csr_era = (unsigned long)p->ainsn.insn;
173	} else {
174		/* simulate single steping */
175		insn.word = p->opcode;
176		arch_simulate_insn(insn, regs);
177		/* now go for post processing */
178		post_kprobe_handler(p, kcb, regs);
179	}
180}
181NOKPROBE_SYMBOL(setup_singlestep);
182
183static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
184			   struct kprobe_ctlblk *kcb)
185{
186	switch (kcb->kprobe_status) {
187	case KPROBE_HIT_SS:
188	case KPROBE_HIT_SSDONE:
189	case KPROBE_HIT_ACTIVE:
190		kprobes_inc_nmissed_count(p);
191		setup_singlestep(p, regs, kcb, 1);
192		break;
193	case KPROBE_REENTER:
194		pr_warn("Failed to recover from reentered kprobes.\n");
195		dump_kprobe(p);
196		WARN_ON_ONCE(1);
197		break;
198	default:
199		WARN_ON(1);
200		return false;
201	}
202
203	return true;
204}
205NOKPROBE_SYMBOL(reenter_kprobe);
206
207bool kprobe_breakpoint_handler(struct pt_regs *regs)
208{
209	struct kprobe_ctlblk *kcb;
210	struct kprobe *p, *cur_kprobe;
211	kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->csr_era;
212
213	/*
214	 * We don't want to be preempted for the entire
215	 * duration of kprobe processing.
216	 */
217	preempt_disable();
218	kcb = get_kprobe_ctlblk();
219	cur_kprobe = kprobe_running();
220
221	p = get_kprobe(addr);
222	if (p) {
223		if (cur_kprobe) {
224			if (reenter_kprobe(p, regs, kcb))
225				return true;
226		} else {
227			/* Probe hit */
228			set_current_kprobe(p);
229			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
230
231			/*
232			 * If we have no pre-handler or it returned 0, we
233			 * continue with normal processing.  If we have a
234			 * pre-handler and it returned non-zero, it will
235			 * modify the execution path and no need to single
236			 * stepping. Let's just reset current kprobe and exit.
237			 *
238			 * pre_handler can hit a breakpoint and can step thru
239			 * before return.
240			 */
241			if (!p->pre_handler || !p->pre_handler(p, regs)) {
242				setup_singlestep(p, regs, kcb, 0);
243			} else {
244				reset_current_kprobe();
245				preempt_enable_no_resched();
246			}
247			return true;
248		}
249	}
250
251	if (*addr != KPROBE_BP_INSN) {
252		/*
253		 * The breakpoint instruction was removed right
254		 * after we hit it.  Another cpu has removed
255		 * either a probepoint or a debugger breakpoint
256		 * at this address.  In either case, no further
257		 * handling of this interrupt is appropriate.
258		 * Return back to original instruction, and continue.
259		 */
260		regs->csr_era = (unsigned long)addr;
261		preempt_enable_no_resched();
262		return true;
263	}
264
265	preempt_enable_no_resched();
266	return false;
267}
268NOKPROBE_SYMBOL(kprobe_breakpoint_handler);
269
270bool kprobe_singlestep_handler(struct pt_regs *regs)
271{
272	struct kprobe *cur = kprobe_running();
273	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
274	unsigned long addr = instruction_pointer(regs);
275
276	if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
277	    ((unsigned long)&cur->ainsn.insn[1] == addr)) {
278		restore_local_irqflag(kcb, regs);
279		post_kprobe_handler(cur, kcb, regs);
280		return true;
281	}
282
283	preempt_enable_no_resched();
284	return false;
285}
286NOKPROBE_SYMBOL(kprobe_singlestep_handler);
287
288bool kprobe_fault_handler(struct pt_regs *regs, int trapnr)
289{
290	struct kprobe *cur = kprobe_running();
291	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
292
293	switch (kcb->kprobe_status) {
294	case KPROBE_HIT_SS:
295	case KPROBE_REENTER:
296		/*
297		 * We are here because the instruction being single
298		 * stepped caused a page fault. We reset the current
299		 * kprobe and the ip points back to the probe address
300		 * and allow the page fault handler to continue as a
301		 * normal page fault.
302		 */
303		regs->csr_era = (unsigned long)cur->addr;
304		WARN_ON_ONCE(!instruction_pointer(regs));
305
306		if (kcb->kprobe_status == KPROBE_REENTER) {
307			restore_previous_kprobe(kcb);
308		} else {
309			restore_local_irqflag(kcb, regs);
310			reset_current_kprobe();
311		}
312		preempt_enable_no_resched();
313		break;
314	}
315	return false;
316}
317NOKPROBE_SYMBOL(kprobe_fault_handler);
318
319/*
320 * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
321 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
322 */
323int __init arch_populate_kprobe_blacklist(void)
324{
325	return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
326					 (unsigned long)__irqentry_text_end);
327}
328
329int __init arch_init_kprobes(void)
330{
331	return 0;
332}
333
334int arch_trampoline_kprobe(struct kprobe *p)
335{
336	return 0;
337}
338NOKPROBE_SYMBOL(arch_trampoline_kprobe);