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1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  Kernel Probes (KProbes)
4  *
5  * Copyright (C) IBM Corporation, 2002, 2004
6  *
7  * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8  *		Probes initial implementation ( includes contributions from
9  *		Rusty Russell).
10  * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
11  *		interface to access function arguments.
12  * 2004-Oct	Jim Keniston <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
13  *		<prasanna@in.ibm.com> adapted for x86_64 from i386.
14  * 2005-Mar	Roland McGrath <roland@redhat.com>
15  *		Fixed to handle %rip-relative addressing mode correctly.
16  * 2005-May	Hien Nguyen <hien@us.ibm.com>, Jim Keniston
17  *		<jkenisto@us.ibm.com> and Prasanna S Panchamukhi
18  *		<prasanna@in.ibm.com> added function-return probes.
19  * 2005-May	Rusty Lynch <rusty.lynch@intel.com>
20  *		Added function return probes functionality
21  * 2006-Feb	Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added
22  *		kprobe-booster and kretprobe-booster for i386.
23  * 2007-Dec	Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster
24  *		and kretprobe-booster for x86-64
25  * 2007-Dec	Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven
26  *		<arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com>
27  *		unified x86 kprobes code.
28  */
29 #include <linux/kprobes.h>
30 #include <linux/ptrace.h>
31 #include <linux/string.h>
32 #include <linux/slab.h>
33 #include <linux/hardirq.h>
34 #include <linux/preempt.h>
35 #include <linux/sched/debug.h>
36 #include <linux/perf_event.h>
37 #include <linux/extable.h>
38 #include <linux/kdebug.h>
39 #include <linux/kallsyms.h>
40 #include <linux/kgdb.h>
41 #include <linux/ftrace.h>
42 #include <linux/kasan.h>
43 #include <linux/moduleloader.h>
44 #include <linux/objtool.h>
45 #include <linux/vmalloc.h>
46 #include <linux/pgtable.h>
47 
48 #include <asm/text-patching.h>
49 #include <asm/cacheflush.h>
50 #include <asm/desc.h>
51 #include <linux/uaccess.h>
52 #include <asm/alternative.h>
53 #include <asm/insn.h>
54 #include <asm/debugreg.h>
55 #include <asm/set_memory.h>
56 
57 #include "common.h"
58 
59 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
60 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
61 
62 #define stack_addr(regs) ((unsigned long *)regs->sp)
63 
64 #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
65 	(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
66 	  (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
67 	  (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
68 	  (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
69 	 << (row % 32))
70 	/*
71 	 * Undefined/reserved opcodes, conditional jump, Opcode Extension
72 	 * Groups, and some special opcodes can not boost.
73 	 * This is non-const and volatile to keep gcc from statically
74 	 * optimizing it out, as variable_test_bit makes gcc think only
75 	 * *(unsigned long*) is used.
76 	 */
77 static volatile u32 twobyte_is_boostable[256 / 32] = {
78 	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
79 	/*      ----------------------------------------------          */
80 	W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
81 	W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
82 	W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
83 	W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
84 	W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
85 	W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
86 	W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
87 	W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
88 	W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
89 	W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
90 	W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
91 	W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
92 	W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
93 	W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
94 	W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
95 	W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0)   /* f0 */
96 	/*      -----------------------------------------------         */
97 	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
98 };
99 #undef W
100 
101 struct kretprobe_blackpoint kretprobe_blacklist[] = {
102 	{"__switch_to", }, /* This function switches only current task, but
103 			      doesn't switch kernel stack.*/
104 	{NULL, NULL}	/* Terminator */
105 };
106 
107 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
108 
109 static nokprobe_inline void
__synthesize_relative_insn(void * dest,void * from,void * to,u8 op)110 __synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
111 {
112 	struct __arch_relative_insn {
113 		u8 op;
114 		s32 raddr;
115 	} __packed *insn;
116 
117 	insn = (struct __arch_relative_insn *)dest;
118 	insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
119 	insn->op = op;
120 }
121 
122 /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
synthesize_reljump(void * dest,void * from,void * to)123 void synthesize_reljump(void *dest, void *from, void *to)
124 {
125 	__synthesize_relative_insn(dest, from, to, JMP32_INSN_OPCODE);
126 }
127 NOKPROBE_SYMBOL(synthesize_reljump);
128 
129 /* Insert a call instruction at address 'from', which calls address 'to'.*/
synthesize_relcall(void * dest,void * from,void * to)130 void synthesize_relcall(void *dest, void *from, void *to)
131 {
132 	__synthesize_relative_insn(dest, from, to, CALL_INSN_OPCODE);
133 }
134 NOKPROBE_SYMBOL(synthesize_relcall);
135 
136 /*
137  * Returns non-zero if INSN is boostable.
138  * RIP relative instructions are adjusted at copying time in 64 bits mode
139  */
can_boost(struct insn * insn,void * addr)140 int can_boost(struct insn *insn, void *addr)
141 {
142 	kprobe_opcode_t opcode;
143 	insn_byte_t prefix;
144 	int i;
145 
146 	if (search_exception_tables((unsigned long)addr))
147 		return 0;	/* Page fault may occur on this address. */
148 
149 	/* 2nd-byte opcode */
150 	if (insn->opcode.nbytes == 2)
151 		return test_bit(insn->opcode.bytes[1],
152 				(unsigned long *)twobyte_is_boostable);
153 
154 	if (insn->opcode.nbytes != 1)
155 		return 0;
156 
157 	for_each_insn_prefix(insn, i, prefix) {
158 		insn_attr_t attr;
159 
160 		attr = inat_get_opcode_attribute(prefix);
161 		/* Can't boost Address-size override prefix and CS override prefix */
162 		if (prefix == 0x2e || inat_is_address_size_prefix(attr))
163 			return 0;
164 	}
165 
166 	opcode = insn->opcode.bytes[0];
167 
168 	switch (opcode) {
169 	case 0x62:		/* bound */
170 	case 0x70 ... 0x7f:	/* Conditional jumps */
171 	case 0x9a:		/* Call far */
172 	case 0xc0 ... 0xc1:	/* Grp2 */
173 	case 0xcc ... 0xce:	/* software exceptions */
174 	case 0xd0 ... 0xd3:	/* Grp2 */
175 	case 0xd6:		/* (UD) */
176 	case 0xd8 ... 0xdf:	/* ESC */
177 	case 0xe0 ... 0xe3:	/* LOOP*, JCXZ */
178 	case 0xe8 ... 0xe9:	/* near Call, JMP */
179 	case 0xeb:		/* Short JMP */
180 	case 0xf0 ... 0xf4:	/* LOCK/REP, HLT */
181 	case 0xf6 ... 0xf7:	/* Grp3 */
182 	case 0xfe:		/* Grp4 */
183 		/* ... are not boostable */
184 		return 0;
185 	case 0xff:		/* Grp5 */
186 		/* Only indirect jmp is boostable */
187 		return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
188 	default:
189 		return 1;
190 	}
191 }
192 
193 static unsigned long
__recover_probed_insn(kprobe_opcode_t * buf,unsigned long addr)194 __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
195 {
196 	struct kprobe *kp;
197 	unsigned long faddr;
198 
199 	kp = get_kprobe((void *)addr);
200 	faddr = ftrace_location(addr);
201 	/*
202 	 * Addresses inside the ftrace location are refused by
203 	 * arch_check_ftrace_location(). Something went terribly wrong
204 	 * if such an address is checked here.
205 	 */
206 	if (WARN_ON(faddr && faddr != addr))
207 		return 0UL;
208 	/*
209 	 * Use the current code if it is not modified by Kprobe
210 	 * and it cannot be modified by ftrace.
211 	 */
212 	if (!kp && !faddr)
213 		return addr;
214 
215 	/*
216 	 * Basically, kp->ainsn.insn has an original instruction.
217 	 * However, RIP-relative instruction can not do single-stepping
218 	 * at different place, __copy_instruction() tweaks the displacement of
219 	 * that instruction. In that case, we can't recover the instruction
220 	 * from the kp->ainsn.insn.
221 	 *
222 	 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
223 	 * of the first byte of the probed instruction, which is overwritten
224 	 * by int3. And the instruction at kp->addr is not modified by kprobes
225 	 * except for the first byte, we can recover the original instruction
226 	 * from it and kp->opcode.
227 	 *
228 	 * In case of Kprobes using ftrace, we do not have a copy of
229 	 * the original instruction. In fact, the ftrace location might
230 	 * be modified at anytime and even could be in an inconsistent state.
231 	 * Fortunately, we know that the original code is the ideal 5-byte
232 	 * long NOP.
233 	 */
234 	if (copy_from_kernel_nofault(buf, (void *)addr,
235 		MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
236 		return 0UL;
237 
238 	if (faddr)
239 		memcpy(buf, x86_nops[5], 5);
240 	else
241 		buf[0] = kp->opcode;
242 	return (unsigned long)buf;
243 }
244 
245 /*
246  * Recover the probed instruction at addr for further analysis.
247  * Caller must lock kprobes by kprobe_mutex, or disable preemption
248  * for preventing to release referencing kprobes.
249  * Returns zero if the instruction can not get recovered (or access failed).
250  */
recover_probed_instruction(kprobe_opcode_t * buf,unsigned long addr)251 unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
252 {
253 	unsigned long __addr;
254 
255 	__addr = __recover_optprobed_insn(buf, addr);
256 	if (__addr != addr)
257 		return __addr;
258 
259 	return __recover_probed_insn(buf, addr);
260 }
261 
262 /* Check if paddr is at an instruction boundary */
can_probe(unsigned long paddr)263 static int can_probe(unsigned long paddr)
264 {
265 	unsigned long addr, __addr, offset = 0;
266 	struct insn insn;
267 	kprobe_opcode_t buf[MAX_INSN_SIZE];
268 
269 	if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
270 		return 0;
271 
272 	/* Decode instructions */
273 	addr = paddr - offset;
274 	while (addr < paddr) {
275 		int ret;
276 
277 		/*
278 		 * Check if the instruction has been modified by another
279 		 * kprobe, in which case we replace the breakpoint by the
280 		 * original instruction in our buffer.
281 		 * Also, jump optimization will change the breakpoint to
282 		 * relative-jump. Since the relative-jump itself is
283 		 * normally used, we just go through if there is no kprobe.
284 		 */
285 		__addr = recover_probed_instruction(buf, addr);
286 		if (!__addr)
287 			return 0;
288 
289 		ret = insn_decode_kernel(&insn, (void *)__addr);
290 		if (ret < 0)
291 			return 0;
292 
293 #ifdef CONFIG_KGDB
294 		/*
295 		 * If there is a dynamically installed kgdb sw breakpoint,
296 		 * this function should not be probed.
297 		 */
298 		if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
299 		    kgdb_has_hit_break(addr))
300 			return 0;
301 #endif
302 		addr += insn.length;
303 	}
304 
305 	return (addr == paddr);
306 }
307 
308 /*
309  * Copy an instruction with recovering modified instruction by kprobes
310  * and adjust the displacement if the instruction uses the %rip-relative
311  * addressing mode. Note that since @real will be the final place of copied
312  * instruction, displacement must be adjust by @real, not @dest.
313  * This returns the length of copied instruction, or 0 if it has an error.
314  */
__copy_instruction(u8 * dest,u8 * src,u8 * real,struct insn * insn)315 int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
316 {
317 	kprobe_opcode_t buf[MAX_INSN_SIZE];
318 	unsigned long recovered_insn = recover_probed_instruction(buf, (unsigned long)src);
319 	int ret;
320 
321 	if (!recovered_insn || !insn)
322 		return 0;
323 
324 	/* This can access kernel text if given address is not recovered */
325 	if (copy_from_kernel_nofault(dest, (void *)recovered_insn,
326 			MAX_INSN_SIZE))
327 		return 0;
328 
329 	ret = insn_decode_kernel(insn, dest);
330 	if (ret < 0)
331 		return 0;
332 
333 	/* We can not probe force emulate prefixed instruction */
334 	if (insn_has_emulate_prefix(insn))
335 		return 0;
336 
337 	/* Another subsystem puts a breakpoint, failed to recover */
338 	if (insn->opcode.bytes[0] == INT3_INSN_OPCODE)
339 		return 0;
340 
341 	/* We should not singlestep on the exception masking instructions */
342 	if (insn_masking_exception(insn))
343 		return 0;
344 
345 #ifdef CONFIG_X86_64
346 	/* Only x86_64 has RIP relative instructions */
347 	if (insn_rip_relative(insn)) {
348 		s64 newdisp;
349 		u8 *disp;
350 		/*
351 		 * The copied instruction uses the %rip-relative addressing
352 		 * mode.  Adjust the displacement for the difference between
353 		 * the original location of this instruction and the location
354 		 * of the copy that will actually be run.  The tricky bit here
355 		 * is making sure that the sign extension happens correctly in
356 		 * this calculation, since we need a signed 32-bit result to
357 		 * be sign-extended to 64 bits when it's added to the %rip
358 		 * value and yield the same 64-bit result that the sign-
359 		 * extension of the original signed 32-bit displacement would
360 		 * have given.
361 		 */
362 		newdisp = (u8 *) src + (s64) insn->displacement.value
363 			  - (u8 *) real;
364 		if ((s64) (s32) newdisp != newdisp) {
365 			pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
366 			return 0;
367 		}
368 		disp = (u8 *) dest + insn_offset_displacement(insn);
369 		*(s32 *) disp = (s32) newdisp;
370 	}
371 #endif
372 	return insn->length;
373 }
374 
375 /* Prepare reljump or int3 right after instruction */
prepare_singlestep(kprobe_opcode_t * buf,struct kprobe * p,struct insn * insn)376 static int prepare_singlestep(kprobe_opcode_t *buf, struct kprobe *p,
377 			      struct insn *insn)
378 {
379 	int len = insn->length;
380 
381 	if (!IS_ENABLED(CONFIG_PREEMPTION) &&
382 	    !p->post_handler && can_boost(insn, p->addr) &&
383 	    MAX_INSN_SIZE - len >= JMP32_INSN_SIZE) {
384 		/*
385 		 * These instructions can be executed directly if it
386 		 * jumps back to correct address.
387 		 */
388 		synthesize_reljump(buf + len, p->ainsn.insn + len,
389 				   p->addr + insn->length);
390 		len += JMP32_INSN_SIZE;
391 		p->ainsn.boostable = 1;
392 	} else {
393 		/* Otherwise, put an int3 for trapping singlestep */
394 		if (MAX_INSN_SIZE - len < INT3_INSN_SIZE)
395 			return -ENOSPC;
396 
397 		buf[len] = INT3_INSN_OPCODE;
398 		len += INT3_INSN_SIZE;
399 	}
400 
401 	return len;
402 }
403 
404 /* Make page to RO mode when allocate it */
alloc_insn_page(void)405 void *alloc_insn_page(void)
406 {
407 	void *page;
408 
409 	page = module_alloc(PAGE_SIZE);
410 	if (!page)
411 		return NULL;
412 
413 	set_vm_flush_reset_perms(page);
414 	/*
415 	 * First make the page read-only, and only then make it executable to
416 	 * prevent it from being W+X in between.
417 	 */
418 	set_memory_ro((unsigned long)page, 1);
419 
420 	/*
421 	 * TODO: Once additional kernel code protection mechanisms are set, ensure
422 	 * that the page was not maliciously altered and it is still zeroed.
423 	 */
424 	set_memory_x((unsigned long)page, 1);
425 
426 	return page;
427 }
428 
429 /* Kprobe x86 instruction emulation - only regs->ip or IF flag modifiers */
430 
kprobe_emulate_ifmodifiers(struct kprobe * p,struct pt_regs * regs)431 static void kprobe_emulate_ifmodifiers(struct kprobe *p, struct pt_regs *regs)
432 {
433 	switch (p->ainsn.opcode) {
434 	case 0xfa:	/* cli */
435 		regs->flags &= ~(X86_EFLAGS_IF);
436 		break;
437 	case 0xfb:	/* sti */
438 		regs->flags |= X86_EFLAGS_IF;
439 		break;
440 	case 0x9c:	/* pushf */
441 		int3_emulate_push(regs, regs->flags);
442 		break;
443 	case 0x9d:	/* popf */
444 		regs->flags = int3_emulate_pop(regs);
445 		break;
446 	}
447 	regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
448 }
449 NOKPROBE_SYMBOL(kprobe_emulate_ifmodifiers);
450 
kprobe_emulate_ret(struct kprobe * p,struct pt_regs * regs)451 static void kprobe_emulate_ret(struct kprobe *p, struct pt_regs *regs)
452 {
453 	int3_emulate_ret(regs);
454 }
455 NOKPROBE_SYMBOL(kprobe_emulate_ret);
456 
kprobe_emulate_call(struct kprobe * p,struct pt_regs * regs)457 static void kprobe_emulate_call(struct kprobe *p, struct pt_regs *regs)
458 {
459 	unsigned long func = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
460 
461 	func += p->ainsn.rel32;
462 	int3_emulate_call(regs, func);
463 }
464 NOKPROBE_SYMBOL(kprobe_emulate_call);
465 
466 static nokprobe_inline
__kprobe_emulate_jmp(struct kprobe * p,struct pt_regs * regs,bool cond)467 void __kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond)
468 {
469 	unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
470 
471 	if (cond)
472 		ip += p->ainsn.rel32;
473 	int3_emulate_jmp(regs, ip);
474 }
475 
kprobe_emulate_jmp(struct kprobe * p,struct pt_regs * regs)476 static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)
477 {
478 	__kprobe_emulate_jmp(p, regs, true);
479 }
480 NOKPROBE_SYMBOL(kprobe_emulate_jmp);
481 
482 static const unsigned long jcc_mask[6] = {
483 	[0] = X86_EFLAGS_OF,
484 	[1] = X86_EFLAGS_CF,
485 	[2] = X86_EFLAGS_ZF,
486 	[3] = X86_EFLAGS_CF | X86_EFLAGS_ZF,
487 	[4] = X86_EFLAGS_SF,
488 	[5] = X86_EFLAGS_PF,
489 };
490 
kprobe_emulate_jcc(struct kprobe * p,struct pt_regs * regs)491 static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs)
492 {
493 	bool invert = p->ainsn.jcc.type & 1;
494 	bool match;
495 
496 	if (p->ainsn.jcc.type < 0xc) {
497 		match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1];
498 	} else {
499 		match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^
500 			((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);
501 		if (p->ainsn.jcc.type >= 0xe)
502 			match = match || (regs->flags & X86_EFLAGS_ZF);
503 	}
504 	__kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert));
505 }
506 NOKPROBE_SYMBOL(kprobe_emulate_jcc);
507 
kprobe_emulate_loop(struct kprobe * p,struct pt_regs * regs)508 static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs)
509 {
510 	bool match;
511 
512 	if (p->ainsn.loop.type != 3) {	/* LOOP* */
513 		if (p->ainsn.loop.asize == 32)
514 			match = ((*(u32 *)&regs->cx)--) != 0;
515 #ifdef CONFIG_X86_64
516 		else if (p->ainsn.loop.asize == 64)
517 			match = ((*(u64 *)&regs->cx)--) != 0;
518 #endif
519 		else
520 			match = ((*(u16 *)&regs->cx)--) != 0;
521 	} else {			/* JCXZ */
522 		if (p->ainsn.loop.asize == 32)
523 			match = *(u32 *)(&regs->cx) == 0;
524 #ifdef CONFIG_X86_64
525 		else if (p->ainsn.loop.asize == 64)
526 			match = *(u64 *)(&regs->cx) == 0;
527 #endif
528 		else
529 			match = *(u16 *)(&regs->cx) == 0;
530 	}
531 
532 	if (p->ainsn.loop.type == 0)	/* LOOPNE */
533 		match = match && !(regs->flags & X86_EFLAGS_ZF);
534 	else if (p->ainsn.loop.type == 1)	/* LOOPE */
535 		match = match && (regs->flags & X86_EFLAGS_ZF);
536 
537 	__kprobe_emulate_jmp(p, regs, match);
538 }
539 NOKPROBE_SYMBOL(kprobe_emulate_loop);
540 
541 static const int addrmode_regoffs[] = {
542 	offsetof(struct pt_regs, ax),
543 	offsetof(struct pt_regs, cx),
544 	offsetof(struct pt_regs, dx),
545 	offsetof(struct pt_regs, bx),
546 	offsetof(struct pt_regs, sp),
547 	offsetof(struct pt_regs, bp),
548 	offsetof(struct pt_regs, si),
549 	offsetof(struct pt_regs, di),
550 #ifdef CONFIG_X86_64
551 	offsetof(struct pt_regs, r8),
552 	offsetof(struct pt_regs, r9),
553 	offsetof(struct pt_regs, r10),
554 	offsetof(struct pt_regs, r11),
555 	offsetof(struct pt_regs, r12),
556 	offsetof(struct pt_regs, r13),
557 	offsetof(struct pt_regs, r14),
558 	offsetof(struct pt_regs, r15),
559 #endif
560 };
561 
kprobe_emulate_call_indirect(struct kprobe * p,struct pt_regs * regs)562 static void kprobe_emulate_call_indirect(struct kprobe *p, struct pt_regs *regs)
563 {
564 	unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
565 
566 	int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + p->ainsn.size);
567 	int3_emulate_jmp(regs, regs_get_register(regs, offs));
568 }
569 NOKPROBE_SYMBOL(kprobe_emulate_call_indirect);
570 
kprobe_emulate_jmp_indirect(struct kprobe * p,struct pt_regs * regs)571 static void kprobe_emulate_jmp_indirect(struct kprobe *p, struct pt_regs *regs)
572 {
573 	unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
574 
575 	int3_emulate_jmp(regs, regs_get_register(regs, offs));
576 }
577 NOKPROBE_SYMBOL(kprobe_emulate_jmp_indirect);
578 
prepare_emulation(struct kprobe * p,struct insn * insn)579 static int prepare_emulation(struct kprobe *p, struct insn *insn)
580 {
581 	insn_byte_t opcode = insn->opcode.bytes[0];
582 
583 	switch (opcode) {
584 	case 0xfa:		/* cli */
585 	case 0xfb:		/* sti */
586 	case 0x9c:		/* pushfl */
587 	case 0x9d:		/* popf/popfd */
588 		/*
589 		 * IF modifiers must be emulated since it will enable interrupt while
590 		 * int3 single stepping.
591 		 */
592 		p->ainsn.emulate_op = kprobe_emulate_ifmodifiers;
593 		p->ainsn.opcode = opcode;
594 		break;
595 	case 0xc2:	/* ret/lret */
596 	case 0xc3:
597 	case 0xca:
598 	case 0xcb:
599 		p->ainsn.emulate_op = kprobe_emulate_ret;
600 		break;
601 	case 0x9a:	/* far call absolute -- segment is not supported */
602 	case 0xea:	/* far jmp absolute -- segment is not supported */
603 	case 0xcc:	/* int3 */
604 	case 0xcf:	/* iret -- in-kernel IRET is not supported */
605 		return -EOPNOTSUPP;
606 		break;
607 	case 0xe8:	/* near call relative */
608 		p->ainsn.emulate_op = kprobe_emulate_call;
609 		if (insn->immediate.nbytes == 2)
610 			p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
611 		else
612 			p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
613 		break;
614 	case 0xeb:	/* short jump relative */
615 	case 0xe9:	/* near jump relative */
616 		p->ainsn.emulate_op = kprobe_emulate_jmp;
617 		if (insn->immediate.nbytes == 1)
618 			p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
619 		else if (insn->immediate.nbytes == 2)
620 			p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
621 		else
622 			p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
623 		break;
624 	case 0x70 ... 0x7f:
625 		/* 1 byte conditional jump */
626 		p->ainsn.emulate_op = kprobe_emulate_jcc;
627 		p->ainsn.jcc.type = opcode & 0xf;
628 		p->ainsn.rel32 = *(char *)insn->immediate.bytes;
629 		break;
630 	case 0x0f:
631 		opcode = insn->opcode.bytes[1];
632 		if ((opcode & 0xf0) == 0x80) {
633 			/* 2 bytes Conditional Jump */
634 			p->ainsn.emulate_op = kprobe_emulate_jcc;
635 			p->ainsn.jcc.type = opcode & 0xf;
636 			if (insn->immediate.nbytes == 2)
637 				p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
638 			else
639 				p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
640 		} else if (opcode == 0x01 &&
641 			   X86_MODRM_REG(insn->modrm.bytes[0]) == 0 &&
642 			   X86_MODRM_MOD(insn->modrm.bytes[0]) == 3) {
643 			/* VM extensions - not supported */
644 			return -EOPNOTSUPP;
645 		}
646 		break;
647 	case 0xe0:	/* Loop NZ */
648 	case 0xe1:	/* Loop */
649 	case 0xe2:	/* Loop */
650 	case 0xe3:	/* J*CXZ */
651 		p->ainsn.emulate_op = kprobe_emulate_loop;
652 		p->ainsn.loop.type = opcode & 0x3;
653 		p->ainsn.loop.asize = insn->addr_bytes * 8;
654 		p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
655 		break;
656 	case 0xff:
657 		/*
658 		 * Since the 0xff is an extended group opcode, the instruction
659 		 * is determined by the MOD/RM byte.
660 		 */
661 		opcode = insn->modrm.bytes[0];
662 		if ((opcode & 0x30) == 0x10) {
663 			if ((opcode & 0x8) == 0x8)
664 				return -EOPNOTSUPP;	/* far call */
665 			/* call absolute, indirect */
666 			p->ainsn.emulate_op = kprobe_emulate_call_indirect;
667 		} else if ((opcode & 0x30) == 0x20) {
668 			if ((opcode & 0x8) == 0x8)
669 				return -EOPNOTSUPP;	/* far jmp */
670 			/* jmp near absolute indirect */
671 			p->ainsn.emulate_op = kprobe_emulate_jmp_indirect;
672 		} else
673 			break;
674 
675 		if (insn->addr_bytes != sizeof(unsigned long))
676 			return -EOPNOTSUPP;	/* Don't support different size */
677 		if (X86_MODRM_MOD(opcode) != 3)
678 			return -EOPNOTSUPP;	/* TODO: support memory addressing */
679 
680 		p->ainsn.indirect.reg = X86_MODRM_RM(opcode);
681 #ifdef CONFIG_X86_64
682 		if (X86_REX_B(insn->rex_prefix.value))
683 			p->ainsn.indirect.reg += 8;
684 #endif
685 		break;
686 	default:
687 		break;
688 	}
689 	p->ainsn.size = insn->length;
690 
691 	return 0;
692 }
693 
arch_copy_kprobe(struct kprobe * p)694 static int arch_copy_kprobe(struct kprobe *p)
695 {
696 	struct insn insn;
697 	kprobe_opcode_t buf[MAX_INSN_SIZE];
698 	int ret, len;
699 
700 	/* Copy an instruction with recovering if other optprobe modifies it.*/
701 	len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
702 	if (!len)
703 		return -EINVAL;
704 
705 	/* Analyze the opcode and setup emulate functions */
706 	ret = prepare_emulation(p, &insn);
707 	if (ret < 0)
708 		return ret;
709 
710 	/* Add int3 for single-step or booster jmp */
711 	len = prepare_singlestep(buf, p, &insn);
712 	if (len < 0)
713 		return len;
714 
715 	/* Also, displacement change doesn't affect the first byte */
716 	p->opcode = buf[0];
717 
718 	p->ainsn.tp_len = len;
719 	perf_event_text_poke(p->ainsn.insn, NULL, 0, buf, len);
720 
721 	/* OK, write back the instruction(s) into ROX insn buffer */
722 	text_poke(p->ainsn.insn, buf, len);
723 
724 	return 0;
725 }
726 
arch_prepare_kprobe(struct kprobe * p)727 int arch_prepare_kprobe(struct kprobe *p)
728 {
729 	int ret;
730 
731 	if (alternatives_text_reserved(p->addr, p->addr))
732 		return -EINVAL;
733 
734 	if (!can_probe((unsigned long)p->addr))
735 		return -EILSEQ;
736 
737 	memset(&p->ainsn, 0, sizeof(p->ainsn));
738 
739 	/* insn: must be on special executable page on x86. */
740 	p->ainsn.insn = get_insn_slot();
741 	if (!p->ainsn.insn)
742 		return -ENOMEM;
743 
744 	ret = arch_copy_kprobe(p);
745 	if (ret) {
746 		free_insn_slot(p->ainsn.insn, 0);
747 		p->ainsn.insn = NULL;
748 	}
749 
750 	return ret;
751 }
752 
arch_arm_kprobe(struct kprobe * p)753 void arch_arm_kprobe(struct kprobe *p)
754 {
755 	u8 int3 = INT3_INSN_OPCODE;
756 
757 	text_poke(p->addr, &int3, 1);
758 	text_poke_sync();
759 	perf_event_text_poke(p->addr, &p->opcode, 1, &int3, 1);
760 }
761 
arch_disarm_kprobe(struct kprobe * p)762 void arch_disarm_kprobe(struct kprobe *p)
763 {
764 	u8 int3 = INT3_INSN_OPCODE;
765 
766 	perf_event_text_poke(p->addr, &int3, 1, &p->opcode, 1);
767 	text_poke(p->addr, &p->opcode, 1);
768 	text_poke_sync();
769 }
770 
arch_remove_kprobe(struct kprobe * p)771 void arch_remove_kprobe(struct kprobe *p)
772 {
773 	if (p->ainsn.insn) {
774 		/* Record the perf event before freeing the slot */
775 		perf_event_text_poke(p->ainsn.insn, p->ainsn.insn,
776 				     p->ainsn.tp_len, NULL, 0);
777 		free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
778 		p->ainsn.insn = NULL;
779 	}
780 }
781 
782 static nokprobe_inline void
save_previous_kprobe(struct kprobe_ctlblk * kcb)783 save_previous_kprobe(struct kprobe_ctlblk *kcb)
784 {
785 	kcb->prev_kprobe.kp = kprobe_running();
786 	kcb->prev_kprobe.status = kcb->kprobe_status;
787 	kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
788 	kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
789 }
790 
791 static nokprobe_inline void
restore_previous_kprobe(struct kprobe_ctlblk * kcb)792 restore_previous_kprobe(struct kprobe_ctlblk *kcb)
793 {
794 	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
795 	kcb->kprobe_status = kcb->prev_kprobe.status;
796 	kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
797 	kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
798 }
799 
800 static nokprobe_inline void
set_current_kprobe(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)801 set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
802 		   struct kprobe_ctlblk *kcb)
803 {
804 	__this_cpu_write(current_kprobe, p);
805 	kcb->kprobe_saved_flags = kcb->kprobe_old_flags
806 		= (regs->flags & X86_EFLAGS_IF);
807 }
808 
arch_prepare_kretprobe(struct kretprobe_instance * ri,struct pt_regs * regs)809 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
810 {
811 	unsigned long *sara = stack_addr(regs);
812 
813 	ri->ret_addr = (kprobe_opcode_t *) *sara;
814 	ri->fp = sara;
815 
816 	/* Replace the return addr with trampoline addr */
817 	*sara = (unsigned long) &kretprobe_trampoline;
818 }
819 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
820 
kprobe_post_process(struct kprobe * cur,struct pt_regs * regs,struct kprobe_ctlblk * kcb)821 static void kprobe_post_process(struct kprobe *cur, struct pt_regs *regs,
822 			       struct kprobe_ctlblk *kcb)
823 {
824 	/* Restore back the original saved kprobes variables and continue. */
825 	if (kcb->kprobe_status == KPROBE_REENTER) {
826 		/* This will restore both kcb and current_kprobe */
827 		restore_previous_kprobe(kcb);
828 	} else {
829 		/*
830 		 * Always update the kcb status because
831 		 * reset_curent_kprobe() doesn't update kcb.
832 		 */
833 		kcb->kprobe_status = KPROBE_HIT_SSDONE;
834 		if (cur->post_handler)
835 			cur->post_handler(cur, regs, 0);
836 		reset_current_kprobe();
837 	}
838 }
839 NOKPROBE_SYMBOL(kprobe_post_process);
840 
setup_singlestep(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb,int reenter)841 static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
842 			     struct kprobe_ctlblk *kcb, int reenter)
843 {
844 	if (setup_detour_execution(p, regs, reenter))
845 		return;
846 
847 #if !defined(CONFIG_PREEMPTION)
848 	if (p->ainsn.boostable) {
849 		/* Boost up -- we can execute copied instructions directly */
850 		if (!reenter)
851 			reset_current_kprobe();
852 		/*
853 		 * Reentering boosted probe doesn't reset current_kprobe,
854 		 * nor set current_kprobe, because it doesn't use single
855 		 * stepping.
856 		 */
857 		regs->ip = (unsigned long)p->ainsn.insn;
858 		return;
859 	}
860 #endif
861 	if (reenter) {
862 		save_previous_kprobe(kcb);
863 		set_current_kprobe(p, regs, kcb);
864 		kcb->kprobe_status = KPROBE_REENTER;
865 	} else
866 		kcb->kprobe_status = KPROBE_HIT_SS;
867 
868 	if (p->ainsn.emulate_op) {
869 		p->ainsn.emulate_op(p, regs);
870 		kprobe_post_process(p, regs, kcb);
871 		return;
872 	}
873 
874 	/* Disable interrupt, and set ip register on trampoline */
875 	regs->flags &= ~X86_EFLAGS_IF;
876 	regs->ip = (unsigned long)p->ainsn.insn;
877 }
878 NOKPROBE_SYMBOL(setup_singlestep);
879 
880 /*
881  * Called after single-stepping.  p->addr is the address of the
882  * instruction whose first byte has been replaced by the "int3"
883  * instruction.  To avoid the SMP problems that can occur when we
884  * temporarily put back the original opcode to single-step, we
885  * single-stepped a copy of the instruction.  The address of this
886  * copy is p->ainsn.insn. We also doesn't use trap, but "int3" again
887  * right after the copied instruction.
888  * Different from the trap single-step, "int3" single-step can not
889  * handle the instruction which changes the ip register, e.g. jmp,
890  * call, conditional jmp, and the instructions which changes the IF
891  * flags because interrupt must be disabled around the single-stepping.
892  * Such instructions are software emulated, but others are single-stepped
893  * using "int3".
894  *
895  * When the 2nd "int3" handled, the regs->ip and regs->flags needs to
896  * be adjusted, so that we can resume execution on correct code.
897  */
resume_singlestep(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)898 static void resume_singlestep(struct kprobe *p, struct pt_regs *regs,
899 			      struct kprobe_ctlblk *kcb)
900 {
901 	unsigned long copy_ip = (unsigned long)p->ainsn.insn;
902 	unsigned long orig_ip = (unsigned long)p->addr;
903 
904 	/* Restore saved interrupt flag and ip register */
905 	regs->flags |= kcb->kprobe_saved_flags;
906 	/* Note that regs->ip is executed int3 so must be a step back */
907 	regs->ip += (orig_ip - copy_ip) - INT3_INSN_SIZE;
908 }
909 NOKPROBE_SYMBOL(resume_singlestep);
910 
911 /*
912  * We have reentered the kprobe_handler(), since another probe was hit while
913  * within the handler. We save the original kprobes variables and just single
914  * step on the instruction of the new probe without calling any user handlers.
915  */
reenter_kprobe(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)916 static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
917 			  struct kprobe_ctlblk *kcb)
918 {
919 	switch (kcb->kprobe_status) {
920 	case KPROBE_HIT_SSDONE:
921 	case KPROBE_HIT_ACTIVE:
922 	case KPROBE_HIT_SS:
923 		kprobes_inc_nmissed_count(p);
924 		setup_singlestep(p, regs, kcb, 1);
925 		break;
926 	case KPROBE_REENTER:
927 		/* A probe has been hit in the codepath leading up to, or just
928 		 * after, single-stepping of a probed instruction. This entire
929 		 * codepath should strictly reside in .kprobes.text section.
930 		 * Raise a BUG or we'll continue in an endless reentering loop
931 		 * and eventually a stack overflow.
932 		 */
933 		pr_err("Unrecoverable kprobe detected.\n");
934 		dump_kprobe(p);
935 		BUG();
936 	default:
937 		/* impossible cases */
938 		WARN_ON(1);
939 		return 0;
940 	}
941 
942 	return 1;
943 }
944 NOKPROBE_SYMBOL(reenter_kprobe);
945 
kprobe_is_ss(struct kprobe_ctlblk * kcb)946 static nokprobe_inline int kprobe_is_ss(struct kprobe_ctlblk *kcb)
947 {
948 	return (kcb->kprobe_status == KPROBE_HIT_SS ||
949 		kcb->kprobe_status == KPROBE_REENTER);
950 }
951 
952 /*
953  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
954  * remain disabled throughout this function.
955  */
kprobe_int3_handler(struct pt_regs * regs)956 int kprobe_int3_handler(struct pt_regs *regs)
957 {
958 	kprobe_opcode_t *addr;
959 	struct kprobe *p;
960 	struct kprobe_ctlblk *kcb;
961 
962 	if (user_mode(regs))
963 		return 0;
964 
965 	addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
966 	/*
967 	 * We don't want to be preempted for the entire duration of kprobe
968 	 * processing. Since int3 and debug trap disables irqs and we clear
969 	 * IF while singlestepping, it must be no preemptible.
970 	 */
971 
972 	kcb = get_kprobe_ctlblk();
973 	p = get_kprobe(addr);
974 
975 	if (p) {
976 		if (kprobe_running()) {
977 			if (reenter_kprobe(p, regs, kcb))
978 				return 1;
979 		} else {
980 			set_current_kprobe(p, regs, kcb);
981 			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
982 
983 			/*
984 			 * If we have no pre-handler or it returned 0, we
985 			 * continue with normal processing.  If we have a
986 			 * pre-handler and it returned non-zero, that means
987 			 * user handler setup registers to exit to another
988 			 * instruction, we must skip the single stepping.
989 			 */
990 			if (!p->pre_handler || !p->pre_handler(p, regs))
991 				setup_singlestep(p, regs, kcb, 0);
992 			else
993 				reset_current_kprobe();
994 			return 1;
995 		}
996 	} else if (kprobe_is_ss(kcb)) {
997 		p = kprobe_running();
998 		if ((unsigned long)p->ainsn.insn < regs->ip &&
999 		    (unsigned long)p->ainsn.insn + MAX_INSN_SIZE > regs->ip) {
1000 			/* Most provably this is the second int3 for singlestep */
1001 			resume_singlestep(p, regs, kcb);
1002 			kprobe_post_process(p, regs, kcb);
1003 			return 1;
1004 		}
1005 	}
1006 
1007 	if (*addr != INT3_INSN_OPCODE) {
1008 		/*
1009 		 * The breakpoint instruction was removed right
1010 		 * after we hit it.  Another cpu has removed
1011 		 * either a probepoint or a debugger breakpoint
1012 		 * at this address.  In either case, no further
1013 		 * handling of this interrupt is appropriate.
1014 		 * Back up over the (now missing) int3 and run
1015 		 * the original instruction.
1016 		 */
1017 		regs->ip = (unsigned long)addr;
1018 		return 1;
1019 	} /* else: not a kprobe fault; let the kernel handle it */
1020 
1021 	return 0;
1022 }
1023 NOKPROBE_SYMBOL(kprobe_int3_handler);
1024 
1025 /*
1026  * When a retprobed function returns, this code saves registers and
1027  * calls trampoline_handler() runs, which calls the kretprobe's handler.
1028  */
1029 asm(
1030 	".text\n"
1031 	".global kretprobe_trampoline\n"
1032 	".type kretprobe_trampoline, @function\n"
1033 	"kretprobe_trampoline:\n"
1034 	/* We don't bother saving the ss register */
1035 #ifdef CONFIG_X86_64
1036 	"	pushq %rsp\n"
1037 	"	pushfq\n"
1038 	SAVE_REGS_STRING
1039 	"	movq %rsp, %rdi\n"
1040 	"	call trampoline_handler\n"
1041 	/* Replace saved sp with true return address. */
1042 	"	movq %rax, 19*8(%rsp)\n"
1043 	RESTORE_REGS_STRING
1044 	"	popfq\n"
1045 #else
1046 	"	pushl %esp\n"
1047 	"	pushfl\n"
1048 	SAVE_REGS_STRING
1049 	"	movl %esp, %eax\n"
1050 	"	call trampoline_handler\n"
1051 	/* Replace saved sp with true return address. */
1052 	"	movl %eax, 15*4(%esp)\n"
1053 	RESTORE_REGS_STRING
1054 	"	popfl\n"
1055 #endif
1056 	ASM_RET
1057 	".size kretprobe_trampoline, .-kretprobe_trampoline\n"
1058 );
1059 NOKPROBE_SYMBOL(kretprobe_trampoline);
1060 STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
1061 
1062 
1063 /*
1064  * Called from kretprobe_trampoline
1065  */
trampoline_handler(struct pt_regs * regs)1066 __used __visible void *trampoline_handler(struct pt_regs *regs)
1067 {
1068 	/* fixup registers */
1069 	regs->cs = __KERNEL_CS;
1070 #ifdef CONFIG_X86_32
1071 	regs->gs = 0;
1072 #endif
1073 	regs->ip = (unsigned long)&kretprobe_trampoline;
1074 	regs->orig_ax = ~0UL;
1075 
1076 	return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, &regs->sp);
1077 }
1078 NOKPROBE_SYMBOL(trampoline_handler);
1079 
kprobe_fault_handler(struct pt_regs * regs,int trapnr)1080 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
1081 {
1082 	struct kprobe *cur = kprobe_running();
1083 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1084 
1085 	if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
1086 		/* This must happen on single-stepping */
1087 		WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
1088 			kcb->kprobe_status != KPROBE_REENTER);
1089 		/*
1090 		 * We are here because the instruction being single
1091 		 * stepped caused a page fault. We reset the current
1092 		 * kprobe and the ip points back to the probe address
1093 		 * and allow the page fault handler to continue as a
1094 		 * normal page fault.
1095 		 */
1096 		regs->ip = (unsigned long)cur->addr;
1097 
1098 		/*
1099 		 * If the IF flag was set before the kprobe hit,
1100 		 * don't touch it:
1101 		 */
1102 		regs->flags |= kcb->kprobe_old_flags;
1103 
1104 		if (kcb->kprobe_status == KPROBE_REENTER)
1105 			restore_previous_kprobe(kcb);
1106 		else
1107 			reset_current_kprobe();
1108 	}
1109 
1110 	return 0;
1111 }
1112 NOKPROBE_SYMBOL(kprobe_fault_handler);
1113 
arch_populate_kprobe_blacklist(void)1114 int __init arch_populate_kprobe_blacklist(void)
1115 {
1116 	return kprobe_add_area_blacklist((unsigned long)__entry_text_start,
1117 					 (unsigned long)__entry_text_end);
1118 }
1119 
arch_init_kprobes(void)1120 int __init arch_init_kprobes(void)
1121 {
1122 	return 0;
1123 }
1124 
arch_trampoline_kprobe(struct kprobe * p)1125 int arch_trampoline_kprobe(struct kprobe *p)
1126 {
1127 	return 0;
1128 }
1129