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/ftrace.h>
41 #include <linux/kasan.h>
42 #include <linux/moduleloader.h>
43 #include <linux/objtool.h>
44 #include <linux/vmalloc.h>
45 #include <linux/pgtable.h>
46
47 #include <asm/text-patching.h>
48 #include <asm/cacheflush.h>
49 #include <asm/desc.h>
50 #include <linux/uaccess.h>
51 #include <asm/alternative.h>
52 #include <asm/insn.h>
53 #include <asm/debugreg.h>
54 #include <asm/set_memory.h>
55 #include <asm/ibt.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 bool faddr;
198
199 kp = get_kprobe((void *)addr);
200 faddr = ftrace_location(addr) == addr;
201 /*
202 * Use the current code if it is not modified by Kprobe
203 * and it cannot be modified by ftrace.
204 */
205 if (!kp && !faddr)
206 return addr;
207
208 /*
209 * Basically, kp->ainsn.insn has an original instruction.
210 * However, RIP-relative instruction can not do single-stepping
211 * at different place, __copy_instruction() tweaks the displacement of
212 * that instruction. In that case, we can't recover the instruction
213 * from the kp->ainsn.insn.
214 *
215 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
216 * of the first byte of the probed instruction, which is overwritten
217 * by int3. And the instruction at kp->addr is not modified by kprobes
218 * except for the first byte, we can recover the original instruction
219 * from it and kp->opcode.
220 *
221 * In case of Kprobes using ftrace, we do not have a copy of
222 * the original instruction. In fact, the ftrace location might
223 * be modified at anytime and even could be in an inconsistent state.
224 * Fortunately, we know that the original code is the ideal 5-byte
225 * long NOP.
226 */
227 if (copy_from_kernel_nofault(buf, (void *)addr,
228 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
229 return 0UL;
230
231 if (faddr)
232 memcpy(buf, x86_nops[5], 5);
233 else
234 buf[0] = kp->opcode;
235 return (unsigned long)buf;
236 }
237
238 /*
239 * Recover the probed instruction at addr for further analysis.
240 * Caller must lock kprobes by kprobe_mutex, or disable preemption
241 * for preventing to release referencing kprobes.
242 * Returns zero if the instruction can not get recovered (or access failed).
243 */
recover_probed_instruction(kprobe_opcode_t * buf,unsigned long addr)244 unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
245 {
246 unsigned long __addr;
247
248 __addr = __recover_optprobed_insn(buf, addr);
249 if (__addr != addr)
250 return __addr;
251
252 return __recover_probed_insn(buf, addr);
253 }
254
255 /* Check if paddr is at an instruction boundary */
can_probe(unsigned long paddr)256 static int can_probe(unsigned long paddr)
257 {
258 unsigned long addr, __addr, offset = 0;
259 struct insn insn;
260 kprobe_opcode_t buf[MAX_INSN_SIZE];
261
262 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
263 return 0;
264
265 /* Decode instructions */
266 addr = paddr - offset;
267 while (addr < paddr) {
268 int ret;
269
270 /*
271 * Check if the instruction has been modified by another
272 * kprobe, in which case we replace the breakpoint by the
273 * original instruction in our buffer.
274 * Also, jump optimization will change the breakpoint to
275 * relative-jump. Since the relative-jump itself is
276 * normally used, we just go through if there is no kprobe.
277 */
278 __addr = recover_probed_instruction(buf, addr);
279 if (!__addr)
280 return 0;
281
282 ret = insn_decode_kernel(&insn, (void *)__addr);
283 if (ret < 0)
284 return 0;
285
286 /*
287 * Another debugging subsystem might insert this breakpoint.
288 * In that case, we can't recover it.
289 */
290 if (insn.opcode.bytes[0] == INT3_INSN_OPCODE)
291 return 0;
292 addr += insn.length;
293 }
294
295 return (addr == paddr);
296 }
297
298 /* If x86 supports IBT (ENDBR) it must be skipped. */
arch_adjust_kprobe_addr(unsigned long addr,unsigned long offset,bool * on_func_entry)299 kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
300 bool *on_func_entry)
301 {
302 if (is_endbr(*(u32 *)addr)) {
303 *on_func_entry = !offset || offset == 4;
304 if (*on_func_entry)
305 offset = 4;
306
307 } else {
308 *on_func_entry = !offset;
309 }
310
311 return (kprobe_opcode_t *)(addr + offset);
312 }
313
314 /*
315 * Copy an instruction with recovering modified instruction by kprobes
316 * and adjust the displacement if the instruction uses the %rip-relative
317 * addressing mode. Note that since @real will be the final place of copied
318 * instruction, displacement must be adjust by @real, not @dest.
319 * This returns the length of copied instruction, or 0 if it has an error.
320 */
__copy_instruction(u8 * dest,u8 * src,u8 * real,struct insn * insn)321 int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
322 {
323 kprobe_opcode_t buf[MAX_INSN_SIZE];
324 unsigned long recovered_insn = recover_probed_instruction(buf, (unsigned long)src);
325 int ret;
326
327 if (!recovered_insn || !insn)
328 return 0;
329
330 /* This can access kernel text if given address is not recovered */
331 if (copy_from_kernel_nofault(dest, (void *)recovered_insn,
332 MAX_INSN_SIZE))
333 return 0;
334
335 ret = insn_decode_kernel(insn, dest);
336 if (ret < 0)
337 return 0;
338
339 /* We can not probe force emulate prefixed instruction */
340 if (insn_has_emulate_prefix(insn))
341 return 0;
342
343 /* Another subsystem puts a breakpoint, failed to recover */
344 if (insn->opcode.bytes[0] == INT3_INSN_OPCODE)
345 return 0;
346
347 /* We should not singlestep on the exception masking instructions */
348 if (insn_masking_exception(insn))
349 return 0;
350
351 #ifdef CONFIG_X86_64
352 /* Only x86_64 has RIP relative instructions */
353 if (insn_rip_relative(insn)) {
354 s64 newdisp;
355 u8 *disp;
356 /*
357 * The copied instruction uses the %rip-relative addressing
358 * mode. Adjust the displacement for the difference between
359 * the original location of this instruction and the location
360 * of the copy that will actually be run. The tricky bit here
361 * is making sure that the sign extension happens correctly in
362 * this calculation, since we need a signed 32-bit result to
363 * be sign-extended to 64 bits when it's added to the %rip
364 * value and yield the same 64-bit result that the sign-
365 * extension of the original signed 32-bit displacement would
366 * have given.
367 */
368 newdisp = (u8 *) src + (s64) insn->displacement.value
369 - (u8 *) real;
370 if ((s64) (s32) newdisp != newdisp) {
371 pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
372 return 0;
373 }
374 disp = (u8 *) dest + insn_offset_displacement(insn);
375 *(s32 *) disp = (s32) newdisp;
376 }
377 #endif
378 return insn->length;
379 }
380
381 /* Prepare reljump or int3 right after instruction */
prepare_singlestep(kprobe_opcode_t * buf,struct kprobe * p,struct insn * insn)382 static int prepare_singlestep(kprobe_opcode_t *buf, struct kprobe *p,
383 struct insn *insn)
384 {
385 int len = insn->length;
386
387 if (!IS_ENABLED(CONFIG_PREEMPTION) &&
388 !p->post_handler && can_boost(insn, p->addr) &&
389 MAX_INSN_SIZE - len >= JMP32_INSN_SIZE) {
390 /*
391 * These instructions can be executed directly if it
392 * jumps back to correct address.
393 */
394 synthesize_reljump(buf + len, p->ainsn.insn + len,
395 p->addr + insn->length);
396 len += JMP32_INSN_SIZE;
397 p->ainsn.boostable = 1;
398 } else {
399 /* Otherwise, put an int3 for trapping singlestep */
400 if (MAX_INSN_SIZE - len < INT3_INSN_SIZE)
401 return -ENOSPC;
402
403 buf[len] = INT3_INSN_OPCODE;
404 len += INT3_INSN_SIZE;
405 }
406
407 return len;
408 }
409
410 /* Make page to RO mode when allocate it */
alloc_insn_page(void)411 void *alloc_insn_page(void)
412 {
413 void *page;
414
415 page = module_alloc(PAGE_SIZE);
416 if (!page)
417 return NULL;
418
419 set_vm_flush_reset_perms(page);
420 /*
421 * First make the page read-only, and only then make it executable to
422 * prevent it from being W+X in between.
423 */
424 set_memory_ro((unsigned long)page, 1);
425
426 /*
427 * TODO: Once additional kernel code protection mechanisms are set, ensure
428 * that the page was not maliciously altered and it is still zeroed.
429 */
430 set_memory_x((unsigned long)page, 1);
431
432 return page;
433 }
434
435 /* Kprobe x86 instruction emulation - only regs->ip or IF flag modifiers */
436
kprobe_emulate_ifmodifiers(struct kprobe * p,struct pt_regs * regs)437 static void kprobe_emulate_ifmodifiers(struct kprobe *p, struct pt_regs *regs)
438 {
439 switch (p->ainsn.opcode) {
440 case 0xfa: /* cli */
441 regs->flags &= ~(X86_EFLAGS_IF);
442 break;
443 case 0xfb: /* sti */
444 regs->flags |= X86_EFLAGS_IF;
445 break;
446 case 0x9c: /* pushf */
447 int3_emulate_push(regs, regs->flags);
448 break;
449 case 0x9d: /* popf */
450 regs->flags = int3_emulate_pop(regs);
451 break;
452 }
453 regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
454 }
455 NOKPROBE_SYMBOL(kprobe_emulate_ifmodifiers);
456
kprobe_emulate_ret(struct kprobe * p,struct pt_regs * regs)457 static void kprobe_emulate_ret(struct kprobe *p, struct pt_regs *regs)
458 {
459 int3_emulate_ret(regs);
460 }
461 NOKPROBE_SYMBOL(kprobe_emulate_ret);
462
kprobe_emulate_call(struct kprobe * p,struct pt_regs * regs)463 static void kprobe_emulate_call(struct kprobe *p, struct pt_regs *regs)
464 {
465 unsigned long func = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
466
467 func += p->ainsn.rel32;
468 int3_emulate_call(regs, func);
469 }
470 NOKPROBE_SYMBOL(kprobe_emulate_call);
471
472 static nokprobe_inline
__kprobe_emulate_jmp(struct kprobe * p,struct pt_regs * regs,bool cond)473 void __kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond)
474 {
475 unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
476
477 if (cond)
478 ip += p->ainsn.rel32;
479 int3_emulate_jmp(regs, ip);
480 }
481
kprobe_emulate_jmp(struct kprobe * p,struct pt_regs * regs)482 static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)
483 {
484 __kprobe_emulate_jmp(p, regs, true);
485 }
486 NOKPROBE_SYMBOL(kprobe_emulate_jmp);
487
488 static const unsigned long jcc_mask[6] = {
489 [0] = X86_EFLAGS_OF,
490 [1] = X86_EFLAGS_CF,
491 [2] = X86_EFLAGS_ZF,
492 [3] = X86_EFLAGS_CF | X86_EFLAGS_ZF,
493 [4] = X86_EFLAGS_SF,
494 [5] = X86_EFLAGS_PF,
495 };
496
kprobe_emulate_jcc(struct kprobe * p,struct pt_regs * regs)497 static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs)
498 {
499 bool invert = p->ainsn.jcc.type & 1;
500 bool match;
501
502 if (p->ainsn.jcc.type < 0xc) {
503 match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1];
504 } else {
505 match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^
506 ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);
507 if (p->ainsn.jcc.type >= 0xe)
508 match = match || (regs->flags & X86_EFLAGS_ZF);
509 }
510 __kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert));
511 }
512 NOKPROBE_SYMBOL(kprobe_emulate_jcc);
513
kprobe_emulate_loop(struct kprobe * p,struct pt_regs * regs)514 static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs)
515 {
516 bool match;
517
518 if (p->ainsn.loop.type != 3) { /* LOOP* */
519 if (p->ainsn.loop.asize == 32)
520 match = ((*(u32 *)®s->cx)--) != 0;
521 #ifdef CONFIG_X86_64
522 else if (p->ainsn.loop.asize == 64)
523 match = ((*(u64 *)®s->cx)--) != 0;
524 #endif
525 else
526 match = ((*(u16 *)®s->cx)--) != 0;
527 } else { /* JCXZ */
528 if (p->ainsn.loop.asize == 32)
529 match = *(u32 *)(®s->cx) == 0;
530 #ifdef CONFIG_X86_64
531 else if (p->ainsn.loop.asize == 64)
532 match = *(u64 *)(®s->cx) == 0;
533 #endif
534 else
535 match = *(u16 *)(®s->cx) == 0;
536 }
537
538 if (p->ainsn.loop.type == 0) /* LOOPNE */
539 match = match && !(regs->flags & X86_EFLAGS_ZF);
540 else if (p->ainsn.loop.type == 1) /* LOOPE */
541 match = match && (regs->flags & X86_EFLAGS_ZF);
542
543 __kprobe_emulate_jmp(p, regs, match);
544 }
545 NOKPROBE_SYMBOL(kprobe_emulate_loop);
546
547 static const int addrmode_regoffs[] = {
548 offsetof(struct pt_regs, ax),
549 offsetof(struct pt_regs, cx),
550 offsetof(struct pt_regs, dx),
551 offsetof(struct pt_regs, bx),
552 offsetof(struct pt_regs, sp),
553 offsetof(struct pt_regs, bp),
554 offsetof(struct pt_regs, si),
555 offsetof(struct pt_regs, di),
556 #ifdef CONFIG_X86_64
557 offsetof(struct pt_regs, r8),
558 offsetof(struct pt_regs, r9),
559 offsetof(struct pt_regs, r10),
560 offsetof(struct pt_regs, r11),
561 offsetof(struct pt_regs, r12),
562 offsetof(struct pt_regs, r13),
563 offsetof(struct pt_regs, r14),
564 offsetof(struct pt_regs, r15),
565 #endif
566 };
567
kprobe_emulate_call_indirect(struct kprobe * p,struct pt_regs * regs)568 static void kprobe_emulate_call_indirect(struct kprobe *p, struct pt_regs *regs)
569 {
570 unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
571
572 int3_emulate_call(regs, regs_get_register(regs, offs));
573 }
574 NOKPROBE_SYMBOL(kprobe_emulate_call_indirect);
575
kprobe_emulate_jmp_indirect(struct kprobe * p,struct pt_regs * regs)576 static void kprobe_emulate_jmp_indirect(struct kprobe *p, struct pt_regs *regs)
577 {
578 unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
579
580 int3_emulate_jmp(regs, regs_get_register(regs, offs));
581 }
582 NOKPROBE_SYMBOL(kprobe_emulate_jmp_indirect);
583
prepare_emulation(struct kprobe * p,struct insn * insn)584 static int prepare_emulation(struct kprobe *p, struct insn *insn)
585 {
586 insn_byte_t opcode = insn->opcode.bytes[0];
587
588 switch (opcode) {
589 case 0xfa: /* cli */
590 case 0xfb: /* sti */
591 case 0x9c: /* pushfl */
592 case 0x9d: /* popf/popfd */
593 /*
594 * IF modifiers must be emulated since it will enable interrupt while
595 * int3 single stepping.
596 */
597 p->ainsn.emulate_op = kprobe_emulate_ifmodifiers;
598 p->ainsn.opcode = opcode;
599 break;
600 case 0xc2: /* ret/lret */
601 case 0xc3:
602 case 0xca:
603 case 0xcb:
604 p->ainsn.emulate_op = kprobe_emulate_ret;
605 break;
606 case 0x9a: /* far call absolute -- segment is not supported */
607 case 0xea: /* far jmp absolute -- segment is not supported */
608 case 0xcc: /* int3 */
609 case 0xcf: /* iret -- in-kernel IRET is not supported */
610 return -EOPNOTSUPP;
611 break;
612 case 0xe8: /* near call relative */
613 p->ainsn.emulate_op = kprobe_emulate_call;
614 if (insn->immediate.nbytes == 2)
615 p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
616 else
617 p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
618 break;
619 case 0xeb: /* short jump relative */
620 case 0xe9: /* near jump relative */
621 p->ainsn.emulate_op = kprobe_emulate_jmp;
622 if (insn->immediate.nbytes == 1)
623 p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
624 else if (insn->immediate.nbytes == 2)
625 p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
626 else
627 p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
628 break;
629 case 0x70 ... 0x7f:
630 /* 1 byte conditional jump */
631 p->ainsn.emulate_op = kprobe_emulate_jcc;
632 p->ainsn.jcc.type = opcode & 0xf;
633 p->ainsn.rel32 = *(char *)insn->immediate.bytes;
634 break;
635 case 0x0f:
636 opcode = insn->opcode.bytes[1];
637 if ((opcode & 0xf0) == 0x80) {
638 /* 2 bytes Conditional Jump */
639 p->ainsn.emulate_op = kprobe_emulate_jcc;
640 p->ainsn.jcc.type = opcode & 0xf;
641 if (insn->immediate.nbytes == 2)
642 p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
643 else
644 p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
645 } else if (opcode == 0x01 &&
646 X86_MODRM_REG(insn->modrm.bytes[0]) == 0 &&
647 X86_MODRM_MOD(insn->modrm.bytes[0]) == 3) {
648 /* VM extensions - not supported */
649 return -EOPNOTSUPP;
650 }
651 break;
652 case 0xe0: /* Loop NZ */
653 case 0xe1: /* Loop */
654 case 0xe2: /* Loop */
655 case 0xe3: /* J*CXZ */
656 p->ainsn.emulate_op = kprobe_emulate_loop;
657 p->ainsn.loop.type = opcode & 0x3;
658 p->ainsn.loop.asize = insn->addr_bytes * 8;
659 p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
660 break;
661 case 0xff:
662 /*
663 * Since the 0xff is an extended group opcode, the instruction
664 * is determined by the MOD/RM byte.
665 */
666 opcode = insn->modrm.bytes[0];
667 if ((opcode & 0x30) == 0x10) {
668 if ((opcode & 0x8) == 0x8)
669 return -EOPNOTSUPP; /* far call */
670 /* call absolute, indirect */
671 p->ainsn.emulate_op = kprobe_emulate_call_indirect;
672 } else if ((opcode & 0x30) == 0x20) {
673 if ((opcode & 0x8) == 0x8)
674 return -EOPNOTSUPP; /* far jmp */
675 /* jmp near absolute indirect */
676 p->ainsn.emulate_op = kprobe_emulate_jmp_indirect;
677 } else
678 break;
679
680 if (insn->addr_bytes != sizeof(unsigned long))
681 return -EOPNOTSUPP; /* Don't support different size */
682 if (X86_MODRM_MOD(opcode) != 3)
683 return -EOPNOTSUPP; /* TODO: support memory addressing */
684
685 p->ainsn.indirect.reg = X86_MODRM_RM(opcode);
686 #ifdef CONFIG_X86_64
687 if (X86_REX_B(insn->rex_prefix.value))
688 p->ainsn.indirect.reg += 8;
689 #endif
690 break;
691 default:
692 break;
693 }
694 p->ainsn.size = insn->length;
695
696 return 0;
697 }
698
arch_copy_kprobe(struct kprobe * p)699 static int arch_copy_kprobe(struct kprobe *p)
700 {
701 struct insn insn;
702 kprobe_opcode_t buf[MAX_INSN_SIZE];
703 int ret, len;
704
705 /* Copy an instruction with recovering if other optprobe modifies it.*/
706 len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
707 if (!len)
708 return -EINVAL;
709
710 /* Analyze the opcode and setup emulate functions */
711 ret = prepare_emulation(p, &insn);
712 if (ret < 0)
713 return ret;
714
715 /* Add int3 for single-step or booster jmp */
716 len = prepare_singlestep(buf, p, &insn);
717 if (len < 0)
718 return len;
719
720 /* Also, displacement change doesn't affect the first byte */
721 p->opcode = buf[0];
722
723 p->ainsn.tp_len = len;
724 perf_event_text_poke(p->ainsn.insn, NULL, 0, buf, len);
725
726 /* OK, write back the instruction(s) into ROX insn buffer */
727 text_poke(p->ainsn.insn, buf, len);
728
729 return 0;
730 }
731
arch_prepare_kprobe(struct kprobe * p)732 int arch_prepare_kprobe(struct kprobe *p)
733 {
734 int ret;
735
736 if (alternatives_text_reserved(p->addr, p->addr))
737 return -EINVAL;
738
739 if (!can_probe((unsigned long)p->addr))
740 return -EILSEQ;
741
742 memset(&p->ainsn, 0, sizeof(p->ainsn));
743
744 /* insn: must be on special executable page on x86. */
745 p->ainsn.insn = get_insn_slot();
746 if (!p->ainsn.insn)
747 return -ENOMEM;
748
749 ret = arch_copy_kprobe(p);
750 if (ret) {
751 free_insn_slot(p->ainsn.insn, 0);
752 p->ainsn.insn = NULL;
753 }
754
755 return ret;
756 }
757
arch_arm_kprobe(struct kprobe * p)758 void arch_arm_kprobe(struct kprobe *p)
759 {
760 u8 int3 = INT3_INSN_OPCODE;
761
762 text_poke(p->addr, &int3, 1);
763 text_poke_sync();
764 perf_event_text_poke(p->addr, &p->opcode, 1, &int3, 1);
765 }
766
arch_disarm_kprobe(struct kprobe * p)767 void arch_disarm_kprobe(struct kprobe *p)
768 {
769 u8 int3 = INT3_INSN_OPCODE;
770
771 perf_event_text_poke(p->addr, &int3, 1, &p->opcode, 1);
772 text_poke(p->addr, &p->opcode, 1);
773 text_poke_sync();
774 }
775
arch_remove_kprobe(struct kprobe * p)776 void arch_remove_kprobe(struct kprobe *p)
777 {
778 if (p->ainsn.insn) {
779 /* Record the perf event before freeing the slot */
780 perf_event_text_poke(p->ainsn.insn, p->ainsn.insn,
781 p->ainsn.tp_len, NULL, 0);
782 free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
783 p->ainsn.insn = NULL;
784 }
785 }
786
787 static nokprobe_inline void
save_previous_kprobe(struct kprobe_ctlblk * kcb)788 save_previous_kprobe(struct kprobe_ctlblk *kcb)
789 {
790 kcb->prev_kprobe.kp = kprobe_running();
791 kcb->prev_kprobe.status = kcb->kprobe_status;
792 kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
793 kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
794 }
795
796 static nokprobe_inline void
restore_previous_kprobe(struct kprobe_ctlblk * kcb)797 restore_previous_kprobe(struct kprobe_ctlblk *kcb)
798 {
799 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
800 kcb->kprobe_status = kcb->prev_kprobe.status;
801 kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
802 kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
803 }
804
805 static nokprobe_inline void
set_current_kprobe(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)806 set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
807 struct kprobe_ctlblk *kcb)
808 {
809 __this_cpu_write(current_kprobe, p);
810 kcb->kprobe_saved_flags = kcb->kprobe_old_flags
811 = (regs->flags & X86_EFLAGS_IF);
812 }
813
kprobe_post_process(struct kprobe * cur,struct pt_regs * regs,struct kprobe_ctlblk * kcb)814 static void kprobe_post_process(struct kprobe *cur, struct pt_regs *regs,
815 struct kprobe_ctlblk *kcb)
816 {
817 /* Restore back the original saved kprobes variables and continue. */
818 if (kcb->kprobe_status == KPROBE_REENTER) {
819 /* This will restore both kcb and current_kprobe */
820 restore_previous_kprobe(kcb);
821 } else {
822 /*
823 * Always update the kcb status because
824 * reset_curent_kprobe() doesn't update kcb.
825 */
826 kcb->kprobe_status = KPROBE_HIT_SSDONE;
827 if (cur->post_handler)
828 cur->post_handler(cur, regs, 0);
829 reset_current_kprobe();
830 }
831 }
832 NOKPROBE_SYMBOL(kprobe_post_process);
833
setup_singlestep(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb,int reenter)834 static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
835 struct kprobe_ctlblk *kcb, int reenter)
836 {
837 if (setup_detour_execution(p, regs, reenter))
838 return;
839
840 #if !defined(CONFIG_PREEMPTION)
841 if (p->ainsn.boostable) {
842 /* Boost up -- we can execute copied instructions directly */
843 if (!reenter)
844 reset_current_kprobe();
845 /*
846 * Reentering boosted probe doesn't reset current_kprobe,
847 * nor set current_kprobe, because it doesn't use single
848 * stepping.
849 */
850 regs->ip = (unsigned long)p->ainsn.insn;
851 return;
852 }
853 #endif
854 if (reenter) {
855 save_previous_kprobe(kcb);
856 set_current_kprobe(p, regs, kcb);
857 kcb->kprobe_status = KPROBE_REENTER;
858 } else
859 kcb->kprobe_status = KPROBE_HIT_SS;
860
861 if (p->ainsn.emulate_op) {
862 p->ainsn.emulate_op(p, regs);
863 kprobe_post_process(p, regs, kcb);
864 return;
865 }
866
867 /* Disable interrupt, and set ip register on trampoline */
868 regs->flags &= ~X86_EFLAGS_IF;
869 regs->ip = (unsigned long)p->ainsn.insn;
870 }
871 NOKPROBE_SYMBOL(setup_singlestep);
872
873 /*
874 * Called after single-stepping. p->addr is the address of the
875 * instruction whose first byte has been replaced by the "int3"
876 * instruction. To avoid the SMP problems that can occur when we
877 * temporarily put back the original opcode to single-step, we
878 * single-stepped a copy of the instruction. The address of this
879 * copy is p->ainsn.insn. We also doesn't use trap, but "int3" again
880 * right after the copied instruction.
881 * Different from the trap single-step, "int3" single-step can not
882 * handle the instruction which changes the ip register, e.g. jmp,
883 * call, conditional jmp, and the instructions which changes the IF
884 * flags because interrupt must be disabled around the single-stepping.
885 * Such instructions are software emulated, but others are single-stepped
886 * using "int3".
887 *
888 * When the 2nd "int3" handled, the regs->ip and regs->flags needs to
889 * be adjusted, so that we can resume execution on correct code.
890 */
resume_singlestep(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)891 static void resume_singlestep(struct kprobe *p, struct pt_regs *regs,
892 struct kprobe_ctlblk *kcb)
893 {
894 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
895 unsigned long orig_ip = (unsigned long)p->addr;
896
897 /* Restore saved interrupt flag and ip register */
898 regs->flags |= kcb->kprobe_saved_flags;
899 /* Note that regs->ip is executed int3 so must be a step back */
900 regs->ip += (orig_ip - copy_ip) - INT3_INSN_SIZE;
901 }
902 NOKPROBE_SYMBOL(resume_singlestep);
903
904 /*
905 * We have reentered the kprobe_handler(), since another probe was hit while
906 * within the handler. We save the original kprobes variables and just single
907 * step on the instruction of the new probe without calling any user handlers.
908 */
reenter_kprobe(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)909 static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
910 struct kprobe_ctlblk *kcb)
911 {
912 switch (kcb->kprobe_status) {
913 case KPROBE_HIT_SSDONE:
914 case KPROBE_HIT_ACTIVE:
915 case KPROBE_HIT_SS:
916 kprobes_inc_nmissed_count(p);
917 setup_singlestep(p, regs, kcb, 1);
918 break;
919 case KPROBE_REENTER:
920 /* A probe has been hit in the codepath leading up to, or just
921 * after, single-stepping of a probed instruction. This entire
922 * codepath should strictly reside in .kprobes.text section.
923 * Raise a BUG or we'll continue in an endless reentering loop
924 * and eventually a stack overflow.
925 */
926 pr_err("Unrecoverable kprobe detected.\n");
927 dump_kprobe(p);
928 BUG();
929 default:
930 /* impossible cases */
931 WARN_ON(1);
932 return 0;
933 }
934
935 return 1;
936 }
937 NOKPROBE_SYMBOL(reenter_kprobe);
938
kprobe_is_ss(struct kprobe_ctlblk * kcb)939 static nokprobe_inline int kprobe_is_ss(struct kprobe_ctlblk *kcb)
940 {
941 return (kcb->kprobe_status == KPROBE_HIT_SS ||
942 kcb->kprobe_status == KPROBE_REENTER);
943 }
944
945 /*
946 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
947 * remain disabled throughout this function.
948 */
kprobe_int3_handler(struct pt_regs * regs)949 int kprobe_int3_handler(struct pt_regs *regs)
950 {
951 kprobe_opcode_t *addr;
952 struct kprobe *p;
953 struct kprobe_ctlblk *kcb;
954
955 if (user_mode(regs))
956 return 0;
957
958 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
959 /*
960 * We don't want to be preempted for the entire duration of kprobe
961 * processing. Since int3 and debug trap disables irqs and we clear
962 * IF while singlestepping, it must be no preemptible.
963 */
964
965 kcb = get_kprobe_ctlblk();
966 p = get_kprobe(addr);
967
968 if (p) {
969 if (kprobe_running()) {
970 if (reenter_kprobe(p, regs, kcb))
971 return 1;
972 } else {
973 set_current_kprobe(p, regs, kcb);
974 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
975
976 /*
977 * If we have no pre-handler or it returned 0, we
978 * continue with normal processing. If we have a
979 * pre-handler and it returned non-zero, that means
980 * user handler setup registers to exit to another
981 * instruction, we must skip the single stepping.
982 */
983 if (!p->pre_handler || !p->pre_handler(p, regs))
984 setup_singlestep(p, regs, kcb, 0);
985 else
986 reset_current_kprobe();
987 return 1;
988 }
989 } else if (kprobe_is_ss(kcb)) {
990 p = kprobe_running();
991 if ((unsigned long)p->ainsn.insn < regs->ip &&
992 (unsigned long)p->ainsn.insn + MAX_INSN_SIZE > regs->ip) {
993 /* Most provably this is the second int3 for singlestep */
994 resume_singlestep(p, regs, kcb);
995 kprobe_post_process(p, regs, kcb);
996 return 1;
997 }
998 }
999
1000 if (*addr != INT3_INSN_OPCODE) {
1001 /*
1002 * The breakpoint instruction was removed right
1003 * after we hit it. Another cpu has removed
1004 * either a probepoint or a debugger breakpoint
1005 * at this address. In either case, no further
1006 * handling of this interrupt is appropriate.
1007 * Back up over the (now missing) int3 and run
1008 * the original instruction.
1009 */
1010 regs->ip = (unsigned long)addr;
1011 return 1;
1012 } /* else: not a kprobe fault; let the kernel handle it */
1013
1014 return 0;
1015 }
1016 NOKPROBE_SYMBOL(kprobe_int3_handler);
1017
kprobe_fault_handler(struct pt_regs * regs,int trapnr)1018 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
1019 {
1020 struct kprobe *cur = kprobe_running();
1021 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1022
1023 if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
1024 /* This must happen on single-stepping */
1025 WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
1026 kcb->kprobe_status != KPROBE_REENTER);
1027 /*
1028 * We are here because the instruction being single
1029 * stepped caused a page fault. We reset the current
1030 * kprobe and the ip points back to the probe address
1031 * and allow the page fault handler to continue as a
1032 * normal page fault.
1033 */
1034 regs->ip = (unsigned long)cur->addr;
1035
1036 /*
1037 * If the IF flag was set before the kprobe hit,
1038 * don't touch it:
1039 */
1040 regs->flags |= kcb->kprobe_old_flags;
1041
1042 if (kcb->kprobe_status == KPROBE_REENTER)
1043 restore_previous_kprobe(kcb);
1044 else
1045 reset_current_kprobe();
1046 }
1047
1048 return 0;
1049 }
1050 NOKPROBE_SYMBOL(kprobe_fault_handler);
1051
arch_populate_kprobe_blacklist(void)1052 int __init arch_populate_kprobe_blacklist(void)
1053 {
1054 return kprobe_add_area_blacklist((unsigned long)__entry_text_start,
1055 (unsigned long)__entry_text_end);
1056 }
1057
arch_init_kprobes(void)1058 int __init arch_init_kprobes(void)
1059 {
1060 return 0;
1061 }
1062
arch_trampoline_kprobe(struct kprobe * p)1063 int arch_trampoline_kprobe(struct kprobe *p)
1064 {
1065 return 0;
1066 }
1067