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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/extable.h>
37#include <linux/kdebug.h>
38#include <linux/kallsyms.h>
39#include <linux/ftrace.h>
40#include <linux/frame.h>
41#include <linux/kasan.h>
42#include <linux/moduleloader.h>
43
44#include <asm/text-patching.h>
45#include <asm/cacheflush.h>
46#include <asm/desc.h>
47#include <asm/pgtable.h>
48#include <linux/uaccess.h>
49#include <asm/alternative.h>
50#include <asm/insn.h>
51#include <asm/debugreg.h>
52#include <asm/set_memory.h>
53
54#include "common.h"
55
56DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
57DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
58
59#define stack_addr(regs) ((unsigned long *)regs->sp)
60
61#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
62 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
63 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
64 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
65 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
66 << (row % 32))
67 /*
68 * Undefined/reserved opcodes, conditional jump, Opcode Extension
69 * Groups, and some special opcodes can not boost.
70 * This is non-const and volatile to keep gcc from statically
71 * optimizing it out, as variable_test_bit makes gcc think only
72 * *(unsigned long*) is used.
73 */
74static volatile u32 twobyte_is_boostable[256 / 32] = {
75 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
76 /* ---------------------------------------------- */
77 W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
78 W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
79 W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
80 W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
81 W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
82 W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
83 W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
84 W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
85 W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
86 W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
87 W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
88 W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
89 W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
90 W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
91 W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
92 W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
93 /* ----------------------------------------------- */
94 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
95};
96#undef W
97
98struct kretprobe_blackpoint kretprobe_blacklist[] = {
99 {"__switch_to", }, /* This function switches only current task, but
100 doesn't switch kernel stack.*/
101 {NULL, NULL} /* Terminator */
102};
103
104const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
105
106static nokprobe_inline void
107__synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
108{
109 struct __arch_relative_insn {
110 u8 op;
111 s32 raddr;
112 } __packed *insn;
113
114 insn = (struct __arch_relative_insn *)dest;
115 insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
116 insn->op = op;
117}
118
119/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
120void synthesize_reljump(void *dest, void *from, void *to)
121{
122 __synthesize_relative_insn(dest, from, to, RELATIVEJUMP_OPCODE);
123}
124NOKPROBE_SYMBOL(synthesize_reljump);
125
126/* Insert a call instruction at address 'from', which calls address 'to'.*/
127void synthesize_relcall(void *dest, void *from, void *to)
128{
129 __synthesize_relative_insn(dest, from, to, RELATIVECALL_OPCODE);
130}
131NOKPROBE_SYMBOL(synthesize_relcall);
132
133/*
134 * Skip the prefixes of the instruction.
135 */
136static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn)
137{
138 insn_attr_t attr;
139
140 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
141 while (inat_is_legacy_prefix(attr)) {
142 insn++;
143 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
144 }
145#ifdef CONFIG_X86_64
146 if (inat_is_rex_prefix(attr))
147 insn++;
148#endif
149 return insn;
150}
151NOKPROBE_SYMBOL(skip_prefixes);
152
153/*
154 * Returns non-zero if INSN is boostable.
155 * RIP relative instructions are adjusted at copying time in 64 bits mode
156 */
157int can_boost(struct insn *insn, void *addr)
158{
159 kprobe_opcode_t opcode;
160
161 if (search_exception_tables((unsigned long)addr))
162 return 0; /* Page fault may occur on this address. */
163
164 /* 2nd-byte opcode */
165 if (insn->opcode.nbytes == 2)
166 return test_bit(insn->opcode.bytes[1],
167 (unsigned long *)twobyte_is_boostable);
168
169 if (insn->opcode.nbytes != 1)
170 return 0;
171
172 /* Can't boost Address-size override prefix */
173 if (unlikely(inat_is_address_size_prefix(insn->attr)))
174 return 0;
175
176 opcode = insn->opcode.bytes[0];
177
178 switch (opcode & 0xf0) {
179 case 0x60:
180 /* can't boost "bound" */
181 return (opcode != 0x62);
182 case 0x70:
183 return 0; /* can't boost conditional jump */
184 case 0x90:
185 return opcode != 0x9a; /* can't boost call far */
186 case 0xc0:
187 /* can't boost software-interruptions */
188 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
189 case 0xd0:
190 /* can boost AA* and XLAT */
191 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
192 case 0xe0:
193 /* can boost in/out and absolute jmps */
194 return ((opcode & 0x04) || opcode == 0xea);
195 case 0xf0:
196 /* clear and set flags are boostable */
197 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
198 default:
199 /* CS override prefix and call are not boostable */
200 return (opcode != 0x2e && opcode != 0x9a);
201 }
202}
203
204static unsigned long
205__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
206{
207 struct kprobe *kp;
208 unsigned long faddr;
209
210 kp = get_kprobe((void *)addr);
211 faddr = ftrace_location(addr);
212 /*
213 * Addresses inside the ftrace location are refused by
214 * arch_check_ftrace_location(). Something went terribly wrong
215 * if such an address is checked here.
216 */
217 if (WARN_ON(faddr && faddr != addr))
218 return 0UL;
219 /*
220 * Use the current code if it is not modified by Kprobe
221 * and it cannot be modified by ftrace.
222 */
223 if (!kp && !faddr)
224 return addr;
225
226 /*
227 * Basically, kp->ainsn.insn has an original instruction.
228 * However, RIP-relative instruction can not do single-stepping
229 * at different place, __copy_instruction() tweaks the displacement of
230 * that instruction. In that case, we can't recover the instruction
231 * from the kp->ainsn.insn.
232 *
233 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
234 * of the first byte of the probed instruction, which is overwritten
235 * by int3. And the instruction at kp->addr is not modified by kprobes
236 * except for the first byte, we can recover the original instruction
237 * from it and kp->opcode.
238 *
239 * In case of Kprobes using ftrace, we do not have a copy of
240 * the original instruction. In fact, the ftrace location might
241 * be modified at anytime and even could be in an inconsistent state.
242 * Fortunately, we know that the original code is the ideal 5-byte
243 * long NOP.
244 */
245 if (probe_kernel_read(buf, (void *)addr,
246 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
247 return 0UL;
248
249 if (faddr)
250 memcpy(buf, ideal_nops[NOP_ATOMIC5], 5);
251 else
252 buf[0] = kp->opcode;
253 return (unsigned long)buf;
254}
255
256/*
257 * Recover the probed instruction at addr for further analysis.
258 * Caller must lock kprobes by kprobe_mutex, or disable preemption
259 * for preventing to release referencing kprobes.
260 * Returns zero if the instruction can not get recovered (or access failed).
261 */
262unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
263{
264 unsigned long __addr;
265
266 __addr = __recover_optprobed_insn(buf, addr);
267 if (__addr != addr)
268 return __addr;
269
270 return __recover_probed_insn(buf, addr);
271}
272
273/* Check if paddr is at an instruction boundary */
274static int can_probe(unsigned long paddr)
275{
276 unsigned long addr, __addr, offset = 0;
277 struct insn insn;
278 kprobe_opcode_t buf[MAX_INSN_SIZE];
279
280 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
281 return 0;
282
283 /* Decode instructions */
284 addr = paddr - offset;
285 while (addr < paddr) {
286 /*
287 * Check if the instruction has been modified by another
288 * kprobe, in which case we replace the breakpoint by the
289 * original instruction in our buffer.
290 * Also, jump optimization will change the breakpoint to
291 * relative-jump. Since the relative-jump itself is
292 * normally used, we just go through if there is no kprobe.
293 */
294 __addr = recover_probed_instruction(buf, addr);
295 if (!__addr)
296 return 0;
297 kernel_insn_init(&insn, (void *)__addr, MAX_INSN_SIZE);
298 insn_get_length(&insn);
299
300 /*
301 * Another debugging subsystem might insert this breakpoint.
302 * In that case, we can't recover it.
303 */
304 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
305 return 0;
306 addr += insn.length;
307 }
308
309 return (addr == paddr);
310}
311
312/*
313 * Returns non-zero if opcode modifies the interrupt flag.
314 */
315static int is_IF_modifier(kprobe_opcode_t *insn)
316{
317 /* Skip prefixes */
318 insn = skip_prefixes(insn);
319
320 switch (*insn) {
321 case 0xfa: /* cli */
322 case 0xfb: /* sti */
323 case 0xcf: /* iret/iretd */
324 case 0x9d: /* popf/popfd */
325 return 1;
326 }
327
328 return 0;
329}
330
331/*
332 * Copy an instruction with recovering modified instruction by kprobes
333 * and adjust the displacement if the instruction uses the %rip-relative
334 * addressing mode. Note that since @real will be the final place of copied
335 * instruction, displacement must be adjust by @real, not @dest.
336 * This returns the length of copied instruction, or 0 if it has an error.
337 */
338int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
339{
340 kprobe_opcode_t buf[MAX_INSN_SIZE];
341 unsigned long recovered_insn =
342 recover_probed_instruction(buf, (unsigned long)src);
343
344 if (!recovered_insn || !insn)
345 return 0;
346
347 /* This can access kernel text if given address is not recovered */
348 if (probe_kernel_read(dest, (void *)recovered_insn, MAX_INSN_SIZE))
349 return 0;
350
351 kernel_insn_init(insn, dest, MAX_INSN_SIZE);
352 insn_get_length(insn);
353
354 /* Another subsystem puts a breakpoint, failed to recover */
355 if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
356 return 0;
357
358 /* We should not singlestep on the exception masking instructions */
359 if (insn_masking_exception(insn))
360 return 0;
361
362#ifdef CONFIG_X86_64
363 /* Only x86_64 has RIP relative instructions */
364 if (insn_rip_relative(insn)) {
365 s64 newdisp;
366 u8 *disp;
367 /*
368 * The copied instruction uses the %rip-relative addressing
369 * mode. Adjust the displacement for the difference between
370 * the original location of this instruction and the location
371 * of the copy that will actually be run. The tricky bit here
372 * is making sure that the sign extension happens correctly in
373 * this calculation, since we need a signed 32-bit result to
374 * be sign-extended to 64 bits when it's added to the %rip
375 * value and yield the same 64-bit result that the sign-
376 * extension of the original signed 32-bit displacement would
377 * have given.
378 */
379 newdisp = (u8 *) src + (s64) insn->displacement.value
380 - (u8 *) real;
381 if ((s64) (s32) newdisp != newdisp) {
382 pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
383 return 0;
384 }
385 disp = (u8 *) dest + insn_offset_displacement(insn);
386 *(s32 *) disp = (s32) newdisp;
387 }
388#endif
389 return insn->length;
390}
391
392/* Prepare reljump right after instruction to boost */
393static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p,
394 struct insn *insn)
395{
396 int len = insn->length;
397
398 if (can_boost(insn, p->addr) &&
399 MAX_INSN_SIZE - len >= RELATIVEJUMP_SIZE) {
400 /*
401 * These instructions can be executed directly if it
402 * jumps back to correct address.
403 */
404 synthesize_reljump(buf + len, p->ainsn.insn + len,
405 p->addr + insn->length);
406 len += RELATIVEJUMP_SIZE;
407 p->ainsn.boostable = true;
408 } else {
409 p->ainsn.boostable = false;
410 }
411
412 return len;
413}
414
415/* Make page to RO mode when allocate it */
416void *alloc_insn_page(void)
417{
418 void *page;
419
420 page = module_alloc(PAGE_SIZE);
421 if (!page)
422 return NULL;
423
424 set_vm_flush_reset_perms(page);
425 /*
426 * First make the page read-only, and only then make it executable to
427 * prevent it from being W+X in between.
428 */
429 set_memory_ro((unsigned long)page, 1);
430
431 /*
432 * TODO: Once additional kernel code protection mechanisms are set, ensure
433 * that the page was not maliciously altered and it is still zeroed.
434 */
435 set_memory_x((unsigned long)page, 1);
436
437 return page;
438}
439
440/* Recover page to RW mode before releasing it */
441void free_insn_page(void *page)
442{
443 module_memfree(page);
444}
445
446static int arch_copy_kprobe(struct kprobe *p)
447{
448 struct insn insn;
449 kprobe_opcode_t buf[MAX_INSN_SIZE];
450 int len;
451
452 /* Copy an instruction with recovering if other optprobe modifies it.*/
453 len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
454 if (!len)
455 return -EINVAL;
456
457 /*
458 * __copy_instruction can modify the displacement of the instruction,
459 * but it doesn't affect boostable check.
460 */
461 len = prepare_boost(buf, p, &insn);
462
463 /* Check whether the instruction modifies Interrupt Flag or not */
464 p->ainsn.if_modifier = is_IF_modifier(buf);
465
466 /* Also, displacement change doesn't affect the first byte */
467 p->opcode = buf[0];
468
469 /* OK, write back the instruction(s) into ROX insn buffer */
470 text_poke(p->ainsn.insn, buf, len);
471
472 return 0;
473}
474
475int arch_prepare_kprobe(struct kprobe *p)
476{
477 int ret;
478
479 if (alternatives_text_reserved(p->addr, p->addr))
480 return -EINVAL;
481
482 if (!can_probe((unsigned long)p->addr))
483 return -EILSEQ;
484 /* insn: must be on special executable page on x86. */
485 p->ainsn.insn = get_insn_slot();
486 if (!p->ainsn.insn)
487 return -ENOMEM;
488
489 ret = arch_copy_kprobe(p);
490 if (ret) {
491 free_insn_slot(p->ainsn.insn, 0);
492 p->ainsn.insn = NULL;
493 }
494
495 return ret;
496}
497
498void arch_arm_kprobe(struct kprobe *p)
499{
500 text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
501}
502
503void arch_disarm_kprobe(struct kprobe *p)
504{
505 text_poke(p->addr, &p->opcode, 1);
506}
507
508void arch_remove_kprobe(struct kprobe *p)
509{
510 if (p->ainsn.insn) {
511 free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
512 p->ainsn.insn = NULL;
513 }
514}
515
516static nokprobe_inline void
517save_previous_kprobe(struct kprobe_ctlblk *kcb)
518{
519 kcb->prev_kprobe.kp = kprobe_running();
520 kcb->prev_kprobe.status = kcb->kprobe_status;
521 kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
522 kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
523}
524
525static nokprobe_inline void
526restore_previous_kprobe(struct kprobe_ctlblk *kcb)
527{
528 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
529 kcb->kprobe_status = kcb->prev_kprobe.status;
530 kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
531 kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
532}
533
534static nokprobe_inline void
535set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
536 struct kprobe_ctlblk *kcb)
537{
538 __this_cpu_write(current_kprobe, p);
539 kcb->kprobe_saved_flags = kcb->kprobe_old_flags
540 = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
541 if (p->ainsn.if_modifier)
542 kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
543}
544
545static nokprobe_inline void clear_btf(void)
546{
547 if (test_thread_flag(TIF_BLOCKSTEP)) {
548 unsigned long debugctl = get_debugctlmsr();
549
550 debugctl &= ~DEBUGCTLMSR_BTF;
551 update_debugctlmsr(debugctl);
552 }
553}
554
555static nokprobe_inline void restore_btf(void)
556{
557 if (test_thread_flag(TIF_BLOCKSTEP)) {
558 unsigned long debugctl = get_debugctlmsr();
559
560 debugctl |= DEBUGCTLMSR_BTF;
561 update_debugctlmsr(debugctl);
562 }
563}
564
565void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
566{
567 unsigned long *sara = stack_addr(regs);
568
569 ri->ret_addr = (kprobe_opcode_t *) *sara;
570 ri->fp = sara;
571
572 /* Replace the return addr with trampoline addr */
573 *sara = (unsigned long) &kretprobe_trampoline;
574}
575NOKPROBE_SYMBOL(arch_prepare_kretprobe);
576
577static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
578 struct kprobe_ctlblk *kcb, int reenter)
579{
580 if (setup_detour_execution(p, regs, reenter))
581 return;
582
583#if !defined(CONFIG_PREEMPTION)
584 if (p->ainsn.boostable && !p->post_handler) {
585 /* Boost up -- we can execute copied instructions directly */
586 if (!reenter)
587 reset_current_kprobe();
588 /*
589 * Reentering boosted probe doesn't reset current_kprobe,
590 * nor set current_kprobe, because it doesn't use single
591 * stepping.
592 */
593 regs->ip = (unsigned long)p->ainsn.insn;
594 return;
595 }
596#endif
597 if (reenter) {
598 save_previous_kprobe(kcb);
599 set_current_kprobe(p, regs, kcb);
600 kcb->kprobe_status = KPROBE_REENTER;
601 } else
602 kcb->kprobe_status = KPROBE_HIT_SS;
603 /* Prepare real single stepping */
604 clear_btf();
605 regs->flags |= X86_EFLAGS_TF;
606 regs->flags &= ~X86_EFLAGS_IF;
607 /* single step inline if the instruction is an int3 */
608 if (p->opcode == BREAKPOINT_INSTRUCTION)
609 regs->ip = (unsigned long)p->addr;
610 else
611 regs->ip = (unsigned long)p->ainsn.insn;
612}
613NOKPROBE_SYMBOL(setup_singlestep);
614
615/*
616 * We have reentered the kprobe_handler(), since another probe was hit while
617 * within the handler. We save the original kprobes variables and just single
618 * step on the instruction of the new probe without calling any user handlers.
619 */
620static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
621 struct kprobe_ctlblk *kcb)
622{
623 switch (kcb->kprobe_status) {
624 case KPROBE_HIT_SSDONE:
625 case KPROBE_HIT_ACTIVE:
626 case KPROBE_HIT_SS:
627 kprobes_inc_nmissed_count(p);
628 setup_singlestep(p, regs, kcb, 1);
629 break;
630 case KPROBE_REENTER:
631 /* A probe has been hit in the codepath leading up to, or just
632 * after, single-stepping of a probed instruction. This entire
633 * codepath should strictly reside in .kprobes.text section.
634 * Raise a BUG or we'll continue in an endless reentering loop
635 * and eventually a stack overflow.
636 */
637 pr_err("Unrecoverable kprobe detected.\n");
638 dump_kprobe(p);
639 BUG();
640 default:
641 /* impossible cases */
642 WARN_ON(1);
643 return 0;
644 }
645
646 return 1;
647}
648NOKPROBE_SYMBOL(reenter_kprobe);
649
650/*
651 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
652 * remain disabled throughout this function.
653 */
654int kprobe_int3_handler(struct pt_regs *regs)
655{
656 kprobe_opcode_t *addr;
657 struct kprobe *p;
658 struct kprobe_ctlblk *kcb;
659
660 if (user_mode(regs))
661 return 0;
662
663 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
664 /*
665 * We don't want to be preempted for the entire duration of kprobe
666 * processing. Since int3 and debug trap disables irqs and we clear
667 * IF while singlestepping, it must be no preemptible.
668 */
669
670 kcb = get_kprobe_ctlblk();
671 p = get_kprobe(addr);
672
673 if (p) {
674 if (kprobe_running()) {
675 if (reenter_kprobe(p, regs, kcb))
676 return 1;
677 } else {
678 set_current_kprobe(p, regs, kcb);
679 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
680
681 /*
682 * If we have no pre-handler or it returned 0, we
683 * continue with normal processing. If we have a
684 * pre-handler and it returned non-zero, that means
685 * user handler setup registers to exit to another
686 * instruction, we must skip the single stepping.
687 */
688 if (!p->pre_handler || !p->pre_handler(p, regs))
689 setup_singlestep(p, regs, kcb, 0);
690 else
691 reset_current_kprobe();
692 return 1;
693 }
694 } else if (*addr != BREAKPOINT_INSTRUCTION) {
695 /*
696 * The breakpoint instruction was removed right
697 * after we hit it. Another cpu has removed
698 * either a probepoint or a debugger breakpoint
699 * at this address. In either case, no further
700 * handling of this interrupt is appropriate.
701 * Back up over the (now missing) int3 and run
702 * the original instruction.
703 */
704 regs->ip = (unsigned long)addr;
705 return 1;
706 } /* else: not a kprobe fault; let the kernel handle it */
707
708 return 0;
709}
710NOKPROBE_SYMBOL(kprobe_int3_handler);
711
712/*
713 * When a retprobed function returns, this code saves registers and
714 * calls trampoline_handler() runs, which calls the kretprobe's handler.
715 */
716asm(
717 ".text\n"
718 ".global kretprobe_trampoline\n"
719 ".type kretprobe_trampoline, @function\n"
720 "kretprobe_trampoline:\n"
721 /* We don't bother saving the ss register */
722#ifdef CONFIG_X86_64
723 " pushq %rsp\n"
724 " pushfq\n"
725 SAVE_REGS_STRING
726 " movq %rsp, %rdi\n"
727 " call trampoline_handler\n"
728 /* Replace saved sp with true return address. */
729 " movq %rax, 19*8(%rsp)\n"
730 RESTORE_REGS_STRING
731 " popfq\n"
732#else
733 " pushl %esp\n"
734 " pushfl\n"
735 SAVE_REGS_STRING
736 " movl %esp, %eax\n"
737 " call trampoline_handler\n"
738 /* Replace saved sp with true return address. */
739 " movl %eax, 15*4(%esp)\n"
740 RESTORE_REGS_STRING
741 " popfl\n"
742#endif
743 " ret\n"
744 ".size kretprobe_trampoline, .-kretprobe_trampoline\n"
745);
746NOKPROBE_SYMBOL(kretprobe_trampoline);
747STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
748
749static struct kprobe kretprobe_kprobe = {
750 .addr = (void *)kretprobe_trampoline,
751};
752
753/*
754 * Called from kretprobe_trampoline
755 */
756__used __visible void *trampoline_handler(struct pt_regs *regs)
757{
758 struct kprobe_ctlblk *kcb;
759 struct kretprobe_instance *ri = NULL;
760 struct hlist_head *head, empty_rp;
761 struct hlist_node *tmp;
762 unsigned long flags, orig_ret_address = 0;
763 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
764 kprobe_opcode_t *correct_ret_addr = NULL;
765 void *frame_pointer;
766 bool skipped = false;
767
768 preempt_disable();
769
770 /*
771 * Set a dummy kprobe for avoiding kretprobe recursion.
772 * Since kretprobe never run in kprobe handler, kprobe must not
773 * be running at this point.
774 */
775 kcb = get_kprobe_ctlblk();
776 __this_cpu_write(current_kprobe, &kretprobe_kprobe);
777 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
778
779 INIT_HLIST_HEAD(&empty_rp);
780 kretprobe_hash_lock(current, &head, &flags);
781 /* fixup registers */
782 regs->cs = __KERNEL_CS;
783#ifdef CONFIG_X86_32
784 regs->cs |= get_kernel_rpl();
785 regs->gs = 0;
786#endif
787 /* We use pt_regs->sp for return address holder. */
788 frame_pointer = ®s->sp;
789 regs->ip = trampoline_address;
790 regs->orig_ax = ~0UL;
791
792 /*
793 * It is possible to have multiple instances associated with a given
794 * task either because multiple functions in the call path have
795 * return probes installed on them, and/or more than one
796 * return probe was registered for a target function.
797 *
798 * We can handle this because:
799 * - instances are always pushed into the head of the list
800 * - when multiple return probes are registered for the same
801 * function, the (chronologically) first instance's ret_addr
802 * will be the real return address, and all the rest will
803 * point to kretprobe_trampoline.
804 */
805 hlist_for_each_entry(ri, head, hlist) {
806 if (ri->task != current)
807 /* another task is sharing our hash bucket */
808 continue;
809 /*
810 * Return probes must be pushed on this hash list correct
811 * order (same as return order) so that it can be popped
812 * correctly. However, if we find it is pushed it incorrect
813 * order, this means we find a function which should not be
814 * probed, because the wrong order entry is pushed on the
815 * path of processing other kretprobe itself.
816 */
817 if (ri->fp != frame_pointer) {
818 if (!skipped)
819 pr_warn("kretprobe is stacked incorrectly. Trying to fixup.\n");
820 skipped = true;
821 continue;
822 }
823
824 orig_ret_address = (unsigned long)ri->ret_addr;
825 if (skipped)
826 pr_warn("%ps must be blacklisted because of incorrect kretprobe order\n",
827 ri->rp->kp.addr);
828
829 if (orig_ret_address != trampoline_address)
830 /*
831 * This is the real return address. Any other
832 * instances associated with this task are for
833 * other calls deeper on the call stack
834 */
835 break;
836 }
837
838 kretprobe_assert(ri, orig_ret_address, trampoline_address);
839
840 correct_ret_addr = ri->ret_addr;
841 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
842 if (ri->task != current)
843 /* another task is sharing our hash bucket */
844 continue;
845 if (ri->fp != frame_pointer)
846 continue;
847
848 orig_ret_address = (unsigned long)ri->ret_addr;
849 if (ri->rp && ri->rp->handler) {
850 __this_cpu_write(current_kprobe, &ri->rp->kp);
851 ri->ret_addr = correct_ret_addr;
852 ri->rp->handler(ri, regs);
853 __this_cpu_write(current_kprobe, &kretprobe_kprobe);
854 }
855
856 recycle_rp_inst(ri, &empty_rp);
857
858 if (orig_ret_address != trampoline_address)
859 /*
860 * This is the real return address. Any other
861 * instances associated with this task are for
862 * other calls deeper on the call stack
863 */
864 break;
865 }
866
867 kretprobe_hash_unlock(current, &flags);
868
869 __this_cpu_write(current_kprobe, NULL);
870 preempt_enable();
871
872 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
873 hlist_del(&ri->hlist);
874 kfree(ri);
875 }
876 return (void *)orig_ret_address;
877}
878NOKPROBE_SYMBOL(trampoline_handler);
879
880/*
881 * Called after single-stepping. p->addr is the address of the
882 * instruction whose first byte has been replaced by the "int 3"
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.
887 *
888 * This function prepares to return from the post-single-step
889 * interrupt. We have to fix up the stack as follows:
890 *
891 * 0) Except in the case of absolute or indirect jump or call instructions,
892 * the new ip is relative to the copied instruction. We need to make
893 * it relative to the original instruction.
894 *
895 * 1) If the single-stepped instruction was pushfl, then the TF and IF
896 * flags are set in the just-pushed flags, and may need to be cleared.
897 *
898 * 2) If the single-stepped instruction was a call, the return address
899 * that is atop the stack is the address following the copied instruction.
900 * We need to make it the address following the original instruction.
901 *
902 * If this is the first time we've single-stepped the instruction at
903 * this probepoint, and the instruction is boostable, boost it: add a
904 * jump instruction after the copied instruction, that jumps to the next
905 * instruction after the probepoint.
906 */
907static void resume_execution(struct kprobe *p, struct pt_regs *regs,
908 struct kprobe_ctlblk *kcb)
909{
910 unsigned long *tos = stack_addr(regs);
911 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
912 unsigned long orig_ip = (unsigned long)p->addr;
913 kprobe_opcode_t *insn = p->ainsn.insn;
914
915 /* Skip prefixes */
916 insn = skip_prefixes(insn);
917
918 regs->flags &= ~X86_EFLAGS_TF;
919 switch (*insn) {
920 case 0x9c: /* pushfl */
921 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
922 *tos |= kcb->kprobe_old_flags;
923 break;
924 case 0xc2: /* iret/ret/lret */
925 case 0xc3:
926 case 0xca:
927 case 0xcb:
928 case 0xcf:
929 case 0xea: /* jmp absolute -- ip is correct */
930 /* ip is already adjusted, no more changes required */
931 p->ainsn.boostable = true;
932 goto no_change;
933 case 0xe8: /* call relative - Fix return addr */
934 *tos = orig_ip + (*tos - copy_ip);
935 break;
936#ifdef CONFIG_X86_32
937 case 0x9a: /* call absolute -- same as call absolute, indirect */
938 *tos = orig_ip + (*tos - copy_ip);
939 goto no_change;
940#endif
941 case 0xff:
942 if ((insn[1] & 0x30) == 0x10) {
943 /*
944 * call absolute, indirect
945 * Fix return addr; ip is correct.
946 * But this is not boostable
947 */
948 *tos = orig_ip + (*tos - copy_ip);
949 goto no_change;
950 } else if (((insn[1] & 0x31) == 0x20) ||
951 ((insn[1] & 0x31) == 0x21)) {
952 /*
953 * jmp near and far, absolute indirect
954 * ip is correct. And this is boostable
955 */
956 p->ainsn.boostable = true;
957 goto no_change;
958 }
959 default:
960 break;
961 }
962
963 regs->ip += orig_ip - copy_ip;
964
965no_change:
966 restore_btf();
967}
968NOKPROBE_SYMBOL(resume_execution);
969
970/*
971 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
972 * remain disabled throughout this function.
973 */
974int kprobe_debug_handler(struct pt_regs *regs)
975{
976 struct kprobe *cur = kprobe_running();
977 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
978
979 if (!cur)
980 return 0;
981
982 resume_execution(cur, regs, kcb);
983 regs->flags |= kcb->kprobe_saved_flags;
984
985 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
986 kcb->kprobe_status = KPROBE_HIT_SSDONE;
987 cur->post_handler(cur, regs, 0);
988 }
989
990 /* Restore back the original saved kprobes variables and continue. */
991 if (kcb->kprobe_status == KPROBE_REENTER) {
992 restore_previous_kprobe(kcb);
993 goto out;
994 }
995 reset_current_kprobe();
996out:
997 /*
998 * if somebody else is singlestepping across a probe point, flags
999 * will have TF set, in which case, continue the remaining processing
1000 * of do_debug, as if this is not a probe hit.
1001 */
1002 if (regs->flags & X86_EFLAGS_TF)
1003 return 0;
1004
1005 return 1;
1006}
1007NOKPROBE_SYMBOL(kprobe_debug_handler);
1008
1009int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
1010{
1011 struct kprobe *cur = kprobe_running();
1012 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1013
1014 if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
1015 /* This must happen on single-stepping */
1016 WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
1017 kcb->kprobe_status != KPROBE_REENTER);
1018 /*
1019 * We are here because the instruction being single
1020 * stepped caused a page fault. We reset the current
1021 * kprobe and the ip points back to the probe address
1022 * and allow the page fault handler to continue as a
1023 * normal page fault.
1024 */
1025 regs->ip = (unsigned long)cur->addr;
1026 /*
1027 * Trap flag (TF) has been set here because this fault
1028 * happened where the single stepping will be done.
1029 * So clear it by resetting the current kprobe:
1030 */
1031 regs->flags &= ~X86_EFLAGS_TF;
1032
1033 /*
1034 * If the TF flag was set before the kprobe hit,
1035 * don't touch it:
1036 */
1037 regs->flags |= kcb->kprobe_old_flags;
1038
1039 if (kcb->kprobe_status == KPROBE_REENTER)
1040 restore_previous_kprobe(kcb);
1041 else
1042 reset_current_kprobe();
1043 } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE ||
1044 kcb->kprobe_status == KPROBE_HIT_SSDONE) {
1045 /*
1046 * We increment the nmissed count for accounting,
1047 * we can also use npre/npostfault count for accounting
1048 * these specific fault cases.
1049 */
1050 kprobes_inc_nmissed_count(cur);
1051
1052 /*
1053 * We come here because instructions in the pre/post
1054 * handler caused the page_fault, this could happen
1055 * if handler tries to access user space by
1056 * copy_from_user(), get_user() etc. Let the
1057 * user-specified handler try to fix it first.
1058 */
1059 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
1060 return 1;
1061 }
1062
1063 return 0;
1064}
1065NOKPROBE_SYMBOL(kprobe_fault_handler);
1066
1067int __init arch_populate_kprobe_blacklist(void)
1068{
1069 int ret;
1070
1071 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
1072 (unsigned long)__irqentry_text_end);
1073 if (ret)
1074 return ret;
1075
1076 return kprobe_add_area_blacklist((unsigned long)__entry_text_start,
1077 (unsigned long)__entry_text_end);
1078}
1079
1080int __init arch_init_kprobes(void)
1081{
1082 return 0;
1083}
1084
1085int arch_trampoline_kprobe(struct kprobe *p)
1086{
1087 return 0;
1088}
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
56#include "common.h"
57
58DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
59DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
60
61#define stack_addr(regs) ((unsigned long *)regs->sp)
62
63#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
64 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
65 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
66 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
67 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
68 << (row % 32))
69 /*
70 * Undefined/reserved opcodes, conditional jump, Opcode Extension
71 * Groups, and some special opcodes can not boost.
72 * This is non-const and volatile to keep gcc from statically
73 * optimizing it out, as variable_test_bit makes gcc think only
74 * *(unsigned long*) is used.
75 */
76static volatile u32 twobyte_is_boostable[256 / 32] = {
77 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
78 /* ---------------------------------------------- */
79 W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
80 W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
81 W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
82 W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
83 W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
84 W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
85 W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
86 W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
87 W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
88 W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
89 W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
90 W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
91 W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
92 W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
93 W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
94 W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
95 /* ----------------------------------------------- */
96 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
97};
98#undef W
99
100struct kretprobe_blackpoint kretprobe_blacklist[] = {
101 {"__switch_to", }, /* This function switches only current task, but
102 doesn't switch kernel stack.*/
103 {NULL, NULL} /* Terminator */
104};
105
106const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
107
108static nokprobe_inline void
109__synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
110{
111 struct __arch_relative_insn {
112 u8 op;
113 s32 raddr;
114 } __packed *insn;
115
116 insn = (struct __arch_relative_insn *)dest;
117 insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
118 insn->op = op;
119}
120
121/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
122void synthesize_reljump(void *dest, void *from, void *to)
123{
124 __synthesize_relative_insn(dest, from, to, JMP32_INSN_OPCODE);
125}
126NOKPROBE_SYMBOL(synthesize_reljump);
127
128/* Insert a call instruction at address 'from', which calls address 'to'.*/
129void synthesize_relcall(void *dest, void *from, void *to)
130{
131 __synthesize_relative_insn(dest, from, to, CALL_INSN_OPCODE);
132}
133NOKPROBE_SYMBOL(synthesize_relcall);
134
135/*
136 * Returns non-zero if INSN is boostable.
137 * RIP relative instructions are adjusted at copying time in 64 bits mode
138 */
139int can_boost(struct insn *insn, void *addr)
140{
141 kprobe_opcode_t opcode;
142 insn_byte_t prefix;
143 int i;
144
145 if (search_exception_tables((unsigned long)addr))
146 return 0; /* Page fault may occur on this address. */
147
148 /* 2nd-byte opcode */
149 if (insn->opcode.nbytes == 2)
150 return test_bit(insn->opcode.bytes[1],
151 (unsigned long *)twobyte_is_boostable);
152
153 if (insn->opcode.nbytes != 1)
154 return 0;
155
156 for_each_insn_prefix(insn, i, prefix) {
157 insn_attr_t attr;
158
159 attr = inat_get_opcode_attribute(prefix);
160 /* Can't boost Address-size override prefix and CS override prefix */
161 if (prefix == 0x2e || inat_is_address_size_prefix(attr))
162 return 0;
163 }
164
165 opcode = insn->opcode.bytes[0];
166
167 switch (opcode) {
168 case 0x62: /* bound */
169 case 0x70 ... 0x7f: /* Conditional jumps */
170 case 0x9a: /* Call far */
171 case 0xc0 ... 0xc1: /* Grp2 */
172 case 0xcc ... 0xce: /* software exceptions */
173 case 0xd0 ... 0xd3: /* Grp2 */
174 case 0xd6: /* (UD) */
175 case 0xd8 ... 0xdf: /* ESC */
176 case 0xe0 ... 0xe3: /* LOOP*, JCXZ */
177 case 0xe8 ... 0xe9: /* near Call, JMP */
178 case 0xeb: /* Short JMP */
179 case 0xf0 ... 0xf4: /* LOCK/REP, HLT */
180 case 0xf6 ... 0xf7: /* Grp3 */
181 case 0xfe: /* Grp4 */
182 /* ... are not boostable */
183 return 0;
184 case 0xff: /* Grp5 */
185 /* Only indirect jmp is boostable */
186 return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
187 default:
188 return 1;
189 }
190}
191
192static unsigned long
193__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
194{
195 struct kprobe *kp;
196 unsigned long faddr;
197
198 kp = get_kprobe((void *)addr);
199 faddr = ftrace_location(addr);
200 /*
201 * Addresses inside the ftrace location are refused by
202 * arch_check_ftrace_location(). Something went terribly wrong
203 * if such an address is checked here.
204 */
205 if (WARN_ON(faddr && faddr != addr))
206 return 0UL;
207 /*
208 * Use the current code if it is not modified by Kprobe
209 * and it cannot be modified by ftrace.
210 */
211 if (!kp && !faddr)
212 return addr;
213
214 /*
215 * Basically, kp->ainsn.insn has an original instruction.
216 * However, RIP-relative instruction can not do single-stepping
217 * at different place, __copy_instruction() tweaks the displacement of
218 * that instruction. In that case, we can't recover the instruction
219 * from the kp->ainsn.insn.
220 *
221 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
222 * of the first byte of the probed instruction, which is overwritten
223 * by int3. And the instruction at kp->addr is not modified by kprobes
224 * except for the first byte, we can recover the original instruction
225 * from it and kp->opcode.
226 *
227 * In case of Kprobes using ftrace, we do not have a copy of
228 * the original instruction. In fact, the ftrace location might
229 * be modified at anytime and even could be in an inconsistent state.
230 * Fortunately, we know that the original code is the ideal 5-byte
231 * long NOP.
232 */
233 if (copy_from_kernel_nofault(buf, (void *)addr,
234 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
235 return 0UL;
236
237 if (faddr)
238 memcpy(buf, x86_nops[5], 5);
239 else
240 buf[0] = kp->opcode;
241 return (unsigned long)buf;
242}
243
244/*
245 * Recover the probed instruction at addr for further analysis.
246 * Caller must lock kprobes by kprobe_mutex, or disable preemption
247 * for preventing to release referencing kprobes.
248 * Returns zero if the instruction can not get recovered (or access failed).
249 */
250unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
251{
252 unsigned long __addr;
253
254 __addr = __recover_optprobed_insn(buf, addr);
255 if (__addr != addr)
256 return __addr;
257
258 return __recover_probed_insn(buf, addr);
259}
260
261/* Check if paddr is at an instruction boundary */
262static int can_probe(unsigned long paddr)
263{
264 unsigned long addr, __addr, offset = 0;
265 struct insn insn;
266 kprobe_opcode_t buf[MAX_INSN_SIZE];
267
268 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
269 return 0;
270
271 /* Decode instructions */
272 addr = paddr - offset;
273 while (addr < paddr) {
274 int ret;
275
276 /*
277 * Check if the instruction has been modified by another
278 * kprobe, in which case we replace the breakpoint by the
279 * original instruction in our buffer.
280 * Also, jump optimization will change the breakpoint to
281 * relative-jump. Since the relative-jump itself is
282 * normally used, we just go through if there is no kprobe.
283 */
284 __addr = recover_probed_instruction(buf, addr);
285 if (!__addr)
286 return 0;
287
288 ret = insn_decode_kernel(&insn, (void *)__addr);
289 if (ret < 0)
290 return 0;
291
292 /*
293 * Another debugging subsystem might insert this breakpoint.
294 * In that case, we can't recover it.
295 */
296 if (insn.opcode.bytes[0] == INT3_INSN_OPCODE)
297 return 0;
298 addr += insn.length;
299 }
300
301 return (addr == paddr);
302}
303
304/*
305 * Copy an instruction with recovering modified instruction by kprobes
306 * and adjust the displacement if the instruction uses the %rip-relative
307 * addressing mode. Note that since @real will be the final place of copied
308 * instruction, displacement must be adjust by @real, not @dest.
309 * This returns the length of copied instruction, or 0 if it has an error.
310 */
311int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
312{
313 kprobe_opcode_t buf[MAX_INSN_SIZE];
314 unsigned long recovered_insn = recover_probed_instruction(buf, (unsigned long)src);
315 int ret;
316
317 if (!recovered_insn || !insn)
318 return 0;
319
320 /* This can access kernel text if given address is not recovered */
321 if (copy_from_kernel_nofault(dest, (void *)recovered_insn,
322 MAX_INSN_SIZE))
323 return 0;
324
325 ret = insn_decode_kernel(insn, dest);
326 if (ret < 0)
327 return 0;
328
329 /* We can not probe force emulate prefixed instruction */
330 if (insn_has_emulate_prefix(insn))
331 return 0;
332
333 /* Another subsystem puts a breakpoint, failed to recover */
334 if (insn->opcode.bytes[0] == INT3_INSN_OPCODE)
335 return 0;
336
337 /* We should not singlestep on the exception masking instructions */
338 if (insn_masking_exception(insn))
339 return 0;
340
341#ifdef CONFIG_X86_64
342 /* Only x86_64 has RIP relative instructions */
343 if (insn_rip_relative(insn)) {
344 s64 newdisp;
345 u8 *disp;
346 /*
347 * The copied instruction uses the %rip-relative addressing
348 * mode. Adjust the displacement for the difference between
349 * the original location of this instruction and the location
350 * of the copy that will actually be run. The tricky bit here
351 * is making sure that the sign extension happens correctly in
352 * this calculation, since we need a signed 32-bit result to
353 * be sign-extended to 64 bits when it's added to the %rip
354 * value and yield the same 64-bit result that the sign-
355 * extension of the original signed 32-bit displacement would
356 * have given.
357 */
358 newdisp = (u8 *) src + (s64) insn->displacement.value
359 - (u8 *) real;
360 if ((s64) (s32) newdisp != newdisp) {
361 pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
362 return 0;
363 }
364 disp = (u8 *) dest + insn_offset_displacement(insn);
365 *(s32 *) disp = (s32) newdisp;
366 }
367#endif
368 return insn->length;
369}
370
371/* Prepare reljump or int3 right after instruction */
372static int prepare_singlestep(kprobe_opcode_t *buf, struct kprobe *p,
373 struct insn *insn)
374{
375 int len = insn->length;
376
377 if (!IS_ENABLED(CONFIG_PREEMPTION) &&
378 !p->post_handler && can_boost(insn, p->addr) &&
379 MAX_INSN_SIZE - len >= JMP32_INSN_SIZE) {
380 /*
381 * These instructions can be executed directly if it
382 * jumps back to correct address.
383 */
384 synthesize_reljump(buf + len, p->ainsn.insn + len,
385 p->addr + insn->length);
386 len += JMP32_INSN_SIZE;
387 p->ainsn.boostable = 1;
388 } else {
389 /* Otherwise, put an int3 for trapping singlestep */
390 if (MAX_INSN_SIZE - len < INT3_INSN_SIZE)
391 return -ENOSPC;
392
393 buf[len] = INT3_INSN_OPCODE;
394 len += INT3_INSN_SIZE;
395 }
396
397 return len;
398}
399
400/* Make page to RO mode when allocate it */
401void *alloc_insn_page(void)
402{
403 void *page;
404
405 page = module_alloc(PAGE_SIZE);
406 if (!page)
407 return NULL;
408
409 set_vm_flush_reset_perms(page);
410 /*
411 * First make the page read-only, and only then make it executable to
412 * prevent it from being W+X in between.
413 */
414 set_memory_ro((unsigned long)page, 1);
415
416 /*
417 * TODO: Once additional kernel code protection mechanisms are set, ensure
418 * that the page was not maliciously altered and it is still zeroed.
419 */
420 set_memory_x((unsigned long)page, 1);
421
422 return page;
423}
424
425/* Kprobe x86 instruction emulation - only regs->ip or IF flag modifiers */
426
427static void kprobe_emulate_ifmodifiers(struct kprobe *p, struct pt_regs *regs)
428{
429 switch (p->ainsn.opcode) {
430 case 0xfa: /* cli */
431 regs->flags &= ~(X86_EFLAGS_IF);
432 break;
433 case 0xfb: /* sti */
434 regs->flags |= X86_EFLAGS_IF;
435 break;
436 case 0x9c: /* pushf */
437 int3_emulate_push(regs, regs->flags);
438 break;
439 case 0x9d: /* popf */
440 regs->flags = int3_emulate_pop(regs);
441 break;
442 }
443 regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
444}
445NOKPROBE_SYMBOL(kprobe_emulate_ifmodifiers);
446
447static void kprobe_emulate_ret(struct kprobe *p, struct pt_regs *regs)
448{
449 int3_emulate_ret(regs);
450}
451NOKPROBE_SYMBOL(kprobe_emulate_ret);
452
453static void kprobe_emulate_call(struct kprobe *p, struct pt_regs *regs)
454{
455 unsigned long func = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
456
457 func += p->ainsn.rel32;
458 int3_emulate_call(regs, func);
459}
460NOKPROBE_SYMBOL(kprobe_emulate_call);
461
462static nokprobe_inline
463void __kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond)
464{
465 unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
466
467 if (cond)
468 ip += p->ainsn.rel32;
469 int3_emulate_jmp(regs, ip);
470}
471
472static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)
473{
474 __kprobe_emulate_jmp(p, regs, true);
475}
476NOKPROBE_SYMBOL(kprobe_emulate_jmp);
477
478static const unsigned long jcc_mask[6] = {
479 [0] = X86_EFLAGS_OF,
480 [1] = X86_EFLAGS_CF,
481 [2] = X86_EFLAGS_ZF,
482 [3] = X86_EFLAGS_CF | X86_EFLAGS_ZF,
483 [4] = X86_EFLAGS_SF,
484 [5] = X86_EFLAGS_PF,
485};
486
487static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs)
488{
489 bool invert = p->ainsn.jcc.type & 1;
490 bool match;
491
492 if (p->ainsn.jcc.type < 0xc) {
493 match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1];
494 } else {
495 match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^
496 ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);
497 if (p->ainsn.jcc.type >= 0xe)
498 match = match && (regs->flags & X86_EFLAGS_ZF);
499 }
500 __kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert));
501}
502NOKPROBE_SYMBOL(kprobe_emulate_jcc);
503
504static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs)
505{
506 bool match;
507
508 if (p->ainsn.loop.type != 3) { /* LOOP* */
509 if (p->ainsn.loop.asize == 32)
510 match = ((*(u32 *)®s->cx)--) != 0;
511#ifdef CONFIG_X86_64
512 else if (p->ainsn.loop.asize == 64)
513 match = ((*(u64 *)®s->cx)--) != 0;
514#endif
515 else
516 match = ((*(u16 *)®s->cx)--) != 0;
517 } else { /* JCXZ */
518 if (p->ainsn.loop.asize == 32)
519 match = *(u32 *)(®s->cx) == 0;
520#ifdef CONFIG_X86_64
521 else if (p->ainsn.loop.asize == 64)
522 match = *(u64 *)(®s->cx) == 0;
523#endif
524 else
525 match = *(u16 *)(®s->cx) == 0;
526 }
527
528 if (p->ainsn.loop.type == 0) /* LOOPNE */
529 match = match && !(regs->flags & X86_EFLAGS_ZF);
530 else if (p->ainsn.loop.type == 1) /* LOOPE */
531 match = match && (regs->flags & X86_EFLAGS_ZF);
532
533 __kprobe_emulate_jmp(p, regs, match);
534}
535NOKPROBE_SYMBOL(kprobe_emulate_loop);
536
537static const int addrmode_regoffs[] = {
538 offsetof(struct pt_regs, ax),
539 offsetof(struct pt_regs, cx),
540 offsetof(struct pt_regs, dx),
541 offsetof(struct pt_regs, bx),
542 offsetof(struct pt_regs, sp),
543 offsetof(struct pt_regs, bp),
544 offsetof(struct pt_regs, si),
545 offsetof(struct pt_regs, di),
546#ifdef CONFIG_X86_64
547 offsetof(struct pt_regs, r8),
548 offsetof(struct pt_regs, r9),
549 offsetof(struct pt_regs, r10),
550 offsetof(struct pt_regs, r11),
551 offsetof(struct pt_regs, r12),
552 offsetof(struct pt_regs, r13),
553 offsetof(struct pt_regs, r14),
554 offsetof(struct pt_regs, r15),
555#endif
556};
557
558static void kprobe_emulate_call_indirect(struct kprobe *p, struct pt_regs *regs)
559{
560 unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
561
562 int3_emulate_call(regs, regs_get_register(regs, offs));
563}
564NOKPROBE_SYMBOL(kprobe_emulate_call_indirect);
565
566static void kprobe_emulate_jmp_indirect(struct kprobe *p, struct pt_regs *regs)
567{
568 unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
569
570 int3_emulate_jmp(regs, regs_get_register(regs, offs));
571}
572NOKPROBE_SYMBOL(kprobe_emulate_jmp_indirect);
573
574static int prepare_emulation(struct kprobe *p, struct insn *insn)
575{
576 insn_byte_t opcode = insn->opcode.bytes[0];
577
578 switch (opcode) {
579 case 0xfa: /* cli */
580 case 0xfb: /* sti */
581 case 0x9c: /* pushfl */
582 case 0x9d: /* popf/popfd */
583 /*
584 * IF modifiers must be emulated since it will enable interrupt while
585 * int3 single stepping.
586 */
587 p->ainsn.emulate_op = kprobe_emulate_ifmodifiers;
588 p->ainsn.opcode = opcode;
589 break;
590 case 0xc2: /* ret/lret */
591 case 0xc3:
592 case 0xca:
593 case 0xcb:
594 p->ainsn.emulate_op = kprobe_emulate_ret;
595 break;
596 case 0x9a: /* far call absolute -- segment is not supported */
597 case 0xea: /* far jmp absolute -- segment is not supported */
598 case 0xcc: /* int3 */
599 case 0xcf: /* iret -- in-kernel IRET is not supported */
600 return -EOPNOTSUPP;
601 break;
602 case 0xe8: /* near call relative */
603 p->ainsn.emulate_op = kprobe_emulate_call;
604 if (insn->immediate.nbytes == 2)
605 p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
606 else
607 p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
608 break;
609 case 0xeb: /* short jump relative */
610 case 0xe9: /* near jump relative */
611 p->ainsn.emulate_op = kprobe_emulate_jmp;
612 if (insn->immediate.nbytes == 1)
613 p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
614 else 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 0x70 ... 0x7f:
620 /* 1 byte conditional jump */
621 p->ainsn.emulate_op = kprobe_emulate_jcc;
622 p->ainsn.jcc.type = opcode & 0xf;
623 p->ainsn.rel32 = *(char *)insn->immediate.bytes;
624 break;
625 case 0x0f:
626 opcode = insn->opcode.bytes[1];
627 if ((opcode & 0xf0) == 0x80) {
628 /* 2 bytes Conditional Jump */
629 p->ainsn.emulate_op = kprobe_emulate_jcc;
630 p->ainsn.jcc.type = opcode & 0xf;
631 if (insn->immediate.nbytes == 2)
632 p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
633 else
634 p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
635 } else if (opcode == 0x01 &&
636 X86_MODRM_REG(insn->modrm.bytes[0]) == 0 &&
637 X86_MODRM_MOD(insn->modrm.bytes[0]) == 3) {
638 /* VM extensions - not supported */
639 return -EOPNOTSUPP;
640 }
641 break;
642 case 0xe0: /* Loop NZ */
643 case 0xe1: /* Loop */
644 case 0xe2: /* Loop */
645 case 0xe3: /* J*CXZ */
646 p->ainsn.emulate_op = kprobe_emulate_loop;
647 p->ainsn.loop.type = opcode & 0x3;
648 p->ainsn.loop.asize = insn->addr_bytes * 8;
649 p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
650 break;
651 case 0xff:
652 /*
653 * Since the 0xff is an extended group opcode, the instruction
654 * is determined by the MOD/RM byte.
655 */
656 opcode = insn->modrm.bytes[0];
657 if ((opcode & 0x30) == 0x10) {
658 if ((opcode & 0x8) == 0x8)
659 return -EOPNOTSUPP; /* far call */
660 /* call absolute, indirect */
661 p->ainsn.emulate_op = kprobe_emulate_call_indirect;
662 } else if ((opcode & 0x30) == 0x20) {
663 if ((opcode & 0x8) == 0x8)
664 return -EOPNOTSUPP; /* far jmp */
665 /* jmp near absolute indirect */
666 p->ainsn.emulate_op = kprobe_emulate_jmp_indirect;
667 } else
668 break;
669
670 if (insn->addr_bytes != sizeof(unsigned long))
671 return -EOPNOTSUPP; /* Don't support different size */
672 if (X86_MODRM_MOD(opcode) != 3)
673 return -EOPNOTSUPP; /* TODO: support memory addressing */
674
675 p->ainsn.indirect.reg = X86_MODRM_RM(opcode);
676#ifdef CONFIG_X86_64
677 if (X86_REX_B(insn->rex_prefix.value))
678 p->ainsn.indirect.reg += 8;
679#endif
680 break;
681 default:
682 break;
683 }
684 p->ainsn.size = insn->length;
685
686 return 0;
687}
688
689static int arch_copy_kprobe(struct kprobe *p)
690{
691 struct insn insn;
692 kprobe_opcode_t buf[MAX_INSN_SIZE];
693 int ret, len;
694
695 /* Copy an instruction with recovering if other optprobe modifies it.*/
696 len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
697 if (!len)
698 return -EINVAL;
699
700 /* Analyze the opcode and setup emulate functions */
701 ret = prepare_emulation(p, &insn);
702 if (ret < 0)
703 return ret;
704
705 /* Add int3 for single-step or booster jmp */
706 len = prepare_singlestep(buf, p, &insn);
707 if (len < 0)
708 return len;
709
710 /* Also, displacement change doesn't affect the first byte */
711 p->opcode = buf[0];
712
713 p->ainsn.tp_len = len;
714 perf_event_text_poke(p->ainsn.insn, NULL, 0, buf, len);
715
716 /* OK, write back the instruction(s) into ROX insn buffer */
717 text_poke(p->ainsn.insn, buf, len);
718
719 return 0;
720}
721
722int arch_prepare_kprobe(struct kprobe *p)
723{
724 int ret;
725
726 if (alternatives_text_reserved(p->addr, p->addr))
727 return -EINVAL;
728
729 if (!can_probe((unsigned long)p->addr))
730 return -EILSEQ;
731
732 memset(&p->ainsn, 0, sizeof(p->ainsn));
733
734 /* insn: must be on special executable page on x86. */
735 p->ainsn.insn = get_insn_slot();
736 if (!p->ainsn.insn)
737 return -ENOMEM;
738
739 ret = arch_copy_kprobe(p);
740 if (ret) {
741 free_insn_slot(p->ainsn.insn, 0);
742 p->ainsn.insn = NULL;
743 }
744
745 return ret;
746}
747
748void arch_arm_kprobe(struct kprobe *p)
749{
750 u8 int3 = INT3_INSN_OPCODE;
751
752 text_poke(p->addr, &int3, 1);
753 text_poke_sync();
754 perf_event_text_poke(p->addr, &p->opcode, 1, &int3, 1);
755}
756
757void arch_disarm_kprobe(struct kprobe *p)
758{
759 u8 int3 = INT3_INSN_OPCODE;
760
761 perf_event_text_poke(p->addr, &int3, 1, &p->opcode, 1);
762 text_poke(p->addr, &p->opcode, 1);
763 text_poke_sync();
764}
765
766void arch_remove_kprobe(struct kprobe *p)
767{
768 if (p->ainsn.insn) {
769 /* Record the perf event before freeing the slot */
770 perf_event_text_poke(p->ainsn.insn, p->ainsn.insn,
771 p->ainsn.tp_len, NULL, 0);
772 free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
773 p->ainsn.insn = NULL;
774 }
775}
776
777static nokprobe_inline void
778save_previous_kprobe(struct kprobe_ctlblk *kcb)
779{
780 kcb->prev_kprobe.kp = kprobe_running();
781 kcb->prev_kprobe.status = kcb->kprobe_status;
782 kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
783 kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
784}
785
786static nokprobe_inline void
787restore_previous_kprobe(struct kprobe_ctlblk *kcb)
788{
789 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
790 kcb->kprobe_status = kcb->prev_kprobe.status;
791 kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
792 kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
793}
794
795static nokprobe_inline void
796set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
797 struct kprobe_ctlblk *kcb)
798{
799 __this_cpu_write(current_kprobe, p);
800 kcb->kprobe_saved_flags = kcb->kprobe_old_flags
801 = (regs->flags & X86_EFLAGS_IF);
802}
803
804void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
805{
806 unsigned long *sara = stack_addr(regs);
807
808 ri->ret_addr = (kprobe_opcode_t *) *sara;
809 ri->fp = sara;
810
811 /* Replace the return addr with trampoline addr */
812 *sara = (unsigned long) &kretprobe_trampoline;
813}
814NOKPROBE_SYMBOL(arch_prepare_kretprobe);
815
816static void kprobe_post_process(struct kprobe *cur, struct pt_regs *regs,
817 struct kprobe_ctlblk *kcb)
818{
819 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
820 kcb->kprobe_status = KPROBE_HIT_SSDONE;
821 cur->post_handler(cur, regs, 0);
822 }
823
824 /* Restore back the original saved kprobes variables and continue. */
825 if (kcb->kprobe_status == KPROBE_REENTER)
826 restore_previous_kprobe(kcb);
827 else
828 reset_current_kprobe();
829}
830NOKPROBE_SYMBOL(kprobe_post_process);
831
832static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
833 struct kprobe_ctlblk *kcb, int reenter)
834{
835 if (setup_detour_execution(p, regs, reenter))
836 return;
837
838#if !defined(CONFIG_PREEMPTION)
839 if (p->ainsn.boostable) {
840 /* Boost up -- we can execute copied instructions directly */
841 if (!reenter)
842 reset_current_kprobe();
843 /*
844 * Reentering boosted probe doesn't reset current_kprobe,
845 * nor set current_kprobe, because it doesn't use single
846 * stepping.
847 */
848 regs->ip = (unsigned long)p->ainsn.insn;
849 return;
850 }
851#endif
852 if (reenter) {
853 save_previous_kprobe(kcb);
854 set_current_kprobe(p, regs, kcb);
855 kcb->kprobe_status = KPROBE_REENTER;
856 } else
857 kcb->kprobe_status = KPROBE_HIT_SS;
858
859 if (p->ainsn.emulate_op) {
860 p->ainsn.emulate_op(p, regs);
861 kprobe_post_process(p, regs, kcb);
862 return;
863 }
864
865 /* Disable interrupt, and set ip register on trampoline */
866 regs->flags &= ~X86_EFLAGS_IF;
867 regs->ip = (unsigned long)p->ainsn.insn;
868}
869NOKPROBE_SYMBOL(setup_singlestep);
870
871/*
872 * Called after single-stepping. p->addr is the address of the
873 * instruction whose first byte has been replaced by the "int3"
874 * instruction. To avoid the SMP problems that can occur when we
875 * temporarily put back the original opcode to single-step, we
876 * single-stepped a copy of the instruction. The address of this
877 * copy is p->ainsn.insn. We also doesn't use trap, but "int3" again
878 * right after the copied instruction.
879 * Different from the trap single-step, "int3" single-step can not
880 * handle the instruction which changes the ip register, e.g. jmp,
881 * call, conditional jmp, and the instructions which changes the IF
882 * flags because interrupt must be disabled around the single-stepping.
883 * Such instructions are software emulated, but others are single-stepped
884 * using "int3".
885 *
886 * When the 2nd "int3" handled, the regs->ip and regs->flags needs to
887 * be adjusted, so that we can resume execution on correct code.
888 */
889static void resume_singlestep(struct kprobe *p, struct pt_regs *regs,
890 struct kprobe_ctlblk *kcb)
891{
892 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
893 unsigned long orig_ip = (unsigned long)p->addr;
894
895 /* Restore saved interrupt flag and ip register */
896 regs->flags |= kcb->kprobe_saved_flags;
897 /* Note that regs->ip is executed int3 so must be a step back */
898 regs->ip += (orig_ip - copy_ip) - INT3_INSN_SIZE;
899}
900NOKPROBE_SYMBOL(resume_singlestep);
901
902/*
903 * We have reentered the kprobe_handler(), since another probe was hit while
904 * within the handler. We save the original kprobes variables and just single
905 * step on the instruction of the new probe without calling any user handlers.
906 */
907static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
908 struct kprobe_ctlblk *kcb)
909{
910 switch (kcb->kprobe_status) {
911 case KPROBE_HIT_SSDONE:
912 case KPROBE_HIT_ACTIVE:
913 case KPROBE_HIT_SS:
914 kprobes_inc_nmissed_count(p);
915 setup_singlestep(p, regs, kcb, 1);
916 break;
917 case KPROBE_REENTER:
918 /* A probe has been hit in the codepath leading up to, or just
919 * after, single-stepping of a probed instruction. This entire
920 * codepath should strictly reside in .kprobes.text section.
921 * Raise a BUG or we'll continue in an endless reentering loop
922 * and eventually a stack overflow.
923 */
924 pr_err("Unrecoverable kprobe detected.\n");
925 dump_kprobe(p);
926 BUG();
927 default:
928 /* impossible cases */
929 WARN_ON(1);
930 return 0;
931 }
932
933 return 1;
934}
935NOKPROBE_SYMBOL(reenter_kprobe);
936
937static nokprobe_inline int kprobe_is_ss(struct kprobe_ctlblk *kcb)
938{
939 return (kcb->kprobe_status == KPROBE_HIT_SS ||
940 kcb->kprobe_status == KPROBE_REENTER);
941}
942
943/*
944 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
945 * remain disabled throughout this function.
946 */
947int kprobe_int3_handler(struct pt_regs *regs)
948{
949 kprobe_opcode_t *addr;
950 struct kprobe *p;
951 struct kprobe_ctlblk *kcb;
952
953 if (user_mode(regs))
954 return 0;
955
956 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
957 /*
958 * We don't want to be preempted for the entire duration of kprobe
959 * processing. Since int3 and debug trap disables irqs and we clear
960 * IF while singlestepping, it must be no preemptible.
961 */
962
963 kcb = get_kprobe_ctlblk();
964 p = get_kprobe(addr);
965
966 if (p) {
967 if (kprobe_running()) {
968 if (reenter_kprobe(p, regs, kcb))
969 return 1;
970 } else {
971 set_current_kprobe(p, regs, kcb);
972 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
973
974 /*
975 * If we have no pre-handler or it returned 0, we
976 * continue with normal processing. If we have a
977 * pre-handler and it returned non-zero, that means
978 * user handler setup registers to exit to another
979 * instruction, we must skip the single stepping.
980 */
981 if (!p->pre_handler || !p->pre_handler(p, regs))
982 setup_singlestep(p, regs, kcb, 0);
983 else
984 reset_current_kprobe();
985 return 1;
986 }
987 } else if (kprobe_is_ss(kcb)) {
988 p = kprobe_running();
989 if ((unsigned long)p->ainsn.insn < regs->ip &&
990 (unsigned long)p->ainsn.insn + MAX_INSN_SIZE > regs->ip) {
991 /* Most provably this is the second int3 for singlestep */
992 resume_singlestep(p, regs, kcb);
993 kprobe_post_process(p, regs, kcb);
994 return 1;
995 }
996 }
997
998 if (*addr != INT3_INSN_OPCODE) {
999 /*
1000 * The breakpoint instruction was removed right
1001 * after we hit it. Another cpu has removed
1002 * either a probepoint or a debugger breakpoint
1003 * at this address. In either case, no further
1004 * handling of this interrupt is appropriate.
1005 * Back up over the (now missing) int3 and run
1006 * the original instruction.
1007 */
1008 regs->ip = (unsigned long)addr;
1009 return 1;
1010 } /* else: not a kprobe fault; let the kernel handle it */
1011
1012 return 0;
1013}
1014NOKPROBE_SYMBOL(kprobe_int3_handler);
1015
1016/*
1017 * When a retprobed function returns, this code saves registers and
1018 * calls trampoline_handler() runs, which calls the kretprobe's handler.
1019 */
1020asm(
1021 ".text\n"
1022 ".global kretprobe_trampoline\n"
1023 ".type kretprobe_trampoline, @function\n"
1024 "kretprobe_trampoline:\n"
1025 /* We don't bother saving the ss register */
1026#ifdef CONFIG_X86_64
1027 " pushq %rsp\n"
1028 " pushfq\n"
1029 SAVE_REGS_STRING
1030 " movq %rsp, %rdi\n"
1031 " call trampoline_handler\n"
1032 /* Replace saved sp with true return address. */
1033 " movq %rax, 19*8(%rsp)\n"
1034 RESTORE_REGS_STRING
1035 " popfq\n"
1036#else
1037 " pushl %esp\n"
1038 " pushfl\n"
1039 SAVE_REGS_STRING
1040 " movl %esp, %eax\n"
1041 " call trampoline_handler\n"
1042 /* Replace saved sp with true return address. */
1043 " movl %eax, 15*4(%esp)\n"
1044 RESTORE_REGS_STRING
1045 " popfl\n"
1046#endif
1047 " ret\n"
1048 ".size kretprobe_trampoline, .-kretprobe_trampoline\n"
1049);
1050NOKPROBE_SYMBOL(kretprobe_trampoline);
1051STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
1052
1053
1054/*
1055 * Called from kretprobe_trampoline
1056 */
1057__used __visible void *trampoline_handler(struct pt_regs *regs)
1058{
1059 /* fixup registers */
1060 regs->cs = __KERNEL_CS;
1061#ifdef CONFIG_X86_32
1062 regs->gs = 0;
1063#endif
1064 regs->ip = (unsigned long)&kretprobe_trampoline;
1065 regs->orig_ax = ~0UL;
1066
1067 return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, ®s->sp);
1068}
1069NOKPROBE_SYMBOL(trampoline_handler);
1070
1071int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
1072{
1073 struct kprobe *cur = kprobe_running();
1074 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1075
1076 if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
1077 /* This must happen on single-stepping */
1078 WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
1079 kcb->kprobe_status != KPROBE_REENTER);
1080 /*
1081 * We are here because the instruction being single
1082 * stepped caused a page fault. We reset the current
1083 * kprobe and the ip points back to the probe address
1084 * and allow the page fault handler to continue as a
1085 * normal page fault.
1086 */
1087 regs->ip = (unsigned long)cur->addr;
1088
1089 /*
1090 * If the IF flag was set before the kprobe hit,
1091 * don't touch it:
1092 */
1093 regs->flags |= kcb->kprobe_old_flags;
1094
1095 if (kcb->kprobe_status == KPROBE_REENTER)
1096 restore_previous_kprobe(kcb);
1097 else
1098 reset_current_kprobe();
1099 }
1100
1101 return 0;
1102}
1103NOKPROBE_SYMBOL(kprobe_fault_handler);
1104
1105int __init arch_populate_kprobe_blacklist(void)
1106{
1107 return kprobe_add_area_blacklist((unsigned long)__entry_text_start,
1108 (unsigned long)__entry_text_end);
1109}
1110
1111int __init arch_init_kprobes(void)
1112{
1113 return 0;
1114}
1115
1116int arch_trampoline_kprobe(struct kprobe *p)
1117{
1118 return 0;
1119}