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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/*
2 * Kernel Probes (KProbes)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2004
19 *
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
22 * Rusty Russell).
23 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24 * interface to access function arguments.
25 * 2004-Oct Jim Keniston <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
26 * <prasanna@in.ibm.com> adapted for x86_64 from i386.
27 * 2005-Mar Roland McGrath <roland@redhat.com>
28 * Fixed to handle %rip-relative addressing mode correctly.
29 * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
30 * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
31 * <prasanna@in.ibm.com> added function-return probes.
32 * 2005-May Rusty Lynch <rusty.lynch@intel.com>
33 * Added function return probes functionality
34 * 2006-Feb Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added
35 * kprobe-booster and kretprobe-booster for i386.
36 * 2007-Dec Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster
37 * and kretprobe-booster for x86-64
38 * 2007-Dec Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven
39 * <arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com>
40 * unified x86 kprobes code.
41 */
42#include <linux/kprobes.h>
43#include <linux/ptrace.h>
44#include <linux/string.h>
45#include <linux/slab.h>
46#include <linux/hardirq.h>
47#include <linux/preempt.h>
48#include <linux/module.h>
49#include <linux/kdebug.h>
50#include <linux/kallsyms.h>
51#include <linux/ftrace.h>
52#include <linux/frame.h>
53
54#include <asm/cacheflush.h>
55#include <asm/desc.h>
56#include <asm/pgtable.h>
57#include <asm/uaccess.h>
58#include <asm/alternative.h>
59#include <asm/insn.h>
60#include <asm/debugreg.h>
61
62#include "common.h"
63
64void jprobe_return_end(void);
65
66DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
67DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
68
69#define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
70
71#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
72 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
73 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
74 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
75 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
76 << (row % 32))
77 /*
78 * Undefined/reserved opcodes, conditional jump, Opcode Extension
79 * Groups, and some special opcodes can not boost.
80 * This is non-const and volatile to keep gcc from statically
81 * optimizing it out, as variable_test_bit makes gcc think only
82 * *(unsigned long*) is used.
83 */
84static volatile u32 twobyte_is_boostable[256 / 32] = {
85 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
86 /* ---------------------------------------------- */
87 W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
88 W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
89 W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
90 W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
91 W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
92 W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
93 W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
94 W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
95 W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
96 W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
97 W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
98 W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
99 W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
100 W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
101 W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
102 W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
103 /* ----------------------------------------------- */
104 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
105};
106#undef W
107
108struct kretprobe_blackpoint kretprobe_blacklist[] = {
109 {"__switch_to", }, /* This function switches only current task, but
110 doesn't switch kernel stack.*/
111 {NULL, NULL} /* Terminator */
112};
113
114const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
115
116static nokprobe_inline void
117__synthesize_relative_insn(void *from, void *to, u8 op)
118{
119 struct __arch_relative_insn {
120 u8 op;
121 s32 raddr;
122 } __packed *insn;
123
124 insn = (struct __arch_relative_insn *)from;
125 insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
126 insn->op = op;
127}
128
129/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
130void synthesize_reljump(void *from, void *to)
131{
132 __synthesize_relative_insn(from, to, RELATIVEJUMP_OPCODE);
133}
134NOKPROBE_SYMBOL(synthesize_reljump);
135
136/* Insert a call instruction at address 'from', which calls address 'to'.*/
137void synthesize_relcall(void *from, void *to)
138{
139 __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE);
140}
141NOKPROBE_SYMBOL(synthesize_relcall);
142
143/*
144 * Skip the prefixes of the instruction.
145 */
146static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn)
147{
148 insn_attr_t attr;
149
150 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
151 while (inat_is_legacy_prefix(attr)) {
152 insn++;
153 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
154 }
155#ifdef CONFIG_X86_64
156 if (inat_is_rex_prefix(attr))
157 insn++;
158#endif
159 return insn;
160}
161NOKPROBE_SYMBOL(skip_prefixes);
162
163/*
164 * Returns non-zero if opcode is boostable.
165 * RIP relative instructions are adjusted at copying time in 64 bits mode
166 */
167int can_boost(kprobe_opcode_t *opcodes)
168{
169 kprobe_opcode_t opcode;
170 kprobe_opcode_t *orig_opcodes = opcodes;
171
172 if (search_exception_tables((unsigned long)opcodes))
173 return 0; /* Page fault may occur on this address. */
174
175retry:
176 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
177 return 0;
178 opcode = *(opcodes++);
179
180 /* 2nd-byte opcode */
181 if (opcode == 0x0f) {
182 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
183 return 0;
184 return test_bit(*opcodes,
185 (unsigned long *)twobyte_is_boostable);
186 }
187
188 switch (opcode & 0xf0) {
189#ifdef CONFIG_X86_64
190 case 0x40:
191 goto retry; /* REX prefix is boostable */
192#endif
193 case 0x60:
194 if (0x63 < opcode && opcode < 0x67)
195 goto retry; /* prefixes */
196 /* can't boost Address-size override and bound */
197 return (opcode != 0x62 && opcode != 0x67);
198 case 0x70:
199 return 0; /* can't boost conditional jump */
200 case 0xc0:
201 /* can't boost software-interruptions */
202 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
203 case 0xd0:
204 /* can boost AA* and XLAT */
205 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
206 case 0xe0:
207 /* can boost in/out and absolute jmps */
208 return ((opcode & 0x04) || opcode == 0xea);
209 case 0xf0:
210 if ((opcode & 0x0c) == 0 && opcode != 0xf1)
211 goto retry; /* lock/rep(ne) prefix */
212 /* clear and set flags are boostable */
213 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
214 default:
215 /* segment override prefixes are boostable */
216 if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
217 goto retry; /* prefixes */
218 /* CS override prefix and call are not boostable */
219 return (opcode != 0x2e && opcode != 0x9a);
220 }
221}
222
223static unsigned long
224__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
225{
226 struct kprobe *kp;
227 unsigned long faddr;
228
229 kp = get_kprobe((void *)addr);
230 faddr = ftrace_location(addr);
231 /*
232 * Addresses inside the ftrace location are refused by
233 * arch_check_ftrace_location(). Something went terribly wrong
234 * if such an address is checked here.
235 */
236 if (WARN_ON(faddr && faddr != addr))
237 return 0UL;
238 /*
239 * Use the current code if it is not modified by Kprobe
240 * and it cannot be modified by ftrace.
241 */
242 if (!kp && !faddr)
243 return addr;
244
245 /*
246 * Basically, kp->ainsn.insn has an original instruction.
247 * However, RIP-relative instruction can not do single-stepping
248 * at different place, __copy_instruction() tweaks the displacement of
249 * that instruction. In that case, we can't recover the instruction
250 * from the kp->ainsn.insn.
251 *
252 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
253 * of the first byte of the probed instruction, which is overwritten
254 * by int3. And the instruction at kp->addr is not modified by kprobes
255 * except for the first byte, we can recover the original instruction
256 * from it and kp->opcode.
257 *
258 * In case of Kprobes using ftrace, we do not have a copy of
259 * the original instruction. In fact, the ftrace location might
260 * be modified at anytime and even could be in an inconsistent state.
261 * Fortunately, we know that the original code is the ideal 5-byte
262 * long NOP.
263 */
264 memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
265 if (faddr)
266 memcpy(buf, ideal_nops[NOP_ATOMIC5], 5);
267 else
268 buf[0] = kp->opcode;
269 return (unsigned long)buf;
270}
271
272/*
273 * Recover the probed instruction at addr for further analysis.
274 * Caller must lock kprobes by kprobe_mutex, or disable preemption
275 * for preventing to release referencing kprobes.
276 * Returns zero if the instruction can not get recovered.
277 */
278unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
279{
280 unsigned long __addr;
281
282 __addr = __recover_optprobed_insn(buf, addr);
283 if (__addr != addr)
284 return __addr;
285
286 return __recover_probed_insn(buf, addr);
287}
288
289/* Check if paddr is at an instruction boundary */
290static int can_probe(unsigned long paddr)
291{
292 unsigned long addr, __addr, offset = 0;
293 struct insn insn;
294 kprobe_opcode_t buf[MAX_INSN_SIZE];
295
296 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
297 return 0;
298
299 /* Decode instructions */
300 addr = paddr - offset;
301 while (addr < paddr) {
302 /*
303 * Check if the instruction has been modified by another
304 * kprobe, in which case we replace the breakpoint by the
305 * original instruction in our buffer.
306 * Also, jump optimization will change the breakpoint to
307 * relative-jump. Since the relative-jump itself is
308 * normally used, we just go through if there is no kprobe.
309 */
310 __addr = recover_probed_instruction(buf, addr);
311 if (!__addr)
312 return 0;
313 kernel_insn_init(&insn, (void *)__addr, MAX_INSN_SIZE);
314 insn_get_length(&insn);
315
316 /*
317 * Another debugging subsystem might insert this breakpoint.
318 * In that case, we can't recover it.
319 */
320 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
321 return 0;
322 addr += insn.length;
323 }
324
325 return (addr == paddr);
326}
327
328/*
329 * Returns non-zero if opcode modifies the interrupt flag.
330 */
331static int is_IF_modifier(kprobe_opcode_t *insn)
332{
333 /* Skip prefixes */
334 insn = skip_prefixes(insn);
335
336 switch (*insn) {
337 case 0xfa: /* cli */
338 case 0xfb: /* sti */
339 case 0xcf: /* iret/iretd */
340 case 0x9d: /* popf/popfd */
341 return 1;
342 }
343
344 return 0;
345}
346
347/*
348 * Copy an instruction and adjust the displacement if the instruction
349 * uses the %rip-relative addressing mode.
350 * If it does, Return the address of the 32-bit displacement word.
351 * If not, return null.
352 * Only applicable to 64-bit x86.
353 */
354int __copy_instruction(u8 *dest, u8 *src)
355{
356 struct insn insn;
357 kprobe_opcode_t buf[MAX_INSN_SIZE];
358 int length;
359 unsigned long recovered_insn =
360 recover_probed_instruction(buf, (unsigned long)src);
361
362 if (!recovered_insn)
363 return 0;
364 kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
365 insn_get_length(&insn);
366 length = insn.length;
367
368 /* Another subsystem puts a breakpoint, failed to recover */
369 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
370 return 0;
371 memcpy(dest, insn.kaddr, length);
372
373#ifdef CONFIG_X86_64
374 if (insn_rip_relative(&insn)) {
375 s64 newdisp;
376 u8 *disp;
377 kernel_insn_init(&insn, dest, length);
378 insn_get_displacement(&insn);
379 /*
380 * The copied instruction uses the %rip-relative addressing
381 * mode. Adjust the displacement for the difference between
382 * the original location of this instruction and the location
383 * of the copy that will actually be run. The tricky bit here
384 * is making sure that the sign extension happens correctly in
385 * this calculation, since we need a signed 32-bit result to
386 * be sign-extended to 64 bits when it's added to the %rip
387 * value and yield the same 64-bit result that the sign-
388 * extension of the original signed 32-bit displacement would
389 * have given.
390 */
391 newdisp = (u8 *) src + (s64) insn.displacement.value - (u8 *) dest;
392 if ((s64) (s32) newdisp != newdisp) {
393 pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
394 pr_err("\tSrc: %p, Dest: %p, old disp: %x\n", src, dest, insn.displacement.value);
395 return 0;
396 }
397 disp = (u8 *) dest + insn_offset_displacement(&insn);
398 *(s32 *) disp = (s32) newdisp;
399 }
400#endif
401 return length;
402}
403
404static int arch_copy_kprobe(struct kprobe *p)
405{
406 int ret;
407
408 /* Copy an instruction with recovering if other optprobe modifies it.*/
409 ret = __copy_instruction(p->ainsn.insn, p->addr);
410 if (!ret)
411 return -EINVAL;
412
413 /*
414 * __copy_instruction can modify the displacement of the instruction,
415 * but it doesn't affect boostable check.
416 */
417 if (can_boost(p->ainsn.insn))
418 p->ainsn.boostable = 0;
419 else
420 p->ainsn.boostable = -1;
421
422 /* Check whether the instruction modifies Interrupt Flag or not */
423 p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn);
424
425 /* Also, displacement change doesn't affect the first byte */
426 p->opcode = p->ainsn.insn[0];
427
428 return 0;
429}
430
431int arch_prepare_kprobe(struct kprobe *p)
432{
433 if (alternatives_text_reserved(p->addr, p->addr))
434 return -EINVAL;
435
436 if (!can_probe((unsigned long)p->addr))
437 return -EILSEQ;
438 /* insn: must be on special executable page on x86. */
439 p->ainsn.insn = get_insn_slot();
440 if (!p->ainsn.insn)
441 return -ENOMEM;
442
443 return arch_copy_kprobe(p);
444}
445
446void arch_arm_kprobe(struct kprobe *p)
447{
448 text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
449}
450
451void arch_disarm_kprobe(struct kprobe *p)
452{
453 text_poke(p->addr, &p->opcode, 1);
454}
455
456void arch_remove_kprobe(struct kprobe *p)
457{
458 if (p->ainsn.insn) {
459 free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1));
460 p->ainsn.insn = NULL;
461 }
462}
463
464static nokprobe_inline void
465save_previous_kprobe(struct kprobe_ctlblk *kcb)
466{
467 kcb->prev_kprobe.kp = kprobe_running();
468 kcb->prev_kprobe.status = kcb->kprobe_status;
469 kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
470 kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
471}
472
473static nokprobe_inline void
474restore_previous_kprobe(struct kprobe_ctlblk *kcb)
475{
476 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
477 kcb->kprobe_status = kcb->prev_kprobe.status;
478 kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
479 kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
480}
481
482static nokprobe_inline void
483set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
484 struct kprobe_ctlblk *kcb)
485{
486 __this_cpu_write(current_kprobe, p);
487 kcb->kprobe_saved_flags = kcb->kprobe_old_flags
488 = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
489 if (p->ainsn.if_modifier)
490 kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
491}
492
493static nokprobe_inline void clear_btf(void)
494{
495 if (test_thread_flag(TIF_BLOCKSTEP)) {
496 unsigned long debugctl = get_debugctlmsr();
497
498 debugctl &= ~DEBUGCTLMSR_BTF;
499 update_debugctlmsr(debugctl);
500 }
501}
502
503static nokprobe_inline void restore_btf(void)
504{
505 if (test_thread_flag(TIF_BLOCKSTEP)) {
506 unsigned long debugctl = get_debugctlmsr();
507
508 debugctl |= DEBUGCTLMSR_BTF;
509 update_debugctlmsr(debugctl);
510 }
511}
512
513void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
514{
515 unsigned long *sara = stack_addr(regs);
516
517 ri->ret_addr = (kprobe_opcode_t *) *sara;
518
519 /* Replace the return addr with trampoline addr */
520 *sara = (unsigned long) &kretprobe_trampoline;
521}
522NOKPROBE_SYMBOL(arch_prepare_kretprobe);
523
524static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
525 struct kprobe_ctlblk *kcb, int reenter)
526{
527 if (setup_detour_execution(p, regs, reenter))
528 return;
529
530#if !defined(CONFIG_PREEMPT)
531 if (p->ainsn.boostable == 1 && !p->post_handler) {
532 /* Boost up -- we can execute copied instructions directly */
533 if (!reenter)
534 reset_current_kprobe();
535 /*
536 * Reentering boosted probe doesn't reset current_kprobe,
537 * nor set current_kprobe, because it doesn't use single
538 * stepping.
539 */
540 regs->ip = (unsigned long)p->ainsn.insn;
541 preempt_enable_no_resched();
542 return;
543 }
544#endif
545 if (reenter) {
546 save_previous_kprobe(kcb);
547 set_current_kprobe(p, regs, kcb);
548 kcb->kprobe_status = KPROBE_REENTER;
549 } else
550 kcb->kprobe_status = KPROBE_HIT_SS;
551 /* Prepare real single stepping */
552 clear_btf();
553 regs->flags |= X86_EFLAGS_TF;
554 regs->flags &= ~X86_EFLAGS_IF;
555 /* single step inline if the instruction is an int3 */
556 if (p->opcode == BREAKPOINT_INSTRUCTION)
557 regs->ip = (unsigned long)p->addr;
558 else
559 regs->ip = (unsigned long)p->ainsn.insn;
560}
561NOKPROBE_SYMBOL(setup_singlestep);
562
563/*
564 * We have reentered the kprobe_handler(), since another probe was hit while
565 * within the handler. We save the original kprobes variables and just single
566 * step on the instruction of the new probe without calling any user handlers.
567 */
568static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
569 struct kprobe_ctlblk *kcb)
570{
571 switch (kcb->kprobe_status) {
572 case KPROBE_HIT_SSDONE:
573 case KPROBE_HIT_ACTIVE:
574 case KPROBE_HIT_SS:
575 kprobes_inc_nmissed_count(p);
576 setup_singlestep(p, regs, kcb, 1);
577 break;
578 case KPROBE_REENTER:
579 /* A probe has been hit in the codepath leading up to, or just
580 * after, single-stepping of a probed instruction. This entire
581 * codepath should strictly reside in .kprobes.text section.
582 * Raise a BUG or we'll continue in an endless reentering loop
583 * and eventually a stack overflow.
584 */
585 printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n",
586 p->addr);
587 dump_kprobe(p);
588 BUG();
589 default:
590 /* impossible cases */
591 WARN_ON(1);
592 return 0;
593 }
594
595 return 1;
596}
597NOKPROBE_SYMBOL(reenter_kprobe);
598
599/*
600 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
601 * remain disabled throughout this function.
602 */
603int kprobe_int3_handler(struct pt_regs *regs)
604{
605 kprobe_opcode_t *addr;
606 struct kprobe *p;
607 struct kprobe_ctlblk *kcb;
608
609 if (user_mode(regs))
610 return 0;
611
612 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
613 /*
614 * We don't want to be preempted for the entire
615 * duration of kprobe processing. We conditionally
616 * re-enable preemption at the end of this function,
617 * and also in reenter_kprobe() and setup_singlestep().
618 */
619 preempt_disable();
620
621 kcb = get_kprobe_ctlblk();
622 p = get_kprobe(addr);
623
624 if (p) {
625 if (kprobe_running()) {
626 if (reenter_kprobe(p, regs, kcb))
627 return 1;
628 } else {
629 set_current_kprobe(p, regs, kcb);
630 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
631
632 /*
633 * If we have no pre-handler or it returned 0, we
634 * continue with normal processing. If we have a
635 * pre-handler and it returned non-zero, it prepped
636 * for calling the break_handler below on re-entry
637 * for jprobe processing, so get out doing nothing
638 * more here.
639 */
640 if (!p->pre_handler || !p->pre_handler(p, regs))
641 setup_singlestep(p, regs, kcb, 0);
642 return 1;
643 }
644 } else if (*addr != BREAKPOINT_INSTRUCTION) {
645 /*
646 * The breakpoint instruction was removed right
647 * after we hit it. Another cpu has removed
648 * either a probepoint or a debugger breakpoint
649 * at this address. In either case, no further
650 * handling of this interrupt is appropriate.
651 * Back up over the (now missing) int3 and run
652 * the original instruction.
653 */
654 regs->ip = (unsigned long)addr;
655 preempt_enable_no_resched();
656 return 1;
657 } else if (kprobe_running()) {
658 p = __this_cpu_read(current_kprobe);
659 if (p->break_handler && p->break_handler(p, regs)) {
660 if (!skip_singlestep(p, regs, kcb))
661 setup_singlestep(p, regs, kcb, 0);
662 return 1;
663 }
664 } /* else: not a kprobe fault; let the kernel handle it */
665
666 preempt_enable_no_resched();
667 return 0;
668}
669NOKPROBE_SYMBOL(kprobe_int3_handler);
670
671/*
672 * When a retprobed function returns, this code saves registers and
673 * calls trampoline_handler() runs, which calls the kretprobe's handler.
674 */
675asm(
676 ".global kretprobe_trampoline\n"
677 ".type kretprobe_trampoline, @function\n"
678 "kretprobe_trampoline:\n"
679#ifdef CONFIG_X86_64
680 /* We don't bother saving the ss register */
681 " pushq %rsp\n"
682 " pushfq\n"
683 SAVE_REGS_STRING
684 " movq %rsp, %rdi\n"
685 " call trampoline_handler\n"
686 /* Replace saved sp with true return address. */
687 " movq %rax, 152(%rsp)\n"
688 RESTORE_REGS_STRING
689 " popfq\n"
690#else
691 " pushf\n"
692 SAVE_REGS_STRING
693 " movl %esp, %eax\n"
694 " call trampoline_handler\n"
695 /* Move flags to cs */
696 " movl 56(%esp), %edx\n"
697 " movl %edx, 52(%esp)\n"
698 /* Replace saved flags with true return address. */
699 " movl %eax, 56(%esp)\n"
700 RESTORE_REGS_STRING
701 " popf\n"
702#endif
703 " ret\n"
704 ".size kretprobe_trampoline, .-kretprobe_trampoline\n"
705);
706NOKPROBE_SYMBOL(kretprobe_trampoline);
707STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
708
709/*
710 * Called from kretprobe_trampoline
711 */
712__visible __used void *trampoline_handler(struct pt_regs *regs)
713{
714 struct kretprobe_instance *ri = NULL;
715 struct hlist_head *head, empty_rp;
716 struct hlist_node *tmp;
717 unsigned long flags, orig_ret_address = 0;
718 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
719 kprobe_opcode_t *correct_ret_addr = NULL;
720
721 INIT_HLIST_HEAD(&empty_rp);
722 kretprobe_hash_lock(current, &head, &flags);
723 /* fixup registers */
724#ifdef CONFIG_X86_64
725 regs->cs = __KERNEL_CS;
726#else
727 regs->cs = __KERNEL_CS | get_kernel_rpl();
728 regs->gs = 0;
729#endif
730 regs->ip = trampoline_address;
731 regs->orig_ax = ~0UL;
732
733 /*
734 * It is possible to have multiple instances associated with a given
735 * task either because multiple functions in the call path have
736 * return probes installed on them, and/or more than one
737 * return probe was registered for a target function.
738 *
739 * We can handle this because:
740 * - instances are always pushed into the head of the list
741 * - when multiple return probes are registered for the same
742 * function, the (chronologically) first instance's ret_addr
743 * will be the real return address, and all the rest will
744 * point to kretprobe_trampoline.
745 */
746 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
747 if (ri->task != current)
748 /* another task is sharing our hash bucket */
749 continue;
750
751 orig_ret_address = (unsigned long)ri->ret_addr;
752
753 if (orig_ret_address != trampoline_address)
754 /*
755 * This is the real return address. Any other
756 * instances associated with this task are for
757 * other calls deeper on the call stack
758 */
759 break;
760 }
761
762 kretprobe_assert(ri, orig_ret_address, trampoline_address);
763
764 correct_ret_addr = ri->ret_addr;
765 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
766 if (ri->task != current)
767 /* another task is sharing our hash bucket */
768 continue;
769
770 orig_ret_address = (unsigned long)ri->ret_addr;
771 if (ri->rp && ri->rp->handler) {
772 __this_cpu_write(current_kprobe, &ri->rp->kp);
773 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
774 ri->ret_addr = correct_ret_addr;
775 ri->rp->handler(ri, regs);
776 __this_cpu_write(current_kprobe, NULL);
777 }
778
779 recycle_rp_inst(ri, &empty_rp);
780
781 if (orig_ret_address != trampoline_address)
782 /*
783 * This is the real return address. Any other
784 * instances associated with this task are for
785 * other calls deeper on the call stack
786 */
787 break;
788 }
789
790 kretprobe_hash_unlock(current, &flags);
791
792 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
793 hlist_del(&ri->hlist);
794 kfree(ri);
795 }
796 return (void *)orig_ret_address;
797}
798NOKPROBE_SYMBOL(trampoline_handler);
799
800/*
801 * Called after single-stepping. p->addr is the address of the
802 * instruction whose first byte has been replaced by the "int 3"
803 * instruction. To avoid the SMP problems that can occur when we
804 * temporarily put back the original opcode to single-step, we
805 * single-stepped a copy of the instruction. The address of this
806 * copy is p->ainsn.insn.
807 *
808 * This function prepares to return from the post-single-step
809 * interrupt. We have to fix up the stack as follows:
810 *
811 * 0) Except in the case of absolute or indirect jump or call instructions,
812 * the new ip is relative to the copied instruction. We need to make
813 * it relative to the original instruction.
814 *
815 * 1) If the single-stepped instruction was pushfl, then the TF and IF
816 * flags are set in the just-pushed flags, and may need to be cleared.
817 *
818 * 2) If the single-stepped instruction was a call, the return address
819 * that is atop the stack is the address following the copied instruction.
820 * We need to make it the address following the original instruction.
821 *
822 * If this is the first time we've single-stepped the instruction at
823 * this probepoint, and the instruction is boostable, boost it: add a
824 * jump instruction after the copied instruction, that jumps to the next
825 * instruction after the probepoint.
826 */
827static void resume_execution(struct kprobe *p, struct pt_regs *regs,
828 struct kprobe_ctlblk *kcb)
829{
830 unsigned long *tos = stack_addr(regs);
831 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
832 unsigned long orig_ip = (unsigned long)p->addr;
833 kprobe_opcode_t *insn = p->ainsn.insn;
834
835 /* Skip prefixes */
836 insn = skip_prefixes(insn);
837
838 regs->flags &= ~X86_EFLAGS_TF;
839 switch (*insn) {
840 case 0x9c: /* pushfl */
841 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
842 *tos |= kcb->kprobe_old_flags;
843 break;
844 case 0xc2: /* iret/ret/lret */
845 case 0xc3:
846 case 0xca:
847 case 0xcb:
848 case 0xcf:
849 case 0xea: /* jmp absolute -- ip is correct */
850 /* ip is already adjusted, no more changes required */
851 p->ainsn.boostable = 1;
852 goto no_change;
853 case 0xe8: /* call relative - Fix return addr */
854 *tos = orig_ip + (*tos - copy_ip);
855 break;
856#ifdef CONFIG_X86_32
857 case 0x9a: /* call absolute -- same as call absolute, indirect */
858 *tos = orig_ip + (*tos - copy_ip);
859 goto no_change;
860#endif
861 case 0xff:
862 if ((insn[1] & 0x30) == 0x10) {
863 /*
864 * call absolute, indirect
865 * Fix return addr; ip is correct.
866 * But this is not boostable
867 */
868 *tos = orig_ip + (*tos - copy_ip);
869 goto no_change;
870 } else if (((insn[1] & 0x31) == 0x20) ||
871 ((insn[1] & 0x31) == 0x21)) {
872 /*
873 * jmp near and far, absolute indirect
874 * ip is correct. And this is boostable
875 */
876 p->ainsn.boostable = 1;
877 goto no_change;
878 }
879 default:
880 break;
881 }
882
883 if (p->ainsn.boostable == 0) {
884 if ((regs->ip > copy_ip) &&
885 (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
886 /*
887 * These instructions can be executed directly if it
888 * jumps back to correct address.
889 */
890 synthesize_reljump((void *)regs->ip,
891 (void *)orig_ip + (regs->ip - copy_ip));
892 p->ainsn.boostable = 1;
893 } else {
894 p->ainsn.boostable = -1;
895 }
896 }
897
898 regs->ip += orig_ip - copy_ip;
899
900no_change:
901 restore_btf();
902}
903NOKPROBE_SYMBOL(resume_execution);
904
905/*
906 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
907 * remain disabled throughout this function.
908 */
909int kprobe_debug_handler(struct pt_regs *regs)
910{
911 struct kprobe *cur = kprobe_running();
912 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
913
914 if (!cur)
915 return 0;
916
917 resume_execution(cur, regs, kcb);
918 regs->flags |= kcb->kprobe_saved_flags;
919
920 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
921 kcb->kprobe_status = KPROBE_HIT_SSDONE;
922 cur->post_handler(cur, regs, 0);
923 }
924
925 /* Restore back the original saved kprobes variables and continue. */
926 if (kcb->kprobe_status == KPROBE_REENTER) {
927 restore_previous_kprobe(kcb);
928 goto out;
929 }
930 reset_current_kprobe();
931out:
932 preempt_enable_no_resched();
933
934 /*
935 * if somebody else is singlestepping across a probe point, flags
936 * will have TF set, in which case, continue the remaining processing
937 * of do_debug, as if this is not a probe hit.
938 */
939 if (regs->flags & X86_EFLAGS_TF)
940 return 0;
941
942 return 1;
943}
944NOKPROBE_SYMBOL(kprobe_debug_handler);
945
946int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
947{
948 struct kprobe *cur = kprobe_running();
949 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
950
951 if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
952 /* This must happen on single-stepping */
953 WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
954 kcb->kprobe_status != KPROBE_REENTER);
955 /*
956 * We are here because the instruction being single
957 * stepped caused a page fault. We reset the current
958 * kprobe and the ip points back to the probe address
959 * and allow the page fault handler to continue as a
960 * normal page fault.
961 */
962 regs->ip = (unsigned long)cur->addr;
963 regs->flags |= kcb->kprobe_old_flags;
964 if (kcb->kprobe_status == KPROBE_REENTER)
965 restore_previous_kprobe(kcb);
966 else
967 reset_current_kprobe();
968 preempt_enable_no_resched();
969 } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE ||
970 kcb->kprobe_status == KPROBE_HIT_SSDONE) {
971 /*
972 * We increment the nmissed count for accounting,
973 * we can also use npre/npostfault count for accounting
974 * these specific fault cases.
975 */
976 kprobes_inc_nmissed_count(cur);
977
978 /*
979 * We come here because instructions in the pre/post
980 * handler caused the page_fault, this could happen
981 * if handler tries to access user space by
982 * copy_from_user(), get_user() etc. Let the
983 * user-specified handler try to fix it first.
984 */
985 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
986 return 1;
987
988 /*
989 * In case the user-specified fault handler returned
990 * zero, try to fix up.
991 */
992 if (fixup_exception(regs, trapnr))
993 return 1;
994
995 /*
996 * fixup routine could not handle it,
997 * Let do_page_fault() fix it.
998 */
999 }
1000
1001 return 0;
1002}
1003NOKPROBE_SYMBOL(kprobe_fault_handler);
1004
1005/*
1006 * Wrapper routine for handling exceptions.
1007 */
1008int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
1009 void *data)
1010{
1011 struct die_args *args = data;
1012 int ret = NOTIFY_DONE;
1013
1014 if (args->regs && user_mode(args->regs))
1015 return ret;
1016
1017 if (val == DIE_GPF) {
1018 /*
1019 * To be potentially processing a kprobe fault and to
1020 * trust the result from kprobe_running(), we have
1021 * be non-preemptible.
1022 */
1023 if (!preemptible() && kprobe_running() &&
1024 kprobe_fault_handler(args->regs, args->trapnr))
1025 ret = NOTIFY_STOP;
1026 }
1027 return ret;
1028}
1029NOKPROBE_SYMBOL(kprobe_exceptions_notify);
1030
1031int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
1032{
1033 struct jprobe *jp = container_of(p, struct jprobe, kp);
1034 unsigned long addr;
1035 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1036
1037 kcb->jprobe_saved_regs = *regs;
1038 kcb->jprobe_saved_sp = stack_addr(regs);
1039 addr = (unsigned long)(kcb->jprobe_saved_sp);
1040
1041 /*
1042 * As Linus pointed out, gcc assumes that the callee
1043 * owns the argument space and could overwrite it, e.g.
1044 * tailcall optimization. So, to be absolutely safe
1045 * we also save and restore enough stack bytes to cover
1046 * the argument area.
1047 */
1048 memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
1049 MIN_STACK_SIZE(addr));
1050 regs->flags &= ~X86_EFLAGS_IF;
1051 trace_hardirqs_off();
1052 regs->ip = (unsigned long)(jp->entry);
1053
1054 /*
1055 * jprobes use jprobe_return() which skips the normal return
1056 * path of the function, and this messes up the accounting of the
1057 * function graph tracer to get messed up.
1058 *
1059 * Pause function graph tracing while performing the jprobe function.
1060 */
1061 pause_graph_tracing();
1062 return 1;
1063}
1064NOKPROBE_SYMBOL(setjmp_pre_handler);
1065
1066void jprobe_return(void)
1067{
1068 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1069
1070 asm volatile (
1071#ifdef CONFIG_X86_64
1072 " xchg %%rbx,%%rsp \n"
1073#else
1074 " xchgl %%ebx,%%esp \n"
1075#endif
1076 " int3 \n"
1077 " .globl jprobe_return_end\n"
1078 " jprobe_return_end: \n"
1079 " nop \n"::"b"
1080 (kcb->jprobe_saved_sp):"memory");
1081}
1082NOKPROBE_SYMBOL(jprobe_return);
1083NOKPROBE_SYMBOL(jprobe_return_end);
1084
1085int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
1086{
1087 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1088 u8 *addr = (u8 *) (regs->ip - 1);
1089 struct jprobe *jp = container_of(p, struct jprobe, kp);
1090 void *saved_sp = kcb->jprobe_saved_sp;
1091
1092 if ((addr > (u8 *) jprobe_return) &&
1093 (addr < (u8 *) jprobe_return_end)) {
1094 if (stack_addr(regs) != saved_sp) {
1095 struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
1096 printk(KERN_ERR
1097 "current sp %p does not match saved sp %p\n",
1098 stack_addr(regs), saved_sp);
1099 printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
1100 show_regs(saved_regs);
1101 printk(KERN_ERR "Current registers\n");
1102 show_regs(regs);
1103 BUG();
1104 }
1105 /* It's OK to start function graph tracing again */
1106 unpause_graph_tracing();
1107 *regs = kcb->jprobe_saved_regs;
1108 memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp));
1109 preempt_enable_no_resched();
1110 return 1;
1111 }
1112 return 0;
1113}
1114NOKPROBE_SYMBOL(longjmp_break_handler);
1115
1116bool arch_within_kprobe_blacklist(unsigned long addr)
1117{
1118 return (addr >= (unsigned long)__kprobes_text_start &&
1119 addr < (unsigned long)__kprobes_text_end) ||
1120 (addr >= (unsigned long)__entry_text_start &&
1121 addr < (unsigned long)__entry_text_end);
1122}
1123
1124int __init arch_init_kprobes(void)
1125{
1126 return 0;
1127}
1128
1129int arch_trampoline_kprobe(struct kprobe *p)
1130{
1131 return 0;
1132}