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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/sched/debug.h>
49#include <linux/extable.h>
50#include <linux/kdebug.h>
51#include <linux/kallsyms.h>
52#include <linux/ftrace.h>
53#include <linux/frame.h>
54#include <linux/kasan.h>
55#include <linux/moduleloader.h>
56
57#include <asm/text-patching.h>
58#include <asm/cacheflush.h>
59#include <asm/desc.h>
60#include <asm/pgtable.h>
61#include <linux/uaccess.h>
62#include <asm/alternative.h>
63#include <asm/insn.h>
64#include <asm/debugreg.h>
65#include <asm/set_memory.h>
66
67#include "common.h"
68
69void jprobe_return_end(void);
70
71DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
72DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
73
74#define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
75
76#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
77 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
78 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
79 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
80 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
81 << (row % 32))
82 /*
83 * Undefined/reserved opcodes, conditional jump, Opcode Extension
84 * Groups, and some special opcodes can not boost.
85 * This is non-const and volatile to keep gcc from statically
86 * optimizing it out, as variable_test_bit makes gcc think only
87 * *(unsigned long*) is used.
88 */
89static volatile u32 twobyte_is_boostable[256 / 32] = {
90 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
91 /* ---------------------------------------------- */
92 W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
93 W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
94 W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
95 W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
96 W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
97 W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
98 W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
99 W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
100 W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
101 W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
102 W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
103 W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
104 W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
105 W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
106 W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
107 W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
108 /* ----------------------------------------------- */
109 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
110};
111#undef W
112
113struct kretprobe_blackpoint kretprobe_blacklist[] = {
114 {"__switch_to", }, /* This function switches only current task, but
115 doesn't switch kernel stack.*/
116 {NULL, NULL} /* Terminator */
117};
118
119const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
120
121static nokprobe_inline void
122__synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
123{
124 struct __arch_relative_insn {
125 u8 op;
126 s32 raddr;
127 } __packed *insn;
128
129 insn = (struct __arch_relative_insn *)dest;
130 insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
131 insn->op = op;
132}
133
134/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
135void synthesize_reljump(void *dest, void *from, void *to)
136{
137 __synthesize_relative_insn(dest, from, to, RELATIVEJUMP_OPCODE);
138}
139NOKPROBE_SYMBOL(synthesize_reljump);
140
141/* Insert a call instruction at address 'from', which calls address 'to'.*/
142void synthesize_relcall(void *dest, void *from, void *to)
143{
144 __synthesize_relative_insn(dest, from, to, RELATIVECALL_OPCODE);
145}
146NOKPROBE_SYMBOL(synthesize_relcall);
147
148/*
149 * Skip the prefixes of the instruction.
150 */
151static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn)
152{
153 insn_attr_t attr;
154
155 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
156 while (inat_is_legacy_prefix(attr)) {
157 insn++;
158 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
159 }
160#ifdef CONFIG_X86_64
161 if (inat_is_rex_prefix(attr))
162 insn++;
163#endif
164 return insn;
165}
166NOKPROBE_SYMBOL(skip_prefixes);
167
168/*
169 * Returns non-zero if INSN is boostable.
170 * RIP relative instructions are adjusted at copying time in 64 bits mode
171 */
172int can_boost(struct insn *insn, void *addr)
173{
174 kprobe_opcode_t opcode;
175
176 if (search_exception_tables((unsigned long)addr))
177 return 0; /* Page fault may occur on this address. */
178
179 /* 2nd-byte opcode */
180 if (insn->opcode.nbytes == 2)
181 return test_bit(insn->opcode.bytes[1],
182 (unsigned long *)twobyte_is_boostable);
183
184 if (insn->opcode.nbytes != 1)
185 return 0;
186
187 /* Can't boost Address-size override prefix */
188 if (unlikely(inat_is_address_size_prefix(insn->attr)))
189 return 0;
190
191 opcode = insn->opcode.bytes[0];
192
193 switch (opcode & 0xf0) {
194 case 0x60:
195 /* can't boost "bound" */
196 return (opcode != 0x62);
197 case 0x70:
198 return 0; /* can't boost conditional jump */
199 case 0x90:
200 return opcode != 0x9a; /* can't boost call far */
201 case 0xc0:
202 /* can't boost software-interruptions */
203 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
204 case 0xd0:
205 /* can boost AA* and XLAT */
206 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
207 case 0xe0:
208 /* can boost in/out and absolute jmps */
209 return ((opcode & 0x04) || opcode == 0xea);
210 case 0xf0:
211 /* clear and set flags are boostable */
212 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
213 default:
214 /* CS override prefix and call are not boostable */
215 return (opcode != 0x2e && opcode != 0x9a);
216 }
217}
218
219static unsigned long
220__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
221{
222 struct kprobe *kp;
223 unsigned long faddr;
224
225 kp = get_kprobe((void *)addr);
226 faddr = ftrace_location(addr);
227 /*
228 * Addresses inside the ftrace location are refused by
229 * arch_check_ftrace_location(). Something went terribly wrong
230 * if such an address is checked here.
231 */
232 if (WARN_ON(faddr && faddr != addr))
233 return 0UL;
234 /*
235 * Use the current code if it is not modified by Kprobe
236 * and it cannot be modified by ftrace.
237 */
238 if (!kp && !faddr)
239 return addr;
240
241 /*
242 * Basically, kp->ainsn.insn has an original instruction.
243 * However, RIP-relative instruction can not do single-stepping
244 * at different place, __copy_instruction() tweaks the displacement of
245 * that instruction. In that case, we can't recover the instruction
246 * from the kp->ainsn.insn.
247 *
248 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
249 * of the first byte of the probed instruction, which is overwritten
250 * by int3. And the instruction at kp->addr is not modified by kprobes
251 * except for the first byte, we can recover the original instruction
252 * from it and kp->opcode.
253 *
254 * In case of Kprobes using ftrace, we do not have a copy of
255 * the original instruction. In fact, the ftrace location might
256 * be modified at anytime and even could be in an inconsistent state.
257 * Fortunately, we know that the original code is the ideal 5-byte
258 * long NOP.
259 */
260 if (probe_kernel_read(buf, (void *)addr,
261 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
262 return 0UL;
263
264 if (faddr)
265 memcpy(buf, ideal_nops[NOP_ATOMIC5], 5);
266 else
267 buf[0] = kp->opcode;
268 return (unsigned long)buf;
269}
270
271/*
272 * Recover the probed instruction at addr for further analysis.
273 * Caller must lock kprobes by kprobe_mutex, or disable preemption
274 * for preventing to release referencing kprobes.
275 * Returns zero if the instruction can not get recovered (or access failed).
276 */
277unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
278{
279 unsigned long __addr;
280
281 __addr = __recover_optprobed_insn(buf, addr);
282 if (__addr != addr)
283 return __addr;
284
285 return __recover_probed_insn(buf, addr);
286}
287
288/* Check if paddr is at an instruction boundary */
289static int can_probe(unsigned long paddr)
290{
291 unsigned long addr, __addr, offset = 0;
292 struct insn insn;
293 kprobe_opcode_t buf[MAX_INSN_SIZE];
294
295 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
296 return 0;
297
298 /* Decode instructions */
299 addr = paddr - offset;
300 while (addr < paddr) {
301 /*
302 * Check if the instruction has been modified by another
303 * kprobe, in which case we replace the breakpoint by the
304 * original instruction in our buffer.
305 * Also, jump optimization will change the breakpoint to
306 * relative-jump. Since the relative-jump itself is
307 * normally used, we just go through if there is no kprobe.
308 */
309 __addr = recover_probed_instruction(buf, addr);
310 if (!__addr)
311 return 0;
312 kernel_insn_init(&insn, (void *)__addr, MAX_INSN_SIZE);
313 insn_get_length(&insn);
314
315 /*
316 * Another debugging subsystem might insert this breakpoint.
317 * In that case, we can't recover it.
318 */
319 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
320 return 0;
321 addr += insn.length;
322 }
323
324 return (addr == paddr);
325}
326
327/*
328 * Returns non-zero if opcode modifies the interrupt flag.
329 */
330static int is_IF_modifier(kprobe_opcode_t *insn)
331{
332 /* Skip prefixes */
333 insn = skip_prefixes(insn);
334
335 switch (*insn) {
336 case 0xfa: /* cli */
337 case 0xfb: /* sti */
338 case 0xcf: /* iret/iretd */
339 case 0x9d: /* popf/popfd */
340 return 1;
341 }
342
343 return 0;
344}
345
346/*
347 * Copy an instruction with recovering modified instruction by kprobes
348 * and adjust the displacement if the instruction uses the %rip-relative
349 * addressing mode. Note that since @real will be the final place of copied
350 * instruction, displacement must be adjust by @real, not @dest.
351 * This returns the length of copied instruction, or 0 if it has an error.
352 */
353int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
354{
355 kprobe_opcode_t buf[MAX_INSN_SIZE];
356 unsigned long recovered_insn =
357 recover_probed_instruction(buf, (unsigned long)src);
358
359 if (!recovered_insn || !insn)
360 return 0;
361
362 /* This can access kernel text if given address is not recovered */
363 if (probe_kernel_read(dest, (void *)recovered_insn, MAX_INSN_SIZE))
364 return 0;
365
366 kernel_insn_init(insn, dest, MAX_INSN_SIZE);
367 insn_get_length(insn);
368
369 /* Another subsystem puts a breakpoint, failed to recover */
370 if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
371 return 0;
372
373 /* We should not singlestep on the exception masking instructions */
374 if (insn_masking_exception(insn))
375 return 0;
376
377#ifdef CONFIG_X86_64
378 /* Only x86_64 has RIP relative instructions */
379 if (insn_rip_relative(insn)) {
380 s64 newdisp;
381 u8 *disp;
382 /*
383 * The copied instruction uses the %rip-relative addressing
384 * mode. Adjust the displacement for the difference between
385 * the original location of this instruction and the location
386 * of the copy that will actually be run. The tricky bit here
387 * is making sure that the sign extension happens correctly in
388 * this calculation, since we need a signed 32-bit result to
389 * be sign-extended to 64 bits when it's added to the %rip
390 * value and yield the same 64-bit result that the sign-
391 * extension of the original signed 32-bit displacement would
392 * have given.
393 */
394 newdisp = (u8 *) src + (s64) insn->displacement.value
395 - (u8 *) real;
396 if ((s64) (s32) newdisp != newdisp) {
397 pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
398 pr_err("\tSrc: %p, Dest: %p, old disp: %x\n",
399 src, real, insn->displacement.value);
400 return 0;
401 }
402 disp = (u8 *) dest + insn_offset_displacement(insn);
403 *(s32 *) disp = (s32) newdisp;
404 }
405#endif
406 return insn->length;
407}
408
409/* Prepare reljump right after instruction to boost */
410static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p,
411 struct insn *insn)
412{
413 int len = insn->length;
414
415 if (can_boost(insn, p->addr) &&
416 MAX_INSN_SIZE - len >= RELATIVEJUMP_SIZE) {
417 /*
418 * These instructions can be executed directly if it
419 * jumps back to correct address.
420 */
421 synthesize_reljump(buf + len, p->ainsn.insn + len,
422 p->addr + insn->length);
423 len += RELATIVEJUMP_SIZE;
424 p->ainsn.boostable = true;
425 } else {
426 p->ainsn.boostable = false;
427 }
428
429 return len;
430}
431
432/* Make page to RO mode when allocate it */
433void *alloc_insn_page(void)
434{
435 void *page;
436
437 page = module_alloc(PAGE_SIZE);
438 if (page)
439 set_memory_ro((unsigned long)page & PAGE_MASK, 1);
440
441 return page;
442}
443
444/* Recover page to RW mode before releasing it */
445void free_insn_page(void *page)
446{
447 set_memory_nx((unsigned long)page & PAGE_MASK, 1);
448 set_memory_rw((unsigned long)page & PAGE_MASK, 1);
449 module_memfree(page);
450}
451
452static int arch_copy_kprobe(struct kprobe *p)
453{
454 struct insn insn;
455 kprobe_opcode_t buf[MAX_INSN_SIZE];
456 int len;
457
458 /* Copy an instruction with recovering if other optprobe modifies it.*/
459 len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
460 if (!len)
461 return -EINVAL;
462
463 /*
464 * __copy_instruction can modify the displacement of the instruction,
465 * but it doesn't affect boostable check.
466 */
467 len = prepare_boost(buf, p, &insn);
468
469 /* Check whether the instruction modifies Interrupt Flag or not */
470 p->ainsn.if_modifier = is_IF_modifier(buf);
471
472 /* Also, displacement change doesn't affect the first byte */
473 p->opcode = buf[0];
474
475 /* OK, write back the instruction(s) into ROX insn buffer */
476 text_poke(p->ainsn.insn, buf, len);
477
478 return 0;
479}
480
481int arch_prepare_kprobe(struct kprobe *p)
482{
483 int ret;
484
485 if (alternatives_text_reserved(p->addr, p->addr))
486 return -EINVAL;
487
488 if (!can_probe((unsigned long)p->addr))
489 return -EILSEQ;
490 /* insn: must be on special executable page on x86. */
491 p->ainsn.insn = get_insn_slot();
492 if (!p->ainsn.insn)
493 return -ENOMEM;
494
495 ret = arch_copy_kprobe(p);
496 if (ret) {
497 free_insn_slot(p->ainsn.insn, 0);
498 p->ainsn.insn = NULL;
499 }
500
501 return ret;
502}
503
504void arch_arm_kprobe(struct kprobe *p)
505{
506 text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
507}
508
509void arch_disarm_kprobe(struct kprobe *p)
510{
511 text_poke(p->addr, &p->opcode, 1);
512}
513
514void arch_remove_kprobe(struct kprobe *p)
515{
516 if (p->ainsn.insn) {
517 free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
518 p->ainsn.insn = NULL;
519 }
520}
521
522static nokprobe_inline void
523save_previous_kprobe(struct kprobe_ctlblk *kcb)
524{
525 kcb->prev_kprobe.kp = kprobe_running();
526 kcb->prev_kprobe.status = kcb->kprobe_status;
527 kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
528 kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
529}
530
531static nokprobe_inline void
532restore_previous_kprobe(struct kprobe_ctlblk *kcb)
533{
534 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
535 kcb->kprobe_status = kcb->prev_kprobe.status;
536 kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
537 kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
538}
539
540static nokprobe_inline void
541set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
542 struct kprobe_ctlblk *kcb)
543{
544 __this_cpu_write(current_kprobe, p);
545 kcb->kprobe_saved_flags = kcb->kprobe_old_flags
546 = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
547 if (p->ainsn.if_modifier)
548 kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
549}
550
551static nokprobe_inline void clear_btf(void)
552{
553 if (test_thread_flag(TIF_BLOCKSTEP)) {
554 unsigned long debugctl = get_debugctlmsr();
555
556 debugctl &= ~DEBUGCTLMSR_BTF;
557 update_debugctlmsr(debugctl);
558 }
559}
560
561static nokprobe_inline void restore_btf(void)
562{
563 if (test_thread_flag(TIF_BLOCKSTEP)) {
564 unsigned long debugctl = get_debugctlmsr();
565
566 debugctl |= DEBUGCTLMSR_BTF;
567 update_debugctlmsr(debugctl);
568 }
569}
570
571void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
572{
573 unsigned long *sara = stack_addr(regs);
574
575 ri->ret_addr = (kprobe_opcode_t *) *sara;
576
577 /* Replace the return addr with trampoline addr */
578 *sara = (unsigned long) &kretprobe_trampoline;
579}
580NOKPROBE_SYMBOL(arch_prepare_kretprobe);
581
582static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
583 struct kprobe_ctlblk *kcb, int reenter)
584{
585 if (setup_detour_execution(p, regs, reenter))
586 return;
587
588#if !defined(CONFIG_PREEMPT)
589 if (p->ainsn.boostable && !p->post_handler) {
590 /* Boost up -- we can execute copied instructions directly */
591 if (!reenter)
592 reset_current_kprobe();
593 /*
594 * Reentering boosted probe doesn't reset current_kprobe,
595 * nor set current_kprobe, because it doesn't use single
596 * stepping.
597 */
598 regs->ip = (unsigned long)p->ainsn.insn;
599 preempt_enable_no_resched();
600 return;
601 }
602#endif
603 if (reenter) {
604 save_previous_kprobe(kcb);
605 set_current_kprobe(p, regs, kcb);
606 kcb->kprobe_status = KPROBE_REENTER;
607 } else
608 kcb->kprobe_status = KPROBE_HIT_SS;
609 /* Prepare real single stepping */
610 clear_btf();
611 regs->flags |= X86_EFLAGS_TF;
612 regs->flags &= ~X86_EFLAGS_IF;
613 /* single step inline if the instruction is an int3 */
614 if (p->opcode == BREAKPOINT_INSTRUCTION)
615 regs->ip = (unsigned long)p->addr;
616 else
617 regs->ip = (unsigned long)p->ainsn.insn;
618}
619NOKPROBE_SYMBOL(setup_singlestep);
620
621/*
622 * We have reentered the kprobe_handler(), since another probe was hit while
623 * within the handler. We save the original kprobes variables and just single
624 * step on the instruction of the new probe without calling any user handlers.
625 */
626static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
627 struct kprobe_ctlblk *kcb)
628{
629 switch (kcb->kprobe_status) {
630 case KPROBE_HIT_SSDONE:
631 case KPROBE_HIT_ACTIVE:
632 case KPROBE_HIT_SS:
633 kprobes_inc_nmissed_count(p);
634 setup_singlestep(p, regs, kcb, 1);
635 break;
636 case KPROBE_REENTER:
637 /* A probe has been hit in the codepath leading up to, or just
638 * after, single-stepping of a probed instruction. This entire
639 * codepath should strictly reside in .kprobes.text section.
640 * Raise a BUG or we'll continue in an endless reentering loop
641 * and eventually a stack overflow.
642 */
643 printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n",
644 p->addr);
645 dump_kprobe(p);
646 BUG();
647 default:
648 /* impossible cases */
649 WARN_ON(1);
650 return 0;
651 }
652
653 return 1;
654}
655NOKPROBE_SYMBOL(reenter_kprobe);
656
657/*
658 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
659 * remain disabled throughout this function.
660 */
661int kprobe_int3_handler(struct pt_regs *regs)
662{
663 kprobe_opcode_t *addr;
664 struct kprobe *p;
665 struct kprobe_ctlblk *kcb;
666
667 if (user_mode(regs))
668 return 0;
669
670 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
671 /*
672 * We don't want to be preempted for the entire
673 * duration of kprobe processing. We conditionally
674 * re-enable preemption at the end of this function,
675 * and also in reenter_kprobe() and setup_singlestep().
676 */
677 preempt_disable();
678
679 kcb = get_kprobe_ctlblk();
680 p = get_kprobe(addr);
681
682 if (p) {
683 if (kprobe_running()) {
684 if (reenter_kprobe(p, regs, kcb))
685 return 1;
686 } else {
687 set_current_kprobe(p, regs, kcb);
688 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
689
690 /*
691 * If we have no pre-handler or it returned 0, we
692 * continue with normal processing. If we have a
693 * pre-handler and it returned non-zero, it prepped
694 * for calling the break_handler below on re-entry
695 * for jprobe processing, so get out doing nothing
696 * more here.
697 */
698 if (!p->pre_handler || !p->pre_handler(p, regs))
699 setup_singlestep(p, regs, kcb, 0);
700 return 1;
701 }
702 } else if (*addr != BREAKPOINT_INSTRUCTION) {
703 /*
704 * The breakpoint instruction was removed right
705 * after we hit it. Another cpu has removed
706 * either a probepoint or a debugger breakpoint
707 * at this address. In either case, no further
708 * handling of this interrupt is appropriate.
709 * Back up over the (now missing) int3 and run
710 * the original instruction.
711 */
712 regs->ip = (unsigned long)addr;
713 preempt_enable_no_resched();
714 return 1;
715 } else if (kprobe_running()) {
716 p = __this_cpu_read(current_kprobe);
717 if (p->break_handler && p->break_handler(p, regs)) {
718 if (!skip_singlestep(p, regs, kcb))
719 setup_singlestep(p, regs, kcb, 0);
720 return 1;
721 }
722 } /* else: not a kprobe fault; let the kernel handle it */
723
724 preempt_enable_no_resched();
725 return 0;
726}
727NOKPROBE_SYMBOL(kprobe_int3_handler);
728
729/*
730 * When a retprobed function returns, this code saves registers and
731 * calls trampoline_handler() runs, which calls the kretprobe's handler.
732 */
733asm(
734 ".global kretprobe_trampoline\n"
735 ".type kretprobe_trampoline, @function\n"
736 "kretprobe_trampoline:\n"
737#ifdef CONFIG_X86_64
738 /* We don't bother saving the ss register */
739 " pushq %rsp\n"
740 " pushfq\n"
741 SAVE_REGS_STRING
742 " movq %rsp, %rdi\n"
743 " call trampoline_handler\n"
744 /* Replace saved sp with true return address. */
745 " movq %rax, 152(%rsp)\n"
746 RESTORE_REGS_STRING
747 " popfq\n"
748#else
749 " pushf\n"
750 SAVE_REGS_STRING
751 " movl %esp, %eax\n"
752 " call trampoline_handler\n"
753 /* Move flags to cs */
754 " movl 56(%esp), %edx\n"
755 " movl %edx, 52(%esp)\n"
756 /* Replace saved flags with true return address. */
757 " movl %eax, 56(%esp)\n"
758 RESTORE_REGS_STRING
759 " popf\n"
760#endif
761 " ret\n"
762 ".size kretprobe_trampoline, .-kretprobe_trampoline\n"
763);
764NOKPROBE_SYMBOL(kretprobe_trampoline);
765STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
766
767/*
768 * Called from kretprobe_trampoline
769 */
770__visible __used void *trampoline_handler(struct pt_regs *regs)
771{
772 struct kretprobe_instance *ri = NULL;
773 struct hlist_head *head, empty_rp;
774 struct hlist_node *tmp;
775 unsigned long flags, orig_ret_address = 0;
776 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
777 kprobe_opcode_t *correct_ret_addr = NULL;
778
779 INIT_HLIST_HEAD(&empty_rp);
780 kretprobe_hash_lock(current, &head, &flags);
781 /* fixup registers */
782#ifdef CONFIG_X86_64
783 regs->cs = __KERNEL_CS;
784#else
785 regs->cs = __KERNEL_CS | get_kernel_rpl();
786 regs->gs = 0;
787#endif
788 regs->ip = trampoline_address;
789 regs->orig_ax = ~0UL;
790
791 /*
792 * It is possible to have multiple instances associated with a given
793 * task either because multiple functions in the call path have
794 * return probes installed on them, and/or more than one
795 * return probe was registered for a target function.
796 *
797 * We can handle this because:
798 * - instances are always pushed into the head of the list
799 * - when multiple return probes are registered for the same
800 * function, the (chronologically) first instance's ret_addr
801 * will be the real return address, and all the rest will
802 * point to kretprobe_trampoline.
803 */
804 hlist_for_each_entry(ri, head, hlist) {
805 if (ri->task != current)
806 /* another task is sharing our hash bucket */
807 continue;
808
809 orig_ret_address = (unsigned long)ri->ret_addr;
810
811 if (orig_ret_address != trampoline_address)
812 /*
813 * This is the real return address. Any other
814 * instances associated with this task are for
815 * other calls deeper on the call stack
816 */
817 break;
818 }
819
820 kretprobe_assert(ri, orig_ret_address, trampoline_address);
821
822 correct_ret_addr = ri->ret_addr;
823 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
824 if (ri->task != current)
825 /* another task is sharing our hash bucket */
826 continue;
827
828 orig_ret_address = (unsigned long)ri->ret_addr;
829 if (ri->rp && ri->rp->handler) {
830 __this_cpu_write(current_kprobe, &ri->rp->kp);
831 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
832 ri->ret_addr = correct_ret_addr;
833 ri->rp->handler(ri, regs);
834 __this_cpu_write(current_kprobe, NULL);
835 }
836
837 recycle_rp_inst(ri, &empty_rp);
838
839 if (orig_ret_address != trampoline_address)
840 /*
841 * This is the real return address. Any other
842 * instances associated with this task are for
843 * other calls deeper on the call stack
844 */
845 break;
846 }
847
848 kretprobe_hash_unlock(current, &flags);
849
850 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
851 hlist_del(&ri->hlist);
852 kfree(ri);
853 }
854 return (void *)orig_ret_address;
855}
856NOKPROBE_SYMBOL(trampoline_handler);
857
858/*
859 * Called after single-stepping. p->addr is the address of the
860 * instruction whose first byte has been replaced by the "int 3"
861 * instruction. To avoid the SMP problems that can occur when we
862 * temporarily put back the original opcode to single-step, we
863 * single-stepped a copy of the instruction. The address of this
864 * copy is p->ainsn.insn.
865 *
866 * This function prepares to return from the post-single-step
867 * interrupt. We have to fix up the stack as follows:
868 *
869 * 0) Except in the case of absolute or indirect jump or call instructions,
870 * the new ip is relative to the copied instruction. We need to make
871 * it relative to the original instruction.
872 *
873 * 1) If the single-stepped instruction was pushfl, then the TF and IF
874 * flags are set in the just-pushed flags, and may need to be cleared.
875 *
876 * 2) If the single-stepped instruction was a call, the return address
877 * that is atop the stack is the address following the copied instruction.
878 * We need to make it the address following the original instruction.
879 *
880 * If this is the first time we've single-stepped the instruction at
881 * this probepoint, and the instruction is boostable, boost it: add a
882 * jump instruction after the copied instruction, that jumps to the next
883 * instruction after the probepoint.
884 */
885static void resume_execution(struct kprobe *p, struct pt_regs *regs,
886 struct kprobe_ctlblk *kcb)
887{
888 unsigned long *tos = stack_addr(regs);
889 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
890 unsigned long orig_ip = (unsigned long)p->addr;
891 kprobe_opcode_t *insn = p->ainsn.insn;
892
893 /* Skip prefixes */
894 insn = skip_prefixes(insn);
895
896 regs->flags &= ~X86_EFLAGS_TF;
897 switch (*insn) {
898 case 0x9c: /* pushfl */
899 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
900 *tos |= kcb->kprobe_old_flags;
901 break;
902 case 0xc2: /* iret/ret/lret */
903 case 0xc3:
904 case 0xca:
905 case 0xcb:
906 case 0xcf:
907 case 0xea: /* jmp absolute -- ip is correct */
908 /* ip is already adjusted, no more changes required */
909 p->ainsn.boostable = true;
910 goto no_change;
911 case 0xe8: /* call relative - Fix return addr */
912 *tos = orig_ip + (*tos - copy_ip);
913 break;
914#ifdef CONFIG_X86_32
915 case 0x9a: /* call absolute -- same as call absolute, indirect */
916 *tos = orig_ip + (*tos - copy_ip);
917 goto no_change;
918#endif
919 case 0xff:
920 if ((insn[1] & 0x30) == 0x10) {
921 /*
922 * call absolute, indirect
923 * Fix return addr; ip is correct.
924 * But this is not boostable
925 */
926 *tos = orig_ip + (*tos - copy_ip);
927 goto no_change;
928 } else if (((insn[1] & 0x31) == 0x20) ||
929 ((insn[1] & 0x31) == 0x21)) {
930 /*
931 * jmp near and far, absolute indirect
932 * ip is correct. And this is boostable
933 */
934 p->ainsn.boostable = true;
935 goto no_change;
936 }
937 default:
938 break;
939 }
940
941 regs->ip += orig_ip - copy_ip;
942
943no_change:
944 restore_btf();
945}
946NOKPROBE_SYMBOL(resume_execution);
947
948/*
949 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
950 * remain disabled throughout this function.
951 */
952int kprobe_debug_handler(struct pt_regs *regs)
953{
954 struct kprobe *cur = kprobe_running();
955 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
956
957 if (!cur)
958 return 0;
959
960 resume_execution(cur, regs, kcb);
961 regs->flags |= kcb->kprobe_saved_flags;
962
963 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
964 kcb->kprobe_status = KPROBE_HIT_SSDONE;
965 cur->post_handler(cur, regs, 0);
966 }
967
968 /* Restore back the original saved kprobes variables and continue. */
969 if (kcb->kprobe_status == KPROBE_REENTER) {
970 restore_previous_kprobe(kcb);
971 goto out;
972 }
973 reset_current_kprobe();
974out:
975 preempt_enable_no_resched();
976
977 /*
978 * if somebody else is singlestepping across a probe point, flags
979 * will have TF set, in which case, continue the remaining processing
980 * of do_debug, as if this is not a probe hit.
981 */
982 if (regs->flags & X86_EFLAGS_TF)
983 return 0;
984
985 return 1;
986}
987NOKPROBE_SYMBOL(kprobe_debug_handler);
988
989int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
990{
991 struct kprobe *cur = kprobe_running();
992 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
993
994 if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
995 /* This must happen on single-stepping */
996 WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
997 kcb->kprobe_status != KPROBE_REENTER);
998 /*
999 * We are here because the instruction being single
1000 * stepped caused a page fault. We reset the current
1001 * kprobe and the ip points back to the probe address
1002 * and allow the page fault handler to continue as a
1003 * normal page fault.
1004 */
1005 regs->ip = (unsigned long)cur->addr;
1006 /*
1007 * Trap flag (TF) has been set here because this fault
1008 * happened where the single stepping will be done.
1009 * So clear it by resetting the current kprobe:
1010 */
1011 regs->flags &= ~X86_EFLAGS_TF;
1012
1013 /*
1014 * If the TF flag was set before the kprobe hit,
1015 * don't touch it:
1016 */
1017 regs->flags |= kcb->kprobe_old_flags;
1018
1019 if (kcb->kprobe_status == KPROBE_REENTER)
1020 restore_previous_kprobe(kcb);
1021 else
1022 reset_current_kprobe();
1023 preempt_enable_no_resched();
1024 } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE ||
1025 kcb->kprobe_status == KPROBE_HIT_SSDONE) {
1026 /*
1027 * We increment the nmissed count for accounting,
1028 * we can also use npre/npostfault count for accounting
1029 * these specific fault cases.
1030 */
1031 kprobes_inc_nmissed_count(cur);
1032
1033 /*
1034 * We come here because instructions in the pre/post
1035 * handler caused the page_fault, this could happen
1036 * if handler tries to access user space by
1037 * copy_from_user(), get_user() etc. Let the
1038 * user-specified handler try to fix it first.
1039 */
1040 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
1041 return 1;
1042
1043 /*
1044 * In case the user-specified fault handler returned
1045 * zero, try to fix up.
1046 */
1047 if (fixup_exception(regs, trapnr))
1048 return 1;
1049
1050 /*
1051 * fixup routine could not handle it,
1052 * Let do_page_fault() fix it.
1053 */
1054 }
1055
1056 return 0;
1057}
1058NOKPROBE_SYMBOL(kprobe_fault_handler);
1059
1060/*
1061 * Wrapper routine for handling exceptions.
1062 */
1063int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
1064 void *data)
1065{
1066 struct die_args *args = data;
1067 int ret = NOTIFY_DONE;
1068
1069 if (args->regs && user_mode(args->regs))
1070 return ret;
1071
1072 if (val == DIE_GPF) {
1073 /*
1074 * To be potentially processing a kprobe fault and to
1075 * trust the result from kprobe_running(), we have
1076 * be non-preemptible.
1077 */
1078 if (!preemptible() && kprobe_running() &&
1079 kprobe_fault_handler(args->regs, args->trapnr))
1080 ret = NOTIFY_STOP;
1081 }
1082 return ret;
1083}
1084NOKPROBE_SYMBOL(kprobe_exceptions_notify);
1085
1086int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
1087{
1088 struct jprobe *jp = container_of(p, struct jprobe, kp);
1089 unsigned long addr;
1090 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1091
1092 kcb->jprobe_saved_regs = *regs;
1093 kcb->jprobe_saved_sp = stack_addr(regs);
1094 addr = (unsigned long)(kcb->jprobe_saved_sp);
1095
1096 /*
1097 * As Linus pointed out, gcc assumes that the callee
1098 * owns the argument space and could overwrite it, e.g.
1099 * tailcall optimization. So, to be absolutely safe
1100 * we also save and restore enough stack bytes to cover
1101 * the argument area.
1102 * Use __memcpy() to avoid KASAN stack out-of-bounds reports as we copy
1103 * raw stack chunk with redzones:
1104 */
1105 __memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, MIN_STACK_SIZE(addr));
1106 regs->ip = (unsigned long)(jp->entry);
1107
1108 /*
1109 * jprobes use jprobe_return() which skips the normal return
1110 * path of the function, and this messes up the accounting of the
1111 * function graph tracer to get messed up.
1112 *
1113 * Pause function graph tracing while performing the jprobe function.
1114 */
1115 pause_graph_tracing();
1116 return 1;
1117}
1118NOKPROBE_SYMBOL(setjmp_pre_handler);
1119
1120void jprobe_return(void)
1121{
1122 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1123
1124 /* Unpoison stack redzones in the frames we are going to jump over. */
1125 kasan_unpoison_stack_above_sp_to(kcb->jprobe_saved_sp);
1126
1127 asm volatile (
1128#ifdef CONFIG_X86_64
1129 " xchg %%rbx,%%rsp \n"
1130#else
1131 " xchgl %%ebx,%%esp \n"
1132#endif
1133 " int3 \n"
1134 " .globl jprobe_return_end\n"
1135 " jprobe_return_end: \n"
1136 " nop \n"::"b"
1137 (kcb->jprobe_saved_sp):"memory");
1138}
1139NOKPROBE_SYMBOL(jprobe_return);
1140NOKPROBE_SYMBOL(jprobe_return_end);
1141
1142int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
1143{
1144 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1145 u8 *addr = (u8 *) (regs->ip - 1);
1146 struct jprobe *jp = container_of(p, struct jprobe, kp);
1147 void *saved_sp = kcb->jprobe_saved_sp;
1148
1149 if ((addr > (u8 *) jprobe_return) &&
1150 (addr < (u8 *) jprobe_return_end)) {
1151 if (stack_addr(regs) != saved_sp) {
1152 struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
1153 printk(KERN_ERR
1154 "current sp %p does not match saved sp %p\n",
1155 stack_addr(regs), saved_sp);
1156 printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
1157 show_regs(saved_regs);
1158 printk(KERN_ERR "Current registers\n");
1159 show_regs(regs);
1160 BUG();
1161 }
1162 /* It's OK to start function graph tracing again */
1163 unpause_graph_tracing();
1164 *regs = kcb->jprobe_saved_regs;
1165 __memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp));
1166 preempt_enable_no_resched();
1167 return 1;
1168 }
1169 return 0;
1170}
1171NOKPROBE_SYMBOL(longjmp_break_handler);
1172
1173bool arch_within_kprobe_blacklist(unsigned long addr)
1174{
1175 bool is_in_entry_trampoline_section = false;
1176
1177#ifdef CONFIG_X86_64
1178 is_in_entry_trampoline_section =
1179 (addr >= (unsigned long)__entry_trampoline_start &&
1180 addr < (unsigned long)__entry_trampoline_end);
1181#endif
1182 return (addr >= (unsigned long)__kprobes_text_start &&
1183 addr < (unsigned long)__kprobes_text_end) ||
1184 (addr >= (unsigned long)__entry_text_start &&
1185 addr < (unsigned long)__entry_text_end) ||
1186 is_in_entry_trampoline_section;
1187}
1188
1189int __init arch_init_kprobes(void)
1190{
1191 return 0;
1192}
1193
1194int arch_trampoline_kprobe(struct kprobe *p)
1195{
1196 return 0;
1197}