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1/*
2 * Kernel Probes Jump Optimization (Optprobes)
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 * Copyright (C) Hitachi Ltd., 2012
20 */
21#include <linux/kprobes.h>
22#include <linux/ptrace.h>
23#include <linux/string.h>
24#include <linux/slab.h>
25#include <linux/hardirq.h>
26#include <linux/preempt.h>
27#include <linux/module.h>
28#include <linux/kdebug.h>
29#include <linux/kallsyms.h>
30#include <linux/ftrace.h>
31
32#include <asm/cacheflush.h>
33#include <asm/desc.h>
34#include <asm/pgtable.h>
35#include <asm/uaccess.h>
36#include <asm/alternative.h>
37#include <asm/insn.h>
38#include <asm/debugreg.h>
39
40#include "kprobes-common.h"
41
42unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
43{
44 struct optimized_kprobe *op;
45 struct kprobe *kp;
46 long offs;
47 int i;
48
49 for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
50 kp = get_kprobe((void *)addr - i);
51 /* This function only handles jump-optimized kprobe */
52 if (kp && kprobe_optimized(kp)) {
53 op = container_of(kp, struct optimized_kprobe, kp);
54 /* If op->list is not empty, op is under optimizing */
55 if (list_empty(&op->list))
56 goto found;
57 }
58 }
59
60 return addr;
61found:
62 /*
63 * If the kprobe can be optimized, original bytes which can be
64 * overwritten by jump destination address. In this case, original
65 * bytes must be recovered from op->optinsn.copied_insn buffer.
66 */
67 memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
68 if (addr == (unsigned long)kp->addr) {
69 buf[0] = kp->opcode;
70 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
71 } else {
72 offs = addr - (unsigned long)kp->addr - 1;
73 memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
74 }
75
76 return (unsigned long)buf;
77}
78
79/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
80static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
81{
82#ifdef CONFIG_X86_64
83 *addr++ = 0x48;
84 *addr++ = 0xbf;
85#else
86 *addr++ = 0xb8;
87#endif
88 *(unsigned long *)addr = val;
89}
90
91static void __used __kprobes kprobes_optinsn_template_holder(void)
92{
93 asm volatile (
94 ".global optprobe_template_entry\n"
95 "optprobe_template_entry:\n"
96#ifdef CONFIG_X86_64
97 /* We don't bother saving the ss register */
98 " pushq %rsp\n"
99 " pushfq\n"
100 SAVE_REGS_STRING
101 " movq %rsp, %rsi\n"
102 ".global optprobe_template_val\n"
103 "optprobe_template_val:\n"
104 ASM_NOP5
105 ASM_NOP5
106 ".global optprobe_template_call\n"
107 "optprobe_template_call:\n"
108 ASM_NOP5
109 /* Move flags to rsp */
110 " movq 144(%rsp), %rdx\n"
111 " movq %rdx, 152(%rsp)\n"
112 RESTORE_REGS_STRING
113 /* Skip flags entry */
114 " addq $8, %rsp\n"
115 " popfq\n"
116#else /* CONFIG_X86_32 */
117 " pushf\n"
118 SAVE_REGS_STRING
119 " movl %esp, %edx\n"
120 ".global optprobe_template_val\n"
121 "optprobe_template_val:\n"
122 ASM_NOP5
123 ".global optprobe_template_call\n"
124 "optprobe_template_call:\n"
125 ASM_NOP5
126 RESTORE_REGS_STRING
127 " addl $4, %esp\n" /* skip cs */
128 " popf\n"
129#endif
130 ".global optprobe_template_end\n"
131 "optprobe_template_end:\n");
132}
133
134#define TMPL_MOVE_IDX \
135 ((long)&optprobe_template_val - (long)&optprobe_template_entry)
136#define TMPL_CALL_IDX \
137 ((long)&optprobe_template_call - (long)&optprobe_template_entry)
138#define TMPL_END_IDX \
139 ((long)&optprobe_template_end - (long)&optprobe_template_entry)
140
141#define INT3_SIZE sizeof(kprobe_opcode_t)
142
143/* Optimized kprobe call back function: called from optinsn */
144static void __kprobes optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
145{
146 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
147 unsigned long flags;
148
149 /* This is possible if op is under delayed unoptimizing */
150 if (kprobe_disabled(&op->kp))
151 return;
152
153 local_irq_save(flags);
154 if (kprobe_running()) {
155 kprobes_inc_nmissed_count(&op->kp);
156 } else {
157 /* Save skipped registers */
158#ifdef CONFIG_X86_64
159 regs->cs = __KERNEL_CS;
160#else
161 regs->cs = __KERNEL_CS | get_kernel_rpl();
162 regs->gs = 0;
163#endif
164 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
165 regs->orig_ax = ~0UL;
166
167 __this_cpu_write(current_kprobe, &op->kp);
168 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
169 opt_pre_handler(&op->kp, regs);
170 __this_cpu_write(current_kprobe, NULL);
171 }
172 local_irq_restore(flags);
173}
174
175static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
176{
177 int len = 0, ret;
178
179 while (len < RELATIVEJUMP_SIZE) {
180 ret = __copy_instruction(dest + len, src + len);
181 if (!ret || !can_boost(dest + len))
182 return -EINVAL;
183 len += ret;
184 }
185 /* Check whether the address range is reserved */
186 if (ftrace_text_reserved(src, src + len - 1) ||
187 alternatives_text_reserved(src, src + len - 1) ||
188 jump_label_text_reserved(src, src + len - 1))
189 return -EBUSY;
190
191 return len;
192}
193
194/* Check whether insn is indirect jump */
195static int __kprobes insn_is_indirect_jump(struct insn *insn)
196{
197 return ((insn->opcode.bytes[0] == 0xff &&
198 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
199 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
200}
201
202/* Check whether insn jumps into specified address range */
203static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
204{
205 unsigned long target = 0;
206
207 switch (insn->opcode.bytes[0]) {
208 case 0xe0: /* loopne */
209 case 0xe1: /* loope */
210 case 0xe2: /* loop */
211 case 0xe3: /* jcxz */
212 case 0xe9: /* near relative jump */
213 case 0xeb: /* short relative jump */
214 break;
215 case 0x0f:
216 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
217 break;
218 return 0;
219 default:
220 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
221 break;
222 return 0;
223 }
224 target = (unsigned long)insn->next_byte + insn->immediate.value;
225
226 return (start <= target && target <= start + len);
227}
228
229/* Decode whole function to ensure any instructions don't jump into target */
230static int __kprobes can_optimize(unsigned long paddr)
231{
232 unsigned long addr, size = 0, offset = 0;
233 struct insn insn;
234 kprobe_opcode_t buf[MAX_INSN_SIZE];
235
236 /* Lookup symbol including addr */
237 if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
238 return 0;
239
240 /*
241 * Do not optimize in the entry code due to the unstable
242 * stack handling.
243 */
244 if ((paddr >= (unsigned long)__entry_text_start) &&
245 (paddr < (unsigned long)__entry_text_end))
246 return 0;
247
248 /* Check there is enough space for a relative jump. */
249 if (size - offset < RELATIVEJUMP_SIZE)
250 return 0;
251
252 /* Decode instructions */
253 addr = paddr - offset;
254 while (addr < paddr - offset + size) { /* Decode until function end */
255 if (search_exception_tables(addr))
256 /*
257 * Since some fixup code will jumps into this function,
258 * we can't optimize kprobe in this function.
259 */
260 return 0;
261 kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, addr));
262 insn_get_length(&insn);
263 /* Another subsystem puts a breakpoint */
264 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
265 return 0;
266 /* Recover address */
267 insn.kaddr = (void *)addr;
268 insn.next_byte = (void *)(addr + insn.length);
269 /* Check any instructions don't jump into target */
270 if (insn_is_indirect_jump(&insn) ||
271 insn_jump_into_range(&insn, paddr + INT3_SIZE,
272 RELATIVE_ADDR_SIZE))
273 return 0;
274 addr += insn.length;
275 }
276
277 return 1;
278}
279
280/* Check optimized_kprobe can actually be optimized. */
281int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
282{
283 int i;
284 struct kprobe *p;
285
286 for (i = 1; i < op->optinsn.size; i++) {
287 p = get_kprobe(op->kp.addr + i);
288 if (p && !kprobe_disabled(p))
289 return -EEXIST;
290 }
291
292 return 0;
293}
294
295/* Check the addr is within the optimized instructions. */
296int __kprobes
297arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr)
298{
299 return ((unsigned long)op->kp.addr <= addr &&
300 (unsigned long)op->kp.addr + op->optinsn.size > addr);
301}
302
303/* Free optimized instruction slot */
304static __kprobes
305void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
306{
307 if (op->optinsn.insn) {
308 free_optinsn_slot(op->optinsn.insn, dirty);
309 op->optinsn.insn = NULL;
310 op->optinsn.size = 0;
311 }
312}
313
314void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)
315{
316 __arch_remove_optimized_kprobe(op, 1);
317}
318
319/*
320 * Copy replacing target instructions
321 * Target instructions MUST be relocatable (checked inside)
322 * This is called when new aggr(opt)probe is allocated or reused.
323 */
324int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
325{
326 u8 *buf;
327 int ret;
328 long rel;
329
330 if (!can_optimize((unsigned long)op->kp.addr))
331 return -EILSEQ;
332
333 op->optinsn.insn = get_optinsn_slot();
334 if (!op->optinsn.insn)
335 return -ENOMEM;
336
337 /*
338 * Verify if the address gap is in 2GB range, because this uses
339 * a relative jump.
340 */
341 rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
342 if (abs(rel) > 0x7fffffff)
343 return -ERANGE;
344
345 buf = (u8 *)op->optinsn.insn;
346
347 /* Copy instructions into the out-of-line buffer */
348 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
349 if (ret < 0) {
350 __arch_remove_optimized_kprobe(op, 0);
351 return ret;
352 }
353 op->optinsn.size = ret;
354
355 /* Copy arch-dep-instance from template */
356 memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
357
358 /* Set probe information */
359 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
360
361 /* Set probe function call */
362 synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
363
364 /* Set returning jmp instruction at the tail of out-of-line buffer */
365 synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
366 (u8 *)op->kp.addr + op->optinsn.size);
367
368 flush_icache_range((unsigned long) buf,
369 (unsigned long) buf + TMPL_END_IDX +
370 op->optinsn.size + RELATIVEJUMP_SIZE);
371 return 0;
372}
373
374#define MAX_OPTIMIZE_PROBES 256
375static struct text_poke_param *jump_poke_params;
376static struct jump_poke_buffer {
377 u8 buf[RELATIVEJUMP_SIZE];
378} *jump_poke_bufs;
379
380static void __kprobes setup_optimize_kprobe(struct text_poke_param *tprm,
381 u8 *insn_buf,
382 struct optimized_kprobe *op)
383{
384 s32 rel = (s32)((long)op->optinsn.insn -
385 ((long)op->kp.addr + RELATIVEJUMP_SIZE));
386
387 /* Backup instructions which will be replaced by jump address */
388 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
389 RELATIVE_ADDR_SIZE);
390
391 insn_buf[0] = RELATIVEJUMP_OPCODE;
392 *(s32 *)(&insn_buf[1]) = rel;
393
394 tprm->addr = op->kp.addr;
395 tprm->opcode = insn_buf;
396 tprm->len = RELATIVEJUMP_SIZE;
397}
398
399/*
400 * Replace breakpoints (int3) with relative jumps.
401 * Caller must call with locking kprobe_mutex and text_mutex.
402 */
403void __kprobes arch_optimize_kprobes(struct list_head *oplist)
404{
405 struct optimized_kprobe *op, *tmp;
406 int c = 0;
407
408 list_for_each_entry_safe(op, tmp, oplist, list) {
409 WARN_ON(kprobe_disabled(&op->kp));
410 /* Setup param */
411 setup_optimize_kprobe(&jump_poke_params[c],
412 jump_poke_bufs[c].buf, op);
413 list_del_init(&op->list);
414 if (++c >= MAX_OPTIMIZE_PROBES)
415 break;
416 }
417
418 /*
419 * text_poke_smp doesn't support NMI/MCE code modifying.
420 * However, since kprobes itself also doesn't support NMI/MCE
421 * code probing, it's not a problem.
422 */
423 text_poke_smp_batch(jump_poke_params, c);
424}
425
426static void __kprobes setup_unoptimize_kprobe(struct text_poke_param *tprm,
427 u8 *insn_buf,
428 struct optimized_kprobe *op)
429{
430 /* Set int3 to first byte for kprobes */
431 insn_buf[0] = BREAKPOINT_INSTRUCTION;
432 memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
433
434 tprm->addr = op->kp.addr;
435 tprm->opcode = insn_buf;
436 tprm->len = RELATIVEJUMP_SIZE;
437}
438
439/*
440 * Recover original instructions and breakpoints from relative jumps.
441 * Caller must call with locking kprobe_mutex.
442 */
443extern void arch_unoptimize_kprobes(struct list_head *oplist,
444 struct list_head *done_list)
445{
446 struct optimized_kprobe *op, *tmp;
447 int c = 0;
448
449 list_for_each_entry_safe(op, tmp, oplist, list) {
450 /* Setup param */
451 setup_unoptimize_kprobe(&jump_poke_params[c],
452 jump_poke_bufs[c].buf, op);
453 list_move(&op->list, done_list);
454 if (++c >= MAX_OPTIMIZE_PROBES)
455 break;
456 }
457
458 /*
459 * text_poke_smp doesn't support NMI/MCE code modifying.
460 * However, since kprobes itself also doesn't support NMI/MCE
461 * code probing, it's not a problem.
462 */
463 text_poke_smp_batch(jump_poke_params, c);
464}
465
466/* Replace a relative jump with a breakpoint (int3). */
467void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
468{
469 u8 buf[RELATIVEJUMP_SIZE];
470
471 /* Set int3 to first byte for kprobes */
472 buf[0] = BREAKPOINT_INSTRUCTION;
473 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
474 text_poke_smp(op->kp.addr, buf, RELATIVEJUMP_SIZE);
475}
476
477int __kprobes
478setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
479{
480 struct optimized_kprobe *op;
481
482 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
483 /* This kprobe is really able to run optimized path. */
484 op = container_of(p, struct optimized_kprobe, kp);
485 /* Detour through copied instructions */
486 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
487 if (!reenter)
488 reset_current_kprobe();
489 preempt_enable_no_resched();
490 return 1;
491 }
492 return 0;
493}
494
495int __kprobes arch_init_optprobes(void)
496{
497 /* Allocate code buffer and parameter array */
498 jump_poke_bufs = kmalloc(sizeof(struct jump_poke_buffer) *
499 MAX_OPTIMIZE_PROBES, GFP_KERNEL);
500 if (!jump_poke_bufs)
501 return -ENOMEM;
502
503 jump_poke_params = kmalloc(sizeof(struct text_poke_param) *
504 MAX_OPTIMIZE_PROBES, GFP_KERNEL);
505 if (!jump_poke_params) {
506 kfree(jump_poke_bufs);
507 jump_poke_bufs = NULL;
508 return -ENOMEM;
509 }
510
511 return 0;
512}