1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Kernel Probes Jump Optimization (Optprobes)
5 * Copyright (C) IBM Corporation, 2002, 2004
6 * Copyright (C) Hitachi Ltd., 2012
8 #include <linux/kprobes.h>
9 #include <linux/perf_event.h>
10 #include <linux/ptrace.h>
11 #include <linux/string.h>
12 #include <linux/slab.h>
13 #include <linux/hardirq.h>
14 #include <linux/preempt.h>
15 #include <linux/extable.h>
16 #include <linux/kdebug.h>
17 #include <linux/kallsyms.h>
18 #include <linux/ftrace.h>
19 #include <linux/objtool.h>
20 #include <linux/pgtable.h>
21 #include <linux/static_call.h>
23 #include <asm/text-patching.h>
24 #include <asm/cacheflush.h>
26 #include <linux/uaccess.h>
27 #include <asm/alternative.h>
29 #include <asm/debugreg.h>
30 #include <asm/set_memory.h>
31 #include <asm/sections.h>
32 #include <asm/nospec-branch.h>
36 unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
38 struct optimized_kprobe *op;
43 for (i = 0; i < JMP32_INSN_SIZE; i++) {
44 kp = get_kprobe((void *)addr - i);
45 /* This function only handles jump-optimized kprobe */
46 if (kp && kprobe_optimized(kp)) {
47 op = container_of(kp, struct optimized_kprobe, kp);
48 /* If op->list is not empty, op is under optimizing */
49 if (list_empty(&op->list))
57 * If the kprobe can be optimized, original bytes which can be
58 * overwritten by jump destination address. In this case, original
59 * bytes must be recovered from op->optinsn.copied_insn buffer.
61 if (copy_from_kernel_nofault(buf, (void *)addr,
62 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
65 if (addr == (unsigned long)kp->addr) {
67 memcpy(buf + 1, op->optinsn.copied_insn, DISP32_SIZE);
69 offs = addr - (unsigned long)kp->addr - 1;
70 memcpy(buf, op->optinsn.copied_insn + offs, DISP32_SIZE - offs);
73 return (unsigned long)buf;
76 static void synthesize_clac(kprobe_opcode_t *addr)
79 * Can't be static_cpu_has() due to how objtool treats this feature bit.
80 * This isn't a fast path anyway.
82 if (!boot_cpu_has(X86_FEATURE_SMAP))
85 /* Replace the NOP3 with CLAC */
91 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
92 static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
100 *(unsigned long *)addr = val;
104 ".pushsection .rodata\n"
105 "optprobe_template_func:\n"
106 ".global optprobe_template_entry\n"
107 "optprobe_template_entry:\n"
109 " pushq $" __stringify(__KERNEL_DS) "\n"
110 /* Save the 'sp - 8', this will be fixed later. */
113 ".global optprobe_template_clac\n"
114 "optprobe_template_clac:\n"
118 ".global optprobe_template_val\n"
119 "optprobe_template_val:\n"
122 ".global optprobe_template_call\n"
123 "optprobe_template_call:\n"
125 /* Copy 'regs->flags' into 'regs->ss'. */
126 " movq 18*8(%rsp), %rdx\n"
127 " movq %rdx, 20*8(%rsp)\n"
129 /* Skip 'regs->flags' and 'regs->sp'. */
131 /* And pop flags register from 'regs->ss'. */
133 #else /* CONFIG_X86_32 */
135 /* Save the 'sp - 4', this will be fixed later. */
138 ".global optprobe_template_clac\n"
139 "optprobe_template_clac:\n"
143 ".global optprobe_template_val\n"
144 "optprobe_template_val:\n"
146 ".global optprobe_template_call\n"
147 "optprobe_template_call:\n"
149 /* Copy 'regs->flags' into 'regs->ss'. */
150 " movl 14*4(%esp), %edx\n"
151 " movl %edx, 16*4(%esp)\n"
153 /* Skip 'regs->flags' and 'regs->sp'. */
155 /* And pop flags register from 'regs->ss'. */
158 ".global optprobe_template_end\n"
159 "optprobe_template_end:\n"
162 void optprobe_template_func(void);
163 STACK_FRAME_NON_STANDARD(optprobe_template_func);
165 #define TMPL_CLAC_IDX \
166 ((long)optprobe_template_clac - (long)optprobe_template_entry)
167 #define TMPL_MOVE_IDX \
168 ((long)optprobe_template_val - (long)optprobe_template_entry)
169 #define TMPL_CALL_IDX \
170 ((long)optprobe_template_call - (long)optprobe_template_entry)
171 #define TMPL_END_IDX \
172 ((long)optprobe_template_end - (long)optprobe_template_entry)
174 /* Optimized kprobe call back function: called from optinsn */
176 optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
178 /* This is possible if op is under delayed unoptimizing */
179 if (kprobe_disabled(&op->kp))
183 if (kprobe_running()) {
184 kprobes_inc_nmissed_count(&op->kp);
186 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
187 /* Adjust stack pointer */
188 regs->sp += sizeof(long);
189 /* Save skipped registers */
190 regs->cs = __KERNEL_CS;
194 regs->ip = (unsigned long)op->kp.addr + INT3_INSN_SIZE;
195 regs->orig_ax = ~0UL;
197 __this_cpu_write(current_kprobe, &op->kp);
198 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
199 opt_pre_handler(&op->kp, regs);
200 __this_cpu_write(current_kprobe, NULL);
204 NOKPROBE_SYMBOL(optimized_callback);
206 static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real)
211 while (len < JMP32_INSN_SIZE) {
212 ret = __copy_instruction(dest + len, src + len, real + len, &insn);
213 if (!ret || !can_boost(&insn, src + len))
217 /* Check whether the address range is reserved */
218 if (ftrace_text_reserved(src, src + len - 1) ||
219 alternatives_text_reserved(src, src + len - 1) ||
220 jump_label_text_reserved(src, src + len - 1) ||
221 static_call_text_reserved(src, src + len - 1))
227 /* Check whether insn is indirect jump */
228 static int __insn_is_indirect_jump(struct insn *insn)
230 return ((insn->opcode.bytes[0] == 0xff &&
231 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
232 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
235 /* Check whether insn jumps into specified address range */
236 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
238 unsigned long target = 0;
240 switch (insn->opcode.bytes[0]) {
241 case 0xe0: /* loopne */
242 case 0xe1: /* loope */
243 case 0xe2: /* loop */
244 case 0xe3: /* jcxz */
245 case 0xe9: /* near relative jump */
246 case 0xeb: /* short relative jump */
249 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
253 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
257 target = (unsigned long)insn->next_byte + insn->immediate.value;
259 return (start <= target && target <= start + len);
262 static int insn_is_indirect_jump(struct insn *insn)
264 int ret = __insn_is_indirect_jump(insn);
266 #ifdef CONFIG_RETPOLINE
268 * Jump to x86_indirect_thunk_* is treated as an indirect jump.
269 * Note that even with CONFIG_RETPOLINE=y, the kernel compiled with
270 * older gcc may use indirect jump. So we add this check instead of
271 * replace indirect-jump check.
274 ret = insn_jump_into_range(insn,
275 (unsigned long)__indirect_thunk_start,
276 (unsigned long)__indirect_thunk_end -
277 (unsigned long)__indirect_thunk_start);
282 static bool is_padding_int3(unsigned long addr, unsigned long eaddr)
286 for (; addr < eaddr; addr++) {
287 if (get_kernel_nofault(ops, (void *)addr) < 0 ||
288 ops != INT3_INSN_OPCODE)
295 /* Decode whole function to ensure any instructions don't jump into target */
296 static int can_optimize(unsigned long paddr)
298 unsigned long addr, size = 0, offset = 0;
300 kprobe_opcode_t buf[MAX_INSN_SIZE];
302 /* Lookup symbol including addr */
303 if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
307 * Do not optimize in the entry code due to the unstable
308 * stack handling and registers setup.
310 if (((paddr >= (unsigned long)__entry_text_start) &&
311 (paddr < (unsigned long)__entry_text_end)))
314 /* Check there is enough space for a relative jump. */
315 if (size - offset < JMP32_INSN_SIZE)
318 /* Decode instructions */
319 addr = paddr - offset;
320 while (addr < paddr - offset + size) { /* Decode until function end */
321 unsigned long recovered_insn;
324 if (search_exception_tables(addr))
326 * Since some fixup code will jumps into this function,
327 * we can't optimize kprobe in this function.
330 recovered_insn = recover_probed_instruction(buf, addr);
334 ret = insn_decode_kernel(&insn, (void *)recovered_insn);
339 * In the case of detecting unknown breakpoint, this could be
340 * a padding INT3 between functions. Let's check that all the
341 * rest of the bytes are also INT3.
343 if (insn.opcode.bytes[0] == INT3_INSN_OPCODE)
344 return is_padding_int3(addr, paddr - offset + size) ? 1 : 0;
346 /* Recover address */
347 insn.kaddr = (void *)addr;
348 insn.next_byte = (void *)(addr + insn.length);
349 /* Check any instructions don't jump into target */
350 if (insn_is_indirect_jump(&insn) ||
351 insn_jump_into_range(&insn, paddr + INT3_INSN_SIZE,
360 /* Check optimized_kprobe can actually be optimized. */
361 int arch_check_optimized_kprobe(struct optimized_kprobe *op)
366 for (i = 1; i < op->optinsn.size; i++) {
367 p = get_kprobe(op->kp.addr + i);
368 if (p && !kprobe_disabled(p))
375 /* Check the addr is within the optimized instructions. */
376 int arch_within_optimized_kprobe(struct optimized_kprobe *op,
377 kprobe_opcode_t *addr)
379 return (op->kp.addr <= addr &&
380 op->kp.addr + op->optinsn.size > addr);
383 /* Free optimized instruction slot */
385 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
387 u8 *slot = op->optinsn.insn;
389 int len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE;
391 /* Record the perf event before freeing the slot */
393 perf_event_text_poke(slot, slot, len, NULL, 0);
395 free_optinsn_slot(slot, dirty);
396 op->optinsn.insn = NULL;
397 op->optinsn.size = 0;
401 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
403 __arch_remove_optimized_kprobe(op, 1);
407 * Copy replacing target instructions
408 * Target instructions MUST be relocatable (checked inside)
409 * This is called when new aggr(opt)probe is allocated or reused.
411 int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
412 struct kprobe *__unused)
414 u8 *buf = NULL, *slot;
418 if (!can_optimize((unsigned long)op->kp.addr))
421 buf = kzalloc(MAX_OPTINSN_SIZE, GFP_KERNEL);
425 op->optinsn.insn = slot = get_optinsn_slot();
432 * Verify if the address gap is in 2GB range, because this uses
435 rel = (long)slot - (long)op->kp.addr + JMP32_INSN_SIZE;
436 if (abs(rel) > 0x7fffffff) {
441 /* Copy arch-dep-instance from template */
442 memcpy(buf, optprobe_template_entry, TMPL_END_IDX);
444 /* Copy instructions into the out-of-line buffer */
445 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr,
446 slot + TMPL_END_IDX);
449 op->optinsn.size = ret;
450 len = TMPL_END_IDX + op->optinsn.size;
452 synthesize_clac(buf + TMPL_CLAC_IDX);
454 /* Set probe information */
455 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
457 /* Set probe function call */
458 synthesize_relcall(buf + TMPL_CALL_IDX,
459 slot + TMPL_CALL_IDX, optimized_callback);
461 /* Set returning jmp instruction at the tail of out-of-line buffer */
462 synthesize_reljump(buf + len, slot + len,
463 (u8 *)op->kp.addr + op->optinsn.size);
464 len += JMP32_INSN_SIZE;
467 * Note len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE is also
468 * used in __arch_remove_optimized_kprobe().
471 /* We have to use text_poke() for instruction buffer because it is RO */
472 perf_event_text_poke(slot, NULL, 0, buf, len);
473 text_poke(slot, buf, len);
481 __arch_remove_optimized_kprobe(op, 0);
486 * Replace breakpoints (INT3) with relative jumps (JMP.d32).
487 * Caller must call with locking kprobe_mutex and text_mutex.
489 * The caller will have installed a regular kprobe and after that issued
490 * syncrhonize_rcu_tasks(), this ensures that the instruction(s) that live in
491 * the 4 bytes after the INT3 are unused and can now be overwritten.
493 void arch_optimize_kprobes(struct list_head *oplist)
495 struct optimized_kprobe *op, *tmp;
496 u8 insn_buff[JMP32_INSN_SIZE];
498 list_for_each_entry_safe(op, tmp, oplist, list) {
499 s32 rel = (s32)((long)op->optinsn.insn -
500 ((long)op->kp.addr + JMP32_INSN_SIZE));
502 WARN_ON(kprobe_disabled(&op->kp));
504 /* Backup instructions which will be replaced by jump address */
505 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_INSN_SIZE,
508 insn_buff[0] = JMP32_INSN_OPCODE;
509 *(s32 *)(&insn_buff[1]) = rel;
511 text_poke_bp(op->kp.addr, insn_buff, JMP32_INSN_SIZE, NULL);
513 list_del_init(&op->list);
518 * Replace a relative jump (JMP.d32) with a breakpoint (INT3).
520 * After that, we can restore the 4 bytes after the INT3 to undo what
521 * arch_optimize_kprobes() scribbled. This is safe since those bytes will be
522 * unused once the INT3 lands.
524 void arch_unoptimize_kprobe(struct optimized_kprobe *op)
526 u8 new[JMP32_INSN_SIZE] = { INT3_INSN_OPCODE, };
527 u8 old[JMP32_INSN_SIZE];
528 u8 *addr = op->kp.addr;
530 memcpy(old, op->kp.addr, JMP32_INSN_SIZE);
531 memcpy(new + INT3_INSN_SIZE,
532 op->optinsn.copied_insn,
533 JMP32_INSN_SIZE - INT3_INSN_SIZE);
535 text_poke(addr, new, INT3_INSN_SIZE);
537 text_poke(addr + INT3_INSN_SIZE,
538 new + INT3_INSN_SIZE,
539 JMP32_INSN_SIZE - INT3_INSN_SIZE);
542 perf_event_text_poke(op->kp.addr, old, JMP32_INSN_SIZE, new, JMP32_INSN_SIZE);
546 * Recover original instructions and breakpoints from relative jumps.
547 * Caller must call with locking kprobe_mutex.
549 extern void arch_unoptimize_kprobes(struct list_head *oplist,
550 struct list_head *done_list)
552 struct optimized_kprobe *op, *tmp;
554 list_for_each_entry_safe(op, tmp, oplist, list) {
555 arch_unoptimize_kprobe(op);
556 list_move(&op->list, done_list);
560 int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
562 struct optimized_kprobe *op;
564 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
565 /* This kprobe is really able to run optimized path. */
566 op = container_of(p, struct optimized_kprobe, kp);
567 /* Detour through copied instructions */
568 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
570 reset_current_kprobe();
575 NOKPROBE_SYMBOL(setup_detour_execution);