2 * Kernel Probes Jump Optimization (Optprobes)
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.
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.
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.
18 * Copyright (C) IBM Corporation, 2002, 2004
19 * Copyright (C) Hitachi Ltd., 2012
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/extable.h>
28 #include <linux/kdebug.h>
29 #include <linux/kallsyms.h>
30 #include <linux/ftrace.h>
31 #include <linux/frame.h>
33 #include <asm/text-patching.h>
34 #include <asm/cacheflush.h>
36 #include <asm/pgtable.h>
37 #include <linux/uaccess.h>
38 #include <asm/alternative.h>
40 #include <asm/debugreg.h>
41 #include <asm/set_memory.h>
42 #include <asm/sections.h>
43 #include <asm/nospec-branch.h>
47 unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
49 struct optimized_kprobe *op;
54 for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
55 kp = get_kprobe((void *)addr - i);
56 /* This function only handles jump-optimized kprobe */
57 if (kp && kprobe_optimized(kp)) {
58 op = container_of(kp, struct optimized_kprobe, kp);
59 /* If op is optimized or under unoptimizing */
60 if (list_empty(&op->list) || optprobe_queued_unopt(op))
68 * If the kprobe can be optimized, original bytes which can be
69 * overwritten by jump destination address. In this case, original
70 * bytes must be recovered from op->optinsn.copied_insn buffer.
72 if (probe_kernel_read(buf, (void *)addr,
73 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
76 if (addr == (unsigned long)kp->addr) {
78 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
80 offs = addr - (unsigned long)kp->addr - 1;
81 memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
84 return (unsigned long)buf;
87 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
88 static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
96 *(unsigned long *)addr = val;
100 "optprobe_template_func:\n"
101 ".global optprobe_template_entry\n"
102 "optprobe_template_entry:\n"
104 /* We don't bother saving the ss register */
109 ".global optprobe_template_val\n"
110 "optprobe_template_val:\n"
113 ".global optprobe_template_call\n"
114 "optprobe_template_call:\n"
116 /* Move flags to rsp */
117 " movq 144(%rsp), %rdx\n"
118 " movq %rdx, 152(%rsp)\n"
120 /* Skip flags entry */
123 #else /* CONFIG_X86_32 */
127 ".global optprobe_template_val\n"
128 "optprobe_template_val:\n"
130 ".global optprobe_template_call\n"
131 "optprobe_template_call:\n"
134 " addl $4, %esp\n" /* skip cs */
137 ".global optprobe_template_end\n"
138 "optprobe_template_end:\n"
139 ".type optprobe_template_func, @function\n"
140 ".size optprobe_template_func, .-optprobe_template_func\n");
142 void optprobe_template_func(void);
143 STACK_FRAME_NON_STANDARD(optprobe_template_func);
144 NOKPROBE_SYMBOL(optprobe_template_func);
145 NOKPROBE_SYMBOL(optprobe_template_entry);
146 NOKPROBE_SYMBOL(optprobe_template_val);
147 NOKPROBE_SYMBOL(optprobe_template_call);
148 NOKPROBE_SYMBOL(optprobe_template_end);
150 #define TMPL_MOVE_IDX \
151 ((long)optprobe_template_val - (long)optprobe_template_entry)
152 #define TMPL_CALL_IDX \
153 ((long)optprobe_template_call - (long)optprobe_template_entry)
154 #define TMPL_END_IDX \
155 ((long)optprobe_template_end - (long)optprobe_template_entry)
157 #define INT3_SIZE sizeof(kprobe_opcode_t)
159 /* Optimized kprobe call back function: called from optinsn */
161 optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
163 /* This is possible if op is under delayed unoptimizing */
164 if (kprobe_disabled(&op->kp))
168 if (kprobe_running()) {
169 kprobes_inc_nmissed_count(&op->kp);
171 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
172 /* Save skipped registers */
174 regs->cs = __KERNEL_CS;
176 regs->cs = __KERNEL_CS | get_kernel_rpl();
179 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
180 regs->orig_ax = ~0UL;
182 __this_cpu_write(current_kprobe, &op->kp);
183 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
184 opt_pre_handler(&op->kp, regs);
185 __this_cpu_write(current_kprobe, NULL);
189 NOKPROBE_SYMBOL(optimized_callback);
191 static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real)
196 while (len < RELATIVEJUMP_SIZE) {
197 ret = __copy_instruction(dest + len, src + len, real + len, &insn);
198 if (!ret || !can_boost(&insn, src + len))
202 /* Check whether the address range is reserved */
203 if (ftrace_text_reserved(src, src + len - 1) ||
204 alternatives_text_reserved(src, src + len - 1) ||
205 jump_label_text_reserved(src, src + len - 1))
211 /* Check whether insn is indirect jump */
212 static int __insn_is_indirect_jump(struct insn *insn)
214 return ((insn->opcode.bytes[0] == 0xff &&
215 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
216 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
219 /* Check whether insn jumps into specified address range */
220 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
222 unsigned long target = 0;
224 switch (insn->opcode.bytes[0]) {
225 case 0xe0: /* loopne */
226 case 0xe1: /* loope */
227 case 0xe2: /* loop */
228 case 0xe3: /* jcxz */
229 case 0xe9: /* near relative jump */
230 case 0xeb: /* short relative jump */
233 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
237 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
241 target = (unsigned long)insn->next_byte + insn->immediate.value;
243 return (start <= target && target <= start + len);
246 static int insn_is_indirect_jump(struct insn *insn)
248 int ret = __insn_is_indirect_jump(insn);
250 #ifdef CONFIG_RETPOLINE
252 * Jump to x86_indirect_thunk_* is treated as an indirect jump.
253 * Note that even with CONFIG_RETPOLINE=y, the kernel compiled with
254 * older gcc may use indirect jump. So we add this check instead of
255 * replace indirect-jump check.
258 ret = insn_jump_into_range(insn,
259 (unsigned long)__indirect_thunk_start,
260 (unsigned long)__indirect_thunk_end -
261 (unsigned long)__indirect_thunk_start);
266 /* Decode whole function to ensure any instructions don't jump into target */
267 static int can_optimize(unsigned long paddr)
269 unsigned long addr, size = 0, offset = 0;
271 kprobe_opcode_t buf[MAX_INSN_SIZE];
273 /* Lookup symbol including addr */
274 if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
278 * Do not optimize in the entry code due to the unstable
279 * stack handling and registers setup.
281 if (((paddr >= (unsigned long)__entry_text_start) &&
282 (paddr < (unsigned long)__entry_text_end)) ||
283 ((paddr >= (unsigned long)__irqentry_text_start) &&
284 (paddr < (unsigned long)__irqentry_text_end)))
287 /* Check there is enough space for a relative jump. */
288 if (size - offset < RELATIVEJUMP_SIZE)
291 /* Decode instructions */
292 addr = paddr - offset;
293 while (addr < paddr - offset + size) { /* Decode until function end */
294 unsigned long recovered_insn;
295 if (search_exception_tables(addr))
297 * Since some fixup code will jumps into this function,
298 * we can't optimize kprobe in this function.
301 recovered_insn = recover_probed_instruction(buf, addr);
304 kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
305 insn_get_length(&insn);
306 /* Another subsystem puts a breakpoint */
307 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
309 /* Recover address */
310 insn.kaddr = (void *)addr;
311 insn.next_byte = (void *)(addr + insn.length);
312 /* Check any instructions don't jump into target */
313 if (insn_is_indirect_jump(&insn) ||
314 insn_jump_into_range(&insn, paddr + INT3_SIZE,
323 /* Check optimized_kprobe can actually be optimized. */
324 int arch_check_optimized_kprobe(struct optimized_kprobe *op)
329 for (i = 1; i < op->optinsn.size; i++) {
330 p = get_kprobe(op->kp.addr + i);
331 if (p && !kprobe_disarmed(p))
338 /* Check the addr is within the optimized instructions. */
339 int arch_within_optimized_kprobe(struct optimized_kprobe *op,
342 return ((unsigned long)op->kp.addr <= addr &&
343 (unsigned long)op->kp.addr + op->optinsn.size > addr);
346 /* Free optimized instruction slot */
348 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
350 if (op->optinsn.insn) {
351 free_optinsn_slot(op->optinsn.insn, dirty);
352 op->optinsn.insn = NULL;
353 op->optinsn.size = 0;
357 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
359 __arch_remove_optimized_kprobe(op, 1);
363 * Copy replacing target instructions
364 * Target instructions MUST be relocatable (checked inside)
365 * This is called when new aggr(opt)probe is allocated or reused.
367 int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
368 struct kprobe *__unused)
370 u8 *buf = NULL, *slot;
374 if (!can_optimize((unsigned long)op->kp.addr))
377 buf = kzalloc(MAX_OPTINSN_SIZE, GFP_KERNEL);
381 op->optinsn.insn = slot = get_optinsn_slot();
388 * Verify if the address gap is in 2GB range, because this uses
391 rel = (long)slot - (long)op->kp.addr + RELATIVEJUMP_SIZE;
392 if (abs(rel) > 0x7fffffff) {
397 /* Copy arch-dep-instance from template */
398 memcpy(buf, optprobe_template_entry, TMPL_END_IDX);
400 /* Copy instructions into the out-of-line buffer */
401 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr,
402 slot + TMPL_END_IDX);
405 op->optinsn.size = ret;
406 len = TMPL_END_IDX + op->optinsn.size;
408 /* Set probe information */
409 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
411 /* Set probe function call */
412 synthesize_relcall(buf + TMPL_CALL_IDX,
413 slot + TMPL_CALL_IDX, optimized_callback);
415 /* Set returning jmp instruction at the tail of out-of-line buffer */
416 synthesize_reljump(buf + len, slot + len,
417 (u8 *)op->kp.addr + op->optinsn.size);
418 len += RELATIVEJUMP_SIZE;
420 /* We have to use text_poke for instuction buffer because it is RO */
421 text_poke(slot, buf, len);
428 __arch_remove_optimized_kprobe(op, 0);
433 * Replace breakpoints (int3) with relative jumps.
434 * Caller must call with locking kprobe_mutex and text_mutex.
436 void arch_optimize_kprobes(struct list_head *oplist)
438 struct optimized_kprobe *op, *tmp;
439 u8 insn_buf[RELATIVEJUMP_SIZE];
441 list_for_each_entry_safe(op, tmp, oplist, list) {
442 s32 rel = (s32)((long)op->optinsn.insn -
443 ((long)op->kp.addr + RELATIVEJUMP_SIZE));
445 WARN_ON(kprobe_disabled(&op->kp));
447 /* Backup instructions which will be replaced by jump address */
448 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
451 insn_buf[0] = RELATIVEJUMP_OPCODE;
452 *(s32 *)(&insn_buf[1]) = rel;
454 text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
457 list_del_init(&op->list);
461 /* Replace a relative jump with a breakpoint (int3). */
462 void arch_unoptimize_kprobe(struct optimized_kprobe *op)
464 u8 insn_buf[RELATIVEJUMP_SIZE];
466 /* Set int3 to first byte for kprobes */
467 insn_buf[0] = BREAKPOINT_INSTRUCTION;
468 memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
469 text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
474 * Recover original instructions and breakpoints from relative jumps.
475 * Caller must call with locking kprobe_mutex.
477 extern void arch_unoptimize_kprobes(struct list_head *oplist,
478 struct list_head *done_list)
480 struct optimized_kprobe *op, *tmp;
482 list_for_each_entry_safe(op, tmp, oplist, list) {
483 arch_unoptimize_kprobe(op);
484 list_move(&op->list, done_list);
488 int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
490 struct optimized_kprobe *op;
492 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
493 /* This kprobe is really able to run optimized path. */
494 op = container_of(p, struct optimized_kprobe, kp);
495 /* Detour through copied instructions */
496 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
498 reset_current_kprobe();
503 NOKPROBE_SYMBOL(setup_detour_execution);