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/module.h>
28 #include <linux/kdebug.h>
29 #include <linux/kallsyms.h>
30 #include <linux/ftrace.h>
32 #include <asm/cacheflush.h>
34 #include <asm/pgtable.h>
35 #include <asm/uaccess.h>
36 #include <asm/alternative.h>
38 #include <asm/debugreg.h>
42 unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
44 struct optimized_kprobe *op;
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))
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.
67 memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
68 if (addr == (unsigned long)kp->addr) {
70 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
72 offs = addr - (unsigned long)kp->addr - 1;
73 memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
76 return (unsigned long)buf;
79 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
80 static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
88 *(unsigned long *)addr = val;
92 ".global optprobe_template_entry\n"
93 "optprobe_template_entry:\n"
95 /* We don't bother saving the ss register */
100 ".global optprobe_template_val\n"
101 "optprobe_template_val:\n"
104 ".global optprobe_template_call\n"
105 "optprobe_template_call:\n"
107 /* Move flags to rsp */
108 " movq 144(%rsp), %rdx\n"
109 " movq %rdx, 152(%rsp)\n"
111 /* Skip flags entry */
114 #else /* CONFIG_X86_32 */
118 ".global optprobe_template_val\n"
119 "optprobe_template_val:\n"
121 ".global optprobe_template_call\n"
122 "optprobe_template_call:\n"
125 " addl $4, %esp\n" /* skip cs */
128 ".global optprobe_template_end\n"
129 "optprobe_template_end:\n");
131 #define TMPL_MOVE_IDX \
132 ((long)&optprobe_template_val - (long)&optprobe_template_entry)
133 #define TMPL_CALL_IDX \
134 ((long)&optprobe_template_call - (long)&optprobe_template_entry)
135 #define TMPL_END_IDX \
136 ((long)&optprobe_template_end - (long)&optprobe_template_entry)
138 #define INT3_SIZE sizeof(kprobe_opcode_t)
140 /* Optimized kprobe call back function: called from optinsn */
142 optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
144 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
147 /* This is possible if op is under delayed unoptimizing */
148 if (kprobe_disabled(&op->kp))
151 local_irq_save(flags);
152 if (kprobe_running()) {
153 kprobes_inc_nmissed_count(&op->kp);
155 /* Save skipped registers */
157 regs->cs = __KERNEL_CS;
159 regs->cs = __KERNEL_CS | get_kernel_rpl();
162 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
163 regs->orig_ax = ~0UL;
165 __this_cpu_write(current_kprobe, &op->kp);
166 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
167 opt_pre_handler(&op->kp, regs);
168 __this_cpu_write(current_kprobe, NULL);
170 local_irq_restore(flags);
172 NOKPROBE_SYMBOL(optimized_callback);
174 static int copy_optimized_instructions(u8 *dest, u8 *src)
178 while (len < RELATIVEJUMP_SIZE) {
179 ret = __copy_instruction(dest + len, src + len);
180 if (!ret || !can_boost(dest + len))
184 /* Check whether the address range is reserved */
185 if (ftrace_text_reserved(src, src + len - 1) ||
186 alternatives_text_reserved(src, src + len - 1) ||
187 jump_label_text_reserved(src, src + len - 1))
193 /* Check whether insn is indirect jump */
194 static int insn_is_indirect_jump(struct insn *insn)
196 return ((insn->opcode.bytes[0] == 0xff &&
197 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
198 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
201 /* Check whether insn jumps into specified address range */
202 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
204 unsigned long target = 0;
206 switch (insn->opcode.bytes[0]) {
207 case 0xe0: /* loopne */
208 case 0xe1: /* loope */
209 case 0xe2: /* loop */
210 case 0xe3: /* jcxz */
211 case 0xe9: /* near relative jump */
212 case 0xeb: /* short relative jump */
215 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
219 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
223 target = (unsigned long)insn->next_byte + insn->immediate.value;
225 return (start <= target && target <= start + len);
228 /* Decode whole function to ensure any instructions don't jump into target */
229 static int can_optimize(unsigned long paddr)
231 unsigned long addr, size = 0, offset = 0;
233 kprobe_opcode_t buf[MAX_INSN_SIZE];
235 /* Lookup symbol including addr */
236 if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
240 * Do not optimize in the entry code due to the unstable
243 if ((paddr >= (unsigned long)__entry_text_start) &&
244 (paddr < (unsigned long)__entry_text_end))
247 /* Check there is enough space for a relative jump. */
248 if (size - offset < RELATIVEJUMP_SIZE)
251 /* Decode instructions */
252 addr = paddr - offset;
253 while (addr < paddr - offset + size) { /* Decode until function end */
254 unsigned long recovered_insn;
255 if (search_exception_tables(addr))
257 * Since some fixup code will jumps into this function,
258 * we can't optimize kprobe in this function.
261 recovered_insn = recover_probed_instruction(buf, addr);
264 kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
265 insn_get_length(&insn);
266 /* Another subsystem puts a breakpoint */
267 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
269 /* Recover address */
270 insn.kaddr = (void *)addr;
271 insn.next_byte = (void *)(addr + insn.length);
272 /* Check any instructions don't jump into target */
273 if (insn_is_indirect_jump(&insn) ||
274 insn_jump_into_range(&insn, paddr + INT3_SIZE,
283 /* Check optimized_kprobe can actually be optimized. */
284 int arch_check_optimized_kprobe(struct optimized_kprobe *op)
289 for (i = 1; i < op->optinsn.size; i++) {
290 p = get_kprobe(op->kp.addr + i);
291 if (p && !kprobe_disabled(p))
298 /* Check the addr is within the optimized instructions. */
299 int arch_within_optimized_kprobe(struct optimized_kprobe *op,
302 return ((unsigned long)op->kp.addr <= addr &&
303 (unsigned long)op->kp.addr + op->optinsn.size > addr);
306 /* Free optimized instruction slot */
308 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
310 if (op->optinsn.insn) {
311 free_optinsn_slot(op->optinsn.insn, dirty);
312 op->optinsn.insn = NULL;
313 op->optinsn.size = 0;
317 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
319 __arch_remove_optimized_kprobe(op, 1);
323 * Copy replacing target instructions
324 * Target instructions MUST be relocatable (checked inside)
325 * This is called when new aggr(opt)probe is allocated or reused.
327 int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
328 struct kprobe *__unused)
334 if (!can_optimize((unsigned long)op->kp.addr))
337 op->optinsn.insn = get_optinsn_slot();
338 if (!op->optinsn.insn)
342 * Verify if the address gap is in 2GB range, because this uses
345 rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
346 if (abs(rel) > 0x7fffffff) {
347 __arch_remove_optimized_kprobe(op, 0);
351 buf = (u8 *)op->optinsn.insn;
353 /* Copy instructions into the out-of-line buffer */
354 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
356 __arch_remove_optimized_kprobe(op, 0);
359 op->optinsn.size = ret;
361 /* Copy arch-dep-instance from template */
362 memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
364 /* Set probe information */
365 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
367 /* Set probe function call */
368 synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
370 /* Set returning jmp instruction at the tail of out-of-line buffer */
371 synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
372 (u8 *)op->kp.addr + op->optinsn.size);
374 flush_icache_range((unsigned long) buf,
375 (unsigned long) buf + TMPL_END_IDX +
376 op->optinsn.size + RELATIVEJUMP_SIZE);
381 * Replace breakpoints (int3) with relative jumps.
382 * Caller must call with locking kprobe_mutex and text_mutex.
384 void arch_optimize_kprobes(struct list_head *oplist)
386 struct optimized_kprobe *op, *tmp;
387 u8 insn_buf[RELATIVEJUMP_SIZE];
389 list_for_each_entry_safe(op, tmp, oplist, list) {
390 s32 rel = (s32)((long)op->optinsn.insn -
391 ((long)op->kp.addr + RELATIVEJUMP_SIZE));
393 WARN_ON(kprobe_disabled(&op->kp));
395 /* Backup instructions which will be replaced by jump address */
396 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
399 insn_buf[0] = RELATIVEJUMP_OPCODE;
400 *(s32 *)(&insn_buf[1]) = rel;
402 text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
405 list_del_init(&op->list);
409 /* Replace a relative jump with a breakpoint (int3). */
410 void arch_unoptimize_kprobe(struct optimized_kprobe *op)
412 u8 insn_buf[RELATIVEJUMP_SIZE];
414 /* Set int3 to first byte for kprobes */
415 insn_buf[0] = BREAKPOINT_INSTRUCTION;
416 memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
417 text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
422 * Recover original instructions and breakpoints from relative jumps.
423 * Caller must call with locking kprobe_mutex.
425 extern void arch_unoptimize_kprobes(struct list_head *oplist,
426 struct list_head *done_list)
428 struct optimized_kprobe *op, *tmp;
430 list_for_each_entry_safe(op, tmp, oplist, list) {
431 arch_unoptimize_kprobe(op);
432 list_move(&op->list, done_list);
436 int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
438 struct optimized_kprobe *op;
440 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
441 /* This kprobe is really able to run optimized path. */
442 op = container_of(p, struct optimized_kprobe, kp);
443 /* Detour through copied instructions */
444 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
446 reset_current_kprobe();
447 preempt_enable_no_resched();
452 NOKPROBE_SYMBOL(setup_detour_execution);