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/text-patching.h>
33 #include <asm/cacheflush.h>
35 #include <asm/pgtable.h>
36 #include <asm/uaccess.h>
37 #include <asm/alternative.h>
39 #include <asm/debugreg.h>
43 unsigned long __recover_optprobed_insn(kprobe_opcode_t
*buf
, unsigned long addr
)
45 struct optimized_kprobe
*op
;
50 for (i
= 0; i
< RELATIVEJUMP_SIZE
; i
++) {
51 kp
= get_kprobe((void *)addr
- i
);
52 /* This function only handles jump-optimized kprobe */
53 if (kp
&& kprobe_optimized(kp
)) {
54 op
= container_of(kp
, struct optimized_kprobe
, kp
);
55 /* If op->list is not empty, op is under optimizing */
56 if (list_empty(&op
->list
))
64 * If the kprobe can be optimized, original bytes which can be
65 * overwritten by jump destination address. In this case, original
66 * bytes must be recovered from op->optinsn.copied_insn buffer.
68 memcpy(buf
, (void *)addr
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
69 if (addr
== (unsigned long)kp
->addr
) {
71 memcpy(buf
+ 1, op
->optinsn
.copied_insn
, RELATIVE_ADDR_SIZE
);
73 offs
= addr
- (unsigned long)kp
->addr
- 1;
74 memcpy(buf
, op
->optinsn
.copied_insn
+ offs
, RELATIVE_ADDR_SIZE
- offs
);
77 return (unsigned long)buf
;
80 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
81 static void synthesize_set_arg1(kprobe_opcode_t
*addr
, unsigned long val
)
89 *(unsigned long *)addr
= val
;
93 ".global optprobe_template_entry\n"
94 "optprobe_template_entry:\n"
96 /* We don't bother saving the ss register */
101 ".global optprobe_template_val\n"
102 "optprobe_template_val:\n"
105 ".global optprobe_template_call\n"
106 "optprobe_template_call:\n"
108 /* Move flags to rsp */
109 " movq 144(%rsp), %rdx\n"
110 " movq %rdx, 152(%rsp)\n"
112 /* Skip flags entry */
115 #else /* CONFIG_X86_32 */
119 ".global optprobe_template_val\n"
120 "optprobe_template_val:\n"
122 ".global optprobe_template_call\n"
123 "optprobe_template_call:\n"
126 " addl $4, %esp\n" /* skip cs */
129 ".global optprobe_template_end\n"
130 "optprobe_template_end:\n");
132 #define TMPL_MOVE_IDX \
133 ((long)&optprobe_template_val - (long)&optprobe_template_entry)
134 #define TMPL_CALL_IDX \
135 ((long)&optprobe_template_call - (long)&optprobe_template_entry)
136 #define TMPL_END_IDX \
137 ((long)&optprobe_template_end - (long)&optprobe_template_entry)
139 #define INT3_SIZE sizeof(kprobe_opcode_t)
141 /* Optimized kprobe call back function: called from optinsn */
143 optimized_callback(struct optimized_kprobe
*op
, struct pt_regs
*regs
)
145 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
148 /* This is possible if op is under delayed unoptimizing */
149 if (kprobe_disabled(&op
->kp
))
152 local_irq_save(flags
);
153 if (kprobe_running()) {
154 kprobes_inc_nmissed_count(&op
->kp
);
156 /* Save skipped registers */
158 regs
->cs
= __KERNEL_CS
;
160 regs
->cs
= __KERNEL_CS
| get_kernel_rpl();
163 regs
->ip
= (unsigned long)op
->kp
.addr
+ INT3_SIZE
;
164 regs
->orig_ax
= ~0UL;
166 __this_cpu_write(current_kprobe
, &op
->kp
);
167 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
168 opt_pre_handler(&op
->kp
, regs
);
169 __this_cpu_write(current_kprobe
, NULL
);
171 local_irq_restore(flags
);
173 NOKPROBE_SYMBOL(optimized_callback
);
175 static int copy_optimized_instructions(u8
*dest
, u8
*src
)
179 while (len
< RELATIVEJUMP_SIZE
) {
180 ret
= __copy_instruction(dest
+ len
, src
+ len
);
181 if (!ret
|| !can_boost(dest
+ len
))
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))
194 /* Check whether insn is indirect jump */
195 static int insn_is_indirect_jump(struct insn
*insn
)
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 */
202 /* Check whether insn jumps into specified address range */
203 static int insn_jump_into_range(struct insn
*insn
, unsigned long start
, int len
)
205 unsigned long target
= 0;
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 */
216 if ((insn
->opcode
.bytes
[1] & 0xf0) == 0x80) /* jcc near */
220 if ((insn
->opcode
.bytes
[0] & 0xf0) == 0x70) /* jcc short */
224 target
= (unsigned long)insn
->next_byte
+ insn
->immediate
.value
;
226 return (start
<= target
&& target
<= start
+ len
);
229 /* Decode whole function to ensure any instructions don't jump into target */
230 static int can_optimize(unsigned long paddr
)
232 unsigned long addr
, size
= 0, offset
= 0;
234 kprobe_opcode_t buf
[MAX_INSN_SIZE
];
236 /* Lookup symbol including addr */
237 if (!kallsyms_lookup_size_offset(paddr
, &size
, &offset
))
241 * Do not optimize in the entry code due to the unstable
244 if ((paddr
>= (unsigned long)__entry_text_start
) &&
245 (paddr
< (unsigned long)__entry_text_end
))
248 /* Check there is enough space for a relative jump. */
249 if (size
- offset
< RELATIVEJUMP_SIZE
)
252 /* Decode instructions */
253 addr
= paddr
- offset
;
254 while (addr
< paddr
- offset
+ size
) { /* Decode until function end */
255 unsigned long recovered_insn
;
256 if (search_exception_tables(addr
))
258 * Since some fixup code will jumps into this function,
259 * we can't optimize kprobe in this function.
262 recovered_insn
= recover_probed_instruction(buf
, addr
);
265 kernel_insn_init(&insn
, (void *)recovered_insn
, MAX_INSN_SIZE
);
266 insn_get_length(&insn
);
267 /* Another subsystem puts a breakpoint */
268 if (insn
.opcode
.bytes
[0] == BREAKPOINT_INSTRUCTION
)
270 /* Recover address */
271 insn
.kaddr
= (void *)addr
;
272 insn
.next_byte
= (void *)(addr
+ insn
.length
);
273 /* Check any instructions don't jump into target */
274 if (insn_is_indirect_jump(&insn
) ||
275 insn_jump_into_range(&insn
, paddr
+ INT3_SIZE
,
284 /* Check optimized_kprobe can actually be optimized. */
285 int arch_check_optimized_kprobe(struct optimized_kprobe
*op
)
290 for (i
= 1; i
< op
->optinsn
.size
; i
++) {
291 p
= get_kprobe(op
->kp
.addr
+ i
);
292 if (p
&& !kprobe_disabled(p
))
299 /* Check the addr is within the optimized instructions. */
300 int arch_within_optimized_kprobe(struct optimized_kprobe
*op
,
303 return ((unsigned long)op
->kp
.addr
<= addr
&&
304 (unsigned long)op
->kp
.addr
+ op
->optinsn
.size
> addr
);
307 /* Free optimized instruction slot */
309 void __arch_remove_optimized_kprobe(struct optimized_kprobe
*op
, int dirty
)
311 if (op
->optinsn
.insn
) {
312 free_optinsn_slot(op
->optinsn
.insn
, dirty
);
313 op
->optinsn
.insn
= NULL
;
314 op
->optinsn
.size
= 0;
318 void arch_remove_optimized_kprobe(struct optimized_kprobe
*op
)
320 __arch_remove_optimized_kprobe(op
, 1);
324 * Copy replacing target instructions
325 * Target instructions MUST be relocatable (checked inside)
326 * This is called when new aggr(opt)probe is allocated or reused.
328 int arch_prepare_optimized_kprobe(struct optimized_kprobe
*op
,
329 struct kprobe
*__unused
)
335 if (!can_optimize((unsigned long)op
->kp
.addr
))
338 op
->optinsn
.insn
= get_optinsn_slot();
339 if (!op
->optinsn
.insn
)
343 * Verify if the address gap is in 2GB range, because this uses
346 rel
= (long)op
->optinsn
.insn
- (long)op
->kp
.addr
+ RELATIVEJUMP_SIZE
;
347 if (abs(rel
) > 0x7fffffff) {
348 __arch_remove_optimized_kprobe(op
, 0);
352 buf
= (u8
*)op
->optinsn
.insn
;
354 /* Copy instructions into the out-of-line buffer */
355 ret
= copy_optimized_instructions(buf
+ TMPL_END_IDX
, op
->kp
.addr
);
357 __arch_remove_optimized_kprobe(op
, 0);
360 op
->optinsn
.size
= ret
;
362 /* Copy arch-dep-instance from template */
363 memcpy(buf
, &optprobe_template_entry
, TMPL_END_IDX
);
365 /* Set probe information */
366 synthesize_set_arg1(buf
+ TMPL_MOVE_IDX
, (unsigned long)op
);
368 /* Set probe function call */
369 synthesize_relcall(buf
+ TMPL_CALL_IDX
, optimized_callback
);
371 /* Set returning jmp instruction at the tail of out-of-line buffer */
372 synthesize_reljump(buf
+ TMPL_END_IDX
+ op
->optinsn
.size
,
373 (u8
*)op
->kp
.addr
+ op
->optinsn
.size
);
375 flush_icache_range((unsigned long) buf
,
376 (unsigned long) buf
+ TMPL_END_IDX
+
377 op
->optinsn
.size
+ RELATIVEJUMP_SIZE
);
382 * Replace breakpoints (int3) with relative jumps.
383 * Caller must call with locking kprobe_mutex and text_mutex.
385 void arch_optimize_kprobes(struct list_head
*oplist
)
387 struct optimized_kprobe
*op
, *tmp
;
388 u8 insn_buf
[RELATIVEJUMP_SIZE
];
390 list_for_each_entry_safe(op
, tmp
, oplist
, list
) {
391 s32 rel
= (s32
)((long)op
->optinsn
.insn
-
392 ((long)op
->kp
.addr
+ RELATIVEJUMP_SIZE
));
394 WARN_ON(kprobe_disabled(&op
->kp
));
396 /* Backup instructions which will be replaced by jump address */
397 memcpy(op
->optinsn
.copied_insn
, op
->kp
.addr
+ INT3_SIZE
,
400 insn_buf
[0] = RELATIVEJUMP_OPCODE
;
401 *(s32
*)(&insn_buf
[1]) = rel
;
403 text_poke_bp(op
->kp
.addr
, insn_buf
, RELATIVEJUMP_SIZE
,
406 list_del_init(&op
->list
);
410 /* Replace a relative jump with a breakpoint (int3). */
411 void arch_unoptimize_kprobe(struct optimized_kprobe
*op
)
413 u8 insn_buf
[RELATIVEJUMP_SIZE
];
415 /* Set int3 to first byte for kprobes */
416 insn_buf
[0] = BREAKPOINT_INSTRUCTION
;
417 memcpy(insn_buf
+ 1, op
->optinsn
.copied_insn
, RELATIVE_ADDR_SIZE
);
418 text_poke_bp(op
->kp
.addr
, insn_buf
, RELATIVEJUMP_SIZE
,
423 * Recover original instructions and breakpoints from relative jumps.
424 * Caller must call with locking kprobe_mutex.
426 extern void arch_unoptimize_kprobes(struct list_head
*oplist
,
427 struct list_head
*done_list
)
429 struct optimized_kprobe
*op
, *tmp
;
431 list_for_each_entry_safe(op
, tmp
, oplist
, list
) {
432 arch_unoptimize_kprobe(op
);
433 list_move(&op
->list
, done_list
);
437 int setup_detour_execution(struct kprobe
*p
, struct pt_regs
*regs
, int reenter
)
439 struct optimized_kprobe
*op
;
441 if (p
->flags
& KPROBE_FLAG_OPTIMIZED
) {
442 /* This kprobe is really able to run optimized path. */
443 op
= container_of(p
, struct optimized_kprobe
, kp
);
444 /* Detour through copied instructions */
445 regs
->ip
= (unsigned long)op
->optinsn
.insn
+ TMPL_END_IDX
;
447 reset_current_kprobe();
448 preempt_enable_no_resched();
453 NOKPROBE_SYMBOL(setup_detour_execution
);
This page took 0.073949 seconds and 6 git commands to generate.