Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris...
[linux/fpc-iii.git] / arch / x86 / kernel / kprobes / opt.c
blob898160b42e4392daddd224c55ab62fb467752dd7
1 /*
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>
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>
40 #include "common.h"
42 unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
44 struct optimized_kprobe *op;
45 struct kprobe *kp;
46 long offs;
47 int i;
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;
60 return addr;
61 found:
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) {
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);
76 return (unsigned long)buf;
79 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
80 static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
82 #ifdef CONFIG_X86_64
83 *addr++ = 0x48;
84 *addr++ = 0xbf;
85 #else
86 *addr++ = 0xb8;
87 #endif
88 *(unsigned long *)addr = val;
91 asm (
92 ".global optprobe_template_entry\n"
93 "optprobe_template_entry:\n"
94 #ifdef CONFIG_X86_64
95 /* We don't bother saving the ss register */
96 " pushq %rsp\n"
97 " pushfq\n"
98 SAVE_REGS_STRING
99 " movq %rsp, %rsi\n"
100 ".global optprobe_template_val\n"
101 "optprobe_template_val:\n"
102 ASM_NOP5
103 ASM_NOP5
104 ".global optprobe_template_call\n"
105 "optprobe_template_call:\n"
106 ASM_NOP5
107 /* Move flags to rsp */
108 " movq 144(%rsp), %rdx\n"
109 " movq %rdx, 152(%rsp)\n"
110 RESTORE_REGS_STRING
111 /* Skip flags entry */
112 " addq $8, %rsp\n"
113 " popfq\n"
114 #else /* CONFIG_X86_32 */
115 " pushf\n"
116 SAVE_REGS_STRING
117 " movl %esp, %edx\n"
118 ".global optprobe_template_val\n"
119 "optprobe_template_val:\n"
120 ASM_NOP5
121 ".global optprobe_template_call\n"
122 "optprobe_template_call:\n"
123 ASM_NOP5
124 RESTORE_REGS_STRING
125 " addl $4, %esp\n" /* skip cs */
126 " popf\n"
127 #endif
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 */
141 static void __kprobes optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
143 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
144 unsigned long flags;
146 /* This is possible if op is under delayed unoptimizing */
147 if (kprobe_disabled(&op->kp))
148 return;
150 local_irq_save(flags);
151 if (kprobe_running()) {
152 kprobes_inc_nmissed_count(&op->kp);
153 } else {
154 /* Save skipped registers */
155 #ifdef CONFIG_X86_64
156 regs->cs = __KERNEL_CS;
157 #else
158 regs->cs = __KERNEL_CS | get_kernel_rpl();
159 regs->gs = 0;
160 #endif
161 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
162 regs->orig_ax = ~0UL;
164 __this_cpu_write(current_kprobe, &op->kp);
165 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
166 opt_pre_handler(&op->kp, regs);
167 __this_cpu_write(current_kprobe, NULL);
169 local_irq_restore(flags);
172 static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
174 int len = 0, ret;
176 while (len < RELATIVEJUMP_SIZE) {
177 ret = __copy_instruction(dest + len, src + len);
178 if (!ret || !can_boost(dest + len))
179 return -EINVAL;
180 len += ret;
182 /* Check whether the address range is reserved */
183 if (ftrace_text_reserved(src, src + len - 1) ||
184 alternatives_text_reserved(src, src + len - 1) ||
185 jump_label_text_reserved(src, src + len - 1))
186 return -EBUSY;
188 return len;
191 /* Check whether insn is indirect jump */
192 static int __kprobes insn_is_indirect_jump(struct insn *insn)
194 return ((insn->opcode.bytes[0] == 0xff &&
195 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
196 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
199 /* Check whether insn jumps into specified address range */
200 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
202 unsigned long target = 0;
204 switch (insn->opcode.bytes[0]) {
205 case 0xe0: /* loopne */
206 case 0xe1: /* loope */
207 case 0xe2: /* loop */
208 case 0xe3: /* jcxz */
209 case 0xe9: /* near relative jump */
210 case 0xeb: /* short relative jump */
211 break;
212 case 0x0f:
213 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
214 break;
215 return 0;
216 default:
217 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
218 break;
219 return 0;
221 target = (unsigned long)insn->next_byte + insn->immediate.value;
223 return (start <= target && target <= start + len);
226 /* Decode whole function to ensure any instructions don't jump into target */
227 static int __kprobes can_optimize(unsigned long paddr)
229 unsigned long addr, size = 0, offset = 0;
230 struct insn insn;
231 kprobe_opcode_t buf[MAX_INSN_SIZE];
233 /* Lookup symbol including addr */
234 if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
235 return 0;
238 * Do not optimize in the entry code due to the unstable
239 * stack handling.
241 if ((paddr >= (unsigned long)__entry_text_start) &&
242 (paddr < (unsigned long)__entry_text_end))
243 return 0;
245 /* Check there is enough space for a relative jump. */
246 if (size - offset < RELATIVEJUMP_SIZE)
247 return 0;
249 /* Decode instructions */
250 addr = paddr - offset;
251 while (addr < paddr - offset + size) { /* Decode until function end */
252 if (search_exception_tables(addr))
254 * Since some fixup code will jumps into this function,
255 * we can't optimize kprobe in this function.
257 return 0;
258 kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, addr));
259 insn_get_length(&insn);
260 /* Another subsystem puts a breakpoint */
261 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
262 return 0;
263 /* Recover address */
264 insn.kaddr = (void *)addr;
265 insn.next_byte = (void *)(addr + insn.length);
266 /* Check any instructions don't jump into target */
267 if (insn_is_indirect_jump(&insn) ||
268 insn_jump_into_range(&insn, paddr + INT3_SIZE,
269 RELATIVE_ADDR_SIZE))
270 return 0;
271 addr += insn.length;
274 return 1;
277 /* Check optimized_kprobe can actually be optimized. */
278 int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
280 int i;
281 struct kprobe *p;
283 for (i = 1; i < op->optinsn.size; i++) {
284 p = get_kprobe(op->kp.addr + i);
285 if (p && !kprobe_disabled(p))
286 return -EEXIST;
289 return 0;
292 /* Check the addr is within the optimized instructions. */
293 int __kprobes
294 arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr)
296 return ((unsigned long)op->kp.addr <= addr &&
297 (unsigned long)op->kp.addr + op->optinsn.size > addr);
300 /* Free optimized instruction slot */
301 static __kprobes
302 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
304 if (op->optinsn.insn) {
305 free_optinsn_slot(op->optinsn.insn, dirty);
306 op->optinsn.insn = NULL;
307 op->optinsn.size = 0;
311 void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)
313 __arch_remove_optimized_kprobe(op, 1);
317 * Copy replacing target instructions
318 * Target instructions MUST be relocatable (checked inside)
319 * This is called when new aggr(opt)probe is allocated or reused.
321 int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
323 u8 *buf;
324 int ret;
325 long rel;
327 if (!can_optimize((unsigned long)op->kp.addr))
328 return -EILSEQ;
330 op->optinsn.insn = get_optinsn_slot();
331 if (!op->optinsn.insn)
332 return -ENOMEM;
335 * Verify if the address gap is in 2GB range, because this uses
336 * a relative jump.
338 rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
339 if (abs(rel) > 0x7fffffff)
340 return -ERANGE;
342 buf = (u8 *)op->optinsn.insn;
344 /* Copy instructions into the out-of-line buffer */
345 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
346 if (ret < 0) {
347 __arch_remove_optimized_kprobe(op, 0);
348 return ret;
350 op->optinsn.size = ret;
352 /* Copy arch-dep-instance from template */
353 memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
355 /* Set probe information */
356 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
358 /* Set probe function call */
359 synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
361 /* Set returning jmp instruction at the tail of out-of-line buffer */
362 synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
363 (u8 *)op->kp.addr + op->optinsn.size);
365 flush_icache_range((unsigned long) buf,
366 (unsigned long) buf + TMPL_END_IDX +
367 op->optinsn.size + RELATIVEJUMP_SIZE);
368 return 0;
372 * Replace breakpoints (int3) with relative jumps.
373 * Caller must call with locking kprobe_mutex and text_mutex.
375 void __kprobes arch_optimize_kprobes(struct list_head *oplist)
377 struct optimized_kprobe *op, *tmp;
378 u8 insn_buf[RELATIVEJUMP_SIZE];
380 list_for_each_entry_safe(op, tmp, oplist, list) {
381 s32 rel = (s32)((long)op->optinsn.insn -
382 ((long)op->kp.addr + RELATIVEJUMP_SIZE));
384 WARN_ON(kprobe_disabled(&op->kp));
386 /* Backup instructions which will be replaced by jump address */
387 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
388 RELATIVE_ADDR_SIZE);
390 insn_buf[0] = RELATIVEJUMP_OPCODE;
391 *(s32 *)(&insn_buf[1]) = rel;
393 text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
394 op->optinsn.insn);
396 list_del_init(&op->list);
400 /* Replace a relative jump with a breakpoint (int3). */
401 void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
403 u8 insn_buf[RELATIVEJUMP_SIZE];
405 /* Set int3 to first byte for kprobes */
406 insn_buf[0] = BREAKPOINT_INSTRUCTION;
407 memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
408 text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
409 op->optinsn.insn);
413 * Recover original instructions and breakpoints from relative jumps.
414 * Caller must call with locking kprobe_mutex.
416 extern void arch_unoptimize_kprobes(struct list_head *oplist,
417 struct list_head *done_list)
419 struct optimized_kprobe *op, *tmp;
421 list_for_each_entry_safe(op, tmp, oplist, list) {
422 arch_unoptimize_kprobe(op);
423 list_move(&op->list, done_list);
427 int __kprobes
428 setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
430 struct optimized_kprobe *op;
432 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
433 /* This kprobe is really able to run optimized path. */
434 op = container_of(p, struct optimized_kprobe, kp);
435 /* Detour through copied instructions */
436 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
437 if (!reenter)
438 reset_current_kprobe();
439 preempt_enable_no_resched();
440 return 1;
442 return 0;