ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing
[pandora-kernel.git] / arch / x86 / kernel / kprobes.c
1 /*
2  *  Kernel Probes (KProbes)
3  *
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.
8  *
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.
13  *
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.
17  *
18  * Copyright (C) IBM Corporation, 2002, 2004
19  *
20  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21  *              Probes initial implementation ( includes contributions from
22  *              Rusty Russell).
23  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24  *              interface to access function arguments.
25  * 2004-Oct     Jim Keniston <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
26  *              <prasanna@in.ibm.com> adapted for x86_64 from i386.
27  * 2005-Mar     Roland McGrath <roland@redhat.com>
28  *              Fixed to handle %rip-relative addressing mode correctly.
29  * 2005-May     Hien Nguyen <hien@us.ibm.com>, Jim Keniston
30  *              <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
31  *              <prasanna@in.ibm.com> added function-return probes.
32  * 2005-May     Rusty Lynch <rusty.lynch@intel.com>
33  *              Added function return probes functionality
34  * 2006-Feb     Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added
35  *              kprobe-booster and kretprobe-booster for i386.
36  * 2007-Dec     Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster
37  *              and kretprobe-booster for x86-64
38  * 2007-Dec     Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven
39  *              <arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com>
40  *              unified x86 kprobes code.
41  */
42
43 #include <linux/kprobes.h>
44 #include <linux/ptrace.h>
45 #include <linux/string.h>
46 #include <linux/slab.h>
47 #include <linux/hardirq.h>
48 #include <linux/preempt.h>
49 #include <linux/module.h>
50 #include <linux/kdebug.h>
51 #include <linux/kallsyms.h>
52 #include <linux/ftrace.h>
53
54 #include <asm/cacheflush.h>
55 #include <asm/desc.h>
56 #include <asm/pgtable.h>
57 #include <asm/uaccess.h>
58 #include <asm/alternative.h>
59 #include <asm/insn.h>
60 #include <asm/debugreg.h>
61
62 void jprobe_return_end(void);
63
64 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
65 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
66
67 #define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
68
69 #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
70         (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
71           (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
72           (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
73           (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
74          << (row % 32))
75         /*
76          * Undefined/reserved opcodes, conditional jump, Opcode Extension
77          * Groups, and some special opcodes can not boost.
78          * This is non-const and volatile to keep gcc from statically
79          * optimizing it out, as variable_test_bit makes gcc think only
80          * *(unsigned long*) is used. 
81          */
82 static volatile u32 twobyte_is_boostable[256 / 32] = {
83         /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
84         /*      ----------------------------------------------          */
85         W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
86         W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
87         W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
88         W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
89         W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
90         W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
91         W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
92         W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
93         W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
94         W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
95         W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
96         W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
97         W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
98         W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
99         W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
100         W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0)   /* f0 */
101         /*      -----------------------------------------------         */
102         /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
103 };
104 #undef W
105
106 struct kretprobe_blackpoint kretprobe_blacklist[] = {
107         {"__switch_to", }, /* This function switches only current task, but
108                               doesn't switch kernel stack.*/
109         {NULL, NULL}    /* Terminator */
110 };
111 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
112
113 static void __kprobes __synthesize_relative_insn(void *from, void *to, u8 op)
114 {
115         struct __arch_relative_insn {
116                 u8 op;
117                 s32 raddr;
118         } __attribute__((packed)) *insn;
119
120         insn = (struct __arch_relative_insn *)from;
121         insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
122         insn->op = op;
123 }
124
125 /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
126 static void __kprobes synthesize_reljump(void *from, void *to)
127 {
128         __synthesize_relative_insn(from, to, RELATIVEJUMP_OPCODE);
129 }
130
131 /*
132  * Skip the prefixes of the instruction.
133  */
134 static kprobe_opcode_t *__kprobes skip_prefixes(kprobe_opcode_t *insn)
135 {
136         insn_attr_t attr;
137
138         attr = inat_get_opcode_attribute((insn_byte_t)*insn);
139         while (inat_is_legacy_prefix(attr)) {
140                 insn++;
141                 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
142         }
143 #ifdef CONFIG_X86_64
144         if (inat_is_rex_prefix(attr))
145                 insn++;
146 #endif
147         return insn;
148 }
149
150 /*
151  * Returns non-zero if opcode is boostable.
152  * RIP relative instructions are adjusted at copying time in 64 bits mode
153  */
154 static int __kprobes can_boost(kprobe_opcode_t *opcodes)
155 {
156         kprobe_opcode_t opcode;
157         kprobe_opcode_t *orig_opcodes = opcodes;
158
159         if (search_exception_tables((unsigned long)opcodes))
160                 return 0;       /* Page fault may occur on this address. */
161
162 retry:
163         if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
164                 return 0;
165         opcode = *(opcodes++);
166
167         /* 2nd-byte opcode */
168         if (opcode == 0x0f) {
169                 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
170                         return 0;
171                 return test_bit(*opcodes,
172                                 (unsigned long *)twobyte_is_boostable);
173         }
174
175         switch (opcode & 0xf0) {
176 #ifdef CONFIG_X86_64
177         case 0x40:
178                 goto retry; /* REX prefix is boostable */
179 #endif
180         case 0x60:
181                 if (0x63 < opcode && opcode < 0x67)
182                         goto retry; /* prefixes */
183                 /* can't boost Address-size override and bound */
184                 return (opcode != 0x62 && opcode != 0x67);
185         case 0x70:
186                 return 0; /* can't boost conditional jump */
187         case 0xc0:
188                 /* can't boost software-interruptions */
189                 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
190         case 0xd0:
191                 /* can boost AA* and XLAT */
192                 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
193         case 0xe0:
194                 /* can boost in/out and absolute jmps */
195                 return ((opcode & 0x04) || opcode == 0xea);
196         case 0xf0:
197                 if ((opcode & 0x0c) == 0 && opcode != 0xf1)
198                         goto retry; /* lock/rep(ne) prefix */
199                 /* clear and set flags are boostable */
200                 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
201         default:
202                 /* segment override prefixes are boostable */
203                 if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
204                         goto retry; /* prefixes */
205                 /* CS override prefix and call are not boostable */
206                 return (opcode != 0x2e && opcode != 0x9a);
207         }
208 }
209
210 /* Recover the probed instruction at addr for further analysis. */
211 static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
212 {
213         struct kprobe *kp;
214         kp = get_kprobe((void *)addr);
215         if (!kp)
216                 return -EINVAL;
217
218         /*
219          *  Basically, kp->ainsn.insn has an original instruction.
220          *  However, RIP-relative instruction can not do single-stepping
221          *  at different place, __copy_instruction() tweaks the displacement of
222          *  that instruction. In that case, we can't recover the instruction
223          *  from the kp->ainsn.insn.
224          *
225          *  On the other hand, kp->opcode has a copy of the first byte of
226          *  the probed instruction, which is overwritten by int3. And
227          *  the instruction at kp->addr is not modified by kprobes except
228          *  for the first byte, we can recover the original instruction
229          *  from it and kp->opcode.
230          */
231         memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
232         buf[0] = kp->opcode;
233         return 0;
234 }
235
236 /* Check if paddr is at an instruction boundary */
237 static int __kprobes can_probe(unsigned long paddr)
238 {
239         int ret;
240         unsigned long addr, offset = 0;
241         struct insn insn;
242         kprobe_opcode_t buf[MAX_INSN_SIZE];
243
244         if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
245                 return 0;
246
247         /* Decode instructions */
248         addr = paddr - offset;
249         while (addr < paddr) {
250                 kernel_insn_init(&insn, (void *)addr);
251                 insn_get_opcode(&insn);
252
253                 /*
254                  * Check if the instruction has been modified by another
255                  * kprobe, in which case we replace the breakpoint by the
256                  * original instruction in our buffer.
257                  */
258                 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
259                         ret = recover_probed_instruction(buf, addr);
260                         if (ret)
261                                 /*
262                                  * Another debugging subsystem might insert
263                                  * this breakpoint. In that case, we can't
264                                  * recover it.
265                                  */
266                                 return 0;
267                         kernel_insn_init(&insn, buf);
268                 }
269                 insn_get_length(&insn);
270                 addr += insn.length;
271         }
272
273         return (addr == paddr);
274 }
275
276 /*
277  * Returns non-zero if opcode modifies the interrupt flag.
278  */
279 static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
280 {
281         /* Skip prefixes */
282         insn = skip_prefixes(insn);
283
284         switch (*insn) {
285         case 0xfa:              /* cli */
286         case 0xfb:              /* sti */
287         case 0xcf:              /* iret/iretd */
288         case 0x9d:              /* popf/popfd */
289                 return 1;
290         }
291
292         return 0;
293 }
294
295 /*
296  * Copy an instruction and adjust the displacement if the instruction
297  * uses the %rip-relative addressing mode.
298  * If it does, Return the address of the 32-bit displacement word.
299  * If not, return null.
300  * Only applicable to 64-bit x86.
301  */
302 static int __kprobes __copy_instruction(u8 *dest, u8 *src, int recover)
303 {
304         struct insn insn;
305         int ret;
306         kprobe_opcode_t buf[MAX_INSN_SIZE];
307
308         kernel_insn_init(&insn, src);
309         if (recover) {
310                 insn_get_opcode(&insn);
311                 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
312                         ret = recover_probed_instruction(buf,
313                                                          (unsigned long)src);
314                         if (ret)
315                                 return 0;
316                         kernel_insn_init(&insn, buf);
317                 }
318         }
319         insn_get_length(&insn);
320         memcpy(dest, insn.kaddr, insn.length);
321
322 #ifdef CONFIG_X86_64
323         if (insn_rip_relative(&insn)) {
324                 s64 newdisp;
325                 u8 *disp;
326                 kernel_insn_init(&insn, dest);
327                 insn_get_displacement(&insn);
328                 /*
329                  * The copied instruction uses the %rip-relative addressing
330                  * mode.  Adjust the displacement for the difference between
331                  * the original location of this instruction and the location
332                  * of the copy that will actually be run.  The tricky bit here
333                  * is making sure that the sign extension happens correctly in
334                  * this calculation, since we need a signed 32-bit result to
335                  * be sign-extended to 64 bits when it's added to the %rip
336                  * value and yield the same 64-bit result that the sign-
337                  * extension of the original signed 32-bit displacement would
338                  * have given.
339                  */
340                 newdisp = (u8 *) src + (s64) insn.displacement.value -
341                           (u8 *) dest;
342                 BUG_ON((s64) (s32) newdisp != newdisp); /* Sanity check.  */
343                 disp = (u8 *) dest + insn_offset_displacement(&insn);
344                 *(s32 *) disp = (s32) newdisp;
345         }
346 #endif
347         return insn.length;
348 }
349
350 static void __kprobes arch_copy_kprobe(struct kprobe *p)
351 {
352         /*
353          * Copy an instruction without recovering int3, because it will be
354          * put by another subsystem.
355          */
356         __copy_instruction(p->ainsn.insn, p->addr, 0);
357
358         if (can_boost(p->addr))
359                 p->ainsn.boostable = 0;
360         else
361                 p->ainsn.boostable = -1;
362
363         p->opcode = *p->addr;
364 }
365
366 int __kprobes arch_prepare_kprobe(struct kprobe *p)
367 {
368         if (alternatives_text_reserved(p->addr, p->addr))
369                 return -EINVAL;
370
371         if (!can_probe((unsigned long)p->addr))
372                 return -EILSEQ;
373         /* insn: must be on special executable page on x86. */
374         p->ainsn.insn = get_insn_slot();
375         if (!p->ainsn.insn)
376                 return -ENOMEM;
377         arch_copy_kprobe(p);
378         return 0;
379 }
380
381 void __kprobes arch_arm_kprobe(struct kprobe *p)
382 {
383         text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
384 }
385
386 void __kprobes arch_disarm_kprobe(struct kprobe *p)
387 {
388         text_poke(p->addr, &p->opcode, 1);
389 }
390
391 void __kprobes arch_remove_kprobe(struct kprobe *p)
392 {
393         if (p->ainsn.insn) {
394                 free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1));
395                 p->ainsn.insn = NULL;
396         }
397 }
398
399 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
400 {
401         kcb->prev_kprobe.kp = kprobe_running();
402         kcb->prev_kprobe.status = kcb->kprobe_status;
403         kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
404         kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
405 }
406
407 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
408 {
409         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
410         kcb->kprobe_status = kcb->prev_kprobe.status;
411         kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
412         kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
413 }
414
415 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
416                                 struct kprobe_ctlblk *kcb)
417 {
418         __this_cpu_write(current_kprobe, p);
419         kcb->kprobe_saved_flags = kcb->kprobe_old_flags
420                 = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
421         if (is_IF_modifier(p->ainsn.insn))
422                 kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
423 }
424
425 static void __kprobes clear_btf(void)
426 {
427         if (test_thread_flag(TIF_BLOCKSTEP)) {
428                 unsigned long debugctl = get_debugctlmsr();
429
430                 debugctl &= ~DEBUGCTLMSR_BTF;
431                 update_debugctlmsr(debugctl);
432         }
433 }
434
435 static void __kprobes restore_btf(void)
436 {
437         if (test_thread_flag(TIF_BLOCKSTEP)) {
438                 unsigned long debugctl = get_debugctlmsr();
439
440                 debugctl |= DEBUGCTLMSR_BTF;
441                 update_debugctlmsr(debugctl);
442         }
443 }
444
445 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
446                                       struct pt_regs *regs)
447 {
448         unsigned long *sara = stack_addr(regs);
449
450         ri->ret_addr = (kprobe_opcode_t *) *sara;
451
452         /* Replace the return addr with trampoline addr */
453         *sara = (unsigned long) &kretprobe_trampoline;
454 }
455
456 #ifdef CONFIG_OPTPROBES
457 static int  __kprobes setup_detour_execution(struct kprobe *p,
458                                              struct pt_regs *regs,
459                                              int reenter);
460 #else
461 #define setup_detour_execution(p, regs, reenter) (0)
462 #endif
463
464 static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
465                                        struct kprobe_ctlblk *kcb, int reenter)
466 {
467         if (setup_detour_execution(p, regs, reenter))
468                 return;
469
470 #if !defined(CONFIG_PREEMPT)
471         if (p->ainsn.boostable == 1 && !p->post_handler) {
472                 /* Boost up -- we can execute copied instructions directly */
473                 if (!reenter)
474                         reset_current_kprobe();
475                 /*
476                  * Reentering boosted probe doesn't reset current_kprobe,
477                  * nor set current_kprobe, because it doesn't use single
478                  * stepping.
479                  */
480                 regs->ip = (unsigned long)p->ainsn.insn;
481                 preempt_enable_no_resched();
482                 return;
483         }
484 #endif
485         if (reenter) {
486                 save_previous_kprobe(kcb);
487                 set_current_kprobe(p, regs, kcb);
488                 kcb->kprobe_status = KPROBE_REENTER;
489         } else
490                 kcb->kprobe_status = KPROBE_HIT_SS;
491         /* Prepare real single stepping */
492         clear_btf();
493         regs->flags |= X86_EFLAGS_TF;
494         regs->flags &= ~X86_EFLAGS_IF;
495         /* single step inline if the instruction is an int3 */
496         if (p->opcode == BREAKPOINT_INSTRUCTION)
497                 regs->ip = (unsigned long)p->addr;
498         else
499                 regs->ip = (unsigned long)p->ainsn.insn;
500 }
501
502 /*
503  * We have reentered the kprobe_handler(), since another probe was hit while
504  * within the handler. We save the original kprobes variables and just single
505  * step on the instruction of the new probe without calling any user handlers.
506  */
507 static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
508                                     struct kprobe_ctlblk *kcb)
509 {
510         switch (kcb->kprobe_status) {
511         case KPROBE_HIT_SSDONE:
512         case KPROBE_HIT_ACTIVE:
513                 kprobes_inc_nmissed_count(p);
514                 setup_singlestep(p, regs, kcb, 1);
515                 break;
516         case KPROBE_HIT_SS:
517                 /* A probe has been hit in the codepath leading up to, or just
518                  * after, single-stepping of a probed instruction. This entire
519                  * codepath should strictly reside in .kprobes.text section.
520                  * Raise a BUG or we'll continue in an endless reentering loop
521                  * and eventually a stack overflow.
522                  */
523                 printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n",
524                        p->addr);
525                 dump_kprobe(p);
526                 BUG();
527         default:
528                 /* impossible cases */
529                 WARN_ON(1);
530                 return 0;
531         }
532
533         return 1;
534 }
535
536 /*
537  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
538  * remain disabled throughout this function.
539  */
540 static int __kprobes kprobe_handler(struct pt_regs *regs)
541 {
542         kprobe_opcode_t *addr;
543         struct kprobe *p;
544         struct kprobe_ctlblk *kcb;
545
546         addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
547         /*
548          * We don't want to be preempted for the entire
549          * duration of kprobe processing. We conditionally
550          * re-enable preemption at the end of this function,
551          * and also in reenter_kprobe() and setup_singlestep().
552          */
553         preempt_disable();
554
555         kcb = get_kprobe_ctlblk();
556         p = get_kprobe(addr);
557
558         if (p) {
559                 if (kprobe_running()) {
560                         if (reenter_kprobe(p, regs, kcb))
561                                 return 1;
562                 } else {
563                         set_current_kprobe(p, regs, kcb);
564                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
565
566                         /*
567                          * If we have no pre-handler or it returned 0, we
568                          * continue with normal processing.  If we have a
569                          * pre-handler and it returned non-zero, it prepped
570                          * for calling the break_handler below on re-entry
571                          * for jprobe processing, so get out doing nothing
572                          * more here.
573                          */
574                         if (!p->pre_handler || !p->pre_handler(p, regs))
575                                 setup_singlestep(p, regs, kcb, 0);
576                         return 1;
577                 }
578         } else if (*addr != BREAKPOINT_INSTRUCTION) {
579                 /*
580                  * The breakpoint instruction was removed right
581                  * after we hit it.  Another cpu has removed
582                  * either a probepoint or a debugger breakpoint
583                  * at this address.  In either case, no further
584                  * handling of this interrupt is appropriate.
585                  * Back up over the (now missing) int3 and run
586                  * the original instruction.
587                  */
588                 regs->ip = (unsigned long)addr;
589                 preempt_enable_no_resched();
590                 return 1;
591         } else if (kprobe_running()) {
592                 p = __this_cpu_read(current_kprobe);
593                 if (p->break_handler && p->break_handler(p, regs)) {
594                         setup_singlestep(p, regs, kcb, 0);
595                         return 1;
596                 }
597         } /* else: not a kprobe fault; let the kernel handle it */
598
599         preempt_enable_no_resched();
600         return 0;
601 }
602
603 #ifdef CONFIG_X86_64
604 #define SAVE_REGS_STRING                \
605         /* Skip cs, ip, orig_ax. */     \
606         "       subq $24, %rsp\n"       \
607         "       pushq %rdi\n"           \
608         "       pushq %rsi\n"           \
609         "       pushq %rdx\n"           \
610         "       pushq %rcx\n"           \
611         "       pushq %rax\n"           \
612         "       pushq %r8\n"            \
613         "       pushq %r9\n"            \
614         "       pushq %r10\n"           \
615         "       pushq %r11\n"           \
616         "       pushq %rbx\n"           \
617         "       pushq %rbp\n"           \
618         "       pushq %r12\n"           \
619         "       pushq %r13\n"           \
620         "       pushq %r14\n"           \
621         "       pushq %r15\n"
622 #define RESTORE_REGS_STRING             \
623         "       popq %r15\n"            \
624         "       popq %r14\n"            \
625         "       popq %r13\n"            \
626         "       popq %r12\n"            \
627         "       popq %rbp\n"            \
628         "       popq %rbx\n"            \
629         "       popq %r11\n"            \
630         "       popq %r10\n"            \
631         "       popq %r9\n"             \
632         "       popq %r8\n"             \
633         "       popq %rax\n"            \
634         "       popq %rcx\n"            \
635         "       popq %rdx\n"            \
636         "       popq %rsi\n"            \
637         "       popq %rdi\n"            \
638         /* Skip orig_ax, ip, cs */      \
639         "       addq $24, %rsp\n"
640 #else
641 #define SAVE_REGS_STRING                \
642         /* Skip cs, ip, orig_ax and gs. */      \
643         "       subl $16, %esp\n"       \
644         "       pushl %fs\n"            \
645         "       pushl %es\n"            \
646         "       pushl %ds\n"            \
647         "       pushl %eax\n"           \
648         "       pushl %ebp\n"           \
649         "       pushl %edi\n"           \
650         "       pushl %esi\n"           \
651         "       pushl %edx\n"           \
652         "       pushl %ecx\n"           \
653         "       pushl %ebx\n"
654 #define RESTORE_REGS_STRING             \
655         "       popl %ebx\n"            \
656         "       popl %ecx\n"            \
657         "       popl %edx\n"            \
658         "       popl %esi\n"            \
659         "       popl %edi\n"            \
660         "       popl %ebp\n"            \
661         "       popl %eax\n"            \
662         /* Skip ds, es, fs, gs, orig_ax, and ip. Note: don't pop cs here*/\
663         "       addl $24, %esp\n"
664 #endif
665
666 /*
667  * When a retprobed function returns, this code saves registers and
668  * calls trampoline_handler() runs, which calls the kretprobe's handler.
669  */
670 static void __used __kprobes kretprobe_trampoline_holder(void)
671 {
672         asm volatile (
673                         ".global kretprobe_trampoline\n"
674                         "kretprobe_trampoline: \n"
675 #ifdef CONFIG_X86_64
676                         /* We don't bother saving the ss register */
677                         "       pushq %rsp\n"
678                         "       pushfq\n"
679                         SAVE_REGS_STRING
680                         "       movq %rsp, %rdi\n"
681                         "       call trampoline_handler\n"
682                         /* Replace saved sp with true return address. */
683                         "       movq %rax, 152(%rsp)\n"
684                         RESTORE_REGS_STRING
685                         "       popfq\n"
686 #else
687                         "       pushf\n"
688                         SAVE_REGS_STRING
689                         "       movl %esp, %eax\n"
690                         "       call trampoline_handler\n"
691                         /* Move flags to cs */
692                         "       movl 56(%esp), %edx\n"
693                         "       movl %edx, 52(%esp)\n"
694                         /* Replace saved flags with true return address. */
695                         "       movl %eax, 56(%esp)\n"
696                         RESTORE_REGS_STRING
697                         "       popf\n"
698 #endif
699                         "       ret\n");
700 }
701
702 /*
703  * Called from kretprobe_trampoline
704  */
705 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
706 {
707         struct kretprobe_instance *ri = NULL;
708         struct hlist_head *head, empty_rp;
709         struct hlist_node *node, *tmp;
710         unsigned long flags, orig_ret_address = 0;
711         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
712         kprobe_opcode_t *correct_ret_addr = NULL;
713
714         INIT_HLIST_HEAD(&empty_rp);
715         kretprobe_hash_lock(current, &head, &flags);
716         /* fixup registers */
717 #ifdef CONFIG_X86_64
718         regs->cs = __KERNEL_CS;
719 #else
720         regs->cs = __KERNEL_CS | get_kernel_rpl();
721         regs->gs = 0;
722 #endif
723         regs->ip = trampoline_address;
724         regs->orig_ax = ~0UL;
725
726         /*
727          * It is possible to have multiple instances associated with a given
728          * task either because multiple functions in the call path have
729          * return probes installed on them, and/or more than one
730          * return probe was registered for a target function.
731          *
732          * We can handle this because:
733          *     - instances are always pushed into the head of the list
734          *     - when multiple return probes are registered for the same
735          *       function, the (chronologically) first instance's ret_addr
736          *       will be the real return address, and all the rest will
737          *       point to kretprobe_trampoline.
738          */
739         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
740                 if (ri->task != current)
741                         /* another task is sharing our hash bucket */
742                         continue;
743
744                 orig_ret_address = (unsigned long)ri->ret_addr;
745
746                 if (orig_ret_address != trampoline_address)
747                         /*
748                          * This is the real return address. Any other
749                          * instances associated with this task are for
750                          * other calls deeper on the call stack
751                          */
752                         break;
753         }
754
755         kretprobe_assert(ri, orig_ret_address, trampoline_address);
756
757         correct_ret_addr = ri->ret_addr;
758         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
759                 if (ri->task != current)
760                         /* another task is sharing our hash bucket */
761                         continue;
762
763                 orig_ret_address = (unsigned long)ri->ret_addr;
764                 if (ri->rp && ri->rp->handler) {
765                         __this_cpu_write(current_kprobe, &ri->rp->kp);
766                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
767                         ri->ret_addr = correct_ret_addr;
768                         ri->rp->handler(ri, regs);
769                         __this_cpu_write(current_kprobe, NULL);
770                 }
771
772                 recycle_rp_inst(ri, &empty_rp);
773
774                 if (orig_ret_address != trampoline_address)
775                         /*
776                          * This is the real return address. Any other
777                          * instances associated with this task are for
778                          * other calls deeper on the call stack
779                          */
780                         break;
781         }
782
783         kretprobe_hash_unlock(current, &flags);
784
785         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
786                 hlist_del(&ri->hlist);
787                 kfree(ri);
788         }
789         return (void *)orig_ret_address;
790 }
791
792 /*
793  * Called after single-stepping.  p->addr is the address of the
794  * instruction whose first byte has been replaced by the "int 3"
795  * instruction.  To avoid the SMP problems that can occur when we
796  * temporarily put back the original opcode to single-step, we
797  * single-stepped a copy of the instruction.  The address of this
798  * copy is p->ainsn.insn.
799  *
800  * This function prepares to return from the post-single-step
801  * interrupt.  We have to fix up the stack as follows:
802  *
803  * 0) Except in the case of absolute or indirect jump or call instructions,
804  * the new ip is relative to the copied instruction.  We need to make
805  * it relative to the original instruction.
806  *
807  * 1) If the single-stepped instruction was pushfl, then the TF and IF
808  * flags are set in the just-pushed flags, and may need to be cleared.
809  *
810  * 2) If the single-stepped instruction was a call, the return address
811  * that is atop the stack is the address following the copied instruction.
812  * We need to make it the address following the original instruction.
813  *
814  * If this is the first time we've single-stepped the instruction at
815  * this probepoint, and the instruction is boostable, boost it: add a
816  * jump instruction after the copied instruction, that jumps to the next
817  * instruction after the probepoint.
818  */
819 static void __kprobes resume_execution(struct kprobe *p,
820                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
821 {
822         unsigned long *tos = stack_addr(regs);
823         unsigned long copy_ip = (unsigned long)p->ainsn.insn;
824         unsigned long orig_ip = (unsigned long)p->addr;
825         kprobe_opcode_t *insn = p->ainsn.insn;
826
827         /* Skip prefixes */
828         insn = skip_prefixes(insn);
829
830         regs->flags &= ~X86_EFLAGS_TF;
831         switch (*insn) {
832         case 0x9c:      /* pushfl */
833                 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
834                 *tos |= kcb->kprobe_old_flags;
835                 break;
836         case 0xc2:      /* iret/ret/lret */
837         case 0xc3:
838         case 0xca:
839         case 0xcb:
840         case 0xcf:
841         case 0xea:      /* jmp absolute -- ip is correct */
842                 /* ip is already adjusted, no more changes required */
843                 p->ainsn.boostable = 1;
844                 goto no_change;
845         case 0xe8:      /* call relative - Fix return addr */
846                 *tos = orig_ip + (*tos - copy_ip);
847                 break;
848 #ifdef CONFIG_X86_32
849         case 0x9a:      /* call absolute -- same as call absolute, indirect */
850                 *tos = orig_ip + (*tos - copy_ip);
851                 goto no_change;
852 #endif
853         case 0xff:
854                 if ((insn[1] & 0x30) == 0x10) {
855                         /*
856                          * call absolute, indirect
857                          * Fix return addr; ip is correct.
858                          * But this is not boostable
859                          */
860                         *tos = orig_ip + (*tos - copy_ip);
861                         goto no_change;
862                 } else if (((insn[1] & 0x31) == 0x20) ||
863                            ((insn[1] & 0x31) == 0x21)) {
864                         /*
865                          * jmp near and far, absolute indirect
866                          * ip is correct. And this is boostable
867                          */
868                         p->ainsn.boostable = 1;
869                         goto no_change;
870                 }
871         default:
872                 break;
873         }
874
875         if (p->ainsn.boostable == 0) {
876                 if ((regs->ip > copy_ip) &&
877                     (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
878                         /*
879                          * These instructions can be executed directly if it
880                          * jumps back to correct address.
881                          */
882                         synthesize_reljump((void *)regs->ip,
883                                 (void *)orig_ip + (regs->ip - copy_ip));
884                         p->ainsn.boostable = 1;
885                 } else {
886                         p->ainsn.boostable = -1;
887                 }
888         }
889
890         regs->ip += orig_ip - copy_ip;
891
892 no_change:
893         restore_btf();
894 }
895
896 /*
897  * Interrupts are disabled on entry as trap1 is an interrupt gate and they
898  * remain disabled throughout this function.
899  */
900 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
901 {
902         struct kprobe *cur = kprobe_running();
903         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
904
905         if (!cur)
906                 return 0;
907
908         resume_execution(cur, regs, kcb);
909         regs->flags |= kcb->kprobe_saved_flags;
910
911         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
912                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
913                 cur->post_handler(cur, regs, 0);
914         }
915
916         /* Restore back the original saved kprobes variables and continue. */
917         if (kcb->kprobe_status == KPROBE_REENTER) {
918                 restore_previous_kprobe(kcb);
919                 goto out;
920         }
921         reset_current_kprobe();
922 out:
923         preempt_enable_no_resched();
924
925         /*
926          * if somebody else is singlestepping across a probe point, flags
927          * will have TF set, in which case, continue the remaining processing
928          * of do_debug, as if this is not a probe hit.
929          */
930         if (regs->flags & X86_EFLAGS_TF)
931                 return 0;
932
933         return 1;
934 }
935
936 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
937 {
938         struct kprobe *cur = kprobe_running();
939         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
940
941         switch (kcb->kprobe_status) {
942         case KPROBE_HIT_SS:
943         case KPROBE_REENTER:
944                 /*
945                  * We are here because the instruction being single
946                  * stepped caused a page fault. We reset the current
947                  * kprobe and the ip points back to the probe address
948                  * and allow the page fault handler to continue as a
949                  * normal page fault.
950                  */
951                 regs->ip = (unsigned long)cur->addr;
952                 regs->flags |= kcb->kprobe_old_flags;
953                 if (kcb->kprobe_status == KPROBE_REENTER)
954                         restore_previous_kprobe(kcb);
955                 else
956                         reset_current_kprobe();
957                 preempt_enable_no_resched();
958                 break;
959         case KPROBE_HIT_ACTIVE:
960         case KPROBE_HIT_SSDONE:
961                 /*
962                  * We increment the nmissed count for accounting,
963                  * we can also use npre/npostfault count for accounting
964                  * these specific fault cases.
965                  */
966                 kprobes_inc_nmissed_count(cur);
967
968                 /*
969                  * We come here because instructions in the pre/post
970                  * handler caused the page_fault, this could happen
971                  * if handler tries to access user space by
972                  * copy_from_user(), get_user() etc. Let the
973                  * user-specified handler try to fix it first.
974                  */
975                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
976                         return 1;
977
978                 /*
979                  * In case the user-specified fault handler returned
980                  * zero, try to fix up.
981                  */
982                 if (fixup_exception(regs))
983                         return 1;
984
985                 /*
986                  * fixup routine could not handle it,
987                  * Let do_page_fault() fix it.
988                  */
989                 break;
990         default:
991                 break;
992         }
993         return 0;
994 }
995
996 /*
997  * Wrapper routine for handling exceptions.
998  */
999 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
1000                                        unsigned long val, void *data)
1001 {
1002         struct die_args *args = data;
1003         int ret = NOTIFY_DONE;
1004
1005         if (args->regs && user_mode_vm(args->regs))
1006                 return ret;
1007
1008         switch (val) {
1009         case DIE_INT3:
1010                 if (kprobe_handler(args->regs))
1011                         ret = NOTIFY_STOP;
1012                 break;
1013         case DIE_DEBUG:
1014                 if (post_kprobe_handler(args->regs)) {
1015                         /*
1016                          * Reset the BS bit in dr6 (pointed by args->err) to
1017                          * denote completion of processing
1018                          */
1019                         (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
1020                         ret = NOTIFY_STOP;
1021                 }
1022                 break;
1023         case DIE_GPF:
1024                 /*
1025                  * To be potentially processing a kprobe fault and to
1026                  * trust the result from kprobe_running(), we have
1027                  * be non-preemptible.
1028                  */
1029                 if (!preemptible() && kprobe_running() &&
1030                     kprobe_fault_handler(args->regs, args->trapnr))
1031                         ret = NOTIFY_STOP;
1032                 break;
1033         default:
1034                 break;
1035         }
1036         return ret;
1037 }
1038
1039 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
1040 {
1041         struct jprobe *jp = container_of(p, struct jprobe, kp);
1042         unsigned long addr;
1043         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1044
1045         kcb->jprobe_saved_regs = *regs;
1046         kcb->jprobe_saved_sp = stack_addr(regs);
1047         addr = (unsigned long)(kcb->jprobe_saved_sp);
1048
1049         /*
1050          * As Linus pointed out, gcc assumes that the callee
1051          * owns the argument space and could overwrite it, e.g.
1052          * tailcall optimization. So, to be absolutely safe
1053          * we also save and restore enough stack bytes to cover
1054          * the argument area.
1055          */
1056         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
1057                MIN_STACK_SIZE(addr));
1058         regs->flags &= ~X86_EFLAGS_IF;
1059         trace_hardirqs_off();
1060         regs->ip = (unsigned long)(jp->entry);
1061
1062         /*
1063          * jprobes use jprobe_return() which skips the normal return
1064          * path of the function, and this messes up the accounting of the
1065          * function graph tracer to get messed up.
1066          *
1067          * Pause function graph tracing while performing the jprobe function.
1068          */
1069         pause_graph_tracing();
1070         return 1;
1071 }
1072
1073 void __kprobes jprobe_return(void)
1074 {
1075         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1076
1077         asm volatile (
1078 #ifdef CONFIG_X86_64
1079                         "       xchg   %%rbx,%%rsp      \n"
1080 #else
1081                         "       xchgl   %%ebx,%%esp     \n"
1082 #endif
1083                         "       int3                    \n"
1084                         "       .globl jprobe_return_end\n"
1085                         "       jprobe_return_end:      \n"
1086                         "       nop                     \n"::"b"
1087                         (kcb->jprobe_saved_sp):"memory");
1088 }
1089
1090 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
1091 {
1092         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1093         u8 *addr = (u8 *) (regs->ip - 1);
1094         struct jprobe *jp = container_of(p, struct jprobe, kp);
1095         void *saved_sp = kcb->jprobe_saved_sp;
1096
1097         if ((addr > (u8 *) jprobe_return) &&
1098             (addr < (u8 *) jprobe_return_end)) {
1099                 if (stack_addr(regs) != saved_sp) {
1100                         struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
1101                         printk(KERN_ERR
1102                                "current sp %p does not match saved sp %p\n",
1103                                stack_addr(regs), saved_sp);
1104                         printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
1105                         show_registers(saved_regs);
1106                         printk(KERN_ERR "Current registers\n");
1107                         show_registers(regs);
1108                         BUG();
1109                 }
1110                 /* It's OK to start function graph tracing again */
1111                 unpause_graph_tracing();
1112                 *regs = kcb->jprobe_saved_regs;
1113                 memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp));
1114                 preempt_enable_no_resched();
1115                 return 1;
1116         }
1117         return 0;
1118 }
1119
1120
1121 #ifdef CONFIG_OPTPROBES
1122
1123 /* Insert a call instruction at address 'from', which calls address 'to'.*/
1124 static void __kprobes synthesize_relcall(void *from, void *to)
1125 {
1126         __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE);
1127 }
1128
1129 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
1130 static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr,
1131                                           unsigned long val)
1132 {
1133 #ifdef CONFIG_X86_64
1134         *addr++ = 0x48;
1135         *addr++ = 0xbf;
1136 #else
1137         *addr++ = 0xb8;
1138 #endif
1139         *(unsigned long *)addr = val;
1140 }
1141
1142 static void __used __kprobes kprobes_optinsn_template_holder(void)
1143 {
1144         asm volatile (
1145                         ".global optprobe_template_entry\n"
1146                         "optprobe_template_entry: \n"
1147 #ifdef CONFIG_X86_64
1148                         /* We don't bother saving the ss register */
1149                         "       pushq %rsp\n"
1150                         "       pushfq\n"
1151                         SAVE_REGS_STRING
1152                         "       movq %rsp, %rsi\n"
1153                         ".global optprobe_template_val\n"
1154                         "optprobe_template_val: \n"
1155                         ASM_NOP5
1156                         ASM_NOP5
1157                         ".global optprobe_template_call\n"
1158                         "optprobe_template_call: \n"
1159                         ASM_NOP5
1160                         /* Move flags to rsp */
1161                         "       movq 144(%rsp), %rdx\n"
1162                         "       movq %rdx, 152(%rsp)\n"
1163                         RESTORE_REGS_STRING
1164                         /* Skip flags entry */
1165                         "       addq $8, %rsp\n"
1166                         "       popfq\n"
1167 #else /* CONFIG_X86_32 */
1168                         "       pushf\n"
1169                         SAVE_REGS_STRING
1170                         "       movl %esp, %edx\n"
1171                         ".global optprobe_template_val\n"
1172                         "optprobe_template_val: \n"
1173                         ASM_NOP5
1174                         ".global optprobe_template_call\n"
1175                         "optprobe_template_call: \n"
1176                         ASM_NOP5
1177                         RESTORE_REGS_STRING
1178                         "       addl $4, %esp\n"        /* skip cs */
1179                         "       popf\n"
1180 #endif
1181                         ".global optprobe_template_end\n"
1182                         "optprobe_template_end: \n");
1183 }
1184
1185 #define TMPL_MOVE_IDX \
1186         ((long)&optprobe_template_val - (long)&optprobe_template_entry)
1187 #define TMPL_CALL_IDX \
1188         ((long)&optprobe_template_call - (long)&optprobe_template_entry)
1189 #define TMPL_END_IDX \
1190         ((long)&optprobe_template_end - (long)&optprobe_template_entry)
1191
1192 #define INT3_SIZE sizeof(kprobe_opcode_t)
1193
1194 /* Optimized kprobe call back function: called from optinsn */
1195 static void __kprobes optimized_callback(struct optimized_kprobe *op,
1196                                          struct pt_regs *regs)
1197 {
1198         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1199         unsigned long flags;
1200
1201         /* This is possible if op is under delayed unoptimizing */
1202         if (kprobe_disabled(&op->kp))
1203                 return;
1204
1205         local_irq_save(flags);
1206         if (kprobe_running()) {
1207                 kprobes_inc_nmissed_count(&op->kp);
1208         } else {
1209                 /* Save skipped registers */
1210 #ifdef CONFIG_X86_64
1211                 regs->cs = __KERNEL_CS;
1212 #else
1213                 regs->cs = __KERNEL_CS | get_kernel_rpl();
1214                 regs->gs = 0;
1215 #endif
1216                 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
1217                 regs->orig_ax = ~0UL;
1218
1219                 __this_cpu_write(current_kprobe, &op->kp);
1220                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
1221                 opt_pre_handler(&op->kp, regs);
1222                 __this_cpu_write(current_kprobe, NULL);
1223         }
1224         local_irq_restore(flags);
1225 }
1226
1227 static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
1228 {
1229         int len = 0, ret;
1230
1231         while (len < RELATIVEJUMP_SIZE) {
1232                 ret = __copy_instruction(dest + len, src + len, 1);
1233                 if (!ret || !can_boost(dest + len))
1234                         return -EINVAL;
1235                 len += ret;
1236         }
1237         /* Check whether the address range is reserved */
1238         if (ftrace_text_reserved(src, src + len - 1) ||
1239             alternatives_text_reserved(src, src + len - 1) ||
1240             jump_label_text_reserved(src, src + len - 1))
1241                 return -EBUSY;
1242
1243         return len;
1244 }
1245
1246 /* Check whether insn is indirect jump */
1247 static int __kprobes insn_is_indirect_jump(struct insn *insn)
1248 {
1249         return ((insn->opcode.bytes[0] == 0xff &&
1250                 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
1251                 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
1252 }
1253
1254 /* Check whether insn jumps into specified address range */
1255 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
1256 {
1257         unsigned long target = 0;
1258
1259         switch (insn->opcode.bytes[0]) {
1260         case 0xe0:      /* loopne */
1261         case 0xe1:      /* loope */
1262         case 0xe2:      /* loop */
1263         case 0xe3:      /* jcxz */
1264         case 0xe9:      /* near relative jump */
1265         case 0xeb:      /* short relative jump */
1266                 break;
1267         case 0x0f:
1268                 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
1269                         break;
1270                 return 0;
1271         default:
1272                 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
1273                         break;
1274                 return 0;
1275         }
1276         target = (unsigned long)insn->next_byte + insn->immediate.value;
1277
1278         return (start <= target && target <= start + len);
1279 }
1280
1281 /* Decode whole function to ensure any instructions don't jump into target */
1282 static int __kprobes can_optimize(unsigned long paddr)
1283 {
1284         int ret;
1285         unsigned long addr, size = 0, offset = 0;
1286         struct insn insn;
1287         kprobe_opcode_t buf[MAX_INSN_SIZE];
1288
1289         /* Lookup symbol including addr */
1290         if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
1291                 return 0;
1292
1293         /*
1294          * Do not optimize in the entry code due to the unstable
1295          * stack handling.
1296          */
1297         if ((paddr >= (unsigned long )__entry_text_start) &&
1298             (paddr <  (unsigned long )__entry_text_end))
1299                 return 0;
1300
1301         /* Check there is enough space for a relative jump. */
1302         if (size - offset < RELATIVEJUMP_SIZE)
1303                 return 0;
1304
1305         /* Decode instructions */
1306         addr = paddr - offset;
1307         while (addr < paddr - offset + size) { /* Decode until function end */
1308                 if (search_exception_tables(addr))
1309                         /*
1310                          * Since some fixup code will jumps into this function,
1311                          * we can't optimize kprobe in this function.
1312                          */
1313                         return 0;
1314                 kernel_insn_init(&insn, (void *)addr);
1315                 insn_get_opcode(&insn);
1316                 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
1317                         ret = recover_probed_instruction(buf, addr);
1318                         if (ret)
1319                                 return 0;
1320                         kernel_insn_init(&insn, buf);
1321                 }
1322                 insn_get_length(&insn);
1323                 /* Recover address */
1324                 insn.kaddr = (void *)addr;
1325                 insn.next_byte = (void *)(addr + insn.length);
1326                 /* Check any instructions don't jump into target */
1327                 if (insn_is_indirect_jump(&insn) ||
1328                     insn_jump_into_range(&insn, paddr + INT3_SIZE,
1329                                          RELATIVE_ADDR_SIZE))
1330                         return 0;
1331                 addr += insn.length;
1332         }
1333
1334         return 1;
1335 }
1336
1337 /* Check optimized_kprobe can actually be optimized. */
1338 int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
1339 {
1340         int i;
1341         struct kprobe *p;
1342
1343         for (i = 1; i < op->optinsn.size; i++) {
1344                 p = get_kprobe(op->kp.addr + i);
1345                 if (p && !kprobe_disabled(p))
1346                         return -EEXIST;
1347         }
1348
1349         return 0;
1350 }
1351
1352 /* Check the addr is within the optimized instructions. */
1353 int __kprobes arch_within_optimized_kprobe(struct optimized_kprobe *op,
1354                                            unsigned long addr)
1355 {
1356         return ((unsigned long)op->kp.addr <= addr &&
1357                 (unsigned long)op->kp.addr + op->optinsn.size > addr);
1358 }
1359
1360 /* Free optimized instruction slot */
1361 static __kprobes
1362 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
1363 {
1364         if (op->optinsn.insn) {
1365                 free_optinsn_slot(op->optinsn.insn, dirty);
1366                 op->optinsn.insn = NULL;
1367                 op->optinsn.size = 0;
1368         }
1369 }
1370
1371 void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)
1372 {
1373         __arch_remove_optimized_kprobe(op, 1);
1374 }
1375
1376 /*
1377  * Copy replacing target instructions
1378  * Target instructions MUST be relocatable (checked inside)
1379  */
1380 int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
1381 {
1382         u8 *buf;
1383         int ret;
1384         long rel;
1385
1386         if (!can_optimize((unsigned long)op->kp.addr))
1387                 return -EILSEQ;
1388
1389         op->optinsn.insn = get_optinsn_slot();
1390         if (!op->optinsn.insn)
1391                 return -ENOMEM;
1392
1393         /*
1394          * Verify if the address gap is in 2GB range, because this uses
1395          * a relative jump.
1396          */
1397         rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
1398         if (abs(rel) > 0x7fffffff)
1399                 return -ERANGE;
1400
1401         buf = (u8 *)op->optinsn.insn;
1402
1403         /* Copy instructions into the out-of-line buffer */
1404         ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
1405         if (ret < 0) {
1406                 __arch_remove_optimized_kprobe(op, 0);
1407                 return ret;
1408         }
1409         op->optinsn.size = ret;
1410
1411         /* Copy arch-dep-instance from template */
1412         memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
1413
1414         /* Set probe information */
1415         synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
1416
1417         /* Set probe function call */
1418         synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
1419
1420         /* Set returning jmp instruction at the tail of out-of-line buffer */
1421         synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
1422                            (u8 *)op->kp.addr + op->optinsn.size);
1423
1424         flush_icache_range((unsigned long) buf,
1425                            (unsigned long) buf + TMPL_END_IDX +
1426                            op->optinsn.size + RELATIVEJUMP_SIZE);
1427         return 0;
1428 }
1429
1430 #define MAX_OPTIMIZE_PROBES 256
1431 static struct text_poke_param *jump_poke_params;
1432 static struct jump_poke_buffer {
1433         u8 buf[RELATIVEJUMP_SIZE];
1434 } *jump_poke_bufs;
1435
1436 static void __kprobes setup_optimize_kprobe(struct text_poke_param *tprm,
1437                                             u8 *insn_buf,
1438                                             struct optimized_kprobe *op)
1439 {
1440         s32 rel = (s32)((long)op->optinsn.insn -
1441                         ((long)op->kp.addr + RELATIVEJUMP_SIZE));
1442
1443         /* Backup instructions which will be replaced by jump address */
1444         memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
1445                RELATIVE_ADDR_SIZE);
1446
1447         insn_buf[0] = RELATIVEJUMP_OPCODE;
1448         *(s32 *)(&insn_buf[1]) = rel;
1449
1450         tprm->addr = op->kp.addr;
1451         tprm->opcode = insn_buf;
1452         tprm->len = RELATIVEJUMP_SIZE;
1453 }
1454
1455 /*
1456  * Replace breakpoints (int3) with relative jumps.
1457  * Caller must call with locking kprobe_mutex and text_mutex.
1458  */
1459 void __kprobes arch_optimize_kprobes(struct list_head *oplist)
1460 {
1461         struct optimized_kprobe *op, *tmp;
1462         int c = 0;
1463
1464         list_for_each_entry_safe(op, tmp, oplist, list) {
1465                 WARN_ON(kprobe_disabled(&op->kp));
1466                 /* Setup param */
1467                 setup_optimize_kprobe(&jump_poke_params[c],
1468                                       jump_poke_bufs[c].buf, op);
1469                 list_del_init(&op->list);
1470                 if (++c >= MAX_OPTIMIZE_PROBES)
1471                         break;
1472         }
1473
1474         /*
1475          * text_poke_smp doesn't support NMI/MCE code modifying.
1476          * However, since kprobes itself also doesn't support NMI/MCE
1477          * code probing, it's not a problem.
1478          */
1479         text_poke_smp_batch(jump_poke_params, c);
1480 }
1481
1482 static void __kprobes setup_unoptimize_kprobe(struct text_poke_param *tprm,
1483                                               u8 *insn_buf,
1484                                               struct optimized_kprobe *op)
1485 {
1486         /* Set int3 to first byte for kprobes */
1487         insn_buf[0] = BREAKPOINT_INSTRUCTION;
1488         memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
1489
1490         tprm->addr = op->kp.addr;
1491         tprm->opcode = insn_buf;
1492         tprm->len = RELATIVEJUMP_SIZE;
1493 }
1494
1495 /*
1496  * Recover original instructions and breakpoints from relative jumps.
1497  * Caller must call with locking kprobe_mutex.
1498  */
1499 extern void arch_unoptimize_kprobes(struct list_head *oplist,
1500                                     struct list_head *done_list)
1501 {
1502         struct optimized_kprobe *op, *tmp;
1503         int c = 0;
1504
1505         list_for_each_entry_safe(op, tmp, oplist, list) {
1506                 /* Setup param */
1507                 setup_unoptimize_kprobe(&jump_poke_params[c],
1508                                         jump_poke_bufs[c].buf, op);
1509                 list_move(&op->list, done_list);
1510                 if (++c >= MAX_OPTIMIZE_PROBES)
1511                         break;
1512         }
1513
1514         /*
1515          * text_poke_smp doesn't support NMI/MCE code modifying.
1516          * However, since kprobes itself also doesn't support NMI/MCE
1517          * code probing, it's not a problem.
1518          */
1519         text_poke_smp_batch(jump_poke_params, c);
1520 }
1521
1522 /* Replace a relative jump with a breakpoint (int3).  */
1523 void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
1524 {
1525         u8 buf[RELATIVEJUMP_SIZE];
1526
1527         /* Set int3 to first byte for kprobes */
1528         buf[0] = BREAKPOINT_INSTRUCTION;
1529         memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
1530         text_poke_smp(op->kp.addr, buf, RELATIVEJUMP_SIZE);
1531 }
1532
1533 static int  __kprobes setup_detour_execution(struct kprobe *p,
1534                                              struct pt_regs *regs,
1535                                              int reenter)
1536 {
1537         struct optimized_kprobe *op;
1538
1539         if (p->flags & KPROBE_FLAG_OPTIMIZED) {
1540                 /* This kprobe is really able to run optimized path. */
1541                 op = container_of(p, struct optimized_kprobe, kp);
1542                 /* Detour through copied instructions */
1543                 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
1544                 if (!reenter)
1545                         reset_current_kprobe();
1546                 preempt_enable_no_resched();
1547                 return 1;
1548         }
1549         return 0;
1550 }
1551
1552 static int __kprobes init_poke_params(void)
1553 {
1554         /* Allocate code buffer and parameter array */
1555         jump_poke_bufs = kmalloc(sizeof(struct jump_poke_buffer) *
1556                                  MAX_OPTIMIZE_PROBES, GFP_KERNEL);
1557         if (!jump_poke_bufs)
1558                 return -ENOMEM;
1559
1560         jump_poke_params = kmalloc(sizeof(struct text_poke_param) *
1561                                    MAX_OPTIMIZE_PROBES, GFP_KERNEL);
1562         if (!jump_poke_params) {
1563                 kfree(jump_poke_bufs);
1564                 jump_poke_bufs = NULL;
1565                 return -ENOMEM;
1566         }
1567
1568         return 0;
1569 }
1570 #else   /* !CONFIG_OPTPROBES */
1571 static int __kprobes init_poke_params(void)
1572 {
1573         return 0;
1574 }
1575 #endif
1576
1577 int __init arch_init_kprobes(void)
1578 {
1579         return init_poke_params();
1580 }
1581
1582 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
1583 {
1584         return 0;
1585 }