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TOMOYO Linux Cross Reference
Linux/arch/x86/kernel/kprobes/core.c

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  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 #include <linux/kprobes.h>
 43 #include <linux/ptrace.h>
 44 #include <linux/string.h>
 45 #include <linux/slab.h>
 46 #include <linux/hardirq.h>
 47 #include <linux/preempt.h>
 48 #include <linux/sched/debug.h>
 49 #include <linux/extable.h>
 50 #include <linux/kdebug.h>
 51 #include <linux/kallsyms.h>
 52 #include <linux/ftrace.h>
 53 #include <linux/frame.h>
 54 #include <linux/kasan.h>
 55 #include <linux/moduleloader.h>
 56 
 57 #include <asm/text-patching.h>
 58 #include <asm/cacheflush.h>
 59 #include <asm/desc.h>
 60 #include <asm/pgtable.h>
 61 #include <linux/uaccess.h>
 62 #include <asm/alternative.h>
 63 #include <asm/insn.h>
 64 #include <asm/debugreg.h>
 65 #include <asm/set_memory.h>
 66 
 67 #include "common.h"
 68 
 69 void jprobe_return_end(void);
 70 
 71 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 72 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 73 
 74 #define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
 75 
 76 #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
 77         (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
 78           (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
 79           (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
 80           (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
 81          << (row % 32))
 82         /*
 83          * Undefined/reserved opcodes, conditional jump, Opcode Extension
 84          * Groups, and some special opcodes can not boost.
 85          * This is non-const and volatile to keep gcc from statically
 86          * optimizing it out, as variable_test_bit makes gcc think only
 87          * *(unsigned long*) is used.
 88          */
 89 static volatile u32 twobyte_is_boostable[256 / 32] = {
 90         /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
 91         /*      ----------------------------------------------          */
 92         W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
 93         W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
 94         W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
 95         W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
 96         W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
 97         W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
 98         W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
 99         W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
100         W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
101         W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
102         W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
103         W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
104         W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
105         W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
106         W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
107         W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0)   /* f0 */
108         /*      -----------------------------------------------         */
109         /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
110 };
111 #undef W
112 
113 struct kretprobe_blackpoint kretprobe_blacklist[] = {
114         {"__switch_to", }, /* This function switches only current task, but
115                               doesn't switch kernel stack.*/
116         {NULL, NULL}    /* Terminator */
117 };
118 
119 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
120 
121 static nokprobe_inline void
122 __synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
123 {
124         struct __arch_relative_insn {
125                 u8 op;
126                 s32 raddr;
127         } __packed *insn;
128 
129         insn = (struct __arch_relative_insn *)dest;
130         insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
131         insn->op = op;
132 }
133 
134 /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
135 void synthesize_reljump(void *dest, void *from, void *to)
136 {
137         __synthesize_relative_insn(dest, from, to, RELATIVEJUMP_OPCODE);
138 }
139 NOKPROBE_SYMBOL(synthesize_reljump);
140 
141 /* Insert a call instruction at address 'from', which calls address 'to'.*/
142 void synthesize_relcall(void *dest, void *from, void *to)
143 {
144         __synthesize_relative_insn(dest, from, to, RELATIVECALL_OPCODE);
145 }
146 NOKPROBE_SYMBOL(synthesize_relcall);
147 
148 /*
149  * Skip the prefixes of the instruction.
150  */
151 static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn)
152 {
153         insn_attr_t attr;
154 
155         attr = inat_get_opcode_attribute((insn_byte_t)*insn);
156         while (inat_is_legacy_prefix(attr)) {
157                 insn++;
158                 attr = inat_get_opcode_attribute((insn_byte_t)*insn);
159         }
160 #ifdef CONFIG_X86_64
161         if (inat_is_rex_prefix(attr))
162                 insn++;
163 #endif
164         return insn;
165 }
166 NOKPROBE_SYMBOL(skip_prefixes);
167 
168 /*
169  * Returns non-zero if INSN is boostable.
170  * RIP relative instructions are adjusted at copying time in 64 bits mode
171  */
172 int can_boost(struct insn *insn, void *addr)
173 {
174         kprobe_opcode_t opcode;
175 
176         if (search_exception_tables((unsigned long)addr))
177                 return 0;       /* Page fault may occur on this address. */
178 
179         /* 2nd-byte opcode */
180         if (insn->opcode.nbytes == 2)
181                 return test_bit(insn->opcode.bytes[1],
182                                 (unsigned long *)twobyte_is_boostable);
183 
184         if (insn->opcode.nbytes != 1)
185                 return 0;
186 
187         /* Can't boost Address-size override prefix */
188         if (unlikely(inat_is_address_size_prefix(insn->attr)))
189                 return 0;
190 
191         opcode = insn->opcode.bytes[0];
192 
193         switch (opcode & 0xf0) {
194         case 0x60:
195                 /* can't boost "bound" */
196                 return (opcode != 0x62);
197         case 0x70:
198                 return 0; /* can't boost conditional jump */
199         case 0x90:
200                 return opcode != 0x9a;  /* can't boost call far */
201         case 0xc0:
202                 /* can't boost software-interruptions */
203                 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
204         case 0xd0:
205                 /* can boost AA* and XLAT */
206                 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
207         case 0xe0:
208                 /* can boost in/out and absolute jmps */
209                 return ((opcode & 0x04) || opcode == 0xea);
210         case 0xf0:
211                 /* clear and set flags are boostable */
212                 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
213         default:
214                 /* CS override prefix and call are not boostable */
215                 return (opcode != 0x2e && opcode != 0x9a);
216         }
217 }
218 
219 static unsigned long
220 __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
221 {
222         struct kprobe *kp;
223         unsigned long faddr;
224 
225         kp = get_kprobe((void *)addr);
226         faddr = ftrace_location(addr);
227         /*
228          * Addresses inside the ftrace location are refused by
229          * arch_check_ftrace_location(). Something went terribly wrong
230          * if such an address is checked here.
231          */
232         if (WARN_ON(faddr && faddr != addr))
233                 return 0UL;
234         /*
235          * Use the current code if it is not modified by Kprobe
236          * and it cannot be modified by ftrace.
237          */
238         if (!kp && !faddr)
239                 return addr;
240 
241         /*
242          * Basically, kp->ainsn.insn has an original instruction.
243          * However, RIP-relative instruction can not do single-stepping
244          * at different place, __copy_instruction() tweaks the displacement of
245          * that instruction. In that case, we can't recover the instruction
246          * from the kp->ainsn.insn.
247          *
248          * On the other hand, in case on normal Kprobe, kp->opcode has a copy
249          * of the first byte of the probed instruction, which is overwritten
250          * by int3. And the instruction at kp->addr is not modified by kprobes
251          * except for the first byte, we can recover the original instruction
252          * from it and kp->opcode.
253          *
254          * In case of Kprobes using ftrace, we do not have a copy of
255          * the original instruction. In fact, the ftrace location might
256          * be modified at anytime and even could be in an inconsistent state.
257          * Fortunately, we know that the original code is the ideal 5-byte
258          * long NOP.
259          */
260         if (probe_kernel_read(buf, (void *)addr,
261                 MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
262                 return 0UL;
263 
264         if (faddr)
265                 memcpy(buf, ideal_nops[NOP_ATOMIC5], 5);
266         else
267                 buf[0] = kp->opcode;
268         return (unsigned long)buf;
269 }
270 
271 /*
272  * Recover the probed instruction at addr for further analysis.
273  * Caller must lock kprobes by kprobe_mutex, or disable preemption
274  * for preventing to release referencing kprobes.
275  * Returns zero if the instruction can not get recovered (or access failed).
276  */
277 unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
278 {
279         unsigned long __addr;
280 
281         __addr = __recover_optprobed_insn(buf, addr);
282         if (__addr != addr)
283                 return __addr;
284 
285         return __recover_probed_insn(buf, addr);
286 }
287 
288 /* Check if paddr is at an instruction boundary */
289 static int can_probe(unsigned long paddr)
290 {
291         unsigned long addr, __addr, offset = 0;
292         struct insn insn;
293         kprobe_opcode_t buf[MAX_INSN_SIZE];
294 
295         if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
296                 return 0;
297 
298         /* Decode instructions */
299         addr = paddr - offset;
300         while (addr < paddr) {
301                 /*
302                  * Check if the instruction has been modified by another
303                  * kprobe, in which case we replace the breakpoint by the
304                  * original instruction in our buffer.
305                  * Also, jump optimization will change the breakpoint to
306                  * relative-jump. Since the relative-jump itself is
307                  * normally used, we just go through if there is no kprobe.
308                  */
309                 __addr = recover_probed_instruction(buf, addr);
310                 if (!__addr)
311                         return 0;
312                 kernel_insn_init(&insn, (void *)__addr, MAX_INSN_SIZE);
313                 insn_get_length(&insn);
314 
315                 /*
316                  * Another debugging subsystem might insert this breakpoint.
317                  * In that case, we can't recover it.
318                  */
319                 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
320                         return 0;
321                 addr += insn.length;
322         }
323 
324         return (addr == paddr);
325 }
326 
327 /*
328  * Returns non-zero if opcode modifies the interrupt flag.
329  */
330 static int is_IF_modifier(kprobe_opcode_t *insn)
331 {
332         /* Skip prefixes */
333         insn = skip_prefixes(insn);
334 
335         switch (*insn) {
336         case 0xfa:              /* cli */
337         case 0xfb:              /* sti */
338         case 0xcf:              /* iret/iretd */
339         case 0x9d:              /* popf/popfd */
340                 return 1;
341         }
342 
343         return 0;
344 }
345 
346 /*
347  * Copy an instruction with recovering modified instruction by kprobes
348  * and adjust the displacement if the instruction uses the %rip-relative
349  * addressing mode. Note that since @real will be the final place of copied
350  * instruction, displacement must be adjust by @real, not @dest.
351  * This returns the length of copied instruction, or 0 if it has an error.
352  */
353 int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
354 {
355         kprobe_opcode_t buf[MAX_INSN_SIZE];
356         unsigned long recovered_insn =
357                 recover_probed_instruction(buf, (unsigned long)src);
358 
359         if (!recovered_insn || !insn)
360                 return 0;
361 
362         /* This can access kernel text if given address is not recovered */
363         if (probe_kernel_read(dest, (void *)recovered_insn, MAX_INSN_SIZE))
364                 return 0;
365 
366         kernel_insn_init(insn, dest, MAX_INSN_SIZE);
367         insn_get_length(insn);
368 
369         /* Another subsystem puts a breakpoint, failed to recover */
370         if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
371                 return 0;
372 
373 #ifdef CONFIG_X86_64
374         /* Only x86_64 has RIP relative instructions */
375         if (insn_rip_relative(insn)) {
376                 s64 newdisp;
377                 u8 *disp;
378                 /*
379                  * The copied instruction uses the %rip-relative addressing
380                  * mode.  Adjust the displacement for the difference between
381                  * the original location of this instruction and the location
382                  * of the copy that will actually be run.  The tricky bit here
383                  * is making sure that the sign extension happens correctly in
384                  * this calculation, since we need a signed 32-bit result to
385                  * be sign-extended to 64 bits when it's added to the %rip
386                  * value and yield the same 64-bit result that the sign-
387                  * extension of the original signed 32-bit displacement would
388                  * have given.
389                  */
390                 newdisp = (u8 *) src + (s64) insn->displacement.value
391                           - (u8 *) real;
392                 if ((s64) (s32) newdisp != newdisp) {
393                         pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
394                         pr_err("\tSrc: %p, Dest: %p, old disp: %x\n",
395                                 src, real, insn->displacement.value);
396                         return 0;
397                 }
398                 disp = (u8 *) dest + insn_offset_displacement(insn);
399                 *(s32 *) disp = (s32) newdisp;
400         }
401 #endif
402         return insn->length;
403 }
404 
405 /* Prepare reljump right after instruction to boost */
406 static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p,
407                           struct insn *insn)
408 {
409         int len = insn->length;
410 
411         if (can_boost(insn, p->addr) &&
412             MAX_INSN_SIZE - len >= RELATIVEJUMP_SIZE) {
413                 /*
414                  * These instructions can be executed directly if it
415                  * jumps back to correct address.
416                  */
417                 synthesize_reljump(buf + len, p->ainsn.insn + len,
418                                    p->addr + insn->length);
419                 len += RELATIVEJUMP_SIZE;
420                 p->ainsn.boostable = true;
421         } else {
422                 p->ainsn.boostable = false;
423         }
424 
425         return len;
426 }
427 
428 /* Make page to RO mode when allocate it */
429 void *alloc_insn_page(void)
430 {
431         void *page;
432 
433         page = module_alloc(PAGE_SIZE);
434         if (page)
435                 set_memory_ro((unsigned long)page & PAGE_MASK, 1);
436 
437         return page;
438 }
439 
440 /* Recover page to RW mode before releasing it */
441 void free_insn_page(void *page)
442 {
443         set_memory_nx((unsigned long)page & PAGE_MASK, 1);
444         set_memory_rw((unsigned long)page & PAGE_MASK, 1);
445         module_memfree(page);
446 }
447 
448 static int arch_copy_kprobe(struct kprobe *p)
449 {
450         struct insn insn;
451         kprobe_opcode_t buf[MAX_INSN_SIZE];
452         int len;
453 
454         /* Copy an instruction with recovering if other optprobe modifies it.*/
455         len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
456         if (!len)
457                 return -EINVAL;
458 
459         /*
460          * __copy_instruction can modify the displacement of the instruction,
461          * but it doesn't affect boostable check.
462          */
463         len = prepare_boost(buf, p, &insn);
464 
465         /* Check whether the instruction modifies Interrupt Flag or not */
466         p->ainsn.if_modifier = is_IF_modifier(buf);
467 
468         /* Also, displacement change doesn't affect the first byte */
469         p->opcode = buf[0];
470 
471         /* OK, write back the instruction(s) into ROX insn buffer */
472         text_poke(p->ainsn.insn, buf, len);
473 
474         return 0;
475 }
476 
477 int arch_prepare_kprobe(struct kprobe *p)
478 {
479         int ret;
480 
481         if (alternatives_text_reserved(p->addr, p->addr))
482                 return -EINVAL;
483 
484         if (!can_probe((unsigned long)p->addr))
485                 return -EILSEQ;
486         /* insn: must be on special executable page on x86. */
487         p->ainsn.insn = get_insn_slot();
488         if (!p->ainsn.insn)
489                 return -ENOMEM;
490 
491         ret = arch_copy_kprobe(p);
492         if (ret) {
493                 free_insn_slot(p->ainsn.insn, 0);
494                 p->ainsn.insn = NULL;
495         }
496 
497         return ret;
498 }
499 
500 void arch_arm_kprobe(struct kprobe *p)
501 {
502         text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
503 }
504 
505 void arch_disarm_kprobe(struct kprobe *p)
506 {
507         text_poke(p->addr, &p->opcode, 1);
508 }
509 
510 void arch_remove_kprobe(struct kprobe *p)
511 {
512         if (p->ainsn.insn) {
513                 free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
514                 p->ainsn.insn = NULL;
515         }
516 }
517 
518 static nokprobe_inline void
519 save_previous_kprobe(struct kprobe_ctlblk *kcb)
520 {
521         kcb->prev_kprobe.kp = kprobe_running();
522         kcb->prev_kprobe.status = kcb->kprobe_status;
523         kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
524         kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
525 }
526 
527 static nokprobe_inline void
528 restore_previous_kprobe(struct kprobe_ctlblk *kcb)
529 {
530         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
531         kcb->kprobe_status = kcb->prev_kprobe.status;
532         kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
533         kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
534 }
535 
536 static nokprobe_inline void
537 set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
538                    struct kprobe_ctlblk *kcb)
539 {
540         __this_cpu_write(current_kprobe, p);
541         kcb->kprobe_saved_flags = kcb->kprobe_old_flags
542                 = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
543         if (p->ainsn.if_modifier)
544                 kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
545 }
546 
547 static nokprobe_inline void clear_btf(void)
548 {
549         if (test_thread_flag(TIF_BLOCKSTEP)) {
550                 unsigned long debugctl = get_debugctlmsr();
551 
552                 debugctl &= ~DEBUGCTLMSR_BTF;
553                 update_debugctlmsr(debugctl);
554         }
555 }
556 
557 static nokprobe_inline void restore_btf(void)
558 {
559         if (test_thread_flag(TIF_BLOCKSTEP)) {
560                 unsigned long debugctl = get_debugctlmsr();
561 
562                 debugctl |= DEBUGCTLMSR_BTF;
563                 update_debugctlmsr(debugctl);
564         }
565 }
566 
567 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
568 {
569         unsigned long *sara = stack_addr(regs);
570 
571         ri->ret_addr = (kprobe_opcode_t *) *sara;
572 
573         /* Replace the return addr with trampoline addr */
574         *sara = (unsigned long) &kretprobe_trampoline;
575 }
576 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
577 
578 static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
579                              struct kprobe_ctlblk *kcb, int reenter)
580 {
581         if (setup_detour_execution(p, regs, reenter))
582                 return;
583 
584 #if !defined(CONFIG_PREEMPT)
585         if (p->ainsn.boostable && !p->post_handler) {
586                 /* Boost up -- we can execute copied instructions directly */
587                 if (!reenter)
588                         reset_current_kprobe();
589                 /*
590                  * Reentering boosted probe doesn't reset current_kprobe,
591                  * nor set current_kprobe, because it doesn't use single
592                  * stepping.
593                  */
594                 regs->ip = (unsigned long)p->ainsn.insn;
595                 preempt_enable_no_resched();
596                 return;
597         }
598 #endif
599         if (reenter) {
600                 save_previous_kprobe(kcb);
601                 set_current_kprobe(p, regs, kcb);
602                 kcb->kprobe_status = KPROBE_REENTER;
603         } else
604                 kcb->kprobe_status = KPROBE_HIT_SS;
605         /* Prepare real single stepping */
606         clear_btf();
607         regs->flags |= X86_EFLAGS_TF;
608         regs->flags &= ~X86_EFLAGS_IF;
609         /* single step inline if the instruction is an int3 */
610         if (p->opcode == BREAKPOINT_INSTRUCTION)
611                 regs->ip = (unsigned long)p->addr;
612         else
613                 regs->ip = (unsigned long)p->ainsn.insn;
614 }
615 NOKPROBE_SYMBOL(setup_singlestep);
616 
617 /*
618  * We have reentered the kprobe_handler(), since another probe was hit while
619  * within the handler. We save the original kprobes variables and just single
620  * step on the instruction of the new probe without calling any user handlers.
621  */
622 static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
623                           struct kprobe_ctlblk *kcb)
624 {
625         switch (kcb->kprobe_status) {
626         case KPROBE_HIT_SSDONE:
627         case KPROBE_HIT_ACTIVE:
628         case KPROBE_HIT_SS:
629                 kprobes_inc_nmissed_count(p);
630                 setup_singlestep(p, regs, kcb, 1);
631                 break;
632         case KPROBE_REENTER:
633                 /* A probe has been hit in the codepath leading up to, or just
634                  * after, single-stepping of a probed instruction. This entire
635                  * codepath should strictly reside in .kprobes.text section.
636                  * Raise a BUG or we'll continue in an endless reentering loop
637                  * and eventually a stack overflow.
638                  */
639                 printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n",
640                        p->addr);
641                 dump_kprobe(p);
642                 BUG();
643         default:
644                 /* impossible cases */
645                 WARN_ON(1);
646                 return 0;
647         }
648 
649         return 1;
650 }
651 NOKPROBE_SYMBOL(reenter_kprobe);
652 
653 /*
654  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
655  * remain disabled throughout this function.
656  */
657 int kprobe_int3_handler(struct pt_regs *regs)
658 {
659         kprobe_opcode_t *addr;
660         struct kprobe *p;
661         struct kprobe_ctlblk *kcb;
662 
663         if (user_mode(regs))
664                 return 0;
665 
666         addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
667         /*
668          * We don't want to be preempted for the entire
669          * duration of kprobe processing. We conditionally
670          * re-enable preemption at the end of this function,
671          * and also in reenter_kprobe() and setup_singlestep().
672          */
673         preempt_disable();
674 
675         kcb = get_kprobe_ctlblk();
676         p = get_kprobe(addr);
677 
678         if (p) {
679                 if (kprobe_running()) {
680                         if (reenter_kprobe(p, regs, kcb))
681                                 return 1;
682                 } else {
683                         set_current_kprobe(p, regs, kcb);
684                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
685 
686                         /*
687                          * If we have no pre-handler or it returned 0, we
688                          * continue with normal processing.  If we have a
689                          * pre-handler and it returned non-zero, it prepped
690                          * for calling the break_handler below on re-entry
691                          * for jprobe processing, so get out doing nothing
692                          * more here.
693                          */
694                         if (!p->pre_handler || !p->pre_handler(p, regs))
695                                 setup_singlestep(p, regs, kcb, 0);
696                         return 1;
697                 }
698         } else if (*addr != BREAKPOINT_INSTRUCTION) {
699                 /*
700                  * The breakpoint instruction was removed right
701                  * after we hit it.  Another cpu has removed
702                  * either a probepoint or a debugger breakpoint
703                  * at this address.  In either case, no further
704                  * handling of this interrupt is appropriate.
705                  * Back up over the (now missing) int3 and run
706                  * the original instruction.
707                  */
708                 regs->ip = (unsigned long)addr;
709                 preempt_enable_no_resched();
710                 return 1;
711         } else if (kprobe_running()) {
712                 p = __this_cpu_read(current_kprobe);
713                 if (p->break_handler && p->break_handler(p, regs)) {
714                         if (!skip_singlestep(p, regs, kcb))
715                                 setup_singlestep(p, regs, kcb, 0);
716                         return 1;
717                 }
718         } /* else: not a kprobe fault; let the kernel handle it */
719 
720         preempt_enable_no_resched();
721         return 0;
722 }
723 NOKPROBE_SYMBOL(kprobe_int3_handler);
724 
725 /*
726  * When a retprobed function returns, this code saves registers and
727  * calls trampoline_handler() runs, which calls the kretprobe's handler.
728  */
729 asm(
730         ".global kretprobe_trampoline\n"
731         ".type kretprobe_trampoline, @function\n"
732         "kretprobe_trampoline:\n"
733 #ifdef CONFIG_X86_64
734         /* We don't bother saving the ss register */
735         "       pushq %rsp\n"
736         "       pushfq\n"
737         SAVE_REGS_STRING
738         "       movq %rsp, %rdi\n"
739         "       call trampoline_handler\n"
740         /* Replace saved sp with true return address. */
741         "       movq %rax, 152(%rsp)\n"
742         RESTORE_REGS_STRING
743         "       popfq\n"
744 #else
745         "       pushf\n"
746         SAVE_REGS_STRING
747         "       movl %esp, %eax\n"
748         "       call trampoline_handler\n"
749         /* Move flags to cs */
750         "       movl 56(%esp), %edx\n"
751         "       movl %edx, 52(%esp)\n"
752         /* Replace saved flags with true return address. */
753         "       movl %eax, 56(%esp)\n"
754         RESTORE_REGS_STRING
755         "       popf\n"
756 #endif
757         "       ret\n"
758         ".size kretprobe_trampoline, .-kretprobe_trampoline\n"
759 );
760 NOKPROBE_SYMBOL(kretprobe_trampoline);
761 STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
762 
763 /*
764  * Called from kretprobe_trampoline
765  */
766 __visible __used void *trampoline_handler(struct pt_regs *regs)
767 {
768         struct kretprobe_instance *ri = NULL;
769         struct hlist_head *head, empty_rp;
770         struct hlist_node *tmp;
771         unsigned long flags, orig_ret_address = 0;
772         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
773         kprobe_opcode_t *correct_ret_addr = NULL;
774 
775         INIT_HLIST_HEAD(&empty_rp);
776         kretprobe_hash_lock(current, &head, &flags);
777         /* fixup registers */
778 #ifdef CONFIG_X86_64
779         regs->cs = __KERNEL_CS;
780 #else
781         regs->cs = __KERNEL_CS | get_kernel_rpl();
782         regs->gs = 0;
783 #endif
784         regs->ip = trampoline_address;
785         regs->orig_ax = ~0UL;
786 
787         /*
788          * It is possible to have multiple instances associated with a given
789          * task either because multiple functions in the call path have
790          * return probes installed on them, and/or more than one
791          * return probe was registered for a target function.
792          *
793          * We can handle this because:
794          *     - instances are always pushed into the head of the list
795          *     - when multiple return probes are registered for the same
796          *       function, the (chronologically) first instance's ret_addr
797          *       will be the real return address, and all the rest will
798          *       point to kretprobe_trampoline.
799          */
800         hlist_for_each_entry(ri, head, hlist) {
801                 if (ri->task != current)
802                         /* another task is sharing our hash bucket */
803                         continue;
804 
805                 orig_ret_address = (unsigned long)ri->ret_addr;
806 
807                 if (orig_ret_address != trampoline_address)
808                         /*
809                          * This is the real return address. Any other
810                          * instances associated with this task are for
811                          * other calls deeper on the call stack
812                          */
813                         break;
814         }
815 
816         kretprobe_assert(ri, orig_ret_address, trampoline_address);
817 
818         correct_ret_addr = ri->ret_addr;
819         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
820                 if (ri->task != current)
821                         /* another task is sharing our hash bucket */
822                         continue;
823 
824                 orig_ret_address = (unsigned long)ri->ret_addr;
825                 if (ri->rp && ri->rp->handler) {
826                         __this_cpu_write(current_kprobe, &ri->rp->kp);
827                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
828                         ri->ret_addr = correct_ret_addr;
829                         ri->rp->handler(ri, regs);
830                         __this_cpu_write(current_kprobe, NULL);
831                 }
832 
833                 recycle_rp_inst(ri, &empty_rp);
834 
835                 if (orig_ret_address != trampoline_address)
836                         /*
837                          * This is the real return address. Any other
838                          * instances associated with this task are for
839                          * other calls deeper on the call stack
840                          */
841                         break;
842         }
843 
844         kretprobe_hash_unlock(current, &flags);
845 
846         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
847                 hlist_del(&ri->hlist);
848                 kfree(ri);
849         }
850         return (void *)orig_ret_address;
851 }
852 NOKPROBE_SYMBOL(trampoline_handler);
853 
854 /*
855  * Called after single-stepping.  p->addr is the address of the
856  * instruction whose first byte has been replaced by the "int 3"
857  * instruction.  To avoid the SMP problems that can occur when we
858  * temporarily put back the original opcode to single-step, we
859  * single-stepped a copy of the instruction.  The address of this
860  * copy is p->ainsn.insn.
861  *
862  * This function prepares to return from the post-single-step
863  * interrupt.  We have to fix up the stack as follows:
864  *
865  * 0) Except in the case of absolute or indirect jump or call instructions,
866  * the new ip is relative to the copied instruction.  We need to make
867  * it relative to the original instruction.
868  *
869  * 1) If the single-stepped instruction was pushfl, then the TF and IF
870  * flags are set in the just-pushed flags, and may need to be cleared.
871  *
872  * 2) If the single-stepped instruction was a call, the return address
873  * that is atop the stack is the address following the copied instruction.
874  * We need to make it the address following the original instruction.
875  *
876  * If this is the first time we've single-stepped the instruction at
877  * this probepoint, and the instruction is boostable, boost it: add a
878  * jump instruction after the copied instruction, that jumps to the next
879  * instruction after the probepoint.
880  */
881 static void resume_execution(struct kprobe *p, struct pt_regs *regs,
882                              struct kprobe_ctlblk *kcb)
883 {
884         unsigned long *tos = stack_addr(regs);
885         unsigned long copy_ip = (unsigned long)p->ainsn.insn;
886         unsigned long orig_ip = (unsigned long)p->addr;
887         kprobe_opcode_t *insn = p->ainsn.insn;
888 
889         /* Skip prefixes */
890         insn = skip_prefixes(insn);
891 
892         regs->flags &= ~X86_EFLAGS_TF;
893         switch (*insn) {
894         case 0x9c:      /* pushfl */
895                 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
896                 *tos |= kcb->kprobe_old_flags;
897                 break;
898         case 0xc2:      /* iret/ret/lret */
899         case 0xc3:
900         case 0xca:
901         case 0xcb:
902         case 0xcf:
903         case 0xea:      /* jmp absolute -- ip is correct */
904                 /* ip is already adjusted, no more changes required */
905                 p->ainsn.boostable = true;
906                 goto no_change;
907         case 0xe8:      /* call relative - Fix return addr */
908                 *tos = orig_ip + (*tos - copy_ip);
909                 break;
910 #ifdef CONFIG_X86_32
911         case 0x9a:      /* call absolute -- same as call absolute, indirect */
912                 *tos = orig_ip + (*tos - copy_ip);
913                 goto no_change;
914 #endif
915         case 0xff:
916                 if ((insn[1] & 0x30) == 0x10) {
917                         /*
918                          * call absolute, indirect
919                          * Fix return addr; ip is correct.
920                          * But this is not boostable
921                          */
922                         *tos = orig_ip + (*tos - copy_ip);
923                         goto no_change;
924                 } else if (((insn[1] & 0x31) == 0x20) ||
925                            ((insn[1] & 0x31) == 0x21)) {
926                         /*
927                          * jmp near and far, absolute indirect
928                          * ip is correct. And this is boostable
929                          */
930                         p->ainsn.boostable = true;
931                         goto no_change;
932                 }
933         default:
934                 break;
935         }
936 
937         regs->ip += orig_ip - copy_ip;
938 
939 no_change:
940         restore_btf();
941 }
942 NOKPROBE_SYMBOL(resume_execution);
943 
944 /*
945  * Interrupts are disabled on entry as trap1 is an interrupt gate and they
946  * remain disabled throughout this function.
947  */
948 int kprobe_debug_handler(struct pt_regs *regs)
949 {
950         struct kprobe *cur = kprobe_running();
951         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
952 
953         if (!cur)
954                 return 0;
955 
956         resume_execution(cur, regs, kcb);
957         regs->flags |= kcb->kprobe_saved_flags;
958 
959         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
960                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
961                 cur->post_handler(cur, regs, 0);
962         }
963 
964         /* Restore back the original saved kprobes variables and continue. */
965         if (kcb->kprobe_status == KPROBE_REENTER) {
966                 restore_previous_kprobe(kcb);
967                 goto out;
968         }
969         reset_current_kprobe();
970 out:
971         preempt_enable_no_resched();
972 
973         /*
974          * if somebody else is singlestepping across a probe point, flags
975          * will have TF set, in which case, continue the remaining processing
976          * of do_debug, as if this is not a probe hit.
977          */
978         if (regs->flags & X86_EFLAGS_TF)
979                 return 0;
980 
981         return 1;
982 }
983 NOKPROBE_SYMBOL(kprobe_debug_handler);
984 
985 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
986 {
987         struct kprobe *cur = kprobe_running();
988         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
989 
990         if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
991                 /* This must happen on single-stepping */
992                 WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
993                         kcb->kprobe_status != KPROBE_REENTER);
994                 /*
995                  * We are here because the instruction being single
996                  * stepped caused a page fault. We reset the current
997                  * kprobe and the ip points back to the probe address
998                  * and allow the page fault handler to continue as a
999                  * normal page fault.
1000                  */
1001                 regs->ip = (unsigned long)cur->addr;
1002                 /*
1003                  * Trap flag (TF) has been set here because this fault
1004                  * happened where the single stepping will be done.
1005                  * So clear it by resetting the current kprobe:
1006                  */
1007                 regs->flags &= ~X86_EFLAGS_TF;
1008 
1009                 /*
1010                  * If the TF flag was set before the kprobe hit,
1011                  * don't touch it:
1012                  */
1013                 regs->flags |= kcb->kprobe_old_flags;
1014 
1015                 if (kcb->kprobe_status == KPROBE_REENTER)
1016                         restore_previous_kprobe(kcb);
1017                 else
1018                         reset_current_kprobe();
1019                 preempt_enable_no_resched();
1020         } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE ||
1021                    kcb->kprobe_status == KPROBE_HIT_SSDONE) {
1022                 /*
1023                  * We increment the nmissed count for accounting,
1024                  * we can also use npre/npostfault count for accounting
1025                  * these specific fault cases.
1026                  */
1027                 kprobes_inc_nmissed_count(cur);
1028 
1029                 /*
1030                  * We come here because instructions in the pre/post
1031                  * handler caused the page_fault, this could happen
1032                  * if handler tries to access user space by
1033                  * copy_from_user(), get_user() etc. Let the
1034                  * user-specified handler try to fix it first.
1035                  */
1036                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
1037                         return 1;
1038 
1039                 /*
1040                  * In case the user-specified fault handler returned
1041                  * zero, try to fix up.
1042                  */
1043                 if (fixup_exception(regs, trapnr))
1044                         return 1;
1045 
1046                 /*
1047                  * fixup routine could not handle it,
1048                  * Let do_page_fault() fix it.
1049                  */
1050         }
1051 
1052         return 0;
1053 }
1054 NOKPROBE_SYMBOL(kprobe_fault_handler);
1055 
1056 /*
1057  * Wrapper routine for handling exceptions.
1058  */
1059 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
1060                              void *data)
1061 {
1062         struct die_args *args = data;
1063         int ret = NOTIFY_DONE;
1064 
1065         if (args->regs && user_mode(args->regs))
1066                 return ret;
1067 
1068         if (val == DIE_GPF) {
1069                 /*
1070                  * To be potentially processing a kprobe fault and to
1071                  * trust the result from kprobe_running(), we have
1072                  * be non-preemptible.
1073                  */
1074                 if (!preemptible() && kprobe_running() &&
1075                     kprobe_fault_handler(args->regs, args->trapnr))
1076                         ret = NOTIFY_STOP;
1077         }
1078         return ret;
1079 }
1080 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
1081 
1082 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
1083 {
1084         struct jprobe *jp = container_of(p, struct jprobe, kp);
1085         unsigned long addr;
1086         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1087 
1088         kcb->jprobe_saved_regs = *regs;
1089         kcb->jprobe_saved_sp = stack_addr(regs);
1090         addr = (unsigned long)(kcb->jprobe_saved_sp);
1091 
1092         /*
1093          * As Linus pointed out, gcc assumes that the callee
1094          * owns the argument space and could overwrite it, e.g.
1095          * tailcall optimization. So, to be absolutely safe
1096          * we also save and restore enough stack bytes to cover
1097          * the argument area.
1098          * Use __memcpy() to avoid KASAN stack out-of-bounds reports as we copy
1099          * raw stack chunk with redzones:
1100          */
1101         __memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, MIN_STACK_SIZE(addr));
1102         regs->ip = (unsigned long)(jp->entry);
1103 
1104         /*
1105          * jprobes use jprobe_return() which skips the normal return
1106          * path of the function, and this messes up the accounting of the
1107          * function graph tracer to get messed up.
1108          *
1109          * Pause function graph tracing while performing the jprobe function.
1110          */
1111         pause_graph_tracing();
1112         return 1;
1113 }
1114 NOKPROBE_SYMBOL(setjmp_pre_handler);
1115 
1116 void jprobe_return(void)
1117 {
1118         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1119 
1120         /* Unpoison stack redzones in the frames we are going to jump over. */
1121         kasan_unpoison_stack_above_sp_to(kcb->jprobe_saved_sp);
1122 
1123         asm volatile (
1124 #ifdef CONFIG_X86_64
1125                         "       xchg   %%rbx,%%rsp      \n"
1126 #else
1127                         "       xchgl   %%ebx,%%esp     \n"
1128 #endif
1129                         "       int3                    \n"
1130                         "       .globl jprobe_return_end\n"
1131                         "       jprobe_return_end:      \n"
1132                         "       nop                     \n"::"b"
1133                         (kcb->jprobe_saved_sp):"memory");
1134 }
1135 NOKPROBE_SYMBOL(jprobe_return);
1136 NOKPROBE_SYMBOL(jprobe_return_end);
1137 
1138 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
1139 {
1140         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1141         u8 *addr = (u8 *) (regs->ip - 1);
1142         struct jprobe *jp = container_of(p, struct jprobe, kp);
1143         void *saved_sp = kcb->jprobe_saved_sp;
1144 
1145         if ((addr > (u8 *) jprobe_return) &&
1146             (addr < (u8 *) jprobe_return_end)) {
1147                 if (stack_addr(regs) != saved_sp) {
1148                         struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
1149                         printk(KERN_ERR
1150                                "current sp %p does not match saved sp %p\n",
1151                                stack_addr(regs), saved_sp);
1152                         printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
1153                         show_regs(saved_regs);
1154                         printk(KERN_ERR "Current registers\n");
1155                         show_regs(regs);
1156                         BUG();
1157                 }
1158                 /* It's OK to start function graph tracing again */
1159                 unpause_graph_tracing();
1160                 *regs = kcb->jprobe_saved_regs;
1161                 __memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp));
1162                 preempt_enable_no_resched();
1163                 return 1;
1164         }
1165         return 0;
1166 }
1167 NOKPROBE_SYMBOL(longjmp_break_handler);
1168 
1169 bool arch_within_kprobe_blacklist(unsigned long addr)
1170 {
1171         bool is_in_entry_trampoline_section = false;
1172 
1173 #ifdef CONFIG_X86_64
1174         is_in_entry_trampoline_section =
1175                 (addr >= (unsigned long)__entry_trampoline_start &&
1176                  addr < (unsigned long)__entry_trampoline_end);
1177 #endif
1178         return  (addr >= (unsigned long)__kprobes_text_start &&
1179                  addr < (unsigned long)__kprobes_text_end) ||
1180                 (addr >= (unsigned long)__entry_text_start &&
1181                  addr < (unsigned long)__entry_text_end) ||
1182                 is_in_entry_trampoline_section;
1183 }
1184 
1185 int __init arch_init_kprobes(void)
1186 {
1187         return 0;
1188 }
1189 
1190 int arch_trampoline_kprobe(struct kprobe *p)
1191 {
1192         return 0;
1193 }
1194 

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