Remove obsolete #include <linux/config.h>
[linux-3.10.git] / arch / sparc64 / kernel / kprobes.c
1 /* arch/sparc64/kernel/kprobes.c
2  *
3  * Copyright (C) 2004 David S. Miller <davem@davemloft.net>
4  */
5
6 #include <linux/kernel.h>
7 #include <linux/kprobes.h>
8 #include <linux/module.h>
9 #include <asm/kdebug.h>
10 #include <asm/signal.h>
11 #include <asm/cacheflush.h>
12 #include <asm/uaccess.h>
13
14 /* We do not have hardware single-stepping on sparc64.
15  * So we implement software single-stepping with breakpoint
16  * traps.  The top-level scheme is similar to that used
17  * in the x86 kprobes implementation.
18  *
19  * In the kprobe->ainsn.insn[] array we store the original
20  * instruction at index zero and a break instruction at
21  * index one.
22  *
23  * When we hit a kprobe we:
24  * - Run the pre-handler
25  * - Remember "regs->tnpc" and interrupt level stored in
26  *   "regs->tstate" so we can restore them later
27  * - Disable PIL interrupts
28  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
29  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
30  * - Mark that we are actively in a kprobe
31  *
32  * At this point we wait for the second breakpoint at
33  * kprobe->ainsn.insn[1] to hit.  When it does we:
34  * - Run the post-handler
35  * - Set regs->tpc to "remembered" regs->tnpc stored above,
36  *   restore the PIL interrupt level in "regs->tstate" as well
37  * - Make any adjustments necessary to regs->tnpc in order
38  *   to handle relative branches correctly.  See below.
39  * - Mark that we are no longer actively in a kprobe.
40  */
41
42 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
43 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
44
45 int __kprobes arch_prepare_kprobe(struct kprobe *p)
46 {
47         p->ainsn.insn[0] = *p->addr;
48         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
49         p->opcode = *p->addr;
50         return 0;
51 }
52
53 void __kprobes arch_arm_kprobe(struct kprobe *p)
54 {
55         *p->addr = BREAKPOINT_INSTRUCTION;
56         flushi(p->addr);
57 }
58
59 void __kprobes arch_disarm_kprobe(struct kprobe *p)
60 {
61         *p->addr = p->opcode;
62         flushi(p->addr);
63 }
64
65 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
66 {
67         kcb->prev_kprobe.kp = kprobe_running();
68         kcb->prev_kprobe.status = kcb->kprobe_status;
69         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
70         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
71 }
72
73 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
74 {
75         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
76         kcb->kprobe_status = kcb->prev_kprobe.status;
77         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
78         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
79 }
80
81 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
82                                 struct kprobe_ctlblk *kcb)
83 {
84         __get_cpu_var(current_kprobe) = p;
85         kcb->kprobe_orig_tnpc = regs->tnpc;
86         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
87 }
88
89 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
90                         struct kprobe_ctlblk *kcb)
91 {
92         regs->tstate |= TSTATE_PIL;
93
94         /*single step inline, if it a breakpoint instruction*/
95         if (p->opcode == BREAKPOINT_INSTRUCTION) {
96                 regs->tpc = (unsigned long) p->addr;
97                 regs->tnpc = kcb->kprobe_orig_tnpc;
98         } else {
99                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
100                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
101         }
102 }
103
104 static int __kprobes kprobe_handler(struct pt_regs *regs)
105 {
106         struct kprobe *p;
107         void *addr = (void *) regs->tpc;
108         int ret = 0;
109         struct kprobe_ctlblk *kcb;
110
111         /*
112          * We don't want to be preempted for the entire
113          * duration of kprobe processing
114          */
115         preempt_disable();
116         kcb = get_kprobe_ctlblk();
117
118         if (kprobe_running()) {
119                 p = get_kprobe(addr);
120                 if (p) {
121                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
122                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
123                                         kcb->kprobe_orig_tstate_pil);
124                                 goto no_kprobe;
125                         }
126                         /* We have reentered the kprobe_handler(), since
127                          * another probe was hit while within the handler.
128                          * We here save the original kprobes variables and
129                          * just single step on the instruction of the new probe
130                          * without calling any user handlers.
131                          */
132                         save_previous_kprobe(kcb);
133                         set_current_kprobe(p, regs, kcb);
134                         kprobes_inc_nmissed_count(p);
135                         kcb->kprobe_status = KPROBE_REENTER;
136                         prepare_singlestep(p, regs, kcb);
137                         return 1;
138                 } else {
139                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
140                         /* The breakpoint instruction was removed by
141                          * another cpu right after we hit, no further
142                          * handling of this interrupt is appropriate
143                          */
144                                 ret = 1;
145                                 goto no_kprobe;
146                         }
147                         p = __get_cpu_var(current_kprobe);
148                         if (p->break_handler && p->break_handler(p, regs))
149                                 goto ss_probe;
150                 }
151                 goto no_kprobe;
152         }
153
154         p = get_kprobe(addr);
155         if (!p) {
156                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
157                         /*
158                          * The breakpoint instruction was removed right
159                          * after we hit it.  Another cpu has removed
160                          * either a probepoint or a debugger breakpoint
161                          * at this address.  In either case, no further
162                          * handling of this interrupt is appropriate.
163                          */
164                         ret = 1;
165                 }
166                 /* Not one of ours: let kernel handle it */
167                 goto no_kprobe;
168         }
169
170         set_current_kprobe(p, regs, kcb);
171         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
172         if (p->pre_handler && p->pre_handler(p, regs))
173                 return 1;
174
175 ss_probe:
176         prepare_singlestep(p, regs, kcb);
177         kcb->kprobe_status = KPROBE_HIT_SS;
178         return 1;
179
180 no_kprobe:
181         preempt_enable_no_resched();
182         return ret;
183 }
184
185 /* If INSN is a relative control transfer instruction,
186  * return the corrected branch destination value.
187  *
188  * The original INSN location was REAL_PC, it actually
189  * executed at PC and produced destination address NPC.
190  */
191 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
192                                                unsigned long pc,
193                                                unsigned long npc)
194 {
195         /* Branch not taken, no mods necessary.  */
196         if (npc == pc + 0x4UL)
197                 return real_pc + 0x4UL;
198
199         /* The three cases are call, branch w/prediction,
200          * and traditional branch.
201          */
202         if ((insn & 0xc0000000) == 0x40000000 ||
203             (insn & 0xc1c00000) == 0x00400000 ||
204             (insn & 0xc1c00000) == 0x00800000) {
205                 /* The instruction did all the work for us
206                  * already, just apply the offset to the correct
207                  * instruction location.
208                  */
209                 return (real_pc + (npc - pc));
210         }
211
212         return real_pc + 0x4UL;
213 }
214
215 /* If INSN is an instruction which writes it's PC location
216  * into a destination register, fix that up.
217  */
218 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
219                                   unsigned long real_pc)
220 {
221         unsigned long *slot = NULL;
222
223         /* Simplest cast is call, which always uses %o7 */
224         if ((insn & 0xc0000000) == 0x40000000) {
225                 slot = &regs->u_regs[UREG_I7];
226         }
227
228         /* Jmpl encodes the register inside of the opcode */
229         if ((insn & 0xc1f80000) == 0x81c00000) {
230                 unsigned long rd = ((insn >> 25) & 0x1f);
231
232                 if (rd <= 15) {
233                         slot = &regs->u_regs[rd];
234                 } else {
235                         /* Hard case, it goes onto the stack. */
236                         flushw_all();
237
238                         rd -= 16;
239                         slot = (unsigned long *)
240                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
241                         slot += rd;
242                 }
243         }
244         if (slot != NULL)
245                 *slot = real_pc;
246 }
247
248 /*
249  * Called after single-stepping.  p->addr is the address of the
250  * instruction whose first byte has been replaced by the breakpoint
251  * instruction.  To avoid the SMP problems that can occur when we
252  * temporarily put back the original opcode to single-step, we
253  * single-stepped a copy of the instruction.  The address of this
254  * copy is p->ainsn.insn.
255  *
256  * This function prepares to return from the post-single-step
257  * breakpoint trap.
258  */
259 static void __kprobes resume_execution(struct kprobe *p,
260                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
261 {
262         u32 insn = p->ainsn.insn[0];
263
264         regs->tpc = kcb->kprobe_orig_tnpc;
265         regs->tnpc = relbranch_fixup(insn,
266                                      (unsigned long) p->addr,
267                                      (unsigned long) &p->ainsn.insn[0],
268                                      regs->tnpc);
269         retpc_fixup(regs, insn, (unsigned long) p->addr);
270
271         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
272                         kcb->kprobe_orig_tstate_pil);
273 }
274
275 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
276 {
277         struct kprobe *cur = kprobe_running();
278         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
279
280         if (!cur)
281                 return 0;
282
283         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
284                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
285                 cur->post_handler(cur, regs, 0);
286         }
287
288         resume_execution(cur, regs, kcb);
289
290         /*Restore back the original saved kprobes variables and continue. */
291         if (kcb->kprobe_status == KPROBE_REENTER) {
292                 restore_previous_kprobe(kcb);
293                 goto out;
294         }
295         reset_current_kprobe();
296 out:
297         preempt_enable_no_resched();
298
299         return 1;
300 }
301
302 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
303 {
304         struct kprobe *cur = kprobe_running();
305         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
306         const struct exception_table_entry *entry;
307
308         switch(kcb->kprobe_status) {
309         case KPROBE_HIT_SS:
310         case KPROBE_REENTER:
311                 /*
312                  * We are here because the instruction being single
313                  * stepped caused a page fault. We reset the current
314                  * kprobe and the tpc points back to the probe address
315                  * and allow the page fault handler to continue as a
316                  * normal page fault.
317                  */
318                 regs->tpc = (unsigned long)cur->addr;
319                 regs->tnpc = kcb->kprobe_orig_tnpc;
320                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
321                                 kcb->kprobe_orig_tstate_pil);
322                 if (kcb->kprobe_status == KPROBE_REENTER)
323                         restore_previous_kprobe(kcb);
324                 else
325                         reset_current_kprobe();
326                 preempt_enable_no_resched();
327                 break;
328         case KPROBE_HIT_ACTIVE:
329         case KPROBE_HIT_SSDONE:
330                 /*
331                  * We increment the nmissed count for accounting,
332                  * we can also use npre/npostfault count for accouting
333                  * these specific fault cases.
334                  */
335                 kprobes_inc_nmissed_count(cur);
336
337                 /*
338                  * We come here because instructions in the pre/post
339                  * handler caused the page_fault, this could happen
340                  * if handler tries to access user space by
341                  * copy_from_user(), get_user() etc. Let the
342                  * user-specified handler try to fix it first.
343                  */
344                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
345                         return 1;
346
347                 /*
348                  * In case the user-specified fault handler returned
349                  * zero, try to fix up.
350                  */
351
352                 entry = search_exception_tables(regs->tpc);
353                 if (entry) {
354                         regs->tpc = entry->fixup;
355                         regs->tnpc = regs->tpc + 4;
356                         return 1;
357                 }
358
359                 /*
360                  * fixup_exception() could not handle it,
361                  * Let do_page_fault() fix it.
362                  */
363                 break;
364         default:
365                 break;
366         }
367
368         return 0;
369 }
370
371 /*
372  * Wrapper routine to for handling exceptions.
373  */
374 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
375                                        unsigned long val, void *data)
376 {
377         struct die_args *args = (struct die_args *)data;
378         int ret = NOTIFY_DONE;
379
380         if (args->regs && user_mode(args->regs))
381                 return ret;
382
383         switch (val) {
384         case DIE_DEBUG:
385                 if (kprobe_handler(args->regs))
386                         ret = NOTIFY_STOP;
387                 break;
388         case DIE_DEBUG_2:
389                 if (post_kprobe_handler(args->regs))
390                         ret = NOTIFY_STOP;
391                 break;
392         case DIE_GPF:
393         case DIE_PAGE_FAULT:
394                 /* kprobe_running() needs smp_processor_id() */
395                 preempt_disable();
396                 if (kprobe_running() &&
397                     kprobe_fault_handler(args->regs, args->trapnr))
398                         ret = NOTIFY_STOP;
399                 preempt_enable();
400                 break;
401         default:
402                 break;
403         }
404         return ret;
405 }
406
407 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
408                                       struct pt_regs *regs)
409 {
410         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
411
412         if (user_mode(regs)) {
413                 local_irq_enable();
414                 bad_trap(regs, trap_level);
415                 return;
416         }
417
418         /* trap_level == 0x170 --> ta 0x70
419          * trap_level == 0x171 --> ta 0x71
420          */
421         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
422                        (trap_level == 0x170) ? "debug" : "debug_2",
423                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
424                 bad_trap(regs, trap_level);
425 }
426
427 /* Jprobes support.  */
428 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
429 {
430         struct jprobe *jp = container_of(p, struct jprobe, kp);
431         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
432
433         kcb->jprobe_saved_regs_location = regs;
434         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
435
436         /* Save a whole stack frame, this gets arguments
437          * pushed onto the stack after using up all the
438          * arg registers.
439          */
440         memcpy(&(kcb->jprobe_saved_stack),
441                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
442                sizeof(kcb->jprobe_saved_stack));
443
444         regs->tpc  = (unsigned long) jp->entry;
445         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
446         regs->tstate |= TSTATE_PIL;
447
448         return 1;
449 }
450
451 void __kprobes jprobe_return(void)
452 {
453         __asm__ __volatile__(
454                 ".globl jprobe_return_trap_instruction\n"
455 "jprobe_return_trap_instruction:\n\t"
456                 "ta 0x70");
457 }
458
459 extern void jprobe_return_trap_instruction(void);
460
461 extern void __show_regs(struct pt_regs * regs);
462
463 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
464 {
465         u32 *addr = (u32 *) regs->tpc;
466         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
467
468         if (addr == (u32 *) jprobe_return_trap_instruction) {
469                 if (kcb->jprobe_saved_regs_location != regs) {
470                         printk("JPROBE: Current regs (%p) does not match "
471                                "saved regs (%p).\n",
472                                regs, kcb->jprobe_saved_regs_location);
473                         printk("JPROBE: Saved registers\n");
474                         __show_regs(kcb->jprobe_saved_regs_location);
475                         printk("JPROBE: Current registers\n");
476                         __show_regs(regs);
477                         BUG();
478                 }
479                 /* Restore old register state.  Do pt_regs
480                  * first so that UREG_FP is the original one for
481                  * the stack frame restore.
482                  */
483                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
484
485                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
486                        &(kcb->jprobe_saved_stack),
487                        sizeof(kcb->jprobe_saved_stack));
488
489                 preempt_enable_no_resched();
490                 return 1;
491         }
492         return 0;
493 }
494
495 /* architecture specific initialization */
496 int arch_init_kprobes(void)
497 {
498         return 0;
499 }