Pull trivial1 into release branch
[linux-2.6] / 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/config.h>
7 #include <linux/kernel.h>
8 #include <linux/kprobes.h>
9 #include <linux/module.h>
10 #include <asm/kdebug.h>
11 #include <asm/signal.h>
12 #include <asm/cacheflush.h>
13 #include <asm/uaccess.h>
14
15 /* We do not have hardware single-stepping on sparc64.
16  * So we implement software single-stepping with breakpoint
17  * traps.  The top-level scheme is similar to that used
18  * in the x86 kprobes implementation.
19  *
20  * In the kprobe->ainsn.insn[] array we store the original
21  * instruction at index zero and a break instruction at
22  * index one.
23  *
24  * When we hit a kprobe we:
25  * - Run the pre-handler
26  * - Remember "regs->tnpc" and interrupt level stored in
27  *   "regs->tstate" so we can restore them later
28  * - Disable PIL interrupts
29  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
30  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
31  * - Mark that we are actively in a kprobe
32  *
33  * At this point we wait for the second breakpoint at
34  * kprobe->ainsn.insn[1] to hit.  When it does we:
35  * - Run the post-handler
36  * - Set regs->tpc to "remembered" regs->tnpc stored above,
37  *   restore the PIL interrupt level in "regs->tstate" as well
38  * - Make any adjustments necessary to regs->tnpc in order
39  *   to handle relative branches correctly.  See below.
40  * - Mark that we are no longer actively in a kprobe.
41  */
42
43 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
44 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
45
46 int __kprobes arch_prepare_kprobe(struct kprobe *p)
47 {
48         p->ainsn.insn[0] = *p->addr;
49         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
50         p->opcode = *p->addr;
51         return 0;
52 }
53
54 void __kprobes arch_arm_kprobe(struct kprobe *p)
55 {
56         *p->addr = BREAKPOINT_INSTRUCTION;
57         flushi(p->addr);
58 }
59
60 void __kprobes arch_disarm_kprobe(struct kprobe *p)
61 {
62         *p->addr = p->opcode;
63         flushi(p->addr);
64 }
65
66 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
67 {
68         kcb->prev_kprobe.kp = kprobe_running();
69         kcb->prev_kprobe.status = kcb->kprobe_status;
70         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
71         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
72 }
73
74 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
75 {
76         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
77         kcb->kprobe_status = kcb->prev_kprobe.status;
78         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
79         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
80 }
81
82 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
83                                 struct kprobe_ctlblk *kcb)
84 {
85         __get_cpu_var(current_kprobe) = p;
86         kcb->kprobe_orig_tnpc = regs->tnpc;
87         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
88 }
89
90 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
91                         struct kprobe_ctlblk *kcb)
92 {
93         regs->tstate |= TSTATE_PIL;
94
95         /*single step inline, if it a breakpoint instruction*/
96         if (p->opcode == BREAKPOINT_INSTRUCTION) {
97                 regs->tpc = (unsigned long) p->addr;
98                 regs->tnpc = kcb->kprobe_orig_tnpc;
99         } else {
100                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
101                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
102         }
103 }
104
105 static int __kprobes kprobe_handler(struct pt_regs *regs)
106 {
107         struct kprobe *p;
108         void *addr = (void *) regs->tpc;
109         int ret = 0;
110         struct kprobe_ctlblk *kcb;
111
112         /*
113          * We don't want to be preempted for the entire
114          * duration of kprobe processing
115          */
116         preempt_disable();
117         kcb = get_kprobe_ctlblk();
118
119         if (kprobe_running()) {
120                 p = get_kprobe(addr);
121                 if (p) {
122                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
123                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
124                                         kcb->kprobe_orig_tstate_pil);
125                                 goto no_kprobe;
126                         }
127                         /* We have reentered the kprobe_handler(), since
128                          * another probe was hit while within the handler.
129                          * We here save the original kprobes variables and
130                          * just single step on the instruction of the new probe
131                          * without calling any user handlers.
132                          */
133                         save_previous_kprobe(kcb);
134                         set_current_kprobe(p, regs, kcb);
135                         kprobes_inc_nmissed_count(p);
136                         kcb->kprobe_status = KPROBE_REENTER;
137                         prepare_singlestep(p, regs, kcb);
138                         return 1;
139                 } else {
140                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
141                         /* The breakpoint instruction was removed by
142                          * another cpu right after we hit, no further
143                          * handling of this interrupt is appropriate
144                          */
145                                 ret = 1;
146                                 goto no_kprobe;
147                         }
148                         p = __get_cpu_var(current_kprobe);
149                         if (p->break_handler && p->break_handler(p, regs))
150                                 goto ss_probe;
151                 }
152                 goto no_kprobe;
153         }
154
155         p = get_kprobe(addr);
156         if (!p) {
157                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
158                         /*
159                          * The breakpoint instruction was removed right
160                          * after we hit it.  Another cpu has removed
161                          * either a probepoint or a debugger breakpoint
162                          * at this address.  In either case, no further
163                          * handling of this interrupt is appropriate.
164                          */
165                         ret = 1;
166                 }
167                 /* Not one of ours: let kernel handle it */
168                 goto no_kprobe;
169         }
170
171         set_current_kprobe(p, regs, kcb);
172         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
173         if (p->pre_handler && p->pre_handler(p, regs))
174                 return 1;
175
176 ss_probe:
177         prepare_singlestep(p, regs, kcb);
178         kcb->kprobe_status = KPROBE_HIT_SS;
179         return 1;
180
181 no_kprobe:
182         preempt_enable_no_resched();
183         return ret;
184 }
185
186 /* If INSN is a relative control transfer instruction,
187  * return the corrected branch destination value.
188  *
189  * The original INSN location was REAL_PC, it actually
190  * executed at PC and produced destination address NPC.
191  */
192 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
193                                                unsigned long pc,
194                                                unsigned long npc)
195 {
196         /* Branch not taken, no mods necessary.  */
197         if (npc == pc + 0x4UL)
198                 return real_pc + 0x4UL;
199
200         /* The three cases are call, branch w/prediction,
201          * and traditional branch.
202          */
203         if ((insn & 0xc0000000) == 0x40000000 ||
204             (insn & 0xc1c00000) == 0x00400000 ||
205             (insn & 0xc1c00000) == 0x00800000) {
206                 /* The instruction did all the work for us
207                  * already, just apply the offset to the correct
208                  * instruction location.
209                  */
210                 return (real_pc + (npc - pc));
211         }
212
213         return real_pc + 0x4UL;
214 }
215
216 /* If INSN is an instruction which writes it's PC location
217  * into a destination register, fix that up.
218  */
219 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
220                                   unsigned long real_pc)
221 {
222         unsigned long *slot = NULL;
223
224         /* Simplest cast is call, which always uses %o7 */
225         if ((insn & 0xc0000000) == 0x40000000) {
226                 slot = &regs->u_regs[UREG_I7];
227         }
228
229         /* Jmpl encodes the register inside of the opcode */
230         if ((insn & 0xc1f80000) == 0x81c00000) {
231                 unsigned long rd = ((insn >> 25) & 0x1f);
232
233                 if (rd <= 15) {
234                         slot = &regs->u_regs[rd];
235                 } else {
236                         /* Hard case, it goes onto the stack. */
237                         flushw_all();
238
239                         rd -= 16;
240                         slot = (unsigned long *)
241                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
242                         slot += rd;
243                 }
244         }
245         if (slot != NULL)
246                 *slot = real_pc;
247 }
248
249 /*
250  * Called after single-stepping.  p->addr is the address of the
251  * instruction whose first byte has been replaced by the breakpoint
252  * instruction.  To avoid the SMP problems that can occur when we
253  * temporarily put back the original opcode to single-step, we
254  * single-stepped a copy of the instruction.  The address of this
255  * copy is p->ainsn.insn.
256  *
257  * This function prepares to return from the post-single-step
258  * breakpoint trap.
259  */
260 static void __kprobes resume_execution(struct kprobe *p,
261                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
262 {
263         u32 insn = p->ainsn.insn[0];
264
265         regs->tpc = kcb->kprobe_orig_tnpc;
266         regs->tnpc = relbranch_fixup(insn,
267                                      (unsigned long) p->addr,
268                                      (unsigned long) &p->ainsn.insn[0],
269                                      regs->tnpc);
270         retpc_fixup(regs, insn, (unsigned long) p->addr);
271
272         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
273                         kcb->kprobe_orig_tstate_pil);
274 }
275
276 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
277 {
278         struct kprobe *cur = kprobe_running();
279         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
280
281         if (!cur)
282                 return 0;
283
284         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
285                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
286                 cur->post_handler(cur, regs, 0);
287         }
288
289         resume_execution(cur, regs, kcb);
290
291         /*Restore back the original saved kprobes variables and continue. */
292         if (kcb->kprobe_status == KPROBE_REENTER) {
293                 restore_previous_kprobe(kcb);
294                 goto out;
295         }
296         reset_current_kprobe();
297 out:
298         preempt_enable_no_resched();
299
300         return 1;
301 }
302
303 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
304 {
305         struct kprobe *cur = kprobe_running();
306         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
307         const struct exception_table_entry *entry;
308
309         switch(kcb->kprobe_status) {
310         case KPROBE_HIT_SS:
311         case KPROBE_REENTER:
312                 /*
313                  * We are here because the instruction being single
314                  * stepped caused a page fault. We reset the current
315                  * kprobe and the tpc points back to the probe address
316                  * and allow the page fault handler to continue as a
317                  * normal page fault.
318                  */
319                 regs->tpc = (unsigned long)cur->addr;
320                 regs->tnpc = kcb->kprobe_orig_tnpc;
321                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
322                                 kcb->kprobe_orig_tstate_pil);
323                 if (kcb->kprobe_status == KPROBE_REENTER)
324                         restore_previous_kprobe(kcb);
325                 else
326                         reset_current_kprobe();
327                 preempt_enable_no_resched();
328                 break;
329         case KPROBE_HIT_ACTIVE:
330         case KPROBE_HIT_SSDONE:
331                 /*
332                  * We increment the nmissed count for accounting,
333                  * we can also use npre/npostfault count for accouting
334                  * these specific fault cases.
335                  */
336                 kprobes_inc_nmissed_count(cur);
337
338                 /*
339                  * We come here because instructions in the pre/post
340                  * handler caused the page_fault, this could happen
341                  * if handler tries to access user space by
342                  * copy_from_user(), get_user() etc. Let the
343                  * user-specified handler try to fix it first.
344                  */
345                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
346                         return 1;
347
348                 /*
349                  * In case the user-specified fault handler returned
350                  * zero, try to fix up.
351                  */
352
353                 entry = search_exception_tables(regs->tpc);
354                 if (entry) {
355                         regs->tpc = entry->fixup;
356                         regs->tnpc = regs->tpc + 4;
357                         return 1;
358                 }
359
360                 /*
361                  * fixup_exception() could not handle it,
362                  * Let do_page_fault() fix it.
363                  */
364                 break;
365         default:
366                 break;
367         }
368
369         return 0;
370 }
371
372 /*
373  * Wrapper routine to for handling exceptions.
374  */
375 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
376                                        unsigned long val, void *data)
377 {
378         struct die_args *args = (struct die_args *)data;
379         int ret = NOTIFY_DONE;
380
381         if (args->regs && user_mode(args->regs))
382                 return ret;
383
384         switch (val) {
385         case DIE_DEBUG:
386                 if (kprobe_handler(args->regs))
387                         ret = NOTIFY_STOP;
388                 break;
389         case DIE_DEBUG_2:
390                 if (post_kprobe_handler(args->regs))
391                         ret = NOTIFY_STOP;
392                 break;
393         case DIE_GPF:
394         case DIE_PAGE_FAULT:
395                 /* kprobe_running() needs smp_processor_id() */
396                 preempt_disable();
397                 if (kprobe_running() &&
398                     kprobe_fault_handler(args->regs, args->trapnr))
399                         ret = NOTIFY_STOP;
400                 preempt_enable();
401                 break;
402         default:
403                 break;
404         }
405         return ret;
406 }
407
408 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
409                                       struct pt_regs *regs)
410 {
411         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
412
413         if (user_mode(regs)) {
414                 local_irq_enable();
415                 bad_trap(regs, trap_level);
416                 return;
417         }
418
419         /* trap_level == 0x170 --> ta 0x70
420          * trap_level == 0x171 --> ta 0x71
421          */
422         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
423                        (trap_level == 0x170) ? "debug" : "debug_2",
424                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
425                 bad_trap(regs, trap_level);
426 }
427
428 /* Jprobes support.  */
429 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
430 {
431         struct jprobe *jp = container_of(p, struct jprobe, kp);
432         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
433
434         kcb->jprobe_saved_regs_location = regs;
435         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
436
437         /* Save a whole stack frame, this gets arguments
438          * pushed onto the stack after using up all the
439          * arg registers.
440          */
441         memcpy(&(kcb->jprobe_saved_stack),
442                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
443                sizeof(kcb->jprobe_saved_stack));
444
445         regs->tpc  = (unsigned long) jp->entry;
446         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
447         regs->tstate |= TSTATE_PIL;
448
449         return 1;
450 }
451
452 void __kprobes jprobe_return(void)
453 {
454         __asm__ __volatile__(
455                 ".globl jprobe_return_trap_instruction\n"
456 "jprobe_return_trap_instruction:\n\t"
457                 "ta 0x70");
458 }
459
460 extern void jprobe_return_trap_instruction(void);
461
462 extern void __show_regs(struct pt_regs * regs);
463
464 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
465 {
466         u32 *addr = (u32 *) regs->tpc;
467         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
468
469         if (addr == (u32 *) jprobe_return_trap_instruction) {
470                 if (kcb->jprobe_saved_regs_location != regs) {
471                         printk("JPROBE: Current regs (%p) does not match "
472                                "saved regs (%p).\n",
473                                regs, kcb->jprobe_saved_regs_location);
474                         printk("JPROBE: Saved registers\n");
475                         __show_regs(kcb->jprobe_saved_regs_location);
476                         printk("JPROBE: Current registers\n");
477                         __show_regs(regs);
478                         BUG();
479                 }
480                 /* Restore old register state.  Do pt_regs
481                  * first so that UREG_FP is the original one for
482                  * the stack frame restore.
483                  */
484                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
485
486                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
487                        &(kcb->jprobe_saved_stack),
488                        sizeof(kcb->jprobe_saved_stack));
489
490                 preempt_enable_no_resched();
491                 return 1;
492         }
493         return 0;
494 }
495
496 /* architecture specific initialization */
497 int arch_init_kprobes(void)
498 {
499         return 0;
500 }