Merge master.kernel.org:/pub/scm/linux/kernel/git/mchehab/v4l-dvb
[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 <asm/kdebug.h>
10 #include <asm/signal.h>
11 #include <asm/cacheflush.h>
12
13 /* We do not have hardware single-stepping on sparc64.
14  * So we implement software single-stepping with breakpoint
15  * traps.  The top-level scheme is similar to that used
16  * in the x86 kprobes implementation.
17  *
18  * In the kprobe->ainsn.insn[] array we store the original
19  * instruction at index zero and a break instruction at
20  * index one.
21  *
22  * When we hit a kprobe we:
23  * - Run the pre-handler
24  * - Remember "regs->tnpc" and interrupt level stored in
25  *   "regs->tstate" so we can restore them later
26  * - Disable PIL interrupts
27  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
28  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
29  * - Mark that we are actively in a kprobe
30  *
31  * At this point we wait for the second breakpoint at
32  * kprobe->ainsn.insn[1] to hit.  When it does we:
33  * - Run the post-handler
34  * - Set regs->tpc to "remembered" regs->tnpc stored above,
35  *   restore the PIL interrupt level in "regs->tstate" as well
36  * - Make any adjustments necessary to regs->tnpc in order
37  *   to handle relative branches correctly.  See below.
38  * - Mark that we are no longer actively in a kprobe.
39  */
40
41 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
42 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
43
44 int __kprobes arch_prepare_kprobe(struct kprobe *p)
45 {
46         p->ainsn.insn[0] = *p->addr;
47         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
48         p->opcode = *p->addr;
49         return 0;
50 }
51
52 void __kprobes arch_arm_kprobe(struct kprobe *p)
53 {
54         *p->addr = BREAKPOINT_INSTRUCTION;
55         flushi(p->addr);
56 }
57
58 void __kprobes arch_disarm_kprobe(struct kprobe *p)
59 {
60         *p->addr = p->opcode;
61         flushi(p->addr);
62 }
63
64 static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
65 {
66         kcb->prev_kprobe.kp = kprobe_running();
67         kcb->prev_kprobe.status = kcb->kprobe_status;
68         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
69         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
70 }
71
72 static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
73 {
74         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
75         kcb->kprobe_status = kcb->prev_kprobe.status;
76         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
77         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
78 }
79
80 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
81                                 struct kprobe_ctlblk *kcb)
82 {
83         __get_cpu_var(current_kprobe) = p;
84         kcb->kprobe_orig_tnpc = regs->tnpc;
85         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
86 }
87
88 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
89                         struct kprobe_ctlblk *kcb)
90 {
91         regs->tstate |= TSTATE_PIL;
92
93         /*single step inline, if it a breakpoint instruction*/
94         if (p->opcode == BREAKPOINT_INSTRUCTION) {
95                 regs->tpc = (unsigned long) p->addr;
96                 regs->tnpc = kcb->kprobe_orig_tnpc;
97         } else {
98                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
99                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
100         }
101 }
102
103 static int __kprobes kprobe_handler(struct pt_regs *regs)
104 {
105         struct kprobe *p;
106         void *addr = (void *) regs->tpc;
107         int ret = 0;
108         struct kprobe_ctlblk *kcb;
109
110         /*
111          * We don't want to be preempted for the entire
112          * duration of kprobe processing
113          */
114         preempt_disable();
115         kcb = get_kprobe_ctlblk();
116
117         if (kprobe_running()) {
118                 p = get_kprobe(addr);
119                 if (p) {
120                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
121                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
122                                         kcb->kprobe_orig_tstate_pil);
123                                 goto no_kprobe;
124                         }
125                         /* We have reentered the kprobe_handler(), since
126                          * another probe was hit while within the handler.
127                          * We here save the original kprobes variables and
128                          * just single step on the instruction of the new probe
129                          * without calling any user handlers.
130                          */
131                         save_previous_kprobe(kcb);
132                         set_current_kprobe(p, regs, kcb);
133                         kprobes_inc_nmissed_count(p);
134                         kcb->kprobe_status = KPROBE_REENTER;
135                         prepare_singlestep(p, regs, kcb);
136                         return 1;
137                 } else {
138                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
139                         /* The breakpoint instruction was removed by
140                          * another cpu right after we hit, no further
141                          * handling of this interrupt is appropriate
142                          */
143                                 ret = 1;
144                                 goto no_kprobe;
145                         }
146                         p = __get_cpu_var(current_kprobe);
147                         if (p->break_handler && p->break_handler(p, regs))
148                                 goto ss_probe;
149                 }
150                 goto no_kprobe;
151         }
152
153         p = get_kprobe(addr);
154         if (!p) {
155                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
156                         /*
157                          * The breakpoint instruction was removed right
158                          * after we hit it.  Another cpu has removed
159                          * either a probepoint or a debugger breakpoint
160                          * at this address.  In either case, no further
161                          * handling of this interrupt is appropriate.
162                          */
163                         ret = 1;
164                 }
165                 /* Not one of ours: let kernel handle it */
166                 goto no_kprobe;
167         }
168
169         set_current_kprobe(p, regs, kcb);
170         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
171         if (p->pre_handler && p->pre_handler(p, regs))
172                 return 1;
173
174 ss_probe:
175         prepare_singlestep(p, regs, kcb);
176         kcb->kprobe_status = KPROBE_HIT_SS;
177         return 1;
178
179 no_kprobe:
180         preempt_enable_no_resched();
181         return ret;
182 }
183
184 /* If INSN is a relative control transfer instruction,
185  * return the corrected branch destination value.
186  *
187  * The original INSN location was REAL_PC, it actually
188  * executed at PC and produced destination address NPC.
189  */
190 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
191                                                unsigned long pc,
192                                                unsigned long npc)
193 {
194         /* Branch not taken, no mods necessary.  */
195         if (npc == pc + 0x4UL)
196                 return real_pc + 0x4UL;
197
198         /* The three cases are call, branch w/prediction,
199          * and traditional branch.
200          */
201         if ((insn & 0xc0000000) == 0x40000000 ||
202             (insn & 0xc1c00000) == 0x00400000 ||
203             (insn & 0xc1c00000) == 0x00800000) {
204                 /* The instruction did all the work for us
205                  * already, just apply the offset to the correct
206                  * instruction location.
207                  */
208                 return (real_pc + (npc - pc));
209         }
210
211         return real_pc + 0x4UL;
212 }
213
214 /* If INSN is an instruction which writes it's PC location
215  * into a destination register, fix that up.
216  */
217 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
218                                   unsigned long real_pc)
219 {
220         unsigned long *slot = NULL;
221
222         /* Simplest cast is call, which always uses %o7 */
223         if ((insn & 0xc0000000) == 0x40000000) {
224                 slot = &regs->u_regs[UREG_I7];
225         }
226
227         /* Jmpl encodes the register inside of the opcode */
228         if ((insn & 0xc1f80000) == 0x81c00000) {
229                 unsigned long rd = ((insn >> 25) & 0x1f);
230
231                 if (rd <= 15) {
232                         slot = &regs->u_regs[rd];
233                 } else {
234                         /* Hard case, it goes onto the stack. */
235                         flushw_all();
236
237                         rd -= 16;
238                         slot = (unsigned long *)
239                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
240                         slot += rd;
241                 }
242         }
243         if (slot != NULL)
244                 *slot = real_pc;
245 }
246
247 /*
248  * Called after single-stepping.  p->addr is the address of the
249  * instruction whose first byte has been replaced by the breakpoint
250  * instruction.  To avoid the SMP problems that can occur when we
251  * temporarily put back the original opcode to single-step, we
252  * single-stepped a copy of the instruction.  The address of this
253  * copy is p->ainsn.insn.
254  *
255  * This function prepares to return from the post-single-step
256  * breakpoint trap.
257  */
258 static void __kprobes resume_execution(struct kprobe *p,
259                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
260 {
261         u32 insn = p->ainsn.insn[0];
262
263         regs->tpc = kcb->kprobe_orig_tnpc;
264         regs->tnpc = relbranch_fixup(insn,
265                                      (unsigned long) p->addr,
266                                      (unsigned long) &p->ainsn.insn[0],
267                                      regs->tnpc);
268         retpc_fixup(regs, insn, (unsigned long) p->addr);
269
270         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
271                         kcb->kprobe_orig_tstate_pil);
272 }
273
274 static inline int post_kprobe_handler(struct pt_regs *regs)
275 {
276         struct kprobe *cur = kprobe_running();
277         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
278
279         if (!cur)
280                 return 0;
281
282         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
283                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
284                 cur->post_handler(cur, regs, 0);
285         }
286
287         resume_execution(cur, regs, kcb);
288
289         /*Restore back the original saved kprobes variables and continue. */
290         if (kcb->kprobe_status == KPROBE_REENTER) {
291                 restore_previous_kprobe(kcb);
292                 goto out;
293         }
294         reset_current_kprobe();
295 out:
296         preempt_enable_no_resched();
297
298         return 1;
299 }
300
301 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
302 {
303         struct kprobe *cur = kprobe_running();
304         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
305
306         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
307                 return 1;
308
309         if (kcb->kprobe_status & KPROBE_HIT_SS) {
310                 resume_execution(cur, regs, kcb);
311
312                 reset_current_kprobe();
313                 preempt_enable_no_resched();
314         }
315         return 0;
316 }
317
318 /*
319  * Wrapper routine to for handling exceptions.
320  */
321 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
322                                        unsigned long val, void *data)
323 {
324         struct die_args *args = (struct die_args *)data;
325         int ret = NOTIFY_DONE;
326
327         switch (val) {
328         case DIE_DEBUG:
329                 if (kprobe_handler(args->regs))
330                         ret = NOTIFY_STOP;
331                 break;
332         case DIE_DEBUG_2:
333                 if (post_kprobe_handler(args->regs))
334                         ret = NOTIFY_STOP;
335                 break;
336         case DIE_GPF:
337         case DIE_PAGE_FAULT:
338                 /* kprobe_running() needs smp_processor_id() */
339                 preempt_disable();
340                 if (kprobe_running() &&
341                     kprobe_fault_handler(args->regs, args->trapnr))
342                         ret = NOTIFY_STOP;
343                 preempt_enable();
344                 break;
345         default:
346                 break;
347         }
348         return ret;
349 }
350
351 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
352                                       struct pt_regs *regs)
353 {
354         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
355
356         if (user_mode(regs)) {
357                 local_irq_enable();
358                 bad_trap(regs, trap_level);
359                 return;
360         }
361
362         /* trap_level == 0x170 --> ta 0x70
363          * trap_level == 0x171 --> ta 0x71
364          */
365         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
366                        (trap_level == 0x170) ? "debug" : "debug_2",
367                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
368                 bad_trap(regs, trap_level);
369 }
370
371 /* Jprobes support.  */
372 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
373 {
374         struct jprobe *jp = container_of(p, struct jprobe, kp);
375         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
376
377         kcb->jprobe_saved_regs_location = regs;
378         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
379
380         /* Save a whole stack frame, this gets arguments
381          * pushed onto the stack after using up all the
382          * arg registers.
383          */
384         memcpy(&(kcb->jprobe_saved_stack),
385                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
386                sizeof(kcb->jprobe_saved_stack));
387
388         regs->tpc  = (unsigned long) jp->entry;
389         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
390         regs->tstate |= TSTATE_PIL;
391
392         return 1;
393 }
394
395 void __kprobes jprobe_return(void)
396 {
397         __asm__ __volatile__(
398                 ".globl jprobe_return_trap_instruction\n"
399 "jprobe_return_trap_instruction:\n\t"
400                 "ta 0x70");
401 }
402
403 extern void jprobe_return_trap_instruction(void);
404
405 extern void __show_regs(struct pt_regs * regs);
406
407 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
408 {
409         u32 *addr = (u32 *) regs->tpc;
410         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
411
412         if (addr == (u32 *) jprobe_return_trap_instruction) {
413                 if (kcb->jprobe_saved_regs_location != regs) {
414                         printk("JPROBE: Current regs (%p) does not match "
415                                "saved regs (%p).\n",
416                                regs, kcb->jprobe_saved_regs_location);
417                         printk("JPROBE: Saved registers\n");
418                         __show_regs(kcb->jprobe_saved_regs_location);
419                         printk("JPROBE: Current registers\n");
420                         __show_regs(regs);
421                         BUG();
422                 }
423                 /* Restore old register state.  Do pt_regs
424                  * first so that UREG_FP is the original one for
425                  * the stack frame restore.
426                  */
427                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
428
429                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
430                        &(kcb->jprobe_saved_stack),
431                        sizeof(kcb->jprobe_saved_stack));
432
433                 preempt_enable_no_resched();
434                 return 1;
435         }
436         return 0;
437 }
438
439 /* architecture specific initialization */
440 int arch_init_kprobes(void)
441 {
442         return 0;
443 }