[PATCH] kprobes: fix namespace problem and sparc64 build
[linux-2.6.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/config.h>
7 #include <linux/kernel.h>
8 #include <linux/kprobes.h>
9 #include <asm/kdebug.h>
10 #include <asm/signal.h>
11
12 /* We do not have hardware single-stepping on sparc64.
13  * So we implement software single-stepping with breakpoint
14  * traps.  The top-level scheme is similar to that used
15  * in the x86 kprobes implementation.
16  *
17  * In the kprobe->ainsn.insn[] array we store the original
18  * instruction at index zero and a break instruction at
19  * index one.
20  *
21  * When we hit a kprobe we:
22  * - Run the pre-handler
23  * - Remember "regs->tnpc" and interrupt level stored in
24  *   "regs->tstate" so we can restore them later
25  * - Disable PIL interrupts
26  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
27  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
28  * - Mark that we are actively in a kprobe
29  *
30  * At this point we wait for the second breakpoint at
31  * kprobe->ainsn.insn[1] to hit.  When it does we:
32  * - Run the post-handler
33  * - Set regs->tpc to "remembered" regs->tnpc stored above,
34  *   restore the PIL interrupt level in "regs->tstate" as well
35  * - Make any adjustments necessary to regs->tnpc in order
36  *   to handle relative branches correctly.  See below.
37  * - Mark that we are no longer actively in a kprobe.
38  */
39
40 int arch_prepare_kprobe(struct kprobe *p)
41 {
42         return 0;
43 }
44
45 void arch_copy_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 }
51
52 void arch_arm_kprobe(struct kprobe *p)
53 {
54         *p->addr = BREAKPOINT_INSTRUCTION;
55         flushi(p->addr);
56 }
57
58 void arch_disarm_kprobe(struct kprobe *p)
59 {
60         *p->addr = p->opcode;
61         flushi(p->addr);
62 }
63
64 void arch_remove_kprobe(struct kprobe *p)
65 {
66 }
67
68 static struct kprobe *current_kprobe;
69 static unsigned long current_kprobe_orig_tnpc;
70 static unsigned long current_kprobe_orig_tstate_pil;
71 static unsigned int kprobe_status;
72 static struct kprobe *kprobe_prev;
73 static unsigned long kprobe_orig_tnpc_prev;
74 static unsigned long kprobe_orig_tstate_pil_prev;
75 static unsigned int kprobe_status_prev;
76
77 static inline void save_previous_kprobe(void)
78 {
79         kprobe_status_prev = kprobe_status;
80         kprobe_orig_tnpc_prev = current_kprobe_orig_tnpc;
81         kprobe_orig_tstate_pil_prev = current_kprobe_orig_tstate_pil;
82         kprobe_prev = current_kprobe;
83 }
84
85 static inline void restore_previous_kprobe(void)
86 {
87         kprobe_status = kprobe_status_prev;
88         current_kprobe_orig_tnpc = kprobe_orig_tnpc_prev;
89         current_kprobe_orig_tstate_pil = kprobe_orig_tstate_pil_prev;
90         current_kprobe = kprobe_prev;
91 }
92
93 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
94 {
95         current_kprobe_orig_tnpc = regs->tnpc;
96         current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
97         current_kprobe = p;
98 }
99
100 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
101 {
102         regs->tstate |= TSTATE_PIL;
103
104         /*single step inline, if it a breakpoint instruction*/
105         if (p->opcode == BREAKPOINT_INSTRUCTION) {
106                 regs->tpc = (unsigned long) p->addr;
107                 regs->tnpc = current_kprobe_orig_tnpc;
108         } else {
109                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
110                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
111         }
112 }
113
114 static int kprobe_handler(struct pt_regs *regs)
115 {
116         struct kprobe *p;
117         void *addr = (void *) regs->tpc;
118         int ret = 0;
119
120         preempt_disable();
121
122         if (kprobe_running()) {
123                 /* We *are* holding lock here, so this is safe.
124                  * Disarm the probe we just hit, and ignore it.
125                  */
126                 p = get_kprobe(addr);
127                 if (p) {
128                         if (kprobe_status == KPROBE_HIT_SS) {
129                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
130                                         current_kprobe_orig_tstate_pil);
131                                 unlock_kprobes();
132                                 goto no_kprobe;
133                         }
134                         /* We have reentered the kprobe_handler(), since
135                          * another probe was hit while within the handler.
136                          * We here save the original kprobes variables and
137                          * just single step on the instruction of the new probe
138                          * without calling any user handlers.
139                          */
140                         save_previous_kprobe();
141                         set_current_kprobe(p, regs);
142                         p->nmissed++;
143                         kprobe_status = KPROBE_REENTER;
144                         prepare_singlestep(p, regs);
145                         return 1;
146                 } else {
147                         p = current_kprobe;
148                         if (p->break_handler && p->break_handler(p, regs))
149                                 goto ss_probe;
150                 }
151                 /* If it's not ours, can't be delete race, (we hold lock). */
152                 goto no_kprobe;
153         }
154
155         lock_kprobes();
156         p = get_kprobe(addr);
157         if (!p) {
158                 unlock_kprobes();
159                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
160                         /*
161                          * The breakpoint instruction was removed right
162                          * after we hit it.  Another cpu has removed
163                          * either a probepoint or a debugger breakpoint
164                          * at this address.  In either case, no further
165                          * handling of this interrupt is appropriate.
166                          */
167                         ret = 1;
168                 }
169                 /* Not one of ours: let kernel handle it */
170                 goto no_kprobe;
171         }
172
173         set_current_kprobe(p, regs);
174         kprobe_status = KPROBE_HIT_ACTIVE;
175         if (p->pre_handler && p->pre_handler(p, regs))
176                 return 1;
177
178 ss_probe:
179         prepare_singlestep(p, regs);
180         kprobe_status = KPROBE_HIT_SS;
181         return 1;
182
183 no_kprobe:
184         preempt_enable_no_resched();
185         return ret;
186 }
187
188 /* If INSN is a relative control transfer instruction,
189  * return the corrected branch destination value.
190  *
191  * The original INSN location was REAL_PC, it actually
192  * executed at PC and produced destination address NPC.
193  */
194 static unsigned long relbranch_fixup(u32 insn, unsigned long real_pc,
195                                      unsigned long pc, unsigned long npc)
196 {
197         /* Branch not taken, no mods necessary.  */
198         if (npc == pc + 0x4UL)
199                 return real_pc + 0x4UL;
200
201         /* The three cases are call, branch w/prediction,
202          * and traditional branch.
203          */
204         if ((insn & 0xc0000000) == 0x40000000 ||
205             (insn & 0xc1c00000) == 0x00400000 ||
206             (insn & 0xc1c00000) == 0x00800000) {
207                 /* The instruction did all the work for us
208                  * already, just apply the offset to the correct
209                  * instruction location.
210                  */
211                 return (real_pc + (npc - pc));
212         }
213
214         return real_pc + 0x4UL;
215 }
216
217 /* If INSN is an instruction which writes it's PC location
218  * into a destination register, fix that up.
219  */
220 static void retpc_fixup(struct pt_regs *regs, u32 insn, 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 resume_execution(struct kprobe *p, struct pt_regs *regs)
261 {
262         u32 insn = p->ainsn.insn[0];
263
264         regs->tpc = current_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                         current_kprobe_orig_tstate_pil);
273 }
274
275 static inline int post_kprobe_handler(struct pt_regs *regs)
276 {
277         if (!kprobe_running())
278                 return 0;
279
280         if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
281                 kprobe_status = KPROBE_HIT_SSDONE;
282                 current_kprobe->post_handler(current_kprobe, regs, 0);
283         }
284
285         resume_execution(current_kprobe, regs);
286
287         /*Restore back the original saved kprobes variables and continue. */
288         if (kprobe_status == KPROBE_REENTER) {
289                 restore_previous_kprobe();
290                 goto out;
291         }
292         unlock_kprobes();
293 out:
294         preempt_enable_no_resched();
295
296         return 1;
297 }
298
299 /* Interrupts disabled, kprobe_lock held. */
300 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
301 {
302         if (current_kprobe->fault_handler
303             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
304                 return 1;
305
306         if (kprobe_status & KPROBE_HIT_SS) {
307                 resume_execution(current_kprobe, regs);
308
309                 unlock_kprobes();
310                 preempt_enable_no_resched();
311         }
312         return 0;
313 }
314
315 /*
316  * Wrapper routine to for handling exceptions.
317  */
318 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
319                              void *data)
320 {
321         struct die_args *args = (struct die_args *)data;
322         switch (val) {
323         case DIE_DEBUG:
324                 if (kprobe_handler(args->regs))
325                         return NOTIFY_STOP;
326                 break;
327         case DIE_DEBUG_2:
328                 if (post_kprobe_handler(args->regs))
329                         return NOTIFY_STOP;
330                 break;
331         case DIE_GPF:
332                 if (kprobe_running() &&
333                     kprobe_fault_handler(args->regs, args->trapnr))
334                         return NOTIFY_STOP;
335                 break;
336         case DIE_PAGE_FAULT:
337                 if (kprobe_running() &&
338                     kprobe_fault_handler(args->regs, args->trapnr))
339                         return NOTIFY_STOP;
340                 break;
341         default:
342                 break;
343         }
344         return NOTIFY_DONE;
345 }
346
347 asmlinkage void kprobe_trap(unsigned long trap_level, struct pt_regs *regs)
348 {
349         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
350
351         if (user_mode(regs)) {
352                 local_irq_enable();
353                 bad_trap(regs, trap_level);
354                 return;
355         }
356
357         /* trap_level == 0x170 --> ta 0x70
358          * trap_level == 0x171 --> ta 0x71
359          */
360         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
361                        (trap_level == 0x170) ? "debug" : "debug_2",
362                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
363                 bad_trap(regs, trap_level);
364 }
365
366 /* Jprobes support.  */
367 static struct pt_regs jprobe_saved_regs;
368 static struct pt_regs *jprobe_saved_regs_location;
369 static struct sparc_stackf jprobe_saved_stack;
370
371 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
372 {
373         struct jprobe *jp = container_of(p, struct jprobe, kp);
374
375         jprobe_saved_regs_location = regs;
376         memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
377
378         /* Save a whole stack frame, this gets arguments
379          * pushed onto the stack after using up all the
380          * arg registers.
381          */
382         memcpy(&jprobe_saved_stack,
383                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
384                sizeof(jprobe_saved_stack));
385
386         regs->tpc  = (unsigned long) jp->entry;
387         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
388         regs->tstate |= TSTATE_PIL;
389
390         return 1;
391 }
392
393 void jprobe_return(void)
394 {
395         preempt_enable_no_resched();
396         __asm__ __volatile__(
397                 ".globl jprobe_return_trap_instruction\n"
398 "jprobe_return_trap_instruction:\n\t"
399                 "ta 0x70");
400 }
401
402 extern void jprobe_return_trap_instruction(void);
403
404 extern void __show_regs(struct pt_regs * regs);
405
406 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
407 {
408         u32 *addr = (u32 *) regs->tpc;
409
410         if (addr == (u32 *) jprobe_return_trap_instruction) {
411                 if (jprobe_saved_regs_location != regs) {
412                         printk("JPROBE: Current regs (%p) does not match "
413                                "saved regs (%p).\n",
414                                regs, jprobe_saved_regs_location);
415                         printk("JPROBE: Saved registers\n");
416                         __show_regs(jprobe_saved_regs_location);
417                         printk("JPROBE: Current registers\n");
418                         __show_regs(regs);
419                         BUG();
420                 }
421                 /* Restore old register state.  Do pt_regs
422                  * first so that UREG_FP is the original one for
423                  * the stack frame restore.
424                  */
425                 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
426
427                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
428                        &jprobe_saved_stack,
429                        sizeof(jprobe_saved_stack));
430
431                 return 1;
432         }
433         return 0;
434 }
435
436 /* architecture specific initialization */
437 int arch_init_kprobes(void)
438 {
439         return 0;
440 }