1 /* arch/sparc64/kernel/kprobes.c
3 * Copyright (C) 2004 David S. Miller <davem@davemloft.net>
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>
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.
17 * In the kprobe->ainsn.insn[] array we store the original
18 * instruction at index zero and a break instruction at
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
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.
40 int arch_prepare_kprobe(struct kprobe *p)
45 void arch_copy_kprobe(struct kprobe *p)
47 p->ainsn.insn[0] = *p->addr;
48 p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
52 void arch_arm_kprobe(struct kprobe *p)
54 *p->addr = BREAKPOINT_INSTRUCTION;
58 void arch_disarm_kprobe(struct kprobe *p)
64 void arch_remove_kprobe(struct kprobe *p)
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;
77 static inline void save_previous_kprobe(void)
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;
85 static inline void restore_previous_kprobe(void)
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;
93 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
95 current_kprobe_orig_tnpc = regs->tnpc;
96 current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
100 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
102 regs->tstate |= TSTATE_PIL;
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;
109 regs->tpc = (unsigned long) &p->ainsn.insn[0];
110 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
114 static int kprobe_handler(struct pt_regs *regs)
117 void *addr = (void *) regs->tpc;
122 if (kprobe_running()) {
123 /* We *are* holding lock here, so this is safe.
124 * Disarm the probe we just hit, and ignore it.
126 p = get_kprobe(addr);
128 if (kprobe_status == KPROBE_HIT_SS) {
129 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
130 current_kprobe_orig_tstate_pil);
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.
140 save_previous_kprobe();
141 set_current_kprobe(p, regs);
143 kprobe_status = KPROBE_REENTER;
144 prepare_singlestep(p, regs);
148 if (p->break_handler && p->break_handler(p, regs))
151 /* If it's not ours, can't be delete race, (we hold lock). */
156 p = get_kprobe(addr);
159 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
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.
169 /* Not one of ours: let kernel handle it */
173 set_current_kprobe(p, regs);
174 kprobe_status = KPROBE_HIT_ACTIVE;
175 if (p->pre_handler && p->pre_handler(p, regs))
179 prepare_singlestep(p, regs);
180 kprobe_status = KPROBE_HIT_SS;
184 preempt_enable_no_resched();
188 /* If INSN is a relative control transfer instruction,
189 * return the corrected branch destination value.
191 * The original INSN location was REAL_PC, it actually
192 * executed at PC and produced destination address NPC.
194 static unsigned long relbranch_fixup(u32 insn, unsigned long real_pc,
195 unsigned long pc, unsigned long npc)
197 /* Branch not taken, no mods necessary. */
198 if (npc == pc + 0x4UL)
199 return real_pc + 0x4UL;
201 /* The three cases are call, branch w/prediction,
202 * and traditional branch.
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.
211 return (real_pc + (npc - pc));
214 return real_pc + 0x4UL;
217 /* If INSN is an instruction which writes it's PC location
218 * into a destination register, fix that up.
220 static void retpc_fixup(struct pt_regs *regs, u32 insn, unsigned long real_pc)
222 unsigned long *slot = NULL;
224 /* Simplest cast is call, which always uses %o7 */
225 if ((insn & 0xc0000000) == 0x40000000) {
226 slot = ®s->u_regs[UREG_I7];
229 /* Jmpl encodes the register inside of the opcode */
230 if ((insn & 0xc1f80000) == 0x81c00000) {
231 unsigned long rd = ((insn >> 25) & 0x1f);
234 slot = ®s->u_regs[rd];
236 /* Hard case, it goes onto the stack. */
240 slot = (unsigned long *)
241 (regs->u_regs[UREG_FP] + STACK_BIAS);
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.
257 * This function prepares to return from the post-single-step
260 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
262 u32 insn = p->ainsn.insn[0];
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],
269 retpc_fixup(regs, insn, (unsigned long) p->addr);
271 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
272 current_kprobe_orig_tstate_pil);
275 static inline int post_kprobe_handler(struct pt_regs *regs)
277 if (!kprobe_running())
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);
285 resume_execution(current_kprobe, regs);
287 /*Restore back the original saved kprobes variables and continue. */
288 if (kprobe_status == KPROBE_REENTER) {
289 restore_previous_kprobe();
294 preempt_enable_no_resched();
299 /* Interrupts disabled, kprobe_lock held. */
300 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
302 if (current_kprobe->fault_handler
303 && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
306 if (kprobe_status & KPROBE_HIT_SS) {
307 resume_execution(current_kprobe, regs);
310 preempt_enable_no_resched();
316 * Wrapper routine to for handling exceptions.
318 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
321 struct die_args *args = (struct die_args *)data;
324 if (kprobe_handler(args->regs))
328 if (post_kprobe_handler(args->regs))
332 if (kprobe_running() &&
333 kprobe_fault_handler(args->regs, args->trapnr))
337 if (kprobe_running() &&
338 kprobe_fault_handler(args->regs, args->trapnr))
347 asmlinkage void kprobe_trap(unsigned long trap_level, struct pt_regs *regs)
349 BUG_ON(trap_level != 0x170 && trap_level != 0x171);
351 if (user_mode(regs)) {
353 bad_trap(regs, trap_level);
357 /* trap_level == 0x170 --> ta 0x70
358 * trap_level == 0x171 --> ta 0x71
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);
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;
371 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
373 struct jprobe *jp = container_of(p, struct jprobe, kp);
375 jprobe_saved_regs_location = regs;
376 memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
378 /* Save a whole stack frame, this gets arguments
379 * pushed onto the stack after using up all the
382 memcpy(&jprobe_saved_stack,
383 (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
384 sizeof(jprobe_saved_stack));
386 regs->tpc = (unsigned long) jp->entry;
387 regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
388 regs->tstate |= TSTATE_PIL;
393 void jprobe_return(void)
395 preempt_enable_no_resched();
396 __asm__ __volatile__(
397 ".globl jprobe_return_trap_instruction\n"
398 "jprobe_return_trap_instruction:\n\t"
402 extern void jprobe_return_trap_instruction(void);
404 extern void __show_regs(struct pt_regs * regs);
406 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
408 u32 *addr = (u32 *) regs->tpc;
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");
421 /* Restore old register state. Do pt_regs
422 * first so that UREG_FP is the original one for
423 * the stack frame restore.
425 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
427 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
429 sizeof(jprobe_saved_stack));