arch/avr32/kernel/kprobes.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *
   4  * Copyright (C) 2005-2006 Atmel Corporation
   5  *
   6  * Based on arch/ppc64/kernel/kprobes.c
   7  *  Copyright (C) IBM Corporation, 2002, 2004
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/kprobes.h>
  15 #include <linux/ptrace.h>
  16
  17 #include <asm/cacheflush.h>
  18 #include <asm/kdebug.h>
  19 #include <asm/ocd.h>
  20
  21 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  22 static unsigned long kprobe_status;
  23 static struct pt_regs jprobe_saved_regs;
  24
  25 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  26 {
  27         int ret = 0;
  28
  29         if ((unsigned long)p->addr & 0x01) {
  30                 printk("Attempt to register kprobe at an unaligned address\n");
  31                 ret = -EINVAL;
  32         }
  33
  34         /* XXX: Might be a good idea to check if p->addr is a valid
  35          * kernel address as well... */
  36
  37         if (!ret) {
  38                 pr_debug("copy kprobe at %p\n", p->addr);
  39                 memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  40                 p->opcode = *p->addr;
  41         }
  42
  43         return ret;
  44 }
  45
  46 void __kprobes arch_arm_kprobe(struct kprobe *p)
  47 {
  48         pr_debug("arming kprobe at %p\n", p->addr);
  49         *p->addr = BREAKPOINT_INSTRUCTION;
  50         flush_icache_range((unsigned long)p->addr,
  51                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  52 }
  53
  54 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  55 {
  56         pr_debug("disarming kprobe at %p\n", p->addr);
  57         *p->addr = p->opcode;
  58         flush_icache_range((unsigned long)p->addr,
  59                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  60 }
  61
  62 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
  63 {
  64         unsigned long dc;
  65
  66         pr_debug("preparing to singlestep over %p (PC=%08lx)\n",
  67                  p->addr, regs->pc);
  68
  69         BUG_ON(!(sysreg_read(SR) & SYSREG_BIT(SR_D)));
  70
  71         dc = __mfdr(DBGREG_DC);
  72         dc |= DC_SS;
  73         __mtdr(DBGREG_DC, dc);
  74
  75         /*
  76          * We must run the instruction from its original location
  77          * since it may actually reference PC.
  78          *
  79          * TODO: Do the instruction replacement directly in icache.
  80          */
  81         *p->addr = p->opcode;
  82         flush_icache_range((unsigned long)p->addr,
  83                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  84 }
  85
  86 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
  87 {
  88         unsigned long dc;
  89
  90         pr_debug("resuming execution at PC=%08lx\n", regs->pc);
  91
  92         dc = __mfdr(DBGREG_DC);
  93         dc &= ~DC_SS;
  94         __mtdr(DBGREG_DC, dc);
  95
  96         *p->addr = BREAKPOINT_INSTRUCTION;
  97         flush_icache_range((unsigned long)p->addr,
  98                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  99 }
 100
 101 static void __kprobes set_current_kprobe(struct kprobe *p)
 102 {
 103         __get_cpu_var(current_kprobe) = p;
 104 }
 105
 106 static int __kprobes kprobe_handler(struct pt_regs *regs)
 107 {
 108         struct kprobe *p;
 109         void *addr = (void *)regs->pc;
 110         int ret = 0;
 111
 112         pr_debug("kprobe_handler: kprobe_running=%d\n",
 113                  kprobe_running());
 114
 115         /*
 116          * We don't want to be preempted for the entire
 117          * duration of kprobe processing
 118          */
 119         preempt_disable();
 120
 121         /* Check that we're not recursing */
 122         if (kprobe_running()) {
 123                 p = get_kprobe(addr);
 124                 if (p) {
 125                         if (kprobe_status == KPROBE_HIT_SS) {
 126                                 printk("FIXME: kprobe hit while single-stepping!\n");
 127                                 goto no_kprobe;
 128                         }
 129
 130                         printk("FIXME: kprobe hit while handling another kprobe\n");
 131                         goto no_kprobe;
 132                 } else {
 133                         p = kprobe_running();
 134                         if (p->break_handler && p->break_handler(p, regs))
 135                                 goto ss_probe;
 136                 }
 137                 /* If it's not ours, can't be delete race, (we hold lock). */
 138                 goto no_kprobe;
 139         }
 140
 141         p = get_kprobe(addr);
 142         if (!p)
 143                 goto no_kprobe;
 144
 145         kprobe_status = KPROBE_HIT_ACTIVE;
 146         set_current_kprobe(p);
 147         if (p->pre_handler && p->pre_handler(p, regs))
 148                 /* handler has already set things up, so skip ss setup */
 149                 return 1;
 150
 151 ss_probe:
 152         prepare_singlestep(p, regs);
 153         kprobe_status = KPROBE_HIT_SS;
 154         return 1;
 155
 156 no_kprobe:
 157         return ret;
 158 }
 159
 160 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 161 {
 162         struct kprobe *cur = kprobe_running();
 163
 164         pr_debug("post_kprobe_handler, cur=%p\n", cur);
 165
 166         if (!cur)
 167                 return 0;
 168
 169         if (cur->post_handler) {
 170                 kprobe_status = KPROBE_HIT_SSDONE;
 171                 cur->post_handler(cur, regs, 0);
 172         }
 173
 174         resume_execution(cur, regs);
 175         reset_current_kprobe();
 176         preempt_enable_no_resched();
 177
 178         return 1;
 179 }
 180
 181 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 182 {
 183         struct kprobe *cur = kprobe_running();
 184
 185         pr_debug("kprobe_fault_handler: trapnr=%d\n", trapnr);
 186
 187         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 188                 return 1;
 189
 190         if (kprobe_status & KPROBE_HIT_SS) {
 191                 resume_execution(cur, regs);
 192                 preempt_enable_no_resched();
 193         }
 194         return 0;
 195 }
 196
 197 /*
 198  * Wrapper routine to for handling exceptions.
 199  */
 200 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 201                                        unsigned long val, void *data)
 202 {
 203         struct die_args *args = (struct die_args *)data;
 204         int ret = NOTIFY_DONE;
 205
 206         pr_debug("kprobe_exceptions_notify: val=%lu, data=%p\n",
 207                  val, data);
 208
 209         switch (val) {
 210         case DIE_BREAKPOINT:
 211                 if (kprobe_handler(args->regs))
 212                         ret = NOTIFY_STOP;
 213                 break;
 214         case DIE_SSTEP:
 215                 if (post_kprobe_handler(args->regs))
 216                         ret = NOTIFY_STOP;
 217                 break;
 218         case DIE_FAULT:
 219                 if (kprobe_running()
 220                     && kprobe_fault_handler(args->regs, args->trapnr))
 221                         ret = NOTIFY_STOP;
 222                 break;
 223         default:
 224                 break;
 225         }
 226
 227         return ret;
 228 }
 229
 230 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 231 {
 232         struct jprobe *jp = container_of(p, struct jprobe, kp);
 233
 234         memcpy(&jprobe_saved_regs, regs, sizeof(struct pt_regs));
 235
 236         /*
 237          * TODO: We should probably save some of the stack here as
 238          * well, since gcc may pass arguments on the stack for certain
 239          * functions (lots of arguments, large aggregates, varargs)
 240          */
 241
 242         /* setup return addr to the jprobe handler routine */
 243         regs->pc = (unsigned long)jp->entry;
 244         return 1;
 245 }
 246
 247 void __kprobes jprobe_return(void)
 248 {
 249         asm volatile("breakpoint" ::: "memory");
 250 }
 251
 252 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 253 {
 254         /*
 255          * FIXME - we should ideally be validating that we got here 'cos
 256          * of the "trap" in jprobe_return() above, before restoring the
 257          * saved regs...
 258          */
 259         memcpy(regs, &jprobe_saved_regs, sizeof(struct pt_regs));
 260         return 1;
 261 }
 262
 263 int __init arch_init_kprobes(void)
 264 {
 265         printk("KPROBES: Enabling monitor mode (MM|DBE)...\n");
 266         __mtdr(DBGREG_DC, DC_MM | DC_DBE);
 267
 268         /* TODO: Register kretprobe trampoline */
 269         return 0;
 270 }