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 <linux/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 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  26
  27 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  28 {
  29         int ret = 0;
  30
  31         if ((unsigned long)p->addr & 0x01) {
  32                 printk("Attempt to register kprobe at an unaligned address\n");
  33                 ret = -EINVAL;
  34         }
  35
  36         /* XXX: Might be a good idea to check if p->addr is a valid
  37          * kernel address as well... */
  38
  39         if (!ret) {
  40                 pr_debug("copy kprobe at %p\n", p->addr);
  41                 memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  42                 p->opcode = *p->addr;
  43         }
  44
  45         return ret;
  46 }
  47
  48 void __kprobes arch_arm_kprobe(struct kprobe *p)
  49 {
  50         pr_debug("arming kprobe at %p\n", p->addr);
  51         ocd_enable(NULL);
  52         *p->addr = BREAKPOINT_INSTRUCTION;
  53         flush_icache_range((unsigned long)p->addr,
  54                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  55 }
  56
  57 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  58 {
  59         pr_debug("disarming kprobe at %p\n", p->addr);
  60         ocd_disable(NULL);
  61         *p->addr = p->opcode;
  62         flush_icache_range((unsigned long)p->addr,
  63                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  64 }
  65
  66 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
  67 {
  68         unsigned long dc;
  69
  70         pr_debug("preparing to singlestep over %p (PC=%08lx)\n",
  71                  p->addr, regs->pc);
  72
  73         BUG_ON(!(sysreg_read(SR) & SYSREG_BIT(SR_D)));
  74
  75         dc = ocd_read(DC);
  76         dc |= 1 << OCD_DC_SS_BIT;
  77         ocd_write(DC, dc);
  78
  79         /*
  80          * We must run the instruction from its original location
  81          * since it may actually reference PC.
  82          *
  83          * TODO: Do the instruction replacement directly in icache.
  84          */
  85         *p->addr = p->opcode;
  86         flush_icache_range((unsigned long)p->addr,
  87                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
  88 }
  89
  90 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
  91 {
  92         unsigned long dc;
  93
  94         pr_debug("resuming execution at PC=%08lx\n", regs->pc);
  95
  96         dc = ocd_read(DC);
  97         dc &= ~(1 << OCD_DC_SS_BIT);
  98         ocd_write(DC, dc);
  99
 100         *p->addr = BREAKPOINT_INSTRUCTION;
 101         flush_icache_range((unsigned long)p->addr,
 102                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
 103 }
 104
 105 static void __kprobes set_current_kprobe(struct kprobe *p)
 106 {
 107         __get_cpu_var(current_kprobe) = p;
 108 }
 109
 110 static int __kprobes kprobe_handler(struct pt_regs *regs)
 111 {
 112         struct kprobe *p;
 113         void *addr = (void *)regs->pc;
 114         int ret = 0;
 115
 116         pr_debug("kprobe_handler: kprobe_running=%p\n",
 117                  kprobe_running());
 118
 119         /*
 120          * We don't want to be preempted for the entire
 121          * duration of kprobe processing
 122          */
 123         preempt_disable();
 124
 125         /* Check that we're not recursing */
 126         if (kprobe_running()) {
 127                 p = get_kprobe(addr);
 128                 if (p) {
 129                         if (kprobe_status == KPROBE_HIT_SS) {
 130                                 printk("FIXME: kprobe hit while single-stepping!\n");
 131                                 goto no_kprobe;
 132                         }
 133
 134                         printk("FIXME: kprobe hit while handling another kprobe\n");
 135                         goto no_kprobe;
 136                 } else {
 137                         p = kprobe_running();
 138                         if (p->break_handler && p->break_handler(p, regs))
 139                                 goto ss_probe;
 140                 }
 141                 /* If it's not ours, can't be delete race, (we hold lock). */
 142                 goto no_kprobe;
 143         }
 144
 145         p = get_kprobe(addr);
 146         if (!p)
 147                 goto no_kprobe;
 148
 149         kprobe_status = KPROBE_HIT_ACTIVE;
 150         set_current_kprobe(p);
 151         if (p->pre_handler && p->pre_handler(p, regs))
 152                 /* handler has already set things up, so skip ss setup */
 153                 return 1;
 154
 155 ss_probe:
 156         prepare_singlestep(p, regs);
 157         kprobe_status = KPROBE_HIT_SS;
 158         return 1;
 159
 160 no_kprobe:
 161         preempt_enable_no_resched();
 162         return ret;
 163 }
 164
 165 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 166 {
 167         struct kprobe *cur = kprobe_running();
 168
 169         pr_debug("post_kprobe_handler, cur=%p\n", cur);
 170
 171         if (!cur)
 172                 return 0;
 173
 174         if (cur->post_handler) {
 175                 kprobe_status = KPROBE_HIT_SSDONE;
 176                 cur->post_handler(cur, regs, 0);
 177         }
 178
 179         resume_execution(cur, regs);
 180         reset_current_kprobe();
 181         preempt_enable_no_resched();
 182
 183         return 1;
 184 }
 185
 186 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 187 {
 188         struct kprobe *cur = kprobe_running();
 189
 190         pr_debug("kprobe_fault_handler: trapnr=%d\n", trapnr);
 191
 192         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 193                 return 1;
 194
 195         if (kprobe_status & KPROBE_HIT_SS) {
 196                 resume_execution(cur, regs);
 197                 preempt_enable_no_resched();
 198         }
 199         return 0;
 200 }
 201
 202 /*
 203  * Wrapper routine to for handling exceptions.
 204  */
 205 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 206                                        unsigned long val, void *data)
 207 {
 208         struct die_args *args = (struct die_args *)data;
 209         int ret = NOTIFY_DONE;
 210
 211         pr_debug("kprobe_exceptions_notify: val=%lu, data=%p\n",
 212                  val, data);
 213
 214         switch (val) {
 215         case DIE_BREAKPOINT:
 216                 if (kprobe_handler(args->regs))
 217                         ret = NOTIFY_STOP;
 218                 break;
 219         case DIE_SSTEP:
 220                 if (post_kprobe_handler(args->regs))
 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         /* TODO: Register kretprobe trampoline */
 266         return 0;
 267 }