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Linux/arch/avr32/kernel/kprobes.c

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  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         __this_cpu_write(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 }
268 

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