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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/kernel/kprobes.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/i386/kernel/kprobes.c')
-rw-r--r--arch/i386/kernel/kprobes.c385
1 files changed, 385 insertions, 0 deletions
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
new file mode 100644
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1/*
2 * Kernel Probes (KProbes)
3 * arch/i386/kernel/kprobes.c
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 *
19 * Copyright (C) IBM Corporation, 2002, 2004
20 *
21 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
22 * Probes initial implementation ( includes contributions from
23 * Rusty Russell).
24 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
25 * interface to access function arguments.
26 */
27
28#include <linux/config.h>
29#include <linux/kprobes.h>
30#include <linux/ptrace.h>
31#include <linux/spinlock.h>
32#include <linux/preempt.h>
33#include <asm/kdebug.h>
34#include <asm/desc.h>
35
36/* kprobe_status settings */
37#define KPROBE_HIT_ACTIVE 0x00000001
38#define KPROBE_HIT_SS 0x00000002
39
40static struct kprobe *current_kprobe;
41static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
42static struct pt_regs jprobe_saved_regs;
43static long *jprobe_saved_esp;
44/* copy of the kernel stack at the probe fire time */
45static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
46void jprobe_return_end(void);
47
48/*
49 * returns non-zero if opcode modifies the interrupt flag.
50 */
51static inline int is_IF_modifier(kprobe_opcode_t opcode)
52{
53 switch (opcode) {
54 case 0xfa: /* cli */
55 case 0xfb: /* sti */
56 case 0xcf: /* iret/iretd */
57 case 0x9d: /* popf/popfd */
58 return 1;
59 }
60 return 0;
61}
62
63int arch_prepare_kprobe(struct kprobe *p)
64{
65 return 0;
66}
67
68void arch_copy_kprobe(struct kprobe *p)
69{
70 memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
71}
72
73void arch_remove_kprobe(struct kprobe *p)
74{
75}
76
77static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
78{
79 *p->addr = p->opcode;
80 regs->eip = (unsigned long)p->addr;
81}
82
83static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
84{
85 regs->eflags |= TF_MASK;
86 regs->eflags &= ~IF_MASK;
87 /*single step inline if the instruction is an int3*/
88 if (p->opcode == BREAKPOINT_INSTRUCTION)
89 regs->eip = (unsigned long)p->addr;
90 else
91 regs->eip = (unsigned long)&p->ainsn.insn;
92}
93
94/*
95 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
96 * remain disabled thorough out this function.
97 */
98static int kprobe_handler(struct pt_regs *regs)
99{
100 struct kprobe *p;
101 int ret = 0;
102 kprobe_opcode_t *addr = NULL;
103 unsigned long *lp;
104
105 /* We're in an interrupt, but this is clear and BUG()-safe. */
106 preempt_disable();
107 /* Check if the application is using LDT entry for its code segment and
108 * calculate the address by reading the base address from the LDT entry.
109 */
110 if ((regs->xcs & 4) && (current->mm)) {
111 lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
112 + (char *) current->mm->context.ldt);
113 addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
114 sizeof(kprobe_opcode_t));
115 } else {
116 addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
117 }
118 /* Check we're not actually recursing */
119 if (kprobe_running()) {
120 /* We *are* holding lock here, so this is safe.
121 Disarm the probe we just hit, and ignore it. */
122 p = get_kprobe(addr);
123 if (p) {
124 if (kprobe_status == KPROBE_HIT_SS) {
125 regs->eflags &= ~TF_MASK;
126 regs->eflags |= kprobe_saved_eflags;
127 unlock_kprobes();
128 goto no_kprobe;
129 }
130 disarm_kprobe(p, regs);
131 ret = 1;
132 } else {
133 p = current_kprobe;
134 if (p->break_handler && p->break_handler(p, regs)) {
135 goto ss_probe;
136 }
137 }
138 /* If it's not ours, can't be delete race, (we hold lock). */
139 goto no_kprobe;
140 }
141
142 lock_kprobes();
143 p = get_kprobe(addr);
144 if (!p) {
145 unlock_kprobes();
146 if (regs->eflags & VM_MASK) {
147 /* We are in virtual-8086 mode. Return 0 */
148 goto no_kprobe;
149 }
150
151 if (*addr != BREAKPOINT_INSTRUCTION) {
152 /*
153 * The breakpoint instruction was removed right
154 * after we hit it. Another cpu has removed
155 * either a probepoint or a debugger breakpoint
156 * at this address. In either case, no further
157 * handling of this interrupt is appropriate.
158 */
159 ret = 1;
160 }
161 /* Not one of ours: let kernel handle it */
162 goto no_kprobe;
163 }
164
165 kprobe_status = KPROBE_HIT_ACTIVE;
166 current_kprobe = p;
167 kprobe_saved_eflags = kprobe_old_eflags
168 = (regs->eflags & (TF_MASK | IF_MASK));
169 if (is_IF_modifier(p->opcode))
170 kprobe_saved_eflags &= ~IF_MASK;
171
172 if (p->pre_handler && p->pre_handler(p, regs))
173 /* handler has already set things up, so skip ss setup */
174 return 1;
175
176ss_probe:
177 prepare_singlestep(p, regs);
178 kprobe_status = KPROBE_HIT_SS;
179 return 1;
180
181no_kprobe:
182 preempt_enable_no_resched();
183 return ret;
184}
185
186/*
187 * Called after single-stepping. p->addr is the address of the
188 * instruction whose first byte has been replaced by the "int 3"
189 * instruction. To avoid the SMP problems that can occur when we
190 * temporarily put back the original opcode to single-step, we
191 * single-stepped a copy of the instruction. The address of this
192 * copy is p->ainsn.insn.
193 *
194 * This function prepares to return from the post-single-step
195 * interrupt. We have to fix up the stack as follows:
196 *
197 * 0) Except in the case of absolute or indirect jump or call instructions,
198 * the new eip is relative to the copied instruction. We need to make
199 * it relative to the original instruction.
200 *
201 * 1) If the single-stepped instruction was pushfl, then the TF and IF
202 * flags are set in the just-pushed eflags, and may need to be cleared.
203 *
204 * 2) If the single-stepped instruction was a call, the return address
205 * that is atop the stack is the address following the copied instruction.
206 * We need to make it the address following the original instruction.
207 */
208static void resume_execution(struct kprobe *p, struct pt_regs *regs)
209{
210 unsigned long *tos = (unsigned long *)&regs->esp;
211 unsigned long next_eip = 0;
212 unsigned long copy_eip = (unsigned long)&p->ainsn.insn;
213 unsigned long orig_eip = (unsigned long)p->addr;
214
215 switch (p->ainsn.insn[0]) {
216 case 0x9c: /* pushfl */
217 *tos &= ~(TF_MASK | IF_MASK);
218 *tos |= kprobe_old_eflags;
219 break;
220 case 0xe8: /* call relative - Fix return addr */
221 *tos = orig_eip + (*tos - copy_eip);
222 break;
223 case 0xff:
224 if ((p->ainsn.insn[1] & 0x30) == 0x10) {
225 /* call absolute, indirect */
226 /* Fix return addr; eip is correct. */
227 next_eip = regs->eip;
228 *tos = orig_eip + (*tos - copy_eip);
229 } else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
230 ((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
231 /* eip is correct. */
232 next_eip = regs->eip;
233 }
234 break;
235 case 0xea: /* jmp absolute -- eip is correct */
236 next_eip = regs->eip;
237 break;
238 default:
239 break;
240 }
241
242 regs->eflags &= ~TF_MASK;
243 if (next_eip) {
244 regs->eip = next_eip;
245 } else {
246 regs->eip = orig_eip + (regs->eip - copy_eip);
247 }
248}
249
250/*
251 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
252 * remain disabled thoroughout this function. And we hold kprobe lock.
253 */
254static inline int post_kprobe_handler(struct pt_regs *regs)
255{
256 if (!kprobe_running())
257 return 0;
258
259 if (current_kprobe->post_handler)
260 current_kprobe->post_handler(current_kprobe, regs, 0);
261
262 resume_execution(current_kprobe, regs);
263 regs->eflags |= kprobe_saved_eflags;
264
265 unlock_kprobes();
266 preempt_enable_no_resched();
267
268 /*
269 * if somebody else is singlestepping across a probe point, eflags
270 * will have TF set, in which case, continue the remaining processing
271 * of do_debug, as if this is not a probe hit.
272 */
273 if (regs->eflags & TF_MASK)
274 return 0;
275
276 return 1;
277}
278
279/* Interrupts disabled, kprobe_lock held. */
280static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
281{
282 if (current_kprobe->fault_handler
283 && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
284 return 1;
285
286 if (kprobe_status & KPROBE_HIT_SS) {
287 resume_execution(current_kprobe, regs);
288 regs->eflags |= kprobe_old_eflags;
289
290 unlock_kprobes();
291 preempt_enable_no_resched();
292 }
293 return 0;
294}
295
296/*
297 * Wrapper routine to for handling exceptions.
298 */
299int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
300 void *data)
301{
302 struct die_args *args = (struct die_args *)data;
303 switch (val) {
304 case DIE_INT3:
305 if (kprobe_handler(args->regs))
306 return NOTIFY_STOP;
307 break;
308 case DIE_DEBUG:
309 if (post_kprobe_handler(args->regs))
310 return NOTIFY_STOP;
311 break;
312 case DIE_GPF:
313 if (kprobe_running() &&
314 kprobe_fault_handler(args->regs, args->trapnr))
315 return NOTIFY_STOP;
316 break;
317 case DIE_PAGE_FAULT:
318 if (kprobe_running() &&
319 kprobe_fault_handler(args->regs, args->trapnr))
320 return NOTIFY_STOP;
321 break;
322 default:
323 break;
324 }
325 return NOTIFY_DONE;
326}
327
328int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
329{
330 struct jprobe *jp = container_of(p, struct jprobe, kp);
331 unsigned long addr;
332
333 jprobe_saved_regs = *regs;
334 jprobe_saved_esp = &regs->esp;
335 addr = (unsigned long)jprobe_saved_esp;
336
337 /*
338 * TBD: As Linus pointed out, gcc assumes that the callee
339 * owns the argument space and could overwrite it, e.g.
340 * tailcall optimization. So, to be absolutely safe
341 * we also save and restore enough stack bytes to cover
342 * the argument area.
343 */
344 memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr));
345 regs->eflags &= ~IF_MASK;
346 regs->eip = (unsigned long)(jp->entry);
347 return 1;
348}
349
350void jprobe_return(void)
351{
352 preempt_enable_no_resched();
353 asm volatile (" xchgl %%ebx,%%esp \n"
354 " int3 \n"
355 " .globl jprobe_return_end \n"
356 " jprobe_return_end: \n"
357 " nop \n"::"b"
358 (jprobe_saved_esp):"memory");
359}
360
361int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
362{
363 u8 *addr = (u8 *) (regs->eip - 1);
364 unsigned long stack_addr = (unsigned long)jprobe_saved_esp;
365 struct jprobe *jp = container_of(p, struct jprobe, kp);
366
367 if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
368 if (&regs->esp != jprobe_saved_esp) {
369 struct pt_regs *saved_regs =
370 container_of(jprobe_saved_esp, struct pt_regs, esp);
371 printk("current esp %p does not match saved esp %p\n",
372 &regs->esp, jprobe_saved_esp);
373 printk("Saved registers for jprobe %p\n", jp);
374 show_registers(saved_regs);
375 printk("Current registers\n");
376 show_registers(regs);
377 BUG();
378 }
379 *regs = jprobe_saved_regs;
380 memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,
381 MIN_STACK_SIZE(stack_addr));
382 return 1;
383 }
384 return 0;
385}