7e1048b11c
The architecture independent code of the current kprobes implementation is
arming and disarming kprobes at registration time. The problem is that the
code is assuming that arming and disarming is a just done by a simple write
of some magic value to an address. This is problematic for ia64 where our
instructions look more like structures, and we can not insert break points
by just doing something like:
*p->addr = BREAKPOINT_INSTRUCTION;
The following patch to 2.6.12-rc4-mm2 adds two new architecture dependent
functions:
* void arch_arm_kprobe(struct kprobe *p)
* void arch_disarm_kprobe(struct kprobe *p)
and then adds the new functions for each of the architectures that already
implement kprobes (spar64/ppc64/i386/x86_64).
I thought arch_[dis]arm_kprobe was the most descriptive of what was really
happening, but each of the architectures already had a disarm_kprobe()
function that was really a "disarm and do some other clean-up items as
needed when you stumble across a recursive kprobe." So... I took the
liberty of changing the code that was calling disarm_kprobe() to call
arch_disarm_kprobe(), and then do the cleanup in the block of code dealing
with the recursive kprobe case.
So far this patch as been tested on i386, x86_64, and ppc64, but still
needs to be tested in sparc64.
Signed-off-by: Rusty Lynch <rusty.lynch@intel.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
503 lines
14 KiB
C
503 lines
14 KiB
C
/*
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* Kernel Probes (KProbes)
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* arch/i386/kernel/kprobes.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2002, 2004
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*
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* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
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* Probes initial implementation ( includes contributions from
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* Rusty Russell).
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* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
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* interface to access function arguments.
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* 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
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* <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
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* <prasanna@in.ibm.com> added function-return probes.
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*/
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#include <linux/config.h>
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/spinlock.h>
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#include <linux/preempt.h>
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#include <asm/cacheflush.h>
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#include <asm/kdebug.h>
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#include <asm/desc.h>
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/* kprobe_status settings */
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#define KPROBE_HIT_ACTIVE 0x00000001
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#define KPROBE_HIT_SS 0x00000002
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static struct kprobe *current_kprobe;
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static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
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static struct pt_regs jprobe_saved_regs;
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static long *jprobe_saved_esp;
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/* copy of the kernel stack at the probe fire time */
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static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
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void jprobe_return_end(void);
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/*
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* returns non-zero if opcode modifies the interrupt flag.
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*/
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static inline int is_IF_modifier(kprobe_opcode_t opcode)
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{
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switch (opcode) {
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case 0xfa: /* cli */
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case 0xfb: /* sti */
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case 0xcf: /* iret/iretd */
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case 0x9d: /* popf/popfd */
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return 1;
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}
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return 0;
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}
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int arch_prepare_kprobe(struct kprobe *p)
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{
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return 0;
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}
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void arch_copy_kprobe(struct kprobe *p)
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{
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memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
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p->opcode = *p->addr;
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}
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void arch_arm_kprobe(struct kprobe *p)
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{
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*p->addr = BREAKPOINT_INSTRUCTION;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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void arch_disarm_kprobe(struct kprobe *p)
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{
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*p->addr = p->opcode;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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void arch_remove_kprobe(struct kprobe *p)
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{
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}
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static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
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{
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regs->eflags |= TF_MASK;
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regs->eflags &= ~IF_MASK;
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/*single step inline if the instruction is an int3*/
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if (p->opcode == BREAKPOINT_INSTRUCTION)
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regs->eip = (unsigned long)p->addr;
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else
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regs->eip = (unsigned long)&p->ainsn.insn;
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}
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struct task_struct *arch_get_kprobe_task(void *ptr)
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{
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return ((struct thread_info *) (((unsigned long) ptr) &
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(~(THREAD_SIZE -1))))->task;
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}
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void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
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{
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unsigned long *sara = (unsigned long *)®s->esp;
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struct kretprobe_instance *ri;
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static void *orig_ret_addr;
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/*
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* Save the return address when the return probe hits
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* the first time, and use it to populate the (krprobe
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* instance)->ret_addr for subsequent return probes at
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* the same addrress since stack address would have
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* the kretprobe_trampoline by then.
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*/
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if (((void*) *sara) != kretprobe_trampoline)
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orig_ret_addr = (void*) *sara;
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if ((ri = get_free_rp_inst(rp)) != NULL) {
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ri->rp = rp;
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ri->stack_addr = sara;
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ri->ret_addr = orig_ret_addr;
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add_rp_inst(ri);
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/* Replace the return addr with trampoline addr */
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*sara = (unsigned long) &kretprobe_trampoline;
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} else {
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rp->nmissed++;
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}
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}
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void arch_kprobe_flush_task(struct task_struct *tk, spinlock_t *kp_lock)
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{
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unsigned long flags = 0;
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struct kretprobe_instance *ri;
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spin_lock_irqsave(kp_lock, flags);
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while ((ri = get_rp_inst_tsk(tk)) != NULL) {
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*((unsigned long *)(ri->stack_addr)) =
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(unsigned long) ri->ret_addr;
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recycle_rp_inst(ri);
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}
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spin_unlock_irqrestore(kp_lock, flags);
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}
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/*
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* Interrupts are disabled on entry as trap3 is an interrupt gate and they
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* remain disabled thorough out this function.
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*/
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static int kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p;
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int ret = 0;
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kprobe_opcode_t *addr = NULL;
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unsigned long *lp;
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/* We're in an interrupt, but this is clear and BUG()-safe. */
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preempt_disable();
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/* Check if the application is using LDT entry for its code segment and
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* calculate the address by reading the base address from the LDT entry.
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*/
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if ((regs->xcs & 4) && (current->mm)) {
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lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
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+ (char *) current->mm->context.ldt);
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addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
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sizeof(kprobe_opcode_t));
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} else {
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addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
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}
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/* Check we're not actually recursing */
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if (kprobe_running()) {
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/* We *are* holding lock here, so this is safe.
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Disarm the probe we just hit, and ignore it. */
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p = get_kprobe(addr);
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if (p) {
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if (kprobe_status == KPROBE_HIT_SS) {
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regs->eflags &= ~TF_MASK;
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regs->eflags |= kprobe_saved_eflags;
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unlock_kprobes();
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goto no_kprobe;
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}
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arch_disarm_kprobe(p);
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regs->eip = (unsigned long)p->addr;
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ret = 1;
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} else {
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p = current_kprobe;
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if (p->break_handler && p->break_handler(p, regs)) {
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goto ss_probe;
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}
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}
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/* If it's not ours, can't be delete race, (we hold lock). */
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goto no_kprobe;
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}
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lock_kprobes();
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p = get_kprobe(addr);
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if (!p) {
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unlock_kprobes();
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if (regs->eflags & VM_MASK) {
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/* We are in virtual-8086 mode. Return 0 */
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goto no_kprobe;
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}
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/*
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* The breakpoint instruction was removed right
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* after we hit it. Another cpu has removed
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* either a probepoint or a debugger breakpoint
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* at this address. In either case, no further
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* handling of this interrupt is appropriate.
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*/
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ret = 1;
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}
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/* Not one of ours: let kernel handle it */
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goto no_kprobe;
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}
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kprobe_status = KPROBE_HIT_ACTIVE;
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current_kprobe = p;
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kprobe_saved_eflags = kprobe_old_eflags
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= (regs->eflags & (TF_MASK | IF_MASK));
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if (is_IF_modifier(p->opcode))
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kprobe_saved_eflags &= ~IF_MASK;
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if (p->pre_handler && p->pre_handler(p, regs))
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/* handler has already set things up, so skip ss setup */
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return 1;
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ss_probe:
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prepare_singlestep(p, regs);
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kprobe_status = KPROBE_HIT_SS;
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return 1;
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no_kprobe:
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preempt_enable_no_resched();
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return ret;
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}
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/*
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* For function-return probes, init_kprobes() establishes a probepoint
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* here. When a retprobed function returns, this probe is hit and
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* trampoline_probe_handler() runs, calling the kretprobe's handler.
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*/
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void kretprobe_trampoline_holder(void)
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{
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asm volatile ( ".global kretprobe_trampoline\n"
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"kretprobe_trampoline: \n"
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"nop\n");
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}
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/*
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* Called when we hit the probe point at kretprobe_trampoline
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*/
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int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
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{
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struct task_struct *tsk;
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struct kretprobe_instance *ri;
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struct hlist_head *head;
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struct hlist_node *node;
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unsigned long *sara = ((unsigned long *) ®s->esp) - 1;
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tsk = arch_get_kprobe_task(sara);
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head = kretprobe_inst_table_head(tsk);
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hlist_for_each_entry(ri, node, head, hlist) {
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if (ri->stack_addr == sara && ri->rp) {
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if (ri->rp->handler)
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ri->rp->handler(ri, regs);
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}
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}
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return 0;
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}
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void trampoline_post_handler(struct kprobe *p, struct pt_regs *regs,
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unsigned long flags)
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{
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struct kretprobe_instance *ri;
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/* RA already popped */
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unsigned long *sara = ((unsigned long *)®s->esp) - 1;
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while ((ri = get_rp_inst(sara))) {
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regs->eip = (unsigned long)ri->ret_addr;
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recycle_rp_inst(ri);
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}
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regs->eflags &= ~TF_MASK;
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}
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/*
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* Called after single-stepping. p->addr is the address of the
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* instruction whose first byte has been replaced by the "int 3"
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* instruction. To avoid the SMP problems that can occur when we
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* temporarily put back the original opcode to single-step, we
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* single-stepped a copy of the instruction. The address of this
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* copy is p->ainsn.insn.
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*
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* This function prepares to return from the post-single-step
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* interrupt. We have to fix up the stack as follows:
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*
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* 0) Except in the case of absolute or indirect jump or call instructions,
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* the new eip is relative to the copied instruction. We need to make
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* it relative to the original instruction.
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*
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* 1) If the single-stepped instruction was pushfl, then the TF and IF
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* flags are set in the just-pushed eflags, and may need to be cleared.
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*
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* 2) If the single-stepped instruction was a call, the return address
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* that is atop the stack is the address following the copied instruction.
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* We need to make it the address following the original instruction.
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*/
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static void resume_execution(struct kprobe *p, struct pt_regs *regs)
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{
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unsigned long *tos = (unsigned long *)®s->esp;
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unsigned long next_eip = 0;
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unsigned long copy_eip = (unsigned long)&p->ainsn.insn;
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unsigned long orig_eip = (unsigned long)p->addr;
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switch (p->ainsn.insn[0]) {
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case 0x9c: /* pushfl */
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*tos &= ~(TF_MASK | IF_MASK);
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*tos |= kprobe_old_eflags;
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break;
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case 0xc3: /* ret/lret */
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case 0xcb:
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case 0xc2:
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case 0xca:
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regs->eflags &= ~TF_MASK;
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/* eip is already adjusted, no more changes required*/
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return;
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case 0xe8: /* call relative - Fix return addr */
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*tos = orig_eip + (*tos - copy_eip);
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break;
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case 0xff:
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if ((p->ainsn.insn[1] & 0x30) == 0x10) {
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/* call absolute, indirect */
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/* Fix return addr; eip is correct. */
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next_eip = regs->eip;
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*tos = orig_eip + (*tos - copy_eip);
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} else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
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((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
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/* eip is correct. */
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next_eip = regs->eip;
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}
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break;
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case 0xea: /* jmp absolute -- eip is correct */
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next_eip = regs->eip;
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break;
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default:
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break;
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}
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regs->eflags &= ~TF_MASK;
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if (next_eip) {
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regs->eip = next_eip;
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} else {
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regs->eip = orig_eip + (regs->eip - copy_eip);
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}
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}
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/*
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* Interrupts are disabled on entry as trap1 is an interrupt gate and they
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* remain disabled thoroughout this function. And we hold kprobe lock.
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*/
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static inline int post_kprobe_handler(struct pt_regs *regs)
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{
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if (!kprobe_running())
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return 0;
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if (current_kprobe->post_handler)
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current_kprobe->post_handler(current_kprobe, regs, 0);
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if (current_kprobe->post_handler != trampoline_post_handler)
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resume_execution(current_kprobe, regs);
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regs->eflags |= kprobe_saved_eflags;
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unlock_kprobes();
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preempt_enable_no_resched();
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/*
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* if somebody else is singlestepping across a probe point, eflags
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* will have TF set, in which case, continue the remaining processing
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* of do_debug, as if this is not a probe hit.
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*/
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if (regs->eflags & TF_MASK)
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return 0;
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return 1;
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}
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/* Interrupts disabled, kprobe_lock held. */
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static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
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{
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if (current_kprobe->fault_handler
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&& current_kprobe->fault_handler(current_kprobe, regs, trapnr))
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return 1;
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if (kprobe_status & KPROBE_HIT_SS) {
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resume_execution(current_kprobe, regs);
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regs->eflags |= kprobe_old_eflags;
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unlock_kprobes();
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preempt_enable_no_resched();
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}
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return 0;
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}
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/*
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* Wrapper routine to for handling exceptions.
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*/
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int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
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void *data)
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{
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struct die_args *args = (struct die_args *)data;
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switch (val) {
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case DIE_INT3:
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if (kprobe_handler(args->regs))
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return NOTIFY_STOP;
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break;
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case DIE_DEBUG:
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if (post_kprobe_handler(args->regs))
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return NOTIFY_STOP;
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break;
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case DIE_GPF:
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if (kprobe_running() &&
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kprobe_fault_handler(args->regs, args->trapnr))
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return NOTIFY_STOP;
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break;
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case DIE_PAGE_FAULT:
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if (kprobe_running() &&
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kprobe_fault_handler(args->regs, args->trapnr))
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return NOTIFY_STOP;
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break;
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default:
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break;
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}
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return NOTIFY_DONE;
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}
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int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
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{
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struct jprobe *jp = container_of(p, struct jprobe, kp);
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unsigned long addr;
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jprobe_saved_regs = *regs;
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jprobe_saved_esp = ®s->esp;
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addr = (unsigned long)jprobe_saved_esp;
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/*
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* TBD: As Linus pointed out, gcc assumes that the callee
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* owns the argument space and could overwrite it, e.g.
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* tailcall optimization. So, to be absolutely safe
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* we also save and restore enough stack bytes to cover
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* the argument area.
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*/
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memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr));
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regs->eflags &= ~IF_MASK;
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regs->eip = (unsigned long)(jp->entry);
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return 1;
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}
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void jprobe_return(void)
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{
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preempt_enable_no_resched();
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asm volatile (" xchgl %%ebx,%%esp \n"
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" int3 \n"
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" .globl jprobe_return_end \n"
|
|
" jprobe_return_end: \n"
|
|
" nop \n"::"b"
|
|
(jprobe_saved_esp):"memory");
|
|
}
|
|
|
|
int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
|
|
{
|
|
u8 *addr = (u8 *) (regs->eip - 1);
|
|
unsigned long stack_addr = (unsigned long)jprobe_saved_esp;
|
|
struct jprobe *jp = container_of(p, struct jprobe, kp);
|
|
|
|
if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
|
|
if (®s->esp != jprobe_saved_esp) {
|
|
struct pt_regs *saved_regs =
|
|
container_of(jprobe_saved_esp, struct pt_regs, esp);
|
|
printk("current esp %p does not match saved esp %p\n",
|
|
®s->esp, jprobe_saved_esp);
|
|
printk("Saved registers for jprobe %p\n", jp);
|
|
show_registers(saved_regs);
|
|
printk("Current registers\n");
|
|
show_registers(regs);
|
|
BUG();
|
|
}
|
|
*regs = jprobe_saved_regs;
|
|
memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,
|
|
MIN_STACK_SIZE(stack_addr));
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|