386 lines
11 KiB
C
386 lines
11 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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*/
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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/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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}
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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 disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
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{
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*p->addr = p->opcode;
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regs->eip = (unsigned long)p->addr;
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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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/*
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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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disarm_kprobe(p, regs);
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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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* 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 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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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"
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" jprobe_return_end: \n"
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" nop \n"::"b"
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(jprobe_saved_esp):"memory");
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}
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int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
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{
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u8 *addr = (u8 *) (regs->eip - 1);
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unsigned long stack_addr = (unsigned long)jprobe_saved_esp;
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struct jprobe *jp = container_of(p, struct jprobe, kp);
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if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
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if (®s->esp != jprobe_saved_esp) {
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struct pt_regs *saved_regs =
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container_of(jprobe_saved_esp, struct pt_regs, esp);
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printk("current esp %p does not match saved esp %p\n",
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®s->esp, jprobe_saved_esp);
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printk("Saved registers for jprobe %p\n", jp);
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show_registers(saved_regs);
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printk("Current registers\n");
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show_registers(regs);
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BUG();
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}
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*regs = jprobe_saved_regs;
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memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,
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MIN_STACK_SIZE(stack_addr));
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return 1;
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}
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return 0;
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}
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