552 lines
15 KiB
C
Executable file
552 lines
15 KiB
C
Executable file
// SPDX-License-Identifier: GPL-2.0
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/* arch/sparc64/kernel/kprobes.c
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*
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* Copyright (C) 2004 David S. Miller <davem@davemloft.net>
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*/
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#include <linux/kernel.h>
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#include <linux/kprobes.h>
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#include <linux/extable.h>
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#include <linux/kdebug.h>
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#include <linux/slab.h>
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#include <linux/context_tracking.h>
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#include <asm/signal.h>
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#include <asm/cacheflush.h>
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#include <linux/uaccess.h>
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/* We do not have hardware single-stepping on sparc64.
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* So we implement software single-stepping with breakpoint
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* traps. The top-level scheme is similar to that used
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* in the x86 kprobes implementation.
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*
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* In the kprobe->ainsn.insn[] array we store the original
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* instruction at index zero and a break instruction at
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* index one.
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*
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* When we hit a kprobe we:
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* - Run the pre-handler
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* - Remember "regs->tnpc" and interrupt level stored in
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* "regs->tstate" so we can restore them later
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* - Disable PIL interrupts
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* - Set regs->tpc to point to kprobe->ainsn.insn[0]
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* - Set regs->tnpc to point to kprobe->ainsn.insn[1]
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* - Mark that we are actively in a kprobe
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*
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* At this point we wait for the second breakpoint at
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* kprobe->ainsn.insn[1] to hit. When it does we:
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* - Run the post-handler
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* - Set regs->tpc to "remembered" regs->tnpc stored above,
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* restore the PIL interrupt level in "regs->tstate" as well
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* - Make any adjustments necessary to regs->tnpc in order
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* to handle relative branches correctly. See below.
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* - Mark that we are no longer actively in a kprobe.
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*/
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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
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int __kprobes arch_prepare_kprobe(struct kprobe *p)
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{
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if ((unsigned long) p->addr & 0x3UL)
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return -EILSEQ;
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p->ainsn.insn[0] = *p->addr;
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flushi(&p->ainsn.insn[0]);
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p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
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flushi(&p->ainsn.insn[1]);
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p->opcode = *p->addr;
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return 0;
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}
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void __kprobes arch_arm_kprobe(struct kprobe *p)
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{
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*p->addr = BREAKPOINT_INSTRUCTION;
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flushi(p->addr);
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}
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void __kprobes arch_disarm_kprobe(struct kprobe *p)
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{
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*p->addr = p->opcode;
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flushi(p->addr);
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}
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static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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kcb->prev_kprobe.kp = kprobe_running();
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kcb->prev_kprobe.status = kcb->kprobe_status;
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kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
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kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
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}
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static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
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kcb->kprobe_status = kcb->prev_kprobe.status;
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kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
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kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
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}
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static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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__this_cpu_write(current_kprobe, p);
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kcb->kprobe_orig_tnpc = regs->tnpc;
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kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
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}
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static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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regs->tstate |= TSTATE_PIL;
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/*single step inline, if it a breakpoint instruction*/
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if (p->opcode == BREAKPOINT_INSTRUCTION) {
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regs->tpc = (unsigned long) p->addr;
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regs->tnpc = kcb->kprobe_orig_tnpc;
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} else {
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regs->tpc = (unsigned long) &p->ainsn.insn[0];
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regs->tnpc = (unsigned long) &p->ainsn.insn[1];
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}
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}
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static int __kprobes kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p;
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void *addr = (void *) regs->tpc;
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int ret = 0;
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struct kprobe_ctlblk *kcb;
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/*
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* We don't want to be preempted for the entire
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* duration of kprobe processing
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*/
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preempt_disable();
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kcb = get_kprobe_ctlblk();
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if (kprobe_running()) {
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p = get_kprobe(addr);
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if (p) {
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if (kcb->kprobe_status == KPROBE_HIT_SS) {
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regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
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kcb->kprobe_orig_tstate_pil);
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goto no_kprobe;
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}
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/* We have reentered the kprobe_handler(), since
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* another probe was hit while within the handler.
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* We here save the original kprobes variables and
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* just single step on the instruction of the new probe
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* without calling any user handlers.
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*/
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save_previous_kprobe(kcb);
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set_current_kprobe(p, regs, kcb);
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kprobes_inc_nmissed_count(p);
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kcb->kprobe_status = KPROBE_REENTER;
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prepare_singlestep(p, regs, kcb);
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return 1;
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} else if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
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/* The breakpoint instruction was removed by
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* another cpu right after we hit, 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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goto no_kprobe;
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}
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p = get_kprobe(addr);
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if (!p) {
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if (*(u32 *)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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set_current_kprobe(p, regs, kcb);
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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if (p->pre_handler && p->pre_handler(p, regs)) {
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reset_current_kprobe();
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preempt_enable_no_resched();
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return 1;
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}
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prepare_singlestep(p, regs, kcb);
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kcb->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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/* If INSN is a relative control transfer instruction,
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* return the corrected branch destination value.
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*
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* regs->tpc and regs->tnpc still hold the values of the
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* program counters at the time of trap due to the execution
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* of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1]
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*
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*/
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static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p,
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struct pt_regs *regs)
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{
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unsigned long real_pc = (unsigned long) p->addr;
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/* Branch not taken, no mods necessary. */
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if (regs->tnpc == regs->tpc + 0x4UL)
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return real_pc + 0x8UL;
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/* The three cases are call, branch w/prediction,
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* and traditional branch.
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*/
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if ((insn & 0xc0000000) == 0x40000000 ||
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(insn & 0xc1c00000) == 0x00400000 ||
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(insn & 0xc1c00000) == 0x00800000) {
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unsigned long ainsn_addr;
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ainsn_addr = (unsigned long) &p->ainsn.insn[0];
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/* The instruction did all the work for us
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* already, just apply the offset to the correct
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* instruction location.
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*/
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return (real_pc + (regs->tnpc - ainsn_addr));
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}
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/* It is jmpl or some other absolute PC modification instruction,
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* leave NPC as-is.
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*/
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return regs->tnpc;
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}
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/* If INSN is an instruction which writes it's PC location
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* into a destination register, fix that up.
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*/
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static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
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unsigned long real_pc)
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{
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unsigned long *slot = NULL;
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/* Simplest case is 'call', which always uses %o7 */
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if ((insn & 0xc0000000) == 0x40000000) {
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slot = ®s->u_regs[UREG_I7];
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}
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/* 'jmpl' encodes the register inside of the opcode */
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if ((insn & 0xc1f80000) == 0x81c00000) {
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unsigned long rd = ((insn >> 25) & 0x1f);
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if (rd <= 15) {
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slot = ®s->u_regs[rd];
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} else {
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/* Hard case, it goes onto the stack. */
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flushw_all();
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rd -= 16;
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slot = (unsigned long *)
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(regs->u_regs[UREG_FP] + STACK_BIAS);
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slot += rd;
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}
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}
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if (slot != NULL)
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*slot = real_pc;
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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 which has been replaced by the breakpoint
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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[0].
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*
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* This function prepares to return from the post-single-step
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* breakpoint trap.
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*/
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static void __kprobes resume_execution(struct kprobe *p,
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struct pt_regs *regs, struct kprobe_ctlblk *kcb)
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{
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u32 insn = p->ainsn.insn[0];
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regs->tnpc = relbranch_fixup(insn, p, regs);
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/* This assignment must occur after relbranch_fixup() */
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regs->tpc = kcb->kprobe_orig_tnpc;
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retpc_fixup(regs, insn, (unsigned long) p->addr);
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regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
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kcb->kprobe_orig_tstate_pil);
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}
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static int __kprobes post_kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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if (!cur)
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return 0;
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if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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cur->post_handler(cur, regs, 0);
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}
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resume_execution(cur, regs, kcb);
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/*Restore back the original saved kprobes variables and continue. */
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if (kcb->kprobe_status == KPROBE_REENTER) {
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restore_previous_kprobe(kcb);
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goto out;
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}
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reset_current_kprobe();
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out:
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preempt_enable_no_resched();
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return 1;
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}
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int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
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{
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struct kprobe *cur = kprobe_running();
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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const struct exception_table_entry *entry;
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switch(kcb->kprobe_status) {
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case KPROBE_HIT_SS:
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case KPROBE_REENTER:
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/*
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* We are here because the instruction being single
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* stepped caused a page fault. We reset the current
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* kprobe and the tpc points back to the probe address
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* and allow the page fault handler to continue as a
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* normal page fault.
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*/
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regs->tpc = (unsigned long)cur->addr;
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regs->tnpc = kcb->kprobe_orig_tnpc;
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regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
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kcb->kprobe_orig_tstate_pil);
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if (kcb->kprobe_status == KPROBE_REENTER)
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restore_previous_kprobe(kcb);
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else
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reset_current_kprobe();
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preempt_enable_no_resched();
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break;
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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/*
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* We increment the nmissed count for accounting,
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* we can also use npre/npostfault count for accounting
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* these specific fault cases.
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*/
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kprobes_inc_nmissed_count(cur);
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/*
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* We come here because instructions in the pre/post
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* handler caused the page_fault, this could happen
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* if handler tries to access user space by
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* copy_from_user(), get_user() etc. Let the
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* user-specified handler try to fix it first.
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*/
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if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
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return 1;
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/*
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* In case the user-specified fault handler returned
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* zero, try to fix up.
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*/
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entry = search_exception_tables(regs->tpc);
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if (entry) {
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regs->tpc = entry->fixup;
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regs->tnpc = regs->tpc + 4;
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return 1;
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}
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/*
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* fixup_exception() could not handle it,
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* Let do_page_fault() fix it.
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*/
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break;
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default:
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break;
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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 __kprobes kprobe_exceptions_notify(struct notifier_block *self,
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unsigned long val, void *data)
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{
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struct die_args *args = (struct die_args *)data;
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int ret = NOTIFY_DONE;
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if (args->regs && user_mode(args->regs))
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return ret;
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switch (val) {
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case DIE_DEBUG:
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if (kprobe_handler(args->regs))
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ret = NOTIFY_STOP;
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break;
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case DIE_DEBUG_2:
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if (post_kprobe_handler(args->regs))
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ret = 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 ret;
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}
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asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
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struct pt_regs *regs)
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{
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enum ctx_state prev_state = exception_enter();
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BUG_ON(trap_level != 0x170 && trap_level != 0x171);
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if (user_mode(regs)) {
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local_irq_enable();
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bad_trap(regs, trap_level);
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goto out;
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}
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/* trap_level == 0x170 --> ta 0x70
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* trap_level == 0x171 --> ta 0x71
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*/
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if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
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(trap_level == 0x170) ? "debug" : "debug_2",
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regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
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bad_trap(regs, trap_level);
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out:
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exception_exit(prev_state);
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}
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/* The value stored in the return address register is actually 2
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* instructions before where the callee will return to.
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* Sequences usually look something like this
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*
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* call some_function <--- return register points here
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* nop <--- call delay slot
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* whatever <--- where callee returns to
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*
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* To keep trampoline_probe_handler logic simpler, we normalize the
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* value kept in ri->ret_addr so we don't need to keep adjusting it
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* back and forth.
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*/
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void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
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struct pt_regs *regs)
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{
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ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8);
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/* Replace the return addr with trampoline addr */
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regs->u_regs[UREG_RETPC] =
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((unsigned long)kretprobe_trampoline) - 8;
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}
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/*
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* Called when the probe at kretprobe trampoline is hit
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*/
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static int __kprobes trampoline_probe_handler(struct kprobe *p,
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struct pt_regs *regs)
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{
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struct kretprobe_instance *ri = NULL;
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struct hlist_head *head, empty_rp;
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struct hlist_node *tmp;
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unsigned long flags, orig_ret_address = 0;
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unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
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INIT_HLIST_HEAD(&empty_rp);
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kretprobe_hash_lock(current, &head, &flags);
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/*
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* It is possible to have multiple instances associated with a given
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* task either because an multiple functions in the call path
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* have a return probe installed on them, and/or more than one return
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* return probe was registered for a target function.
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*
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* We can handle this because:
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* - instances are always inserted at the head of the list
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* - when multiple return probes are registered for the same
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* function, the first instance's ret_addr will point to the
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* real return address, and all the rest will point to
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* kretprobe_trampoline
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*/
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hlist_for_each_entry_safe(ri, tmp, head, hlist) {
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if (ri->task != current)
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/* another task is sharing our hash bucket */
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continue;
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if (ri->rp && ri->rp->handler)
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ri->rp->handler(ri, regs);
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orig_ret_address = (unsigned long)ri->ret_addr;
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recycle_rp_inst(ri, &empty_rp);
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if (orig_ret_address != trampoline_address)
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/*
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* This is the real return address. Any other
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* instances associated with this task are for
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* other calls deeper on the call stack
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*/
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break;
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}
|
|
|
|
kretprobe_assert(ri, orig_ret_address, trampoline_address);
|
|
regs->tpc = orig_ret_address;
|
|
regs->tnpc = orig_ret_address + 4;
|
|
|
|
kretprobe_hash_unlock(current, &flags);
|
|
|
|
hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
|
|
hlist_del(&ri->hlist);
|
|
kfree(ri);
|
|
}
|
|
/*
|
|
* By returning a non-zero value, we are telling
|
|
* kprobe_handler() that we don't want the post_handler
|
|
* to run (and have re-enabled preemption)
|
|
*/
|
|
return 1;
|
|
}
|
|
|
|
static void __used kretprobe_trampoline_holder(void)
|
|
{
|
|
asm volatile(".global kretprobe_trampoline\n"
|
|
"kretprobe_trampoline:\n"
|
|
"\tnop\n"
|
|
"\tnop\n");
|
|
}
|
|
static struct kprobe trampoline_p = {
|
|
.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
|
|
.pre_handler = trampoline_probe_handler
|
|
};
|
|
|
|
int __init arch_init_kprobes(void)
|
|
{
|
|
return register_kprobe(&trampoline_p);
|
|
}
|
|
|
|
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
|
|
{
|
|
if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|