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/*
* User-space Probes (UProbes) for powerpc
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright IBM Corporation, 2007-2012
*
* Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com>
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/uprobes.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
#include <asm/sstep.h>
#define UPROBE_TRAP_NR UINT_MAX
/**
* arch_uprobe_analyze_insn
* @mm: the probed address space.
* @arch_uprobe: the probepoint information.
* @addr: vaddr to probe.
* Return 0 on success or a -ve number on error.
*/
int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
struct mm_struct *mm, unsigned long addr)
{
if (addr & 0x03)
return -EINVAL;
/*
* We currently don't support a uprobe on an already
* existing breakpoint instruction underneath
*/
if (is_trap(auprobe->ainsn))
return -ENOTSUPP;
return 0;
}
/*
* arch_uprobe_pre_xol - prepare to execute out of line.
* @auprobe: the probepoint information.
* @regs: reflects the saved user state of current task.
*/
int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct arch_uprobe_task *autask = ¤t->utask->autask;
autask->saved_trap_nr = current->thread.trap_nr;
current->thread.trap_nr = UPROBE_TRAP_NR;
regs->nip = current->utask->xol_vaddr;
return 0;
}
/**
* uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
* @regs: Reflects the saved state of the task after it has hit a breakpoint
* instruction.
* Return the address of the breakpoint instruction.
*/
unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
{
return instruction_pointer(regs);
}
/*
* If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc),
* then detect the case where a singlestepped instruction jumps back to its
* own address. It is assumed that anything like do_page_fault/do_trap/etc
* sets thread.trap_nr != UINT_MAX.
*
* arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
* arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
* UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol().
*/
bool arch_uprobe_xol_was_trapped(struct task_struct *t)
{
if (t->thread.trap_nr != UPROBE_TRAP_NR)
return true;
return false;
}
/*
* Called after single-stepping. To avoid the SMP problems that can
* occur when we temporarily put back the original opcode to
* single-step, we single-stepped a copy of the instruction.
*
* This function prepares to resume execution after the single-step.
*/
int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
current->thread.trap_nr = utask->autask.saved_trap_nr;
/*
* On powerpc, except for loads and stores, most instructions
* including ones that alter code flow (branches, calls, returns)
* are emulated in the kernel. We get here only if the emulation
* support doesn't exist and have to fix-up the next instruction
* to be executed.
*/
regs->nip = utask->vaddr + MAX_UINSN_BYTES;
return 0;
}
/* callback routine for handling exceptions. */
int arch_uprobe_exception_notify(struct notifier_block *self,
unsigned long val, void *data)
{
struct die_args *args = data;
struct pt_regs *regs = args->regs;
/* regs == NULL is a kernel bug */
if (WARN_ON(!regs))
return NOTIFY_DONE;
/* We are only interested in userspace traps */
if (!user_mode(regs))
return NOTIFY_DONE;
switch (val) {
case DIE_BPT:
if (uprobe_pre_sstep_notifier(regs))
return NOTIFY_STOP;
break;
case DIE_SSTEP:
if (uprobe_post_sstep_notifier(regs))
return NOTIFY_STOP;
default:
break;
}
return NOTIFY_DONE;
}
/*
* This function gets called when XOL instruction either gets trapped or
* the thread has a fatal signal, so reset the instruction pointer to its
* probed address.
*/
void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
current->thread.trap_nr = utask->autask.saved_trap_nr;
instruction_pointer_set(regs, utask->vaddr);
}
/*
* See if the instruction can be emulated.
* Returns true if instruction was emulated, false otherwise.
*/
bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
int ret;
/*
* emulate_step() returns 1 if the insn was successfully emulated.
* For all other cases, we need to single-step in hardware.
*/
ret = emulate_step(regs, auprobe->ainsn);
if (ret > 0)
return true;
return false;
}
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