332 lines
9.1 KiB
C
332 lines
9.1 KiB
C
/*
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* User-space Probes (UProbes) for sparc
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*
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* Copyright (C) 2013 Oracle Inc.
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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, see <http://www.gnu.org/licenses/>.
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*
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* Authors:
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* Jose E. Marchesi <jose.marchesi@oracle.com>
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* Eric Saint Etienne <eric.saint.etienne@oracle.com>
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*/
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#include <linux/kernel.h>
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#include <linux/highmem.h>
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#include <linux/uprobes.h>
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#include <linux/uaccess.h>
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#include <linux/sched.h> /* For struct task_struct */
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#include <linux/kdebug.h>
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#include <asm/cacheflush.h>
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#include <linux/uaccess.h>
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/* Compute the address of the breakpoint instruction and return it.
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*
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* Note that uprobe_get_swbp_addr is defined as a weak symbol in
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* kernel/events/uprobe.c.
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*/
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unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
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{
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return instruction_pointer(regs);
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}
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static void copy_to_page(struct page *page, unsigned long vaddr,
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const void *src, int len)
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{
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void *kaddr = kmap_atomic(page);
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memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
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kunmap_atomic(kaddr);
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}
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/* Fill in the xol area with the probed instruction followed by the
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* single-step trap. Some fixups in the copied instruction are
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* performed at this point.
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*
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* Note that uprobe_xol_copy is defined as a weak symbol in
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* kernel/events/uprobe.c.
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*/
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void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
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void *src, unsigned long len)
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{
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const u32 stp_insn = UPROBE_STP_INSN;
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u32 insn = *(u32 *) src;
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/* Branches annulling their delay slot must be fixed to not do
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* so. Clearing the annul bit on these instructions we can be
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* sure the single-step breakpoint in the XOL slot will be
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* executed.
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*/
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u32 op = (insn >> 30) & 0x3;
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u32 op2 = (insn >> 22) & 0x7;
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if (op == 0 &&
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(op2 == 1 || op2 == 2 || op2 == 3 || op2 == 5 || op2 == 6) &&
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(insn & ANNUL_BIT) == ANNUL_BIT)
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insn &= ~ANNUL_BIT;
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copy_to_page(page, vaddr, &insn, len);
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copy_to_page(page, vaddr+len, &stp_insn, 4);
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}
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/* Instruction analysis/validity.
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*
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* This function returns 0 on success or a -ve number on error.
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*/
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int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
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struct mm_struct *mm, unsigned long addr)
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{
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/* Any unsupported instruction? Then return -EINVAL */
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return 0;
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}
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/* If INSN is a relative control transfer instruction, return the
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* corrected branch destination value.
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*
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* Note that regs->tpc and regs->tnpc still hold the values of the
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* program counters at the time of the single-step trap due to the
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* execution of the UPROBE_STP_INSN at utask->xol_vaddr + 4.
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*
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*/
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static unsigned long relbranch_fixup(u32 insn, struct uprobe_task *utask,
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struct pt_regs *regs)
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{
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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 utask->autask.saved_tnpc + 0x4UL;
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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 real_pc = (unsigned long) utask->vaddr;
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unsigned long ixol_addr = utask->xol_vaddr;
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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 - ixol_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 its PC location
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* into a destination register, fix that up.
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*/
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static int 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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int rc = 0;
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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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/* '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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unsigned long fp = regs->u_regs[UREG_FP];
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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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if (test_thread_64bit_stack(fp)) {
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unsigned long __user *uslot =
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(unsigned long __user *) (fp + STACK_BIAS) + rd;
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rc = __put_user(real_pc, uslot);
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} else {
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unsigned int __user *uslot = (unsigned int
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__user *) fp + rd;
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rc = __put_user((u32) real_pc, uslot);
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}
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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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return rc;
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}
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/* Single-stepping can be avoided for certain instructions: NOPs and
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* instructions that can be emulated. This function determines
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* whether the instruction where the uprobe is installed falls in one
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* of these cases and emulates it.
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*
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* This function returns true if the single-stepping can be skipped,
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* false otherwise.
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*/
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bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
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{
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/* We currently only emulate NOP instructions.
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*/
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if (auprobe->ixol == (1 << 24)) {
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regs->tnpc += 4;
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regs->tpc += 4;
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return true;
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}
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return false;
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}
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/* Prepare to execute out of line. At this point
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* current->utask->xol_vaddr points to an allocated XOL slot properly
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* initialized with the original instruction and the single-stepping
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* trap instruction.
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*
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* This function returns 0 on success, any other number on error.
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*/
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int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
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{
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struct uprobe_task *utask = current->utask;
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struct arch_uprobe_task *autask = ¤t->utask->autask;
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/* Save the current program counters so they can be restored
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* later.
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*/
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autask->saved_tpc = regs->tpc;
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autask->saved_tnpc = regs->tnpc;
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/* Adjust PC and NPC so the first instruction in the XOL slot
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* will be executed by the user task.
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*/
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instruction_pointer_set(regs, utask->xol_vaddr);
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return 0;
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}
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/* Prepare to resume execution after the single-step. Called after
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* single-stepping. 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.
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*
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* This function returns 0 on success, any other number on error.
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*/
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int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
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{
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struct uprobe_task *utask = current->utask;
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struct arch_uprobe_task *autask = &utask->autask;
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u32 insn = auprobe->ixol;
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int rc = 0;
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if (utask->state == UTASK_SSTEP_ACK) {
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regs->tnpc = relbranch_fixup(insn, utask, regs);
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regs->tpc = autask->saved_tnpc;
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rc = retpc_fixup(regs, insn, (unsigned long) utask->vaddr);
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} else {
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regs->tnpc = utask->vaddr+4;
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regs->tpc = autask->saved_tnpc+4;
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}
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return rc;
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}
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/* Handler for uprobe traps. This is called from the traps table and
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* triggers the proper die notification.
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*/
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asmlinkage void uprobe_trap(struct pt_regs *regs,
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unsigned long trap_level)
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{
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BUG_ON(trap_level != 0x173 && trap_level != 0x174);
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/* We are only interested in user-mode code. Uprobe traps
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* shall not be present in kernel code.
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*/
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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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return;
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}
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/* trap_level == 0x173 --> ta 0x73
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* trap_level == 0x174 --> ta 0x74
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*/
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if (notify_die((trap_level == 0x173) ? DIE_BPT : DIE_SSTEP,
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(trap_level == 0x173) ? "bpt" : "sstep",
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regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
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bad_trap(regs, trap_level);
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}
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/* Callback routine for handling die notifications.
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*/
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int arch_uprobe_exception_notify(struct notifier_block *self,
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unsigned long val, void *data)
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{
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int ret = NOTIFY_DONE;
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struct die_args *args = (struct die_args *)data;
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/* We are only interested in userspace traps */
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if (args->regs && !user_mode(args->regs))
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return NOTIFY_DONE;
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switch (val) {
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case DIE_BPT:
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if (uprobe_pre_sstep_notifier(args->regs))
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ret = NOTIFY_STOP;
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break;
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case DIE_SSTEP:
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if (uprobe_post_sstep_notifier(args->regs))
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ret = NOTIFY_STOP;
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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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/* This function gets called when a XOL instruction either gets
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* trapped or the thread has a fatal signal, so reset the instruction
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* pointer to its probed address.
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*/
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void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
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{
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struct uprobe_task *utask = current->utask;
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instruction_pointer_set(regs, utask->vaddr);
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}
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/* If xol insn itself traps and generates a signal(Say,
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* SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
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* instruction jumps back to its own address.
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*/
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bool arch_uprobe_xol_was_trapped(struct task_struct *t)
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{
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return false;
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}
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unsigned long
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arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
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struct pt_regs *regs)
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{
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unsigned long orig_ret_vaddr = regs->u_regs[UREG_I7];
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regs->u_regs[UREG_I7] = trampoline_vaddr-8;
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return orig_ret_vaddr + 8;
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}
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