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318 lines
8.5 KiB
318 lines
8.5 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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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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* Authors: |
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* Jose E. Marchesi <[email protected]> |
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* Eric Saint Etienne <[email protected]> |
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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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/* 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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