263 lines
6.5 KiB
C
263 lines
6.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/highmem.h>
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#include <linux/kdebug.h>
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#include <linux/types.h>
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#include <linux/notifier.h>
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#include <linux/sched.h>
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#include <linux/uprobes.h>
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#include <asm/branch.h>
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#include <asm/cpu-features.h>
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#include <asm/ptrace.h>
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#include "probes-common.h"
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static inline int insn_has_delay_slot(const union mips_instruction insn)
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{
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return __insn_has_delay_slot(insn);
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}
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/**
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* arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
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* @mm: the probed address space.
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* @arch_uprobe: the probepoint information.
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* @addr: virtual address at which to install the probepoint
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* Return 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 *aup,
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struct mm_struct *mm, unsigned long addr)
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{
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union mips_instruction inst;
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/*
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* For the time being this also blocks attempts to use uprobes with
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* MIPS16 and microMIPS.
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*/
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if (addr & 0x03)
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return -EINVAL;
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inst.word = aup->insn[0];
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if (__insn_is_compact_branch(inst)) {
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pr_notice("Uprobes for compact branches are not supported\n");
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return -EINVAL;
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}
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aup->ixol[0] = aup->insn[insn_has_delay_slot(inst)];
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aup->ixol[1] = UPROBE_BRK_UPROBE_XOL; /* NOP */
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return 0;
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}
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/**
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* is_trap_insn - check if the instruction is a trap variant
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* @insn: instruction to be checked.
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* Returns true if @insn is a trap variant.
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*
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* This definition overrides the weak definition in kernel/events/uprobes.c.
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* and is needed for the case where an architecture has multiple trap
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* instructions (like PowerPC or MIPS). We treat BREAK just like the more
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* modern conditional trap instructions.
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*/
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bool is_trap_insn(uprobe_opcode_t *insn)
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{
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union mips_instruction inst;
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inst.word = *insn;
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switch (inst.i_format.opcode) {
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case spec_op:
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switch (inst.r_format.func) {
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case break_op:
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case teq_op:
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case tge_op:
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case tgeu_op:
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case tlt_op:
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case tltu_op:
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case tne_op:
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return 1;
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}
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break;
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case bcond_op: /* Yes, really ... */
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switch (inst.u_format.rt) {
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case teqi_op:
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case tgei_op:
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case tgeiu_op:
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case tlti_op:
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case tltiu_op:
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case tnei_op:
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return 1;
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}
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break;
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}
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return 0;
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}
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#define UPROBE_TRAP_NR ULONG_MAX
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/*
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* arch_uprobe_pre_xol - prepare to execute out of line.
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* @auprobe: the probepoint information.
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* @regs: reflects the saved user state of current task.
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*/
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int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs)
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{
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struct uprobe_task *utask = current->utask;
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/*
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* Now find the EPC where to resume after the breakpoint has been
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* dealt with. This may require emulation of a branch.
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*/
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aup->resume_epc = regs->cp0_epc + 4;
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if (insn_has_delay_slot((union mips_instruction) aup->insn[0])) {
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__compute_return_epc_for_insn(regs,
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(union mips_instruction) aup->insn[0]);
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aup->resume_epc = regs->cp0_epc;
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}
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utask->autask.saved_trap_nr = current->thread.trap_nr;
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current->thread.trap_nr = UPROBE_TRAP_NR;
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regs->cp0_epc = current->utask->xol_vaddr;
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return 0;
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}
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int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs)
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{
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struct uprobe_task *utask = current->utask;
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current->thread.trap_nr = utask->autask.saved_trap_nr;
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regs->cp0_epc = aup->resume_epc;
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return 0;
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}
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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. It is assumed that anything
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* like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
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*
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* arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
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* arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
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* UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
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*/
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bool arch_uprobe_xol_was_trapped(struct task_struct *tsk)
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{
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if (tsk->thread.trap_nr != UPROBE_TRAP_NR)
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return true;
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return false;
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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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struct die_args *args = data;
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struct pt_regs *regs = args->regs;
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/* regs == NULL is a kernel bug */
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if (WARN_ON(!regs))
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return NOTIFY_DONE;
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/* We are only interested in userspace traps */
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if (!user_mode(regs))
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return NOTIFY_DONE;
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switch (val) {
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case DIE_UPROBE:
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if (uprobe_pre_sstep_notifier(regs))
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return NOTIFY_STOP;
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break;
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case DIE_UPROBE_XOL:
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if (uprobe_post_sstep_notifier(regs))
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return NOTIFY_STOP;
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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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* This function gets called when XOL instruction either gets trapped or
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* the thread has a fatal signal. Reset the instruction pointer to its
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* probed address for the potential restart or for post mortem analysis.
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*/
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void arch_uprobe_abort_xol(struct arch_uprobe *aup,
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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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unsigned long arch_uretprobe_hijack_return_addr(
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unsigned long trampoline_vaddr, struct pt_regs *regs)
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{
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unsigned long ra;
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ra = regs->regs[31];
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/* Replace the return address with the trampoline address */
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regs->regs[31] = trampoline_vaddr;
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return ra;
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}
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/**
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* set_swbp - store breakpoint at a given address.
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* @auprobe: arch specific probepoint information.
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* @mm: the probed process address space.
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* @vaddr: the virtual address to insert the opcode.
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*
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* For mm @mm, store the breakpoint instruction at @vaddr.
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* Return 0 (success) or a negative errno.
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*
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* This version overrides the weak version in kernel/events/uprobes.c.
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* It is required to handle MIPS16 and microMIPS.
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*/
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int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm,
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unsigned long vaddr)
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{
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return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
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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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unsigned long kaddr, kstart;
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/* Initialize the slot */
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kaddr = (unsigned long)kmap_atomic(page);
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kstart = kaddr + (vaddr & ~PAGE_MASK);
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memcpy((void *)kstart, src, len);
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flush_icache_range(kstart, kstart + len);
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kunmap_atomic((void *)kaddr);
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}
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/**
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* uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
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* @regs: Reflects the saved state of the task after it has hit a breakpoint
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* instruction.
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* Return the address of the breakpoint instruction.
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*
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* This overrides the weak version in kernel/events/uprobes.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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/*
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* See if the instruction can be emulated.
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* Returns true if instruction was emulated, false otherwise.
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*
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* For now we always emulate so this function just returns 0.
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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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return 0;
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}
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