/* * 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 /** * is_trap_insn - check if the instruction is a trap variant * @insn: instruction to be checked. * Returns true if @insn is a trap variant. */ bool is_trap_insn(uprobe_opcode_t *insn) { return (is_trap(*insn)); } /** * 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; 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; user_enable_single_step(current); 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; user_disable_single_step(current); 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); user_disable_single_step(current); } /* * 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->insn); if (ret > 0) return true; return false; } unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) { unsigned long orig_ret_vaddr; orig_ret_vaddr = regs->link; /* Replace the return addr with trampoline addr */ regs->link = trampoline_vaddr; return orig_ret_vaddr; }