arch/powerpc/kernel/uprobes.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * User-space Probes (UProbes) for powerpc
   4  *
   5  * Copyright IBM Corporation, 2007-2012
   6  *
   7  * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com>
   8  */
   9 #include <linux/kernel.h>
  10 #include <linux/sched.h>
  11 #include <linux/ptrace.h>
  12 #include <linux/uprobes.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/kdebug.h>
  15
  16 #include <asm/sstep.h>
  17 #include <asm/inst.h>
  18
  19 #define UPROBE_TRAP_NR  UINT_MAX
  20
  21 /**
  22  * is_trap_insn - check if the instruction is a trap variant
  23  * @insn: instruction to be checked.
  24  * Returns true if @insn is a trap variant.
  25  */
  26 bool is_trap_insn(uprobe_opcode_t *insn)
  27 {
  28         return (is_trap(*insn));
  29 }
  30
  31 /**
  32  * arch_uprobe_analyze_insn
  33  * @mm: the probed address space.
  34  * @arch_uprobe: the probepoint information.
  35  * @addr: vaddr to probe.
  36  * Return 0 on success or a -ve number on error.
  37  */
  38 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
  39                 struct mm_struct *mm, unsigned long addr)
  40 {
  41         if (addr & 0x03)
  42                 return -EINVAL;
  43
  44         return 0;
  45 }
  46
  47 /*
  48  * arch_uprobe_pre_xol - prepare to execute out of line.
  49  * @auprobe: the probepoint information.
  50  * @regs: reflects the saved user state of current task.
  51  */
  52 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  53 {
  54         struct arch_uprobe_task *autask = &current->utask->autask;
  55
  56         autask->saved_trap_nr = current->thread.trap_nr;
  57         current->thread.trap_nr = UPROBE_TRAP_NR;
  58         regs->nip = current->utask->xol_vaddr;
  59
  60         user_enable_single_step(current);
  61         return 0;
  62 }
  63
  64 /**
  65  * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
  66  * @regs: Reflects the saved state of the task after it has hit a breakpoint
  67  * instruction.
  68  * Return the address of the breakpoint instruction.
  69  */
  70 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
  71 {
  72         return instruction_pointer(regs);
  73 }
  74
  75 /*
  76  * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc),
  77  * then detect the case where a singlestepped instruction jumps back to its
  78  * own address. It is assumed that anything like do_page_fault/do_trap/etc
  79  * sets thread.trap_nr != UINT_MAX.
  80  *
  81  * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
  82  * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
  83  * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol().
  84  */
  85 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
  86 {
  87         if (t->thread.trap_nr != UPROBE_TRAP_NR)
  88                 return true;
  89
  90         return false;
  91 }
  92
  93 /*
  94  * Called after single-stepping. To avoid the SMP problems that can
  95  * occur when we temporarily put back the original opcode to
  96  * single-step, we single-stepped a copy of the instruction.
  97  *
  98  * This function prepares to resume execution after the single-step.
  99  */
 100 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 101 {
 102         struct uprobe_task *utask = current->utask;
 103
 104         WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
 105
 106         current->thread.trap_nr = utask->autask.saved_trap_nr;
 107
 108         /*
 109          * On powerpc, except for loads and stores, most instructions
 110          * including ones that alter code flow (branches, calls, returns)
 111          * are emulated in the kernel. We get here only if the emulation
 112          * support doesn't exist and have to fix-up the next instruction
 113          * to be executed.
 114          */
 115         regs->nip = (unsigned long)ppc_inst_next((void *)utask->vaddr, &auprobe->insn);
 116
 117         user_disable_single_step(current);
 118         return 0;
 119 }
 120
 121 /* callback routine for handling exceptions. */
 122 int arch_uprobe_exception_notify(struct notifier_block *self,
 123                                 unsigned long val, void *data)
 124 {
 125         struct die_args *args = data;
 126         struct pt_regs *regs = args->regs;
 127
 128         /* regs == NULL is a kernel bug */
 129         if (WARN_ON(!regs))
 130                 return NOTIFY_DONE;
 131
 132         /* We are only interested in userspace traps */
 133         if (!user_mode(regs))
 134                 return NOTIFY_DONE;
 135
 136         switch (val) {
 137         case DIE_BPT:
 138                 if (uprobe_pre_sstep_notifier(regs))
 139                         return NOTIFY_STOP;
 140                 break;
 141         case DIE_SSTEP:
 142                 if (uprobe_post_sstep_notifier(regs))
 143                         return NOTIFY_STOP;
 144                 break;
 145         default:
 146                 break;
 147         }
 148         return NOTIFY_DONE;
 149 }
 150
 151 /*
 152  * This function gets called when XOL instruction either gets trapped or
 153  * the thread has a fatal signal, so reset the instruction pointer to its
 154  * probed address.
 155  */
 156 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 157 {
 158         struct uprobe_task *utask = current->utask;
 159
 160         current->thread.trap_nr = utask->autask.saved_trap_nr;
 161         instruction_pointer_set(regs, utask->vaddr);
 162
 163         user_disable_single_step(current);
 164 }
 165
 166 /*
 167  * See if the instruction can be emulated.
 168  * Returns true if instruction was emulated, false otherwise.
 169  */
 170 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 171 {
 172         int ret;
 173
 174         /*
 175          * emulate_step() returns 1 if the insn was successfully emulated.
 176          * For all other cases, we need to single-step in hardware.
 177          */
 178         ret = emulate_step(regs, ppc_inst_read(&auprobe->insn));
 179         if (ret > 0)
 180                 return true;
 181
 182         return false;
 183 }
 184
 185 unsigned long
 186 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)
 187 {
 188         unsigned long orig_ret_vaddr;
 189
 190         orig_ret_vaddr = regs->link;
 191
 192         /* Replace the return addr with trampoline addr */
 193         regs->link = trampoline_vaddr;
 194
 195         return orig_ret_vaddr;
 196 }
 197
 198 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
 199                                 struct pt_regs *regs)
 200 {
 201         if (ctx == RP_CHECK_CHAIN_CALL)
 202                 return regs->gpr[1] <= ret->stack;
 203         else
 204                 return regs->gpr[1] < ret->stack;
 205 }