arch/arm/kernel/uprobes-arm.c

   1 /*
   2  * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/types.h>
  11 #include <linux/stddef.h>
  12 #include <linux/wait.h>
  13 #include <linux/uprobes.h>
  14 #include <linux/module.h>
  15
  16 #include "probes.h"
  17 #include "probes-arm.h"
  18 #include "uprobes.h"
  19
  20 static int uprobes_substitute_pc(unsigned long *pinsn, u32 oregs)
  21 {
  22         probes_opcode_t insn = __mem_to_opcode_arm(*pinsn);
  23         probes_opcode_t temp;
  24         probes_opcode_t mask;
  25         int freereg;
  26         u32 free = 0xffff;
  27         u32 regs;
  28
  29         for (regs = oregs; regs; regs >>= 4, insn >>= 4) {
  30                 if ((regs & 0xf) == REG_TYPE_NONE)
  31                         continue;
  32
  33                 free &= ~(1 << (insn & 0xf));
  34         }
  35
  36         /* No PC, no problem */
  37         if (free & (1 << 15))
  38                 return 15;
  39
  40         if (!free)
  41                 return -1;
  42
  43         /*
  44          * fls instead of ffs ensures that for "ldrd r0, r1, [pc]" we would
  45          * pick LR instead of R1.
  46          */
  47         freereg = free = fls(free) - 1;
  48
  49         temp = __mem_to_opcode_arm(*pinsn);
  50         insn = temp;
  51         regs = oregs;
  52         mask = 0xf;
  53
  54         for (; regs; regs >>= 4, mask <<= 4, free <<= 4, temp >>= 4) {
  55                 if ((regs & 0xf) == REG_TYPE_NONE)
  56                         continue;
  57
  58                 if ((temp & 0xf) != 15)
  59                         continue;
  60
  61                 insn &= ~mask;
  62                 insn |= free & mask;
  63         }
  64
  65         *pinsn = __opcode_to_mem_arm(insn);
  66         return freereg;
  67 }
  68
  69 static void uprobe_set_pc(struct arch_uprobe *auprobe,
  70                           struct arch_uprobe_task *autask,
  71                           struct pt_regs *regs)
  72 {
  73         u32 pcreg = auprobe->pcreg;
  74
  75         autask->backup = regs->uregs[pcreg];
  76         regs->uregs[pcreg] = regs->ARM_pc + 8;
  77 }
  78
  79 static void uprobe_unset_pc(struct arch_uprobe *auprobe,
  80                             struct arch_uprobe_task *autask,
  81                             struct pt_regs *regs)
  82 {
  83         /* PC will be taken care of by common code */
  84         regs->uregs[auprobe->pcreg] = autask->backup;
  85 }
  86
  87 static void uprobe_aluwrite_pc(struct arch_uprobe *auprobe,
  88                                struct arch_uprobe_task *autask,
  89                                struct pt_regs *regs)
  90 {
  91         u32 pcreg = auprobe->pcreg;
  92
  93         alu_write_pc(regs->uregs[pcreg], regs);
  94         regs->uregs[pcreg] = autask->backup;
  95 }
  96
  97 static void uprobe_write_pc(struct arch_uprobe *auprobe,
  98                             struct arch_uprobe_task *autask,
  99                             struct pt_regs *regs)
 100 {
 101         u32 pcreg = auprobe->pcreg;
 102
 103         load_write_pc(regs->uregs[pcreg], regs);
 104         regs->uregs[pcreg] = autask->backup;
 105 }
 106
 107 enum probes_insn
 108 decode_pc_ro(probes_opcode_t insn, struct arch_probes_insn *asi,
 109              const struct decode_header *d)
 110 {
 111         struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
 112                                                    asi);
 113         struct decode_emulate *decode = (struct decode_emulate *) d;
 114         u32 regs = decode->header.type_regs.bits >> DECODE_TYPE_BITS;
 115         int reg;
 116
 117         reg = uprobes_substitute_pc(&auprobe->ixol[0], regs);
 118         if (reg == 15)
 119                 return INSN_GOOD;
 120
 121         if (reg == -1)
 122                 return INSN_REJECTED;
 123
 124         auprobe->pcreg = reg;
 125         auprobe->prehandler = uprobe_set_pc;
 126         auprobe->posthandler = uprobe_unset_pc;
 127
 128         return INSN_GOOD;
 129 }
 130
 131 enum probes_insn
 132 decode_wb_pc(probes_opcode_t insn, struct arch_probes_insn *asi,
 133              const struct decode_header *d, bool alu)
 134 {
 135         struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
 136                                                    asi);
 137         enum probes_insn ret = decode_pc_ro(insn, asi, d);
 138
 139         if (((insn >> 12) & 0xf) == 15)
 140                 auprobe->posthandler = alu ? uprobe_aluwrite_pc
 141                                            : uprobe_write_pc;
 142
 143         return ret;
 144 }
 145
 146 enum probes_insn
 147 decode_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
 148                               struct arch_probes_insn *asi,
 149                               const struct decode_header *d)
 150 {
 151         return decode_wb_pc(insn, asi, d, true);
 152 }
 153
 154 enum probes_insn
 155 decode_ldr(probes_opcode_t insn, struct arch_probes_insn *asi,
 156            const struct decode_header *d)
 157 {
 158         return decode_wb_pc(insn, asi, d, false);
 159 }
 160
 161 enum probes_insn
 162 uprobe_decode_ldmstm(probes_opcode_t insn,
 163                      struct arch_probes_insn *asi,
 164                      const struct decode_header *d)
 165 {
 166         struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
 167                                                    asi);
 168         unsigned reglist = insn & 0xffff;
 169         int rn = (insn >> 16) & 0xf;
 170         int lbit = insn & (1 << 20);
 171         unsigned used = reglist | (1 << rn);
 172
 173         if (rn == 15)
 174                 return INSN_REJECTED;
 175
 176         if (!(used & (1 << 15)))
 177                 return INSN_GOOD;
 178
 179         if (used & (1 << 14))
 180                 return INSN_REJECTED;
 181
 182         /* Use LR instead of PC */
 183         insn ^= 0xc000;
 184
 185         auprobe->pcreg = 14;
 186         auprobe->ixol[0] = __opcode_to_mem_arm(insn);
 187
 188         auprobe->prehandler = uprobe_set_pc;
 189         if (lbit)
 190                 auprobe->posthandler = uprobe_write_pc;
 191         else
 192                 auprobe->posthandler = uprobe_unset_pc;
 193
 194         return INSN_GOOD;
 195 }
 196
 197 const union decode_action uprobes_probes_actions[] = {
 198         [PROBES_EMULATE_NONE] = {.handler = probes_simulate_nop},
 199         [PROBES_SIMULATE_NOP] = {.handler = probes_simulate_nop},
 200         [PROBES_PRELOAD_IMM] = {.handler = probes_simulate_nop},
 201         [PROBES_PRELOAD_REG] = {.handler = probes_simulate_nop},
 202         [PROBES_BRANCH_IMM] = {.handler = simulate_blx1},
 203         [PROBES_MRS] = {.handler = simulate_mrs},
 204         [PROBES_BRANCH_REG] = {.handler = simulate_blx2bx},
 205         [PROBES_CLZ] = {.handler = probes_simulate_nop},
 206         [PROBES_SATURATING_ARITHMETIC] = {.handler = probes_simulate_nop},
 207         [PROBES_MUL1] = {.handler = probes_simulate_nop},
 208         [PROBES_MUL2] = {.handler = probes_simulate_nop},
 209         [PROBES_SWP] = {.handler = probes_simulate_nop},
 210         [PROBES_LDRSTRD] = {.decoder = decode_pc_ro},
 211         [PROBES_LOAD_EXTRA] = {.decoder = decode_pc_ro},
 212         [PROBES_LOAD] = {.decoder = decode_ldr},
 213         [PROBES_STORE_EXTRA] = {.decoder = decode_pc_ro},
 214         [PROBES_STORE] = {.decoder = decode_pc_ro},
 215         [PROBES_MOV_IP_SP] = {.handler = simulate_mov_ipsp},
 216         [PROBES_DATA_PROCESSING_REG] = {
 217                 .decoder = decode_rd12rn16rm0rs8_rwflags},
 218         [PROBES_DATA_PROCESSING_IMM] = {
 219                 .decoder = decode_rd12rn16rm0rs8_rwflags},
 220         [PROBES_MOV_HALFWORD] = {.handler = probes_simulate_nop},
 221         [PROBES_SEV] = {.handler = probes_simulate_nop},
 222         [PROBES_WFE] = {.handler = probes_simulate_nop},
 223         [PROBES_SATURATE] = {.handler = probes_simulate_nop},
 224         [PROBES_REV] = {.handler = probes_simulate_nop},
 225         [PROBES_MMI] = {.handler = probes_simulate_nop},
 226         [PROBES_PACK] = {.handler = probes_simulate_nop},
 227         [PROBES_EXTEND] = {.handler = probes_simulate_nop},
 228         [PROBES_EXTEND_ADD] = {.handler = probes_simulate_nop},
 229         [PROBES_MUL_ADD_LONG] = {.handler = probes_simulate_nop},
 230         [PROBES_MUL_ADD] = {.handler = probes_simulate_nop},
 231         [PROBES_BITFIELD] = {.handler = probes_simulate_nop},
 232         [PROBES_BRANCH] = {.handler = simulate_bbl},
 233         [PROBES_LDMSTM] = {.decoder = uprobe_decode_ldmstm}
 234 };