LCOV - code coverage report
Current view: top level - arch/arm/probes - decode.h (source / functions) Hit Total Coverage
Test: Real Lines: 0 8 0.0 %
Date: 2020-10-17 15:46:16 Functions: 0 0 -
Legend: Neither, QEMU, Real, Both Branches: 0 0 -

           Branch data     Line data    Source code
       1                 :            : /* SPDX-License-Identifier: GPL-2.0-only */
       2                 :            : /*
       3                 :            :  * arch/arm/probes/decode.h
       4                 :            :  *
       5                 :            :  * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
       6                 :            :  *
       7                 :            :  * Some contents moved here from arch/arm/include/asm/kprobes.h which is
       8                 :            :  * Copyright (C) 2006, 2007 Motorola Inc.
       9                 :            :  */
      10                 :            : 
      11                 :            : #ifndef _ARM_KERNEL_PROBES_H
      12                 :            : #define  _ARM_KERNEL_PROBES_H
      13                 :            : 
      14                 :            : #include <linux/types.h>
      15                 :            : #include <linux/stddef.h>
      16                 :            : #include <asm/probes.h>
      17                 :            : #include <asm/kprobes.h>
      18                 :            : 
      19                 :            : void __init arm_probes_decode_init(void);
      20                 :            : 
      21                 :            : extern probes_check_cc * const probes_condition_checks[16];
      22                 :            : 
      23                 :            : #if __LINUX_ARM_ARCH__ >= 7
      24                 :            : 
      25                 :            : /* str_pc_offset is architecturally defined from ARMv7 onwards */
      26                 :            : #define str_pc_offset 8
      27                 :            : #define find_str_pc_offset()
      28                 :            : 
      29                 :            : #else /* __LINUX_ARM_ARCH__ < 7 */
      30                 :            : 
      31                 :            : /* We need a run-time check to determine str_pc_offset */
      32                 :            : extern int str_pc_offset;
      33                 :            : void __init find_str_pc_offset(void);
      34                 :            : 
      35                 :            : #endif
      36                 :            : 
      37                 :            : 
      38                 :            : /*
      39                 :            :  * Update ITSTATE after normal execution of an IT block instruction.
      40                 :            :  *
      41                 :            :  * The 8 IT state bits are split into two parts in CPSR:
      42                 :            :  *      ITSTATE<1:0> are in CPSR<26:25>
      43                 :            :  *      ITSTATE<7:2> are in CPSR<15:10>
      44                 :            :  */
      45                 :            : static inline unsigned long it_advance(unsigned long cpsr)
      46                 :            :         {
      47                 :            :         if ((cpsr & 0x06000400) == 0) {
      48                 :            :                 /* ITSTATE<2:0> == 0 means end of IT block, so clear IT state */
      49                 :            :                 cpsr &= ~PSR_IT_MASK;
      50                 :            :         } else {
      51                 :            :                 /* We need to shift left ITSTATE<4:0> */
      52                 :            :                 const unsigned long mask = 0x06001c00;  /* Mask ITSTATE<4:0> */
      53                 :            :                 unsigned long it = cpsr & mask;
      54                 :            :                 it <<= 1;
      55                 :            :                 it |= it >> (27 - 10);  /* Carry ITSTATE<2> to correct place */
      56                 :            :                 it &= mask;
      57                 :            :                 cpsr &= ~mask;
      58                 :            :                 cpsr |= it;
      59                 :            :         }
      60                 :            :         return cpsr;
      61                 :            : }
      62                 :            : 
      63                 :            : static inline void __kprobes bx_write_pc(long pcv, struct pt_regs *regs)
      64                 :            : {
      65                 :          0 :         long cpsr = regs->ARM_cpsr;
      66                 :          0 :         if (pcv & 0x1) {
      67                 :          0 :                 cpsr |= PSR_T_BIT;
      68                 :          0 :                 pcv &= ~0x1;
      69                 :            :         } else {
      70                 :          0 :                 cpsr &= ~PSR_T_BIT;
      71                 :          0 :                 pcv &= ~0x2;        /* Avoid UNPREDICTABLE address allignment */
      72                 :            :         }
      73                 :          0 :         regs->ARM_cpsr = cpsr;
      74                 :          0 :         regs->ARM_pc = pcv;
      75                 :            : }
      76                 :            : 
      77                 :            : 
      78                 :            : #if __LINUX_ARM_ARCH__ >= 6
      79                 :            : 
      80                 :            : /* Kernels built for >= ARMv6 should never run on <= ARMv5 hardware, so... */
      81                 :            : #define load_write_pc_interworks true
      82                 :            : #define test_load_write_pc_interworking()
      83                 :            : 
      84                 :            : #else /* __LINUX_ARM_ARCH__ < 6 */
      85                 :            : 
      86                 :            : /* We need run-time testing to determine if load_write_pc() should interwork. */
      87                 :            : extern bool load_write_pc_interworks;
      88                 :            : void __init test_load_write_pc_interworking(void);
      89                 :            : 
      90                 :            : #endif
      91                 :            : 
      92                 :            : static inline void __kprobes load_write_pc(long pcv, struct pt_regs *regs)
      93                 :            : {
      94                 :            :         if (load_write_pc_interworks)
      95                 :            :                 bx_write_pc(pcv, regs);
      96                 :            :         else
      97                 :            :                 regs->ARM_pc = pcv;
      98                 :            : }
      99                 :            : 
     100                 :            : 
     101                 :            : #if __LINUX_ARM_ARCH__ >= 7
     102                 :            : 
     103                 :            : #define alu_write_pc_interworks true
     104                 :            : #define test_alu_write_pc_interworking()
     105                 :            : 
     106                 :            : #elif __LINUX_ARM_ARCH__ <= 5
     107                 :            : 
     108                 :            : /* Kernels built for <= ARMv5 should never run on >= ARMv6 hardware, so... */
     109                 :            : #define alu_write_pc_interworks false
     110                 :            : #define test_alu_write_pc_interworking()
     111                 :            : 
     112                 :            : #else /* __LINUX_ARM_ARCH__ == 6 */
     113                 :            : 
     114                 :            : /* We could be an ARMv6 binary on ARMv7 hardware so we need a run-time check. */
     115                 :            : extern bool alu_write_pc_interworks;
     116                 :            : void __init test_alu_write_pc_interworking(void);
     117                 :            : 
     118                 :            : #endif /* __LINUX_ARM_ARCH__ == 6 */
     119                 :            : 
     120                 :            : static inline void __kprobes alu_write_pc(long pcv, struct pt_regs *regs)
     121                 :            : {
     122                 :            :         if (alu_write_pc_interworks)
     123                 :            :                 bx_write_pc(pcv, regs);
     124                 :            :         else
     125                 :            :                 regs->ARM_pc = pcv;
     126                 :            : }
     127                 :            : 
     128                 :            : 
     129                 :            : /*
     130                 :            :  * Test if load/store instructions writeback the address register.
     131                 :            :  * if P (bit 24) == 0 or W (bit 21) == 1
     132                 :            :  */
     133                 :            : #define is_writeback(insn) ((insn ^ 0x01000000) & 0x01200000)
     134                 :            : 
     135                 :            : /*
     136                 :            :  * The following definitions and macros are used to build instruction
     137                 :            :  * decoding tables for use by probes_decode_insn.
     138                 :            :  *
     139                 :            :  * These tables are a concatenation of entries each of which consist of one of
     140                 :            :  * the decode_* structs. All of the fields in every type of decode structure
     141                 :            :  * are of the union type decode_item, therefore the entire decode table can be
     142                 :            :  * viewed as an array of these and declared like:
     143                 :            :  *
     144                 :            :  *      static const union decode_item table_name[] = {};
     145                 :            :  *
     146                 :            :  * In order to construct each entry in the table, macros are used to
     147                 :            :  * initialise a number of sequential decode_item values in a layout which
     148                 :            :  * matches the relevant struct. E.g. DECODE_SIMULATE initialise a struct
     149                 :            :  * decode_simulate by initialising four decode_item objects like this...
     150                 :            :  *
     151                 :            :  *      {.bits = _type},
     152                 :            :  *      {.bits = _mask},
     153                 :            :  *      {.bits = _value},
     154                 :            :  *      {.action = _handler},
     155                 :            :  *
     156                 :            :  * Initialising a specified member of the union means that the compiler
     157                 :            :  * will produce a warning if the argument is of an incorrect type.
     158                 :            :  *
     159                 :            :  * Below is a list of each of the macros used to initialise entries and a
     160                 :            :  * description of the action performed when that entry is matched to an
     161                 :            :  * instruction. A match is found when (instruction & mask) == value.
     162                 :            :  *
     163                 :            :  * DECODE_TABLE(mask, value, table)
     164                 :            :  *      Instruction decoding jumps to parsing the new sub-table 'table'.
     165                 :            :  *
     166                 :            :  * DECODE_CUSTOM(mask, value, decoder)
     167                 :            :  *      The value of 'decoder' is used as an index into the array of
     168                 :            :  *      action functions, and the retrieved decoder function is invoked
     169                 :            :  *      to complete decoding of the instruction.
     170                 :            :  *
     171                 :            :  * DECODE_SIMULATE(mask, value, handler)
     172                 :            :  *      The probes instruction handler is set to the value found by
     173                 :            :  *      indexing into the action array using the value of 'handler'. This
     174                 :            :  *      will be used to simulate the instruction when the probe is hit.
     175                 :            :  *      Decoding returns with INSN_GOOD_NO_SLOT.
     176                 :            :  *
     177                 :            :  * DECODE_EMULATE(mask, value, handler)
     178                 :            :  *      The probes instruction handler is set to the value found by
     179                 :            :  *      indexing into the action array using the value of 'handler'. This
     180                 :            :  *      will be used to emulate the instruction when the probe is hit. The
     181                 :            :  *      modified instruction (see below) is placed in the probes instruction
     182                 :            :  *      slot so it may be called by the emulation code. Decoding returns
     183                 :            :  *      with INSN_GOOD.
     184                 :            :  *
     185                 :            :  * DECODE_REJECT(mask, value)
     186                 :            :  *      Instruction decoding fails with INSN_REJECTED
     187                 :            :  *
     188                 :            :  * DECODE_OR(mask, value)
     189                 :            :  *      This allows the mask/value test of multiple table entries to be
     190                 :            :  *      logically ORed. Once an 'or' entry is matched the decoding action to
     191                 :            :  *      be performed is that of the next entry which isn't an 'or'. E.g.
     192                 :            :  *
     193                 :            :  *              DECODE_OR       (mask1, value1)
     194                 :            :  *              DECODE_OR       (mask2, value2)
     195                 :            :  *              DECODE_SIMULATE (mask3, value3, simulation_handler)
     196                 :            :  *
     197                 :            :  *      This means that if any of the three mask/value pairs match the
     198                 :            :  *      instruction being decoded, then 'simulation_handler' will be used
     199                 :            :  *      for it.
     200                 :            :  *
     201                 :            :  * Both the SIMULATE and EMULATE macros have a second form which take an
     202                 :            :  * additional 'regs' argument.
     203                 :            :  *
     204                 :            :  *      DECODE_SIMULATEX(mask, value, handler, regs)
     205                 :            :  *      DECODE_EMULATEX (mask, value, handler, regs)
     206                 :            :  *
     207                 :            :  * These are used to specify what kind of CPU register is encoded in each of the
     208                 :            :  * least significant 5 nibbles of the instruction being decoded. The regs value
     209                 :            :  * is specified using the REGS macro, this takes any of the REG_TYPE_* values
     210                 :            :  * from enum decode_reg_type as arguments; only the '*' part of the name is
     211                 :            :  * given. E.g.
     212                 :            :  *
     213                 :            :  *      REGS(0, ANY, NOPC, 0, ANY)
     214                 :            :  *
     215                 :            :  * This indicates an instruction is encoded like:
     216                 :            :  *
     217                 :            :  *      bits 19..16     ignore
     218                 :            :  *      bits 15..12     any register allowed here
     219                 :            :  *      bits 11.. 8     any register except PC allowed here
     220                 :            :  *      bits  7.. 4     ignore
     221                 :            :  *      bits  3.. 0     any register allowed here
     222                 :            :  *
     223                 :            :  * This register specification is checked after a decode table entry is found to
     224                 :            :  * match an instruction (through the mask/value test). Any invalid register then
     225                 :            :  * found in the instruction will cause decoding to fail with INSN_REJECTED. In
     226                 :            :  * the above example this would happen if bits 11..8 of the instruction were
     227                 :            :  * 1111, indicating R15 or PC.
     228                 :            :  *
     229                 :            :  * As well as checking for legal combinations of registers, this data is also
     230                 :            :  * used to modify the registers encoded in the instructions so that an
     231                 :            :  * emulation routines can use it. (See decode_regs() and INSN_NEW_BITS.)
     232                 :            :  *
     233                 :            :  * Here is a real example which matches ARM instructions of the form
     234                 :            :  * "AND <Rd>,<Rn>,<Rm>,<shift> <Rs>"
     235                 :            :  *
     236                 :            :  *      DECODE_EMULATEX (0x0e000090, 0x00000010, PROBES_DATA_PROCESSING_REG,
     237                 :            :  *                                               REGS(ANY, ANY, NOPC, 0, ANY)),
     238                 :            :  *                                                    ^    ^    ^        ^
     239                 :            :  *                                                    Rn   Rd   Rs       Rm
     240                 :            :  *
     241                 :            :  * Decoding the instruction "AND R4, R5, R6, ASL R15" will be rejected because
     242                 :            :  * Rs == R15
     243                 :            :  *
     244                 :            :  * Decoding the instruction "AND R4, R5, R6, ASL R7" will be accepted and the
     245                 :            :  * instruction will be modified to "AND R0, R2, R3, ASL R1" and then placed into
     246                 :            :  * the kprobes instruction slot. This can then be called later by the handler
     247                 :            :  * function emulate_rd12rn16rm0rs8_rwflags (a pointer to which is retrieved from
     248                 :            :  * the indicated slot in the action array), in order to simulate the instruction.
     249                 :            :  */
     250                 :            : 
     251                 :            : enum decode_type {
     252                 :            :         DECODE_TYPE_END,
     253                 :            :         DECODE_TYPE_TABLE,
     254                 :            :         DECODE_TYPE_CUSTOM,
     255                 :            :         DECODE_TYPE_SIMULATE,
     256                 :            :         DECODE_TYPE_EMULATE,
     257                 :            :         DECODE_TYPE_OR,
     258                 :            :         DECODE_TYPE_REJECT,
     259                 :            :         NUM_DECODE_TYPES /* Must be last enum */
     260                 :            : };
     261                 :            : 
     262                 :            : #define DECODE_TYPE_BITS        4
     263                 :            : #define DECODE_TYPE_MASK        ((1 << DECODE_TYPE_BITS) - 1)
     264                 :            : 
     265                 :            : enum decode_reg_type {
     266                 :            :         REG_TYPE_NONE = 0, /* Not a register, ignore */
     267                 :            :         REG_TYPE_ANY,      /* Any register allowed */
     268                 :            :         REG_TYPE_SAMEAS16, /* Register should be same as that at bits 19..16 */
     269                 :            :         REG_TYPE_SP,       /* Register must be SP */
     270                 :            :         REG_TYPE_PC,       /* Register must be PC */
     271                 :            :         REG_TYPE_NOSP,     /* Register must not be SP */
     272                 :            :         REG_TYPE_NOSPPC,   /* Register must not be SP or PC */
     273                 :            :         REG_TYPE_NOPC,     /* Register must not be PC */
     274                 :            :         REG_TYPE_NOPCWB,   /* No PC if load/store write-back flag also set */
     275                 :            : 
     276                 :            :         /* The following types are used when the encoding for PC indicates
     277                 :            :          * another instruction form. This distiction only matters for test
     278                 :            :          * case coverage checks.
     279                 :            :          */
     280                 :            :         REG_TYPE_NOPCX,    /* Register must not be PC */
     281                 :            :         REG_TYPE_NOSPPCX,  /* Register must not be SP or PC */
     282                 :            : 
     283                 :            :         /* Alias to allow '0' arg to be used in REGS macro. */
     284                 :            :         REG_TYPE_0 = REG_TYPE_NONE
     285                 :            : };
     286                 :            : 
     287                 :            : #define REGS(r16, r12, r8, r4, r0)      \
     288                 :            :         (((REG_TYPE_##r16) << 16) +       \
     289                 :            :         ((REG_TYPE_##r12) << 12) +        \
     290                 :            :         ((REG_TYPE_##r8) << 8) +  \
     291                 :            :         ((REG_TYPE_##r4) << 4) +  \
     292                 :            :         (REG_TYPE_##r0))
     293                 :            : 
     294                 :            : union decode_item {
     295                 :            :         u32                     bits;
     296                 :            :         const union decode_item *table;
     297                 :            :         int                     action;
     298                 :            : };
     299                 :            : 
     300                 :            : struct decode_header;
     301                 :            : typedef enum probes_insn (probes_custom_decode_t)(probes_opcode_t,
     302                 :            :                                                   struct arch_probes_insn *,
     303                 :            :                                                   const struct decode_header *);
     304                 :            : 
     305                 :            : union decode_action {
     306                 :            :         probes_insn_handler_t   *handler;
     307                 :            :         probes_custom_decode_t  *decoder;
     308                 :            : };
     309                 :            : 
     310                 :            : typedef enum probes_insn (probes_check_t)(probes_opcode_t,
     311                 :            :                                            struct arch_probes_insn *,
     312                 :            :                                            const struct decode_header *);
     313                 :            : 
     314                 :            : struct decode_checker {
     315                 :            :         probes_check_t  *checker;
     316                 :            : };
     317                 :            : 
     318                 :            : #define DECODE_END                      \
     319                 :            :         {.bits = DECODE_TYPE_END}
     320                 :            : 
     321                 :            : 
     322                 :            : struct decode_header {
     323                 :            :         union decode_item       type_regs;
     324                 :            :         union decode_item       mask;
     325                 :            :         union decode_item       value;
     326                 :            : };
     327                 :            : 
     328                 :            : #define DECODE_HEADER(_type, _mask, _value, _regs)              \
     329                 :            :         {.bits = (_type) | ((_regs) << DECODE_TYPE_BITS)},        \
     330                 :            :         {.bits = (_mask)},                                      \
     331                 :            :         {.bits = (_value)}
     332                 :            : 
     333                 :            : 
     334                 :            : struct decode_table {
     335                 :            :         struct decode_header    header;
     336                 :            :         union decode_item       table;
     337                 :            : };
     338                 :            : 
     339                 :            : #define DECODE_TABLE(_mask, _value, _table)                     \
     340                 :            :         DECODE_HEADER(DECODE_TYPE_TABLE, _mask, _value, 0),     \
     341                 :            :         {.table = (_table)}
     342                 :            : 
     343                 :            : 
     344                 :            : struct decode_custom {
     345                 :            :         struct decode_header    header;
     346                 :            :         union decode_item       decoder;
     347                 :            : };
     348                 :            : 
     349                 :            : #define DECODE_CUSTOM(_mask, _value, _decoder)                  \
     350                 :            :         DECODE_HEADER(DECODE_TYPE_CUSTOM, _mask, _value, 0),    \
     351                 :            :         {.action = (_decoder)}
     352                 :            : 
     353                 :            : 
     354                 :            : struct decode_simulate {
     355                 :            :         struct decode_header    header;
     356                 :            :         union decode_item       handler;
     357                 :            : };
     358                 :            : 
     359                 :            : #define DECODE_SIMULATEX(_mask, _value, _handler, _regs)                \
     360                 :            :         DECODE_HEADER(DECODE_TYPE_SIMULATE, _mask, _value, _regs),      \
     361                 :            :         {.action = (_handler)}
     362                 :            : 
     363                 :            : #define DECODE_SIMULATE(_mask, _value, _handler)        \
     364                 :            :         DECODE_SIMULATEX(_mask, _value, _handler, 0)
     365                 :            : 
     366                 :            : 
     367                 :            : struct decode_emulate {
     368                 :            :         struct decode_header    header;
     369                 :            :         union decode_item       handler;
     370                 :            : };
     371                 :            : 
     372                 :            : #define DECODE_EMULATEX(_mask, _value, _handler, _regs)                 \
     373                 :            :         DECODE_HEADER(DECODE_TYPE_EMULATE, _mask, _value, _regs),       \
     374                 :            :         {.action = (_handler)}
     375                 :            : 
     376                 :            : #define DECODE_EMULATE(_mask, _value, _handler)         \
     377                 :            :         DECODE_EMULATEX(_mask, _value, _handler, 0)
     378                 :            : 
     379                 :            : 
     380                 :            : struct decode_or {
     381                 :            :         struct decode_header    header;
     382                 :            : };
     383                 :            : 
     384                 :            : #define DECODE_OR(_mask, _value)                                \
     385                 :            :         DECODE_HEADER(DECODE_TYPE_OR, _mask, _value, 0)
     386                 :            : 
     387                 :            : enum probes_insn {
     388                 :            :         INSN_REJECTED,
     389                 :            :         INSN_GOOD,
     390                 :            :         INSN_GOOD_NO_SLOT
     391                 :            : };
     392                 :            : 
     393                 :            : struct decode_reject {
     394                 :            :         struct decode_header    header;
     395                 :            : };
     396                 :            : 
     397                 :            : #define DECODE_REJECT(_mask, _value)                            \
     398                 :            :         DECODE_HEADER(DECODE_TYPE_REJECT, _mask, _value, 0)
     399                 :            : 
     400                 :            : probes_insn_handler_t probes_simulate_nop;
     401                 :            : probes_insn_handler_t probes_emulate_none;
     402                 :            : 
     403                 :            : int __kprobes
     404                 :            : probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
     405                 :            :                 const union decode_item *table, bool thumb, bool emulate,
     406                 :            :                 const union decode_action *actions,
     407                 :            :                 const struct decode_checker **checkers);
     408                 :            : 
     409                 :            : #endif
    

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