/* SPDX-License-Identifier: GPL-2.0-only */
/*
* arch/arm/probes/decode.h
*
* Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
*
* Some contents moved here from arch/arm/include/asm/kprobes.h which is
* Copyright (C) 2006, 2007 Motorola Inc.
*/
#ifndef _ARM_KERNEL_PROBES_H
#define _ARM_KERNEL_PROBES_H
#include <linux/types.h>
#include <linux/stddef.h>
#include <asm/probes.h>
#include <asm/ptrace.h>
#include <asm/kprobes.h>
void __init arm_probes_decode_init(void);
extern probes_check_cc * const probes_condition_checks[16];
#if __LINUX_ARM_ARCH__ >= 7
/* str_pc_offset is architecturally defined from ARMv7 onwards */
#define str_pc_offset 8
#define find_str_pc_offset()
#else /* __LINUX_ARM_ARCH__ < 7 */
/* We need a run-time check to determine str_pc_offset */
extern int str_pc_offset;
void __init find_str_pc_offset(void);
#endif
static inline void __kprobes bx_write_pc(long pcv, struct pt_regs *regs)
{
long cpsr = regs->ARM_cpsr;
if (pcv & 0x1) {
cpsr |= PSR_T_BIT;
pcv &= ~0x1;
} else {
cpsr &= ~PSR_T_BIT;
pcv &= ~0x2; /* Avoid UNPREDICTABLE address allignment */
}
regs->ARM_cpsr = cpsr;
regs->ARM_pc = pcv;
}
#if __LINUX_ARM_ARCH__ >= 6
/* Kernels built for >= ARMv6 should never run on <= ARMv5 hardware, so... */
#define load_write_pc_interworks true
#define test_load_write_pc_interworking()
#else /* __LINUX_ARM_ARCH__ < 6 */
/* We need run-time testing to determine if load_write_pc() should interwork. */
extern bool load_write_pc_interworks;
void __init test_load_write_pc_interworking(void);
#endif
static inline void __kprobes load_write_pc(long pcv, struct pt_regs *regs)
{
if (load_write_pc_interworks)
bx_write_pc(pcv, regs);
else
regs->ARM_pc = pcv;
}
#if __LINUX_ARM_ARCH__ >= 7
#define alu_write_pc_interworks true
#define test_alu_write_pc_interworking()
#elif __LINUX_ARM_ARCH__ <= 5
/* Kernels built for <= ARMv5 should never run on >= ARMv6 hardware, so... */
#define alu_write_pc_interworks false
#define test_alu_write_pc_interworking()
#else /* __LINUX_ARM_ARCH__ == 6 */
/* We could be an ARMv6 binary on ARMv7 hardware so we need a run-time check. */
extern bool alu_write_pc_interworks;
void __init test_alu_write_pc_interworking(void);
#endif /* __LINUX_ARM_ARCH__ == 6 */
static inline void __kprobes alu_write_pc(long pcv, struct pt_regs *regs)
{
if (alu_write_pc_interworks)
bx_write_pc(pcv, regs);
else
regs->ARM_pc = pcv;
}
/*
* Test if load/store instructions writeback the address register.
* if P (bit 24) == 0 or W (bit 21) == 1
*/
#define is_writeback(insn) ((insn ^ 0x01000000) & 0x01200000)
/*
* The following definitions and macros are used to build instruction
* decoding tables for use by probes_decode_insn.
*
* These tables are a concatenation of entries each of which consist of one of
* the decode_* structs. All of the fields in every type of decode structure
* are of the union type decode_item, therefore the entire decode table can be
* viewed as an array of these and declared like:
*
* static const union decode_item table_name[] = {};
*
* In order to construct each entry in the table, macros are used to
* initialise a number of sequential decode_item values in a layout which
* matches the relevant struct. E.g. DECODE_SIMULATE initialise a struct
* decode_simulate by initialising four decode_item objects like this...
*
* {.bits = _type},
* {.bits = _mask},
* {.bits = _value},
* {.action = _handler},
*
* Initialising a specified member of the union means that the compiler
* will produce a warning if the argument is of an incorrect type.
*
* Below is a list of each of the macros used to initialise entries and a
* description of the action performed when that entry is matched to an
* instruction. A match is found when (instruction & mask) == value.
*
* DECODE_TABLE(mask, value, table)
* Instruction decoding jumps to parsing the new sub-table 'table'.
*
* DECODE_CUSTOM(mask, value, decoder)
* The value of 'decoder' is used as an index into the array of
* action functions, and the retrieved decoder function is invoked
* to complete decoding of the instruction.
*
* DECODE_SIMULATE(mask, value, handler)
* The probes instruction handler is set to the value found by
* indexing into the action array using the value of 'handler'. This
* will be used to simulate the instruction when the probe is hit.
* Decoding returns with INSN_GOOD_NO_SLOT.
*
* DECODE_EMULATE(mask, value, handler)
* The probes instruction handler is set to the value found by
* indexing into the action array using the value of 'handler'. This
* will be used to emulate the instruction when the probe is hit. The
* modified instruction (see below) is placed in the probes instruction
* slot so it may be called by the emulation code. Decoding returns
* with INSN_GOOD.
*
* DECODE_REJECT(mask, value)
* Instruction decoding fails with INSN_REJECTED
*
* DECODE_OR(mask, value)
* This allows the mask/value test of multiple table entries to be
* logically ORed. Once an 'or' entry is matched the decoding action to
* be performed is that of the next entry which isn't an 'or'. E.g.
*
* DECODE_OR (mask1, value1)
* DECODE_OR (mask2, value2)
* DECODE_SIMULATE (mask3, value3, simulation_handler)
*
* This means that if any of the three mask/value pairs match the
* instruction being decoded, then 'simulation_handler' will be used
* for it.
*
* Both the SIMULATE and EMULATE macros have a second form which take an
* additional 'regs' argument.
*
* DECODE_SIMULATEX(mask, value, handler, regs)
* DECODE_EMULATEX (mask, value, handler, regs)
*
* These are used to specify what kind of CPU register is encoded in each of the
* least significant 5 nibbles of the instruction being decoded. The regs value
* is specified using the REGS macro, this takes any of the REG_TYPE_* values
* from enum decode_reg_type as arguments; only the '*' part of the name is
* given. E.g.
*
* REGS(0, ANY, NOPC, 0, ANY)
*
* This indicates an instruction is encoded like:
*
* bits 19..16 ignore
* bits 15..12 any register allowed here
* bits 11.. 8 any register except PC allowed here
* bits 7.. 4 ignore
* bits 3.. 0 any register allowed here
*
* This register specification is checked after a decode table entry is found to
* match an instruction (through the mask/value test). Any invalid register then
* found in the instruction will cause decoding to fail with INSN_REJECTED. In
* the above example this would happen if bits 11..8 of the instruction were
* 1111, indicating R15 or PC.
*
* As well as checking for legal combinations of registers, this data is also
* used to modify the registers encoded in the instructions so that an
* emulation routines can use it. (See decode_regs() and INSN_NEW_BITS.)
*
* Here is a real example which matches ARM instructions of the form
* "AND <Rd>,<Rn>,<Rm>,<shift> <Rs>"
*
* DECODE_EMULATEX (0x0e000090, 0x00000010, PROBES_DATA_PROCESSING_REG,
* REGS(ANY, ANY, NOPC, 0, ANY)),
* ^ ^ ^ ^
* Rn Rd Rs Rm
*
* Decoding the instruction "AND R4, R5, R6, ASL R15" will be rejected because
* Rs == R15
*
* Decoding the instruction "AND R4, R5, R6, ASL R7" will be accepted and the
* instruction will be modified to "AND R0, R2, R3, ASL R1" and then placed into
* the kprobes instruction slot. This can then be called later by the handler
* function emulate_rd12rn16rm0rs8_rwflags (a pointer to which is retrieved from
* the indicated slot in the action array), in order to simulate the instruction.
*/
enum decode_type {
DECODE_TYPE_END,
DECODE_TYPE_TABLE,
DECODE_TYPE_CUSTOM,
DECODE_TYPE_SIMULATE,
DECODE_TYPE_EMULATE,
DECODE_TYPE_OR,
DECODE_TYPE_REJECT,
NUM_DECODE_TYPES /* Must be last enum */
};
#define DECODE_TYPE_BITS 4
#define DECODE_TYPE_MASK ((1 << DECODE_TYPE_BITS) - 1)
enum decode_reg_type {
REG_TYPE_NONE = 0, /* Not a register, ignore */
REG_TYPE_ANY, /* Any register allowed */
REG_TYPE_SAMEAS16, /* Register should be same as that at bits 19..16 */
REG_TYPE_SP, /* Register must be SP */
REG_TYPE_PC, /* Register must be PC */
REG_TYPE_NOSP, /* Register must not be SP */
REG_TYPE_NOSPPC, /* Register must not be SP or PC */
REG_TYPE_NOPC, /* Register must not be PC */
REG_TYPE_NOPCWB, /* No PC if load/store write-back flag also set */
/* The following types are used when the encoding for PC indicates
* another instruction form. This distiction only matters for test
* case coverage checks.
*/
REG_TYPE_NOPCX, /* Register must not be PC */
REG_TYPE_NOSPPCX, /* Register must not be SP or PC */
/* Alias to allow '0' arg to be used in REGS macro. */
REG_TYPE_0 = REG_TYPE_NONE
};
#define REGS(r16, r12, r8, r4, r0) \
(((REG_TYPE_##r16) << 16) + \
((REG_TYPE_##r12) << 12) + \
((REG_TYPE_##r8) << 8) + \
((REG_TYPE_##r4) << 4) + \
(REG_TYPE_##r0))
union decode_item {
u32 bits;
const union decode_item *table;
int action;
};
struct decode_header;
typedef enum probes_insn (probes_custom_decode_t)(probes_opcode_t,
struct arch_probes_insn *,
const struct decode_header *);
union decode_action {
probes_insn_handler_t *handler;
probes_custom_decode_t *decoder;
};
typedef enum probes_insn (probes_check_t)(probes_opcode_t,
struct arch_probes_insn *,
const struct decode_header *);
struct decode_checker {
probes_check_t *checker;
};
#define DECODE_END \
{.bits = DECODE_TYPE_END}
struct decode_header {
union decode_item type_regs;
union decode_item mask;
union decode_item value;
};
#define DECODE_HEADER(_type, _mask, _value, _regs) \
{.bits = (_type) | ((_regs) << DECODE_TYPE_BITS)}, \
{.bits = (_mask)}, \
{.bits = (_value)}
struct decode_table {
struct decode_header header;
union decode_item table;
};
#define DECODE_TABLE(_mask, _value, _table) \
DECODE_HEADER(DECODE_TYPE_TABLE, _mask, _value, 0), \
{.table = (_table)}
struct decode_custom {
struct decode_header header;
union decode_item decoder;
};
#define DECODE_CUSTOM(_mask, _value, _decoder) \
DECODE_HEADER(DECODE_TYPE_CUSTOM, _mask, _value, 0), \
{.action = (_decoder)}
struct decode_simulate {
struct decode_header header;
union decode_item handler;
};
#define DECODE_SIMULATEX(_mask, _value, _handler, _regs) \
DECODE_HEADER(DECODE_TYPE_SIMULATE, _mask, _value, _regs), \
{.action = (_handler)}
#define DECODE_SIMULATE(_mask, _value, _handler) \
DECODE_SIMULATEX(_mask, _value, _handler, 0)
struct decode_emulate {
struct decode_header header;
union decode_item handler;
};
#define DECODE_EMULATEX(_mask, _value, _handler, _regs) \
DECODE_HEADER(DECODE_TYPE_EMULATE, _mask, _value, _regs), \
{.action = (_handler)}
#define DECODE_EMULATE(_mask, _value, _handler) \
DECODE_EMULATEX(_mask, _value, _handler, 0)
struct decode_or {
struct decode_header header;
};
#define DECODE_OR(_mask, _value) \
DECODE_HEADER(DECODE_TYPE_OR, _mask, _value, 0)
enum probes_insn {
INSN_REJECTED,
INSN_GOOD,
INSN_GOOD_NO_SLOT
};
struct decode_reject {
struct decode_header header;
};
#define DECODE_REJECT(_mask, _value) \
DECODE_HEADER(DECODE_TYPE_REJECT, _mask, _value, 0)
probes_insn_handler_t probes_simulate_nop;
probes_insn_handler_t probes_emulate_none;
int __kprobes
probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
const union decode_item *table, bool thumb, bool emulate,
const union decode_action *actions,
const struct decode_checker **checkers);
#endif