lkml.org 
[lkml]   [2015]   [Jan]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v19 10/11] ARM: kprobes: check register usage for probed instruction.
    Date
    This patch utilizes previous introduced checker to check register usage
    for probed ARM instruction and saves it in a mask. Futher patch will
    use such information to avoid simuation or emulation.

    Signed-off-by: Wang Nan <wangnan0@huawei.com>
    ---
    arch/arm/include/asm/probes.h | 10 +++
    arch/arm/probes/decode.c | 7 ++
    arch/arm/probes/kprobes/actions-arm.c | 2 +-
    arch/arm/probes/kprobes/checkers-arm.c | 124 +++++++++++++++++++++++++++++++++
    arch/arm/probes/kprobes/checkers.h | 1 +
    5 files changed, 143 insertions(+), 1 deletion(-)

    diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h
    index f0a1ee8..27b65b7 100644
    --- a/arch/arm/include/asm/probes.h
    +++ b/arch/arm/include/asm/probes.h
    @@ -41,6 +41,16 @@ struct arch_probes_insn {
    probes_insn_singlestep_t *insn_singlestep;
    probes_insn_fn_t *insn_fn;
    int stack_space;
    +
    + /* Use 1 bit for a register. */
    +#define REG_NO_USE (0)
    +#define REG_USE (1)
    +#define __register_usage_flag(n, f) ((f) << (n))
    +#define __clean_register_flag(m, n) ((m) & (~(1 << (n))))
    +#define __set_register_flag(m, n, f) (__clean_register_flag(m, n) | __register_usage_flag(n, f))
    +#define set_register_nouse(m, n) do {(m) = __set_register_flag(m, n, REG_NO_USE);} while(0)
    +#define set_register_use(m, n) do {(m) = __set_register_flag(m, n, REG_USE);} while(0)
    + unsigned long register_usage_flag;
    };

    #endif /* __ASSEMBLY__ */
    diff --git a/arch/arm/probes/decode.c b/arch/arm/probes/decode.c
    index f9d7c42..40f9402 100644
    --- a/arch/arm/probes/decode.c
    +++ b/arch/arm/probes/decode.c
    @@ -435,6 +435,13 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
    */
    asi->stack_space = 0;

    + /*
    + * Similay to stack_space, register_usage_flag is filled by
    + * checkers. Its default value is set to ~0, which is 'all
    + * registers are used', to prevent any potential optimization.
    + */
    + asi->register_usage_flag = ~(0UL);
    +
    if (emulate)
    insn = prepare_emulated_insn(insn, asi, thumb);

    diff --git a/arch/arm/probes/kprobes/actions-arm.c b/arch/arm/probes/kprobes/actions-arm.c
    index 4fedd4c..26e435b 100644
    --- a/arch/arm/probes/kprobes/actions-arm.c
    +++ b/arch/arm/probes/kprobes/actions-arm.c
    @@ -340,4 +340,4 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
    [PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
    };

    -const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, NULL};
    +const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, arm_regs_checker, NULL};
    diff --git a/arch/arm/probes/kprobes/checkers-arm.c b/arch/arm/probes/kprobes/checkers-arm.c
    index f817663..1929225 100644
    --- a/arch/arm/probes/kprobes/checkers-arm.c
    +++ b/arch/arm/probes/kprobes/checkers-arm.c
    @@ -97,3 +97,127 @@ const struct decode_checker arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = {
    [PROBES_STORE] = {.checker = arm_check_stack},
    [PROBES_LDMSTM] = {.checker = arm_check_stack},
    };
    +
    +static enum probes_insn __kprobes arm_check_regs_nouse(probes_opcode_t insn,
    + struct arch_probes_insn *asi,
    + const struct decode_header *h)
    +{
    + asi->register_usage_flag = 0;
    + return INSN_GOOD;
    +}
    +
    +static void __arm_check_regs(probes_opcode_t insn,
    + const struct decode_header *h,
    + int *quintuple)
    +{
    + int i;
    + u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS;
    + probes_opcode_t mask, shifted;
    +
    + memset(quintuple, 0xff, sizeof(int) * 5);
    + for (i = 0, shifted = insn, mask = 0xf; regs != 0;
    + regs >>= 4, mask <<= 4, shifted >>= 4, i++)
    + if (regs & 0xf)
    + quintuple[i] = shifted & 0xf;
    +}
    +
    +static enum probes_insn arm_check_regs_normal(probes_opcode_t insn,
    + struct arch_probes_insn *asi,
    + const struct decode_header *h)
    +{
    + int quintuple[5], i;
    + asi->register_usage_flag = 0;
    + __arm_check_regs(insn, h, quintuple);
    + for (i = 0; i < 5; i++) {
    + int r = quintuple[i];
    + if (r < 0)
    + continue;
    + set_register_use(asi->register_usage_flag, r);
    + }
    +
    + return INSN_GOOD;
    +}
    +
    +static enum probes_insn arm_check_regs_ldmstm(probes_opcode_t insn,
    + struct arch_probes_insn *asi,
    + const struct decode_header *h)
    +{
    + unsigned int reglist = insn & 0xffff;
    + unsigned int rn = (insn >> 16) & 0xf;
    + int i;
    +
    + set_register_use(asi->register_usage_flag, rn);
    + for (i = 0; reglist > 0; i++, reglist >>= 1)
    + if (reglist & 1)
    + set_register_use(asi->register_usage_flag, i);
    + return INSN_GOOD;
    +}
    +
    +static enum probes_insn arm_check_regs_mov_ip_sp(probes_opcode_t insn,
    + struct arch_probes_insn *asi,
    + const struct decode_header *h)
    +{
    + /* should be 'mov ip, sp' */
    + set_register_use(asi->register_usage_flag, 12);
    + set_register_use(asi->register_usage_flag, 13);
    + return INSN_GOOD;
    +}
    +
    +/*
    + * | Rn |Rt/d| | Rm |
    + * LDRD (register) cccc 000x x0x0 xxxx xxxx xxxx 1101 xxxx
    + * STRD (register) cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
    + * | Rn |Rt/d| |imm4L|
    + * LDRD (immediate) cccc 000x x1x0 xxxx xxxx xxxx 1101 xxxx
    + * STRD (immediate) cccc 000x x1x0 xxxx xxxx xxxx 1111 xxxx
    + *
    + * Such instructions access Rt/d and its next register, so different
    + * from others, a specific checker is required for Rt/d and Rt2/d2.
    + */
    +static enum probes_insn arm_check_regs_ldrdstrd(probes_opcode_t insn,
    + struct arch_probes_insn *asi,
    + const struct decode_header *h)
    +{
    + int quintuple[5], rn, rdt, rm;
    + asi->register_usage_flag = 0;
    + __arm_check_regs(insn, h, quintuple);
    +
    + rn = quintuple[4];
    + rdt = quintuple[3];
    + rm = quintuple[0];
    + set_register_use(asi->register_usage_flag, rn);
    + set_register_use(asi->register_usage_flag, rdt);
    + set_register_use(asi->register_usage_flag, rdt + 1);
    + if (rm >= 0)
    + set_register_use(asi->register_usage_flag, rm);
    +
    + return INSN_GOOD;
    +}
    +
    +
    +const struct decode_checker arm_regs_checker[NUM_PROBES_ARM_ACTIONS] = {
    + [PROBES_EMULATE_NONE] = {.checker = arm_check_regs_nouse},
    + [PROBES_SIMULATE_NOP] = {.checker = arm_check_regs_nouse},
    + [PROBES_MRS] = {.checker = arm_check_regs_normal},
    + [PROBES_SATURATING_ARITHMETIC] = {.checker = arm_check_regs_normal},
    + [PROBES_MUL1] = {.checker = arm_check_regs_normal},
    + [PROBES_MUL2] = {.checker = arm_check_regs_normal},
    + [PROBES_MUL_ADD_LONG] = {.checker = arm_check_regs_normal},
    + [PROBES_MUL_ADD] = {.checker = arm_check_regs_normal},
    + [PROBES_LOAD] = {.checker = arm_check_regs_normal},
    + [PROBES_LOAD_EXTRA] = {.checker = arm_check_regs_normal},
    + [PROBES_STORE] = {.checker = arm_check_regs_normal},
    + [PROBES_STORE_EXTRA] = {.checker = arm_check_regs_normal},
    + [PROBES_DATA_PROCESSING_REG] = {.checker = arm_check_regs_normal},
    + [PROBES_DATA_PROCESSING_IMM] = {.checker = arm_check_regs_normal},
    + [PROBES_SATURATE] = {.checker = arm_check_regs_normal},
    + [PROBES_REV] = {.checker = arm_check_regs_normal},
    + [PROBES_MMI] = {.checker = arm_check_regs_normal},
    + [PROBES_PACK] = {.checker = arm_check_regs_normal},
    + [PROBES_EXTEND] = {.checker = arm_check_regs_normal},
    + [PROBES_EXTEND_ADD] = {.checker = arm_check_regs_normal},
    + [PROBES_BITFIELD] = {.checker = arm_check_regs_normal},
    + [PROBES_LDMSTM] = {.checker = arm_check_regs_ldmstm},
    + [PROBES_MOV_IP_SP] = {.checker = arm_check_regs_mov_ip_sp},
    + [PROBES_LDRSTRD] = {.checker = arm_check_regs_ldrdstrd},
    +};
    diff --git a/arch/arm/probes/kprobes/checkers.h b/arch/arm/probes/kprobes/checkers.h
    index bddfa0e..cf6c9e7 100644
    --- a/arch/arm/probes/kprobes/checkers.h
    +++ b/arch/arm/probes/kprobes/checkers.h
    @@ -47,6 +47,7 @@ extern const union decode_action stack_check_actions[];

    #ifndef CONFIG_THUMB2_KERNEL
    extern const struct decode_checker arm_stack_checker[];
    +extern const struct decode_checker arm_regs_checker[];
    #else
    #endif
    extern const struct decode_checker t32_stack_checker[];
    --
    1.8.4


    \
     
     \ /
      Last update: 2015-01-05 12:41    [W:4.075 / U:0.216 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site