From 28a1899db30a9325498aef114055506286dc8010 Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Mon, 5 Jan 2015 19:29:44 +0800 Subject: [PATCH] ARM: kprobes: check register usage for probed instruction. This patch utilizes the previously introduced checker to check register usage for probed ARM instruction and saves it in a mask. A further patch will use such information to avoid simulation or emulation. Signed-off-by: Wang Nan Reviewed-by: Jon Medhurst Signed-off-by: Jon Medhurst --- arch/arm/include/asm/probes.h | 1 + arch/arm/probes/decode.c | 7 ++ arch/arm/probes/kprobes/actions-arm.c | 2 +- arch/arm/probes/kprobes/checkers-arm.c | 93 ++++++++++++++++++++++++++ arch/arm/probes/kprobes/checkers.h | 1 + 5 files changed, 103 insertions(+), 1 deletion(-) diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h index cd9e81588d83..b668e60f759c 100644 --- a/arch/arm/include/asm/probes.h +++ b/arch/arm/include/asm/probes.h @@ -41,6 +41,7 @@ struct arch_probes_insn { probes_insn_singlestep_t *insn_singlestep; probes_insn_fn_t *insn_fn; int stack_space; + unsigned long register_usage_flags; }; #endif /* __ASSEMBLY__ */ diff --git a/arch/arm/probes/decode.c b/arch/arm/probes/decode.c index f9d7c423f2cc..880ebe0cdf19 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; + /* + * Similarly to stack_space, register_usage_flags 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_flags = ~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 06988ef7eeb7..b9056d649607 100644 --- a/arch/arm/probes/kprobes/actions-arm.c +++ b/arch/arm/probes/kprobes/actions-arm.c @@ -341,4 +341,4 @@ 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 f8176631d2a5..7b9817333b68 100644 --- a/arch/arm/probes/kprobes/checkers-arm.c +++ b/arch/arm/probes/kprobes/checkers-arm.c @@ -97,3 +97,96 @@ 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_flags = 0; + return INSN_GOOD; +} + +static enum probes_insn arm_check_regs_normal(probes_opcode_t insn, + struct arch_probes_insn *asi, + const struct decode_header *h) +{ + u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS; + int i; + + asi->register_usage_flags = 0; + for (i = 0; i < 5; regs >>= 4, insn >>= 4, i++) + if (regs & 0xf) + asi->register_usage_flags |= 1 << (insn & 0xf); + + 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; + asi->register_usage_flags = reglist | (1 << rn); + 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) +{ + /* Instruction is 'mov ip, sp' i.e. 'mov r12, r13' */ + asi->register_usage_flags = (1 << 12) | (1<< 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 to handle this extra + * implicit register usage. + */ +static enum probes_insn arm_check_regs_ldrdstrd(probes_opcode_t insn, + struct arch_probes_insn *asi, + const struct decode_header *h) +{ + int rdt = (insn >> 12) & 0xf; + arm_check_regs_normal(insn, asi, h); + asi->register_usage_flags |= 1 << (rdt + 1); + return INSN_GOOD; +} + + +const struct decode_checker arm_regs_checker[NUM_PROBES_ARM_ACTIONS] = { + [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_SEV] = {.checker = arm_check_regs_nouse}, + [PROBES_WFE] = {.checker = arm_check_regs_nouse}, + [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 bddfa0e82389..cf6c9e74d666 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[]; -- 2.20.1