[PATCH] ARM: kprobes: check register usage for probed instruction
From: Jon Medhurst (Tixy)
Date: Tue Jan 13 2015 - 11:13:59 EST
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 <wangnan0@xxxxxxxxxx>
Reviewed-by: Jon Medhurst <tixy@xxxxxxxxxx>
Signed-off-by: Jon Medhurst <tixy@xxxxxxxxxx>
---
This patch applies my review comments on "[PATCH v19 10/11] ARM:
kprobes: check register usage for probed instruction."
It is also rebased on top of the kprobes-opt branch at
git://git.linaro.org/people/tixy/kernel.git
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 cd9e815..b668e60 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 f9d7c42..880ebe0 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 06988ef..b9056d6 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 f817663..7b98173 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 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[];
--
2.1.4
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