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 <wangnan0@huawei.com>
Reviewed-by: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>

diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h
index cd9e81588d830bff9d96bad0e7143c4708f46198..b668e60f759cc58e848594f0382a1820347e4038 100644 (file)
--- 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 f9d7c423f2cc0a969123d479027356ae1e785c62..880ebe0cdf1908cb09df34aad2c5339349a8759f 100644 (file)
--- 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 06988ef7eeb7755ef50d49f20b5394e3327c0d18..b9056d649607f359a13a8d9b64bd26d8c780bbcd 100644 (file)
--- 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 f8176631d2a546852198392ed3ce48b820f0b46a..7b9817333b689722740bb2f98a96da0bf635ba74 100644 (file)
--- 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 bddfa0e82389c64b19f2e335848c49514ad8b1be..cf6c9e74d66632de5c5c1d1901709ddeb512f412 100644 (file)
--- 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[];