ARM: kprobes: introduces checker

This patch introdces 'checker' to decoding phase, and calls checkers
when instruction decoding. This allows further decoding for specific
instructions.  This patch introduces a stub call of checkers in kprobe
arch_prepare_kprobe() as an example and for further expansion.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Jon Medhurst <tixy@linaro.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>

diff --git a/arch/arm/probes/decode-arm.c b/arch/arm/probes/decode-arm.c
index 04114f7..f72c33a 100644 (file)
--- a/arch/arm/probes/decode-arm.c
+++ b/arch/arm/probes/decode-arm.c
@@ -726,10 +726,11 @@ static void __kprobes arm_singlestep(probes_opcode_t insn,
  */
 enum probes_insn __kprobes
 arm_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
-                      bool emulate, const union decode_action *actions)
+                      bool emulate, const union decode_action *actions,
+                      const struct decode_checker *checkers[])
 {
        asi->insn_singlestep = arm_singlestep;
        asi->insn_check_cc = probes_condition_checks[insn>>28];
        return probes_decode_insn(insn, asi, probes_decode_arm_table, false,
-                                 emulate, actions);
+                                 emulate, actions, checkers);
 }

diff --git a/arch/arm/probes/decode-arm.h b/arch/arm/probes/decode-arm.h
index cb0b263..b3b80f6 100644 (file)
--- a/arch/arm/probes/decode-arm.h
+++ b/arch/arm/probes/decode-arm.h
@@ -68,6 +68,7 @@ extern const union decode_item probes_decode_arm_table[];
 
 enum probes_insn arm_probes_decode_insn(probes_opcode_t,
                struct arch_probes_insn *, bool emulate,
-               const union decode_action *actions);
+               const union decode_action *actions,
+               const struct decode_checker *checkers[]);
 
 #endif

diff --git a/arch/arm/probes/decode-thumb.c b/arch/arm/probes/decode-thumb.c
index 2f0453a..985e7dd 100644 (file)
--- a/arch/arm/probes/decode-thumb.c
+++ b/arch/arm/probes/decode-thumb.c
@@ -863,20 +863,22 @@ static void __kprobes thumb32_singlestep(probes_opcode_t opcode,
 
 enum probes_insn __kprobes
 thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
-                          bool emulate, const union decode_action *actions)
+                          bool emulate, const union decode_action *actions,
+                          const struct decode_checker *checkers[])
 {
        asi->insn_singlestep = thumb16_singlestep;
        asi->insn_check_cc = thumb_check_cc;
        return probes_decode_insn(insn, asi, probes_decode_thumb16_table, true,
-                                 emulate, actions);
+                                 emulate, actions, checkers);
 }
 
 enum probes_insn __kprobes
 thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
-                          bool emulate, const union decode_action *actions)
+                          bool emulate, const union decode_action *actions,
+                          const struct decode_checker *checkers[])
 {
        asi->insn_singlestep = thumb32_singlestep;
        asi->insn_check_cc = thumb_check_cc;
        return probes_decode_insn(insn, asi, probes_decode_thumb32_table, true,
-                                 emulate, actions);
+                                 emulate, actions, checkers);
 }

diff --git a/arch/arm/probes/decode-thumb.h b/arch/arm/probes/decode-thumb.h
index 039013c..8457add 100644 (file)
--- a/arch/arm/probes/decode-thumb.h
+++ b/arch/arm/probes/decode-thumb.h
@@ -91,9 +91,11 @@ extern const union decode_item probes_decode_thumb16_table[];
 
 enum probes_insn __kprobes
 thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
-               bool emulate, const union decode_action *actions);
+               bool emulate, const union decode_action *actions,
+               const struct decode_checker *checkers[]);
 enum probes_insn __kprobes
 thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
-               bool emulate, const union decode_action *actions);
+               bool emulate, const union decode_action *actions,
+               const struct decode_checker *checkers[]);
 
 #endif

diff --git a/arch/arm/probes/decode.c b/arch/arm/probes/decode.c
index 3b05d57..c7d4420 100644 (file)
--- a/arch/arm/probes/decode.c
+++ b/arch/arm/probes/decode.c
@@ -342,6 +342,31 @@ static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
        [DECODE_TYPE_REJECT]    = sizeof(struct decode_reject)
 };
 
+static int run_checkers(const struct decode_checker *checkers[],
+               int action, probes_opcode_t insn,
+               struct arch_probes_insn *asi,
+               const struct decode_header *h)
+{
+       const struct decode_checker **p;
+
+       if (!checkers)
+               return INSN_GOOD;
+
+       p = checkers;
+       while (*p != NULL) {
+               int retval;
+               probes_check_t *checker_func = (*p)[action].checker;
+
+               retval = INSN_GOOD;
+               if (checker_func)
+                       retval = checker_func(insn, asi, h);
+               if (retval == INSN_REJECTED)
+                       return retval;
+               p++;
+       }
+       return INSN_GOOD;
+}
+
 /*
  * probes_decode_insn operates on data tables in order to decode an ARM
  * architecture instruction onto which a kprobe has been placed.
@@ -388,11 +413,17 @@ static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
 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)
+                  bool emulate, const union decode_action *actions,
+                  const struct decode_checker *checkers[])
 {
        const struct decode_header *h = (struct decode_header *)table;
        const struct decode_header *next;
        bool matched = false;
+       /*
+        * @insn can be modified by decode_regs. Save its original
+        * value for checkers.
+        */
+       probes_opcode_t origin_insn = insn;
 
        if (emulate)
                insn = prepare_emulated_insn(insn, asi, thumb);
@@ -422,24 +453,41 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
                }
 
                case DECODE_TYPE_CUSTOM: {
+                       int err;
                        struct decode_custom *d = (struct decode_custom *)h;
-                       return actions[d->decoder.action].decoder(insn, asi, h);
+                       int action = d->decoder.action;
+
+                       err = run_checkers(checkers, action, origin_insn, asi, h);
+                       if (err == INSN_REJECTED)
+                               return INSN_REJECTED;
+                       return actions[action].decoder(insn, asi, h);
                }
 
                case DECODE_TYPE_SIMULATE: {
+                       int err;
                        struct decode_simulate *d = (struct decode_simulate *)h;
-                       asi->insn_handler = actions[d->handler.action].handler;
+                       int action = d->handler.action;
+
+                       err = run_checkers(checkers, action, origin_insn, asi, h);
+                       if (err == INSN_REJECTED)
+                               return INSN_REJECTED;
+                       asi->insn_handler = actions[action].handler;
                        return INSN_GOOD_NO_SLOT;
                }
 
                case DECODE_TYPE_EMULATE: {
+                       int err;
                        struct decode_emulate *d = (struct decode_emulate *)h;
+                       int action = d->handler.action;
+
+                       err = run_checkers(checkers, action, origin_insn, asi, h);
+                       if (err == INSN_REJECTED)
+                               return INSN_REJECTED;
 
                        if (!emulate)
-                               return actions[d->handler.action].decoder(insn,
-                                       asi, h);
+                               return actions[action].decoder(insn, asi, h);
 
-                       asi->insn_handler = actions[d->handler.action].handler;
+                       asi->insn_handler = actions[action].handler;
                        set_emulated_insn(insn, asi, thumb);
                        return INSN_GOOD;
                }

diff --git a/arch/arm/probes/decode.h b/arch/arm/probes/decode.h
index 1d0b531..f9b08ba 100644 (file)
--- a/arch/arm/probes/decode.h
+++ b/arch/arm/probes/decode.h
@@ -314,6 +314,14 @@ union decode_action {
        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}
 
@@ -402,6 +410,7 @@ 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 union decode_action *actions,
+               const struct decode_checker **checkers);
 
 #endif

diff --git a/arch/arm/probes/kprobes/actions-arm.c b/arch/arm/probes/kprobes/actions-arm.c
index 2206f2d..fbd93a9 100644 (file)
--- a/arch/arm/probes/kprobes/actions-arm.c
+++ b/arch/arm/probes/kprobes/actions-arm.c
@@ -339,3 +339,5 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
        [PROBES_BRANCH] = {.handler = simulate_bbl},
        [PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
 };
+
+const struct decode_checker *kprobes_arm_checkers[] = {NULL};

diff --git a/arch/arm/probes/kprobes/actions-thumb.c b/arch/arm/probes/kprobes/actions-thumb.c
index 6c4e60b..2796121 100644 (file)
--- a/arch/arm/probes/kprobes/actions-thumb.c
+++ b/arch/arm/probes/kprobes/actions-thumb.c
@@ -664,3 +664,6 @@ const union decode_action kprobes_t32_actions[NUM_PROBES_T32_ACTIONS] = {
        [PROBES_T32_MUL_ADD_LONG] = {
                .handler = t32_emulate_rdlo12rdhi8rn16rm0_noflags},
 };
+
+const struct decode_checker *kprobes_t32_checkers[] = {NULL};
+const struct decode_checker *kprobes_t16_checkers[] = {NULL};

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index 701f49d..74f3dc3 100644 (file)
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -61,6 +61,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
        kprobe_decode_insn_t *decode_insn;
        const union decode_action *actions;
        int is;
+       const struct decode_checker **checkers;
 
        if (in_exception_text(addr))
                return -EINVAL;
@@ -74,9 +75,11 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
                insn = __opcode_thumb32_compose(insn, inst2);
                decode_insn = thumb32_probes_decode_insn;
                actions = kprobes_t32_actions;
+               checkers = kprobes_t32_checkers;
        } else {
                decode_insn = thumb16_probes_decode_insn;
                actions = kprobes_t16_actions;
+               checkers = kprobes_t16_checkers;
        }
 #else /* !CONFIG_THUMB2_KERNEL */
        thumb = false;
@@ -85,12 +88,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
        insn = __mem_to_opcode_arm(*p->addr);
        decode_insn = arm_probes_decode_insn;
        actions = kprobes_arm_actions;
+       checkers = kprobes_arm_checkers;
 #endif
 
        p->opcode = insn;
        p->ainsn.insn = tmp_insn;
 
-       switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
+       switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
        case INSN_REJECTED:     /* not supported */
                return -EINVAL;
 

diff --git a/arch/arm/probes/kprobes/core.h b/arch/arm/probes/kprobes/core.h
index 2e1e5a3..f88c79f 100644 (file)
--- a/arch/arm/probes/kprobes/core.h
+++ b/arch/arm/probes/kprobes/core.h
@@ -37,16 +37,19 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_probes_insn *asi,
 typedef enum probes_insn (kprobe_decode_insn_t)(probes_opcode_t,
                                                struct arch_probes_insn *,
                                                bool,
-                                               const union decode_action *);
+                                               const union decode_action *,
+                                               const struct decode_checker *[*]);
 
 #ifdef CONFIG_THUMB2_KERNEL
 
 extern const union decode_action kprobes_t32_actions[];
 extern const union decode_action kprobes_t16_actions[];
-
+extern const struct decode_checker *kprobes_t32_checkers[];
+extern const struct decode_checker *kprobes_t16_checkers[];
 #else /* !CONFIG_THUMB2_KERNEL */
 
 extern const union decode_action kprobes_arm_actions[];
+extern const struct decode_checker *kprobes_arm_checkers[];
 
 #endif
 

diff --git a/arch/arm/probes/uprobes/core.c b/arch/arm/probes/uprobes/core.c
index b2954f6..d1329f1 100644 (file)
--- a/arch/arm/probes/uprobes/core.c
+++ b/arch/arm/probes/uprobes/core.c
@@ -88,7 +88,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
        auprobe->ixol[1] = __opcode_to_mem_arm(UPROBE_SS_ARM_INSN);
 
        ret = arm_probes_decode_insn(insn, &auprobe->asi, false,
-                                    uprobes_probes_actions);
+                                    uprobes_probes_actions, NULL);
        switch (ret) {
        case INSN_REJECTED:
                return -EINVAL;