ARM: Add an emulate flag to the kprobes/uprobes instruction decode functions

Add an emulate flag into the instruction interpreter, primarily for uprobes
support.

Signed-off-by: David A. Long <dave.long@linaro.org>
Acked-by: Jon Medhurst <tixy@linaro.org>

8 files changed, 25 insertions, 16 deletions

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 468d4a980c6c..8795f9f819d5 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -89,7 +89,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
         p->opcode = insn;
         p->ainsn.insn = tmp_insn;
 
-        switch ((*decode_insn)(insn, &p->ainsn, actions)) {
+        switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
         case INSN_REJECTED:     /* not supported */
                 return -EINVAL;
 
diff --git a/arch/arm/kernel/kprobes.h b/arch/arm/kernel/kprobes.h
index eee8089b1b93..d0a24b73bcfa 100644
--- a/arch/arm/kernel/kprobes.h
+++ b/arch/arm/kernel/kprobes.h
@@ -35,6 +35,7 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi,
 
 typedef enum probes_insn (kprobe_decode_insn_t)(probes_opcode_t,
                                                 struct arch_specific_insn *,
+                                                bool,
                                                 const union decode_action *);
 
 #ifdef CONFIG_THUMB2_KERNEL
diff --git a/arch/arm/kernel/probes-arm.c b/arch/arm/kernel/probes-arm.c
index 738e5fc58928..8e7fde876521 100644
--- a/arch/arm/kernel/probes-arm.c
+++ b/arch/arm/kernel/probes-arm.c
@@ -725,10 +725,10 @@ static void __kprobes arm_singlestep(probes_opcode_t insn,
  */
 enum probes_insn __kprobes
 arm_probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
-                       const union decode_action *actions)
+                       bool emulate, const union decode_action *actions)
 {
         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,
-                                  actions);
+                                  emulate, actions);
 }
diff --git a/arch/arm/kernel/probes-arm.h b/arch/arm/kernel/probes-arm.h
index 7a5cce497a9b..ea614dc5aaa3 100644
--- a/arch/arm/kernel/probes-arm.h
+++ b/arch/arm/kernel/probes-arm.h
@@ -67,7 +67,7 @@ void __kprobes simulate_mov_ipsp(probes_opcode_t opcode,
 extern const union decode_item probes_decode_arm_table[];
 
 enum probes_insn arm_probes_decode_insn(probes_opcode_t,
-                struct arch_specific_insn *,
+                struct arch_specific_insn *, bool emulate,
                 const union decode_action *actions);
 
 #endif
diff --git a/arch/arm/kernel/probes-thumb.c b/arch/arm/kernel/probes-thumb.c
index eab440f6b2d4..23e2cbdb37cb 100644
--- a/arch/arm/kernel/probes-thumb.c
+++ b/arch/arm/kernel/probes-thumb.c
@@ -863,20 +863,20 @@ static void __kprobes thumb32_singlestep(probes_opcode_t opcode,
 
 enum probes_insn __kprobes
 thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
-                           const union decode_action *actions)
+                           bool emulate, const union decode_action *actions)
 {
         asi->insn_singlestep = thumb16_singlestep;
         asi->insn_check_cc = thumb_check_cc;
         return probes_decode_insn(insn, asi, probes_decode_thumb16_table, true,
-                                  actions);
+                                  emulate, actions);
 }
 
 enum probes_insn __kprobes
 thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
-                           const union decode_action *actions)
+                           bool emulate, const union decode_action *actions)
 {
         asi->insn_singlestep = thumb32_singlestep;
         asi->insn_check_cc = thumb_check_cc;
         return probes_decode_insn(insn, asi, probes_decode_thumb32_table, true,
-                                  actions);
+                                  emulate, actions);
 }
diff --git a/arch/arm/kernel/probes-thumb.h b/arch/arm/kernel/probes-thumb.h
index d6f67c1df7af..65e4250e9b78 100644
--- a/arch/arm/kernel/probes-thumb.h
+++ b/arch/arm/kernel/probes-thumb.h
@@ -89,9 +89,9 @@ extern const union decode_item probes_decode_thumb16_table[];
 
 enum probes_insn __kprobes
 thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
-                const union decode_action *actions);
+                bool emulate, const union decode_action *actions);
 enum probes_insn __kprobes
 thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
-                const union decode_action *actions);
+                bool emulate, const union decode_action *actions);
 
 #endif
diff --git a/arch/arm/kernel/probes.c b/arch/arm/kernel/probes.c
index b6d9b855273c..f9dff12cf85c 100644
--- a/arch/arm/kernel/probes.c
+++ b/arch/arm/kernel/probes.c
@@ -257,7 +257,7 @@ set_emulated_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
  * non-zero value, the corresponding nibble in pinsn is validated and modified
  * according to the type.
  */
-static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs)
+static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs, bool modify)
 {
         probes_opcode_t insn = *pinsn;
         probes_opcode_t mask = 0xf; /* Start at least significant nibble */
@@ -323,7 +323,9 @@ static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs)
                 insn |= new_bits & mask;
         }
 
-        *pinsn = insn;
+        if (modify)
+                *pinsn = insn;
+
         return true;
 
 reject:
@@ -385,13 +387,14 @@ static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
 int __kprobes
 probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
                    const union decode_item *table, bool thumb,
-                   const union decode_action *actions)
+                   bool emulate, const union decode_action *actions)
 {
         const struct decode_header *h = (struct decode_header *)table;
         const struct decode_header *next;
         bool matched = false;
 
-        insn = prepare_emulated_insn(insn, asi, thumb);
+        if (emulate)
+                insn = prepare_emulated_insn(insn, asi, thumb);
 
         for (;; h = next) {
                 enum decode_type type = h->type_regs.bits & DECODE_TYPE_MASK;
@@ -406,7 +409,7 @@ probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
                 if (!matched && (insn & h->mask.bits) != h->value.bits)
                         continue;
 
-                if (!decode_regs(&insn, regs))
+                if (!decode_regs(&insn, regs, emulate))
                         return INSN_REJECTED;
 
                 switch (type) {
@@ -430,6 +433,11 @@ probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
 
                 case DECODE_TYPE_EMULATE: {
                         struct decode_emulate *d = (struct decode_emulate *)h;
+
+                        if (!emulate)
+                                return actions[d->handler.action].decoder(insn,
+                                        asi, h);
+
                         asi->insn_handler = actions[d->handler.action].handler;
                         set_emulated_insn(insn, asi, thumb);
                         return INSN_GOOD;
diff --git a/arch/arm/kernel/probes.h b/arch/arm/kernel/probes.h
index 0c72e544175d..33cc30c50cf5 100644
--- a/arch/arm/kernel/probes.h
+++ b/arch/arm/kernel/probes.h
@@ -401,7 +401,7 @@ probes_insn_handler_t probes_emulate_none;
 
 int __kprobes
 probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
-                const union decode_item *table, bool thumb,
+                const union decode_item *table, bool thumb, bool emulate,
                 const union decode_action *actions);
 
 #endif