Specify address via parameter

This allows to decode instructions where the address of the buffer is
not the address of the instruction.

decode.c

@@ -358,7 +358,8 @@ struct InstrDesc
 #define DESC_IMM_BYTE(desc) (((desc)->immediate >> 7) & 1)
 
 int
-decode(const uint8_t* buffer, int len, DecodeMode mode, Instr* instr)
+decode(const uint8_t* buffer, int len, DecodeMode mode, uintptr_t address,
+       Instr* instr)
 {
     const uint8_t* decode_table = NULL;
 
@@ -453,7 +454,7 @@ decode(const uint8_t* buffer, int len, DecodeMode mode, Instr* instr)
     instr->flags = prefixes & 0x7f;
     if (mode == DECODE_64)
         instr->flags |= INSTR_FLAG_64;
-    instr->address = (uintptr_t) buffer;
+    instr->address = address;
 
     uint8_t op_size = 0;
     if (desc->gp_size_8)
@@ -630,7 +631,7 @@ decode(const uint8_t* buffer, int len, DecodeMode mode, Instr* instr)
 
         if (imm_control == 4)
         {
-            instr->immediate += (uintptr_t) buffer + off;
+            instr->immediate += instr->address + off;
         }
 
         struct Operand* operand = &instr->operands[DESC_IMM_IDX(desc)];

decode.h

@@ -131,7 +131,8 @@ typedef struct Instr Instr;
 #define INSTR_HAS_REX(instr) ((instr)->flags & INSTR_FLAG_REX)
 #define INSTR_HAS_VEXL(instr) ((instr)->flags & INSTR_FLAG_VEXL)
 
-int decode(const uint8_t* buffer, int len, DecodeMode mode, Instr* out_instr);
+int decode(const uint8_t* buffer, int len, DecodeMode mode, uintptr_t address,
+           Instr* out_instr);
 void instr_format(const Instr* instr, char buffer[128]);
 
 #endif

tests/driver.c

@@ -72,7 +72,8 @@ main(int argc, char** argv)
         while (current_off != length)
         {
             size_t remaining = length - current_off;
-            int retval = decode(code + current_off, remaining, mode, &instr);
+            int retval = decode(code + current_off, remaining, mode, 0x1234000,
+                                &instr);
             if (retval < 0)
                 goto fail;
             current_off += retval;