read_leb128 overflow checking

[thirdparty/binutils-gdb.git] / opcodes / wasm32-dis.c

diff --git a/opcodes/wasm32-dis.c b/opcodes/wasm32-dis.c
index 727a49e1207767a4b6ea0ce25d0870a31e68a5cd..2fe5132e1299ccbe9f4dd4a700d70d095b3107e6 100644 (file)
--- a/opcodes/wasm32-dis.c
+++ b/opcodes/wasm32-dis.c
@@ -29,6 +29,13 @@
 #include "elf/wasm32.h"
 #include "bfd_stdint.h"
 
+#ifdef HAVE_LIMITS_H
+#include <limits.h>
+#endif
+#ifndef CHAR_BIT
+#define CHAR_BIT 8
+#endif
+
 /* Type names for blocks and signatures.  */
 #define BLOCK_TYPE_NONE              0x40
 #define BLOCK_TYPE_I32               0x7f
@@ -192,27 +199,34 @@ wasm_read_leb128 (bfd_vma                   pc,
   unsigned int num_read = 0;
   unsigned int shift = 0;
   unsigned char byte = 0;
+  unsigned char lost, mask;
   int status = 1;
 
   while (info->read_memory_func (pc + num_read, &byte, 1, info) == 0)
     {
       num_read++;
 
-      if (shift < sizeof (result) * 8)
+      if (shift < CHAR_BIT * sizeof (result))
        {
          result |= ((uint64_t) (byte & 0x7f)) << shift;
-         if ((result >> shift) != (byte & 0x7f))
-           /* Overflow.  */
-           status |= 2;
+         /* These bits overflowed.  */
+         lost = byte ^ (result >> shift);
+         /* And this is the mask of possible overflow bits.  */
+         mask = 0x7f ^ ((uint64_t) 0x7f << shift >> shift);
          shift += 7;
        }
-      else if ((byte & 0x7f) != 0)
+      else
+       {
+         lost = byte;
+         mask = 0x7f;
+       }
+      if ((lost & mask) != (sign && (int64_t) result < 0 ? mask : 0))
        status |= 2;
 
       if ((byte & 0x80) == 0)
        {
          status &= ~1;
-         if (sign && (shift < 8 * sizeof (result)) && (byte & 0x40))
+         if (sign && shift < CHAR_BIT * sizeof (result) && (byte & 0x40))
            result |= -((uint64_t) 1 << shift);
          break;
        }