disas/microblaze: Avoid unintended sign extension

In read_insn_microblaze() we assemble 4 bytes into an 'unsigned
long'.  If 'unsigned long' is 64 bits and the high byte has its top
bit set, then C's implicit conversion from 'unsigned char' to 'int'
for the shift will result in an unintended sign extension which sets
the top 32 bits in 'inst'.  Add casts to prevent this.  (Spotted by
Coverity, CID 1005401.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1488556233-31246-5-git-send-email-peter.maydell@linaro.org

diff --git a/disas/microblaze.c b/disas/microblaze.c
index 91b30acbe1aaab922c1d18b2d267fcf542c3d776..407c0a3ffa5f831fd51325a87e031d59c936bfd8 100644 (file)
--- a/disas/microblaze.c
+++ b/disas/microblaze.c
@@ -748,9 +748,11 @@ read_insn_microblaze (bfd_vma memaddr,
     }
 
   if (info->endian == BFD_ENDIAN_BIG)
-    inst = (ibytes[0] << 24) | (ibytes[1] << 16) | (ibytes[2] << 8) | ibytes[3];
+    inst = ((unsigned)ibytes[0] << 24) | (ibytes[1] << 16)
+      | (ibytes[2] << 8) | ibytes[3];
   else if (info->endian == BFD_ENDIAN_LITTLE)
-    inst = (ibytes[3] << 24) | (ibytes[2] << 16) | (ibytes[1] << 8) | ibytes[0];
+    inst = ((unsigned)ibytes[3] << 24) | (ibytes[2] << 16)
+      | (ibytes[1] << 8) | ibytes[0];
   else
     abort ();