ASSERT: missing decode type in core/arch/x86/disassemble.c:227

Created by: abenkhadra

In order to log the actual instructions observed at runtime, one can enable loglevel 3 by issuing the following command:

drrun -debug -loglevel 3  -c any_client -- any_app

This command runs without problems dumping the instructions in DR's own syntax. However, changing the disassembly syntax to intel or att, by adding command line option -syntax_intel or -syntax_att respectively, would trigger the above mentioned assertion which can be found here.

I've debugged this issue a bit and it seems like the assertion is triggered by instruction syscall which is called by ld-linux-x86-64.so.2. The instruction syscall does not have a matching optype. The issue is independent of the client used or the instrumented application since it's triggered by the loader.

I'm using DR 6.2.0 on an x86_64 machine running Ubuntu 16.04