Assembler message on Ubuntu 18.04

[arruah]

I get the error after this gcc demo.c -o demo

demo.c:11: Error: `bound' is not supported in 64-bit mode

[jwilk]

You need to pass -m32 to the compiler.

[mathieujobin]

I have added -m32 to the Makefile under the util folder.
but I am still getting a compilation error on Ubuntu 18.04

mathieu:util :-) (master) $ make 
mkdir -p bin
gcc -m32 check.c -o ./bin/check
In file included from check.c:2:0:
/usr/include/stdio.h:27:10: fatal error: bits/libc-header-start.h: No such file or directory
 #include <bits/libc-header-start.h>
          ^~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
Makefile:4: recipe for target 'bin/check' failed
make: *** [bin/check] Error 1
mathieu:util :-( 1 (master) $ 

please advise

[mathieujobin]

that file seems to be a 64 only flag, which is what is causing it to be missing with m32 flag

/usr/include/x86_64-linux-gnu/bits/libc-header-start.h

[jwilk]

/usr/include/stdio.h:27:10: fatal error: bits/libc-header-start.h: No such file or directory

Looks like you don't have 32-bit glibc development package installed.
I believe on Ubuntu the package name is libc6-dev-i386.

[mathieujobin]

Thank you, I can confirm compilation works with ubuntu 18.04

$ sudo apt install libc6-dev-i386
$ make 
mkdir -p bin
gcc -m32 check.c -o ./bin/check
$ ./bin/check 
! failed to open /dev/cpu/0/msr
$

does that mean I am not vulnerable?

[jwilk]

$ ./bin/check 
! failed to open /dev/cpu/0/msr

does that mean I am not vulnerable?

No; the program didn't check anything, because it couldn't open the device it needed.
It's most likely because you didn't have the msr kernel module loaded.

[brammittendorff-dd]

@jwilk @mathieujobin you can load the msr kernel module with sudo modprobe msr. If you watch the video closely you will see he loads it up to: https://youtu.be/_eSAF_qT_FY?t=47m38s