[gem5 Q&A] Fixed I/O Address Range in x86

Hi all, I’m trying to model the SPEC HPC benchmark suite in gem5 with an x86 ISA using KVM. As a result, I am trying to link the “_addr” version of the m5ops against the binaries in order to model the region of interest. Unfortunately, I get the following error when trying to build the sample hello world example:

File contents (test.c):

#include <gem5/m5ops.h>
#include <m5_mmap.h>

int main(void) {
m5op_addr = 0xffff0000;
map_m5_mem();
m5_exit_addr(0);
return 0;
}

Error output: ``` $ gcc -o test test.c -I/gem5-include/ -I/m5-include/ -L/m5-out -lm5

/usr/bin/ld: /m5-out/libm5.a(m5op_addr.o): relocation R_X86_64_32S against symbol `m5_mem’ can not be used when making a PIE object; recompile with -fPIC /usr/bin/ld: final link failed: Nonrepresentable section on output collect2: error: ld returned 1 exit status

The included headers from $(GEM5_DIR)/include are in the /gem5-include
directory, the m5 utility headers (required to include <m5_mmap.h>) are in
/m5-include, and the libraries and binaries are in /m5-out.

I added -fPIC to the CCFLAGS and CXXFLAGS of the SConscript in util/m5, but
this didn't change the error post compilation. I also tried adding -fno-pie
and get the error on compilation of the m5 binary instead:

LINK build/x86/test/bin/call_type/addr /usr/bin/ld: build/x86/call_type/addr.test.to: relocation R_X86_64_32 against symbol `interceptEnv’ can not be used when making a PIE object; recompile with -fPIE /usr/bin/ld: failed to set dynamic section sizes: bad value collect2: error: ld returned 1 exit status scons: *** [build/x86/test/bin/call_type/addr] Error 1’’)

The error happens if I try to build natively on my Ubuntu 20.04 host
pointing to the files where they naturally are built in the base gem5
directory.

Any advice would be appreciated for where I may be going wrong on this!
Thank you in advance for your help!

My answer
======
Hi Sam,

   ''scons build/x86/out/m5 --verbose'' shows
   

g++ -o build/x86/out/m5 -no-pie -static build/x86/call_type/inst.o build/x86/call_type/addr.o build/x86/args.o …

   
   So I guess in your case either

gcc -o test test.c -I./include -I./util/m5/src -L./util/m5/build/x86/out/ -lm5 -static

   
   or
   

gcc -o test test.c -I./include -I./util/m5/src -L./util/m5/build/x86/out/ -lm5 -no-pie

```

should work. The first method generates a static binary, and the second a dynamic one.

PS. If you do “ar -x libm5.a” and then “readelf –relocs m5op_addr.o” you will see there is no PLT info for symbol m5_mem, which gives you the linker error.

Hope this helps.