x86: 0.448
device: 0.207
mistranslation: 0.196
performance: 0.187
peripherals: 0.174
network: 0.170
i386: 0.168
graphic: 0.155
architecture: 0.148
semantic: 0.143
risc-v: 0.135
user-level: 0.133
vnc: 0.128
ppc: 0.123
register: 0.118
virtual: 0.110
PID: 0.108
hypervisor: 0.106
permissions: 0.103
socket: 0.102
VMM: 0.101
arm: 0.096
boot: 0.094
kernel: 0.094
KVM: 0.089
debug: 0.082
TCG: 0.067
files: 0.059
assembly: 0.050

qemu-x86_64 segment prefixes error

qemu-x86_64 version 4.1.0 (qemu-x86_64 version 4.0.0 also have the issue)

In 64-bit mode (x86_64) the DS, ES, SS or CS segment prefixes should be ignored; qemu-x86_64 does not ignore them.

example: an x86_64 instructions preceded by FS DS (0x64 0x26) segment prefixes have the linear address of its memory reference flat-mapped (as if DS was in action) whereas it should be FS-mapped (offset by FS_base, because the DS, ES, SS or CS are just ignored).


I attach a small C++ program that shows this discrepancy.

$ ./sample
I'm not in QEMU

$ qemu-x86_64 ./sample
I'm in QEMU



The QEMU project is currently considering to move its bug tracking to
another system. For this we need to know which bugs are still valid
and which could be closed already. Thus we are setting older bugs to
"Incomplete" now.

If you still think this bug report here is valid, then please switch
the state back to "New" within the next 60 days, otherwise this report
will be marked as "Expired". Or please mark it as "Fix Released" if
the problem has been solved with a newer version of QEMU already.

Thank you and sorry for the inconvenience.


Repro case in comment #1 still demonstrates bug.



This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/267