instruction: 0.521 runtime: 0.250 syscall: 0.229 qemu-user -g xxx -E LD_PROFILE=xxx segfault Here is two simple steps to reproduce the bug: $ qemu-x86_64 -E LD_PROFILE=libc.so.6 -E LD_PROFILE_OUTPUT=. -g 12345 -L / /bin/ls (libc.so and /bin/ls might change on your system, in this case we just need a binary with a profilable needed library) In a other window launch: $ gdb (gdb) target remote :12345 (gdb) c At this point qemu will segfault. It seems this problem is appends when sigprof passed to gdb. One way I have found to bypass this: patch gdbstub.c gdb_handlesig and ignore sig if sig == TARGET_SIGPROF (which means now I can't catch sigprof on gdb anymore)