# GEM5 TODO get working with a Buildroot recent Linux kernel. GEM5 is used mostly by chip makers, and they they keep everything that really works closed... This documents my failed attempts. Related threads: - - Vs QEMU: - advantage: simulates a generic more realistic CPU cycle by cycle, e.g. memory access, caches and page table manipulations. This allows us to: - do much more realistic performance benchmarking with it - make functional cache observations, e.g. to use Linux kernel APIs that flush memory like DMA, and are used widely in drivers - disadvantage: slow ## Working baseline Working x86 with the pre-built magic image with an ancient 2.6.22.9 kernel starting point: sudo mkdir -p /dist/m5/system sudo chmod 777 /dist/m5/system cd /dist/m5/system # Backed up at: # https://github.com/cirosantilli/media/releases/tag/gem5 wget http://www.gem5.org/dist/current/x86/x86-system.tar.bz2 tar xvf x86-system.tar.bz2 cd x86-system dd if=/dev/zero of=disks/linux-bigswap2.img bs=1024 count=65536 mkswap disks/linux-bigswap2.img cd .. sudo apt-get install libgoogle-perftools-dev mercurial protobuf-compiler git clone https://gem5.googlesource.com/public/gem5 cd gem5 git checkout e519aa4ac2942915355f0ef12e88286322336419 scons -j$(nproc) build_opts/X86/gem5.opt # That old blob has wrong filenames. ./build/X86/gem5.opt \ -d /tmp/output \ --disk-image=/dist/m5/system/disks/linux-x86.img \ --kernel=/dist/m5/system/binaries/x86_64-vmlinux-2.6.22.9 \ configs/example/fs.py On another shell: telnet localhost 3456 ## Unmodified Buildroot images bzImage fails, so we always try with vmlinux obtained from inside build/. rootfs.ext2 and vmlinux from 670366caaded57d318b6dbef34e863e3b30f7f29ails as: Fails as: Global frequency set at 1000000000000 ticks per second warn: DRAM device capacity (8192 Mbytes) does not match the address range assigned (512 Mbytes) info: kernel located at: /data/git/linux-kernel-module-cheat/buildroot/output.x86_64~/build/linux-custom/vmlinux Listening for com_1 connection on port 3456 0: rtc: Real-time clock set to Sun Jan 1 00:00:00 2012 0: system.remote_gdb.listener: listening for remote gdb #0 on port 7000 warn: Reading current count from inactive timer. **** REAL SIMULATION **** info: Entering event queue @ 0. Starting simulation... warn: instruction 'fninit' unimplemented warn: Don't know what interrupt to clear for console. 12516923000: system.pc.com_1.terminal: attach terminal 0 warn: i8042 "Write output port" command not implemented. warn: i8042 "Write keyboard output buffer" command not implemented. warn: Write to unknown i8042 (keyboard controller) command port. hack: Assuming logical destinations are 1 << id. panic: Resetting mouse wrap mode unimplemented. Memory Usage: 1003456 KBytes Program aborted at tick 632745027500 --- BEGIN LIBC BACKTRACE --- ./build/X86/gem5.opt(_Z15print_backtracev+0x15)[0x12b8165] ./build/X86/gem5.opt(_Z12abortHandleri+0x39)[0x12c32f9] /lib/x86_64-linux-gnu/libpthread.so.0(+0x11390)[0x7fe047a71390] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x38)[0x7fe046601428] /lib/x86_64-linux-gnu/libc.so.6(abort+0x16a)[0x7fe04660302a] ./build/X86/gem5.opt(_ZN6X86ISA8PS2Mouse11processDataEh+0xf5)[0x1391095] ./build/X86/gem5.opt(_ZN6X86ISA5I80425writeEP6Packet+0x51c)[0x13927ec] ./build/X86/gem5.opt(_ZN7PioPort10recvAtomicEP6Packet+0x66)[0x139f7b6] ./build/X86/gem5.opt(_ZN15NoncoherentXBar10recvAtomicEP6Packets+0x200)[0x1434af0] ./build/X86/gem5.opt(_ZN6Bridge15BridgeSlavePort10recvAtomicEP6Packet+0x5d)[0x140ee9d] ./build/X86/gem5.opt(_ZN12CoherentXBar10recvAtomicEP6Packets+0x3e7)[0x1415b77] ./build/X86/gem5.opt(_ZN15AtomicSimpleCPU8writeMemEPhjm5FlagsIjEPm+0x327)[0xa790a7] ./build/X86/gem5.opt(_ZN17SimpleExecContext8writeMemEPhjm5FlagsIjEPm+0x19)[0xa856b9] ./build/X86/gem5.opt(_ZNK10X86ISAInst2St7executeEP11ExecContextPN5Trace10InstRecordE+0x235)[0xfb9e65] ./build/X86/gem5.opt(_ZN15AtomicSimpleCPU4tickEv+0x23c)[0xa784fc] ./build/X86/gem5.opt(_ZN10EventQueue10serviceOneEv+0xc5)[0x12be0d5] ./build/X86/gem5.opt(_Z9doSimLoopP10EventQueue+0x38)[0x12cd558] ./build/X86/gem5.opt(_Z8simulatem+0x2eb)[0x12cdbdb] ./build/X86/gem5.opt(_ZZN8pybind1112cpp_function10initializeIRPFP22GlobalSimLoopExitEventmES3_ImEINS_4nameENS_5scopeENS_7siblingENS_5arg_vEEEEvOT_PFT0_DpT1_EDpRKT2_ENUlRNS_6detail13function_callEE1_4_FUNESO_+0x41)[0x13fca11] ./build/X86/gem5.opt(_ZN8pybind1112cpp_function10dispatcherEP7_objectS2_S2_+0x8d8)[0xfc7398] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x7852)[0x7fe047d3b552] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fe047e6501c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x6ffd)[0x7fe047d3acfd] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x7124)[0x7fe047d3ae24] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x7124)[0x7fe047d3ae24] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fe047e6501c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCode+0x19)[0x7fe047d33b89] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x613b)[0x7fe047d39e3b] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fe047e6501c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x6ffd)[0x7fe047d3acfd] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fe047e6501c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCode+0x19)[0x7fe047d33b89] --- END LIBC BACKTRACE --- Aborted (core dumped) Boot goes quite far, on telnet: ALSA device list: No soundcards found. So just looks like we have to disable some Linux configs which GEM5 does not support... so fragile. ## Copy upstream 2.6 configs on 4.9 kernel The magic image provides its kernel configurations, so let's try that. The configs are present at: wget http://www.gem5.org/dist/current/x86/config-x86.tar.bz2 backed up at: Copy `linux-2.6.22.9` into the kernel tree as `.config`, `git checkout v4.9.6`, `make olddefconfig`, `make`, then use the Buildroot filesystem as above, failure: panic: Invalid IDE control register offset: 0 Memory Usage: 931272 KBytes Program aborted at tick 382834812000 --- BEGIN LIBC BACKTRACE --- ./build/X86/gem5.opt(_Z15print_backtracev+0x15)[0x12b8165] ./build/X86/gem5.opt(_Z12abortHandleri+0x39)[0x12c32f9] /lib/x86_64-linux-gnu/libpthread.so.0(+0x11390)[0x7fc2081c6390] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x38)[0x7fc206d56428] /lib/x86_64-linux-gnu/libc.so.6(abort+0x16a)[0x7fc206d5802a] ./build/X86/gem5.opt(_ZN7IdeDisk11readControlEmiPh+0xd9)[0xa96989] ./build/X86/gem5.opt(_ZN13IdeController14dispatchAccessEP6Packetb+0x53e)[0xa947ae] ./build/X86/gem5.opt(_ZN13IdeController4readEP6Packet+0xe)[0xa94a5e] ./build/X86/gem5.opt(_ZN7PioPort10recvAtomicEP6Packet+0x3f)[0x139f78f] ./build/X86/gem5.opt(_ZN15NoncoherentXBar10recvAtomicEP6Packets+0x200)[0x1434af0] ./build/X86/gem5.opt(_ZN6Bridge15BridgeSlavePort10recvAtomicEP6Packet+0x5d)[0x140ee9d] ./build/X86/gem5.opt(_ZN12CoherentXBar10recvAtomicEP6Packets+0x3e7)[0x1415b77] ./build/X86/gem5.opt(_ZN15AtomicSimpleCPU7readMemEmPhj5FlagsIjE+0x3ef)[0xa780ef] ./build/X86/gem5.opt(_ZN17SimpleExecContext7readMemEmPhj5FlagsIjE+0x11)[0xa85671] ./build/X86/gem5.opt(_ZNK10X86ISAInst2Ld7executeEP11ExecContextPN5Trace10InstRecordE+0x130)[0xfb6c00] ./build/X86/gem5.opt(_ZN15AtomicSimpleCPU4tickEv+0x23c)[0xa784fc] ./build/X86/gem5.opt(_ZN10EventQueue10serviceOneEv+0xc5)[0x12be0d5] ./build/X86/gem5.opt(_Z9doSimLoopP10EventQueue+0x38)[0x12cd558] ./build/X86/gem5.opt(_Z8simulatem+0x2eb)[0x12cdbdb] ./build/X86/gem5.opt(_ZZN8pybind1112cpp_function10initializeIRPFP22GlobalSimLoopExitEventmES3_ImEINS_4nameENS_5scopeENS_7siblingENS_5arg_vEEEEvOT_PFT0_DpT1_EDpRKT2_ENUlRNS_6detail13function_callEE1_4_FUNESO_+0x41)[0x13fca11] ./build/X86/gem5.opt(_ZN8pybind1112cpp_function10dispatcherEP7_objectS2_S2_+0x8d8)[0xfc7398] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x7852)[0x7fc208490552] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fc2085ba01c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x6ffd)[0x7fc20848fcfd] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x7124)[0x7fc20848fe24] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x7124)[0x7fc20848fe24] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fc2085ba01c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCode+0x19)[0x7fc208488b89] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x613b)[0x7fc20848ee3b] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fc2085ba01c] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x6ffd)[0x7fc20848fcfd] /usr/lib/x86_64-linux-gnu/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x85c)[0x7fc2085ba01c] --- END LIBC BACKTRACE --- Aborted (core dumped) ## Use upstream 2.6 configs and 2.6 kernel If we checkout to the ancient kernel `v2.6.22.9`, it fails to compile with modern GNU make 4.1: lol