Em Fri, Jan 22, 2016 at 09:27:20AM +0000, Wang Nan escreveu: > There's a bug in LLVM that it can generate unneeded relocation > information. See [1] and [2]. Libbpf should check the target section > of a relocation symbol. > > This patch adds a testcase which reference a global variable (BPF > doesn't support global variable). Before fixing libbpf, the new test > case can be loaded into kernel, the global variable acts like the first > map. It is incorrect. > > Result: > # ~/perf test BPF > 37: Test BPF filter : > 37.1: Test basic BPF filtering : Ok > 37.2: Test BPF prologue generation : Ok > 37.3: Test BPF relocation checker : FAILED!
So I just got a new notebook, a t450s (heya, will be able to test Intel PT, etc) and installed fedora 23 on it, cool, there is clang/llvm in it! And furthermore: [root@jouet ~]# clang --version clang version 3.7.0 (tags/RELEASE_370/final) Target: x86_64-redhat-linux-gnu Thread model: posix [root@jouet ~]# Seems to be the one we need! But... [root@jouet ~]# perf test bpf 37: Test BPF filter : 37.1: Test basic BPF filtering : Skip 37.2: Test BPF prologue generation : Skip [root@jouet ~]# oh well... >From 'perf test -v bpf': ' | $CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS -DLINUX_VERSION_CODE=$LINUX_VERSION_CODE $CLANG_OPTIONS $KERNEL_INC_OPTIONS -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf -O2 -o - error: unable to create target: 'No available targets are compatible with this triple, see -version for the available targets.' ---- And after googling 'list clang supported target' [root@jouet ~]# llc --version LLVM (http://llvm.org/): LLVM version 3.7.0 Optimized build. Built Dec 4 2015 (15:49:18). Default target: x86_64-redhat-linux-gnu Host CPU: broadwell Registered Targets: aarch64 - AArch64 (little endian) aarch64_be - AArch64 (big endian) amdgcn - AMD GCN GPUs arm - ARM arm64 - ARM64 (little endian) armeb - ARM (big endian) cpp - C++ backend nvptx - NVIDIA PTX 32-bit nvptx64 - NVIDIA PTX 64-bit ppc32 - PowerPC 32 ppc64 - PowerPC 64 ppc64le - PowerPC 64 LE r600 - AMD GPUs HD2XXX-HD6XXX systemz - SystemZ thumb - Thumb thumbeb - Thumb (big endian) x86 - 32-bit X86: Pentium-Pro and above x86-64 - 64-bit X86: EM64T and AMD64 [root@jouet ~]# Oops, no bpf, so the good thing is that if we uninstall clang and try that test again: [root@jouet ~]# dnf remove clang llvm Dependencies resolved. ============================================================== Package Arch Version Repository Size ============================================================== Removing: clang x86_64 3.7.0-3.fc23 @updates 45 M clang-libs x86_64 3.7.0-3.fc23 @updates 14 M gcc-c++ x86_64 5.3.1-2.fc23 @updates 24 M libstdc++-devel x86_64 5.3.1-2.fc23 @updates 9.5 M llvm x86_64 3.7.0-3.fc23 @updates 4.9 M Transaction Summary ============================================================== Remove 5 Packages When I try it again I get nice instructions on how to install it! [root@jouet ~]# perf test bpf 37: Test BPF filter : 37.1: Test basic BPF filtering : Skip 37.2: Test BPF prologue generation : Skip [root@jouet ~]# perf test -v bpf 37: Test BPF filter : 37.1: Test basic BPF filtering : --- start --- test child forked, pid 30062 ERROR: unable to find clang. Hint: Try to install latest clang/llvm to support BPF. Check your $PATH and 'clang-path' option in [llvm] section of ~/.perfconfig. LLVM 3.7 or newer is required. Which can be found from http://llvm.org You may want to try git trunk: git clone http://llvm.org/git/llvm.git and git clone http://llvm.org/git/clang.git Or fetch the latest clang/llvm 3.7 from pre-built llvm packages for debian/ubuntu: http://llvm.org/apt If you are using old version of clang, change 'clang-bpf-cmd-template' option in [llvm] section of ~/.perfconfig to: "$CLANG_EXEC $CLANG_OPTIONS $KERNEL_INC_OPTIONS \ -working-directory $WORKING_DIR -c $CLANG_SOURCE \ -emit-llvm -o - | /path/to/llc -march=bpf -filetype=obj -o -" (Replace /path/to/llc with path to your llc) Failed to compile test case: 'Basic BPF llvm compiling test' Unable to get BPF object, fix 'perf test LLVM' first test child finished with -2 ---- end ---- Test BPF filter subtest 0: Skip 37.2: Test BPF prologue generation : --- force skipped --- Test BPF filter subtest 1: Skip [root@jouet ~]# Lets try it... - Arnaldo
