Re: [PATCH bpf-next v3] samples/bpf: Update build procedure for manually compiling LLVM and Clang
From: Nathan Chancellor <hidden>
Date: 2021-01-21 05:39:06
Also in:
bpf, lkml
On Thu, Jan 21, 2021 at 01:27:35PM +0800, Tiezhu Yang wrote:
The current LLVM and Clang build procedure in samples/bpf/README.rst is out of date. See below that the links are not accessible any more. $ git clone http://llvm.org/git/llvm.git Cloning into 'llvm'... fatal: unable to access 'http://llvm.org/git/llvm.git/': Maximum (20) redirects followed $ git clone --depth 1 http://llvm.org/git/clang.git Cloning into 'clang'... fatal: unable to access 'http://llvm.org/git/clang.git/': Maximum (20) redirects followed The LLVM community has adopted new ways to build the compiler. There are different ways to build LLVM and Clang, the Clang Getting Started page [1] has one way. As Yonghong said, it is better to copy the build procedure in Documentation/bpf/bpf_devel_QA.rst to keep consistent. I verified the procedure and it is proved to be feasible, so we should update README.rst to reflect the reality. At the same time, update the related comment in Makefile. Additionally, as Fangrui said, the dir llvm-project/llvm/build/install is not used, BUILD_SHARED_LIBS=OFF is the default option [2], so also change Documentation/bpf/bpf_devel_QA.rst together. [1] https://clang.llvm.org/get_started.html [2] https://www.llvm.org/docs/CMake.html Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Acked-by: Yonghong Song <redacted>
Reviewed-by: Nathan Chancellor <redacted> Small comment below.
quoted hunk ↗ jump to hunk
--- v2: Update the commit message suggested by Yonghong, thank you very much. v3: Remove the default option BUILD_SHARED_LIBS=OFF and just mkdir llvm-project/llvm/build suggested by Fangrui. Documentation/bpf/bpf_devel_QA.rst | 3 +-- samples/bpf/Makefile | 2 +- samples/bpf/README.rst | 16 +++++++++------- 3 files changed, 11 insertions(+), 10 deletions(-)diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst index 5b613d2..18788bb 100644 --- a/Documentation/bpf/bpf_devel_QA.rst +++ b/Documentation/bpf/bpf_devel_QA.rst@@ -506,11 +506,10 @@ that set up, proceed with building the latest LLVM and clang version from the git repositories:: $ git clone https://github.com/llvm/llvm-project.git - $ mkdir -p llvm-project/llvm/build/install + $ mkdir -p llvm-project/llvm/build $ cd llvm-project/llvm/build $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ -DLLVM_ENABLE_PROJECTS="clang" \ - -DBUILD_SHARED_LIBS=OFF \ -DCMAKE_BUILD_TYPE=Release \ -DLLVM_BUILD_RUNTIME=OFF $ ninjadiff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index 26fc96c..d061446 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile@@ -208,7 +208,7 @@ TPROGLDLIBS_xdpsock += -pthread -lcap TPROGLDLIBS_xsk_fwd += -pthread # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline: -# make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang +# make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang LLC ?= llc CLANG ?= clang OPT ?= optdiff --git a/samples/bpf/README.rst b/samples/bpf/README.rst index dd34b2d..23006cb 100644 --- a/samples/bpf/README.rst +++ b/samples/bpf/README.rst@@ -65,17 +65,19 @@ To generate a smaller llc binary one can use:: Quick sniplet for manually compiling LLVM and clang (build dependencies are cmake and gcc-c++)::
Technically, ninja is now a build dependency as well, it might be worth mentioning that here (usually the package is ninja or ninja-build). Regardless of whether that is addressed or not (because it is small), feel free to carry forward my tag in any future revisions unless they drastically change.
- $ git clone http://llvm.org/git/llvm.git - $ cd llvm/tools - $ git clone --depth 1 http://llvm.org/git/clang.git - $ cd ..; mkdir build; cd build - $ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86" - $ make -j $(getconf _NPROCESSORS_ONLN) + $ git clone https://github.com/llvm/llvm-project.git + $ mkdir -p llvm-project/llvm/build + $ cd llvm-project/llvm/build + $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ + -DLLVM_ENABLE_PROJECTS="clang" \ + -DCMAKE_BUILD_TYPE=Release \ + -DLLVM_BUILD_RUNTIME=OFF + $ ninja It is also possible to point make to the newly compiled 'llc' or 'clang' command via redefining LLC or CLANG on the make command line:: - make M=samples/bpf LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang + make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang Cross compiling samples ----------------------- -- 2.1.0