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authorTiezhu Yang <yangtiezhu@loongson.cn>2021-01-22 09:39:44 +0800
committerDaniel Borkmann <daniel@iogearbox.net>2021-01-23 00:09:03 +0100
commit628add78b07ad05ad005f1909dfc3c91e195ac23 (patch)
tree3dfcf7b4ea410419a0ca483bc10a544175d96634 /samples
parent443edcefb8213155c0da22c4a999f4a49858fa39 (diff)
bpf, docs: Update build procedure for manually compiling LLVM and Clang
The current LLVM and Clang build procedure in samples/bpf/README.rst is out of date.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. At last, we recommend that developers who want the fastest incremental builds use the Ninja build system [1], you can find it in your system's package manager, usually the package is ninja or ninja-build [3], so add ninja to build dependencies suggested by Nathan. [1] https://clang.llvm.org/get_started.html [2] https://www.llvm.org/docs/CMake.html [3] https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Acked-by: Yonghong Song <yhs@fb.com> Cc: Fangrui Song <maskray@google.com> Link: https://lore.kernel.org/bpf/1611279584-26047-1-git-send-email-yangtiezhu@loongson.cn
Diffstat (limited to 'samples')
-rw-r--r--samples/bpf/Makefile2
-rw-r--r--samples/bpf/README.rst22
2 files changed, 15 insertions, 9 deletions
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 26fc96ca619e..d06144613ca2 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 ?= opt
diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
index dd34b2d26f1c..60c6494adb1b 100644
--- a/samples/bpf/README.rst
+++ b/samples/bpf/README.rst
@@ -62,20 +62,26 @@ To generate a smaller llc binary one can use::
-DLLVM_TARGETS_TO_BUILD="BPF"
+We recommend that developers who want the fastest incremental builds
+use the Ninja build system, you can find it in your system's package
+manager, usually the package is ninja or ninja-build.
+
Quick sniplet for manually compiling LLVM and clang
-(build dependencies are cmake and gcc-c++)::
+(build dependencies are ninja, cmake and gcc-c++)::
- $ 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
-----------------------

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