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From:   Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
To:     ast@kernel.org, daniel@iogearbox.net, yhs@fb.com,
        davem@davemloft.net, jakub.kicinski@netronome.com, hawk@kernel.org,
        john.fastabend@gmail.com
Cc:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org, clang-built-linux@googlegroups.com,
        ilias.apalodimas@linaro.org, sergei.shtylyov@cogentembedded.com,
        Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Subject: [PATCH v4 bpf-next 15/15] samples/bpf: add preparation steps and sysroot info to readme
Date:   Wed,  9 Oct 2019 23:41:34 +0300
Message-Id: <20191009204134.26960-16-ivan.khoronzhuk@linaro.org>
In-Reply-To: <20191009204134.26960-1-ivan.khoronzhuk@linaro.org>
References: <20191009204134.26960-1-ivan.khoronzhuk@linaro.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add couple preparation steps: clean and configuration. Also add newly
added sysroot support info to cross-compile section.
---
 samples/bpf/README.rst | 41 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
index 5f27e4faca50..cc1f00a1ee06 100644
--- a/samples/bpf/README.rst
+++ b/samples/bpf/README.rst
@@ -14,6 +14,20 @@ Compiling requires having installed:
 Note that LLVM's tool 'llc' must support target 'bpf', list version
 and supported targets with command: ``llc --version``
 
+Clean and configuration
+-----------------------
+
+It can be needed to clean tools, samples or kernel before trying new arch or
+after some changes (on demand)::
+
+ make -C tools clean
+ make -C samples/bpf clean
+ make clean
+
+Configure kernel, defconfig for instance::
+
+ make defconfig
+
 Kernel headers
 --------------
 
@@ -68,9 +82,26 @@ It is also possible to point make to the newly compiled 'llc' or
 Cross compiling samples
 -----------------------
 In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH
-environment variables before calling make. This will direct make to build
-samples for the cross target.
+environment variables before calling make. But do this before clean,
+cofiguration and header install steps described above. This will direct make to
+build samples for the cross target::
+
+ export ARCH=arm64
+ export CROSS_COMPILE="aarch64-linux-gnu-"
+
+Headers can be also installed on RFS of target board if need to keep them in
+sync (not necessarily and it creates a local "usr/include" directory also)::
+
+ make INSTALL_HDR_PATH=~/some_sysroot/usr headers_install
+
+Pointing LLC and CLANG is not necessarily if it's installed on HOST and have
+in its targets appropriate arm64 arch (usually it has several arches).
+Build samples::
+
+ make samples/bpf/
+
+Or build samples with SYSROOT if some header or library is absent in toolchain,
+say libelf, providing address to file system containing headers and libs,
+can be RFS of target board::
 
-export ARCH=arm64
-export CROSS_COMPILE="aarch64-linux-gnu-"
-make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
+ make samples/bpf/ SYSROOT=~/some_sysroot
-- 
2.17.1