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Thu, 28 Nov 2019 09:30:54 -0800 (PST) Subject: Re: [PATCH bpf v3] bpftool: Allow to link libbpf dynamically To: =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , Daniel Borkmann , Alexei Starovoitov Cc: Jiri Olsa , lkml , netdev@vger.kernel.org, bpf@vger.kernel.org, Ingo Molnar , Namhyung Kim , Alexander Shishkin , Peter Zijlstra , Michael Petlan , Jesper Dangaard Brouer , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , Arnaldo Carvalho de Melo References: <20191128160712.1048793-1-toke@redhat.com> From: Quentin Monnet Openpgp: preference=signencrypt Autocrypt: addr=quentin.monnet@netronome.com; prefer-encrypt=mutual; keydata= mQINBFnqRlsBEADfkCdH/bkkfjbglpUeGssNbYr/TD4aopXiDZ0dL2EwafFImsGOWmCIIva2 MofTQHQ0tFbwY3Ir74exzU9X0aUqrtHirQHLkKeMwExgDxJYysYsZGfM5WfW7j8X4aVwYtfs AVRXxAOy6/bw1Mccq8ZMTYKhdCgS3BfC7qK+VYC4bhM2AOWxSQWlH5WKQaRbqGOVLyq8Jlxk 2FGLThUsPRlXKz4nl+GabKCX6x3rioSuNoHoWdoPDKsRgYGbP9LKRRQy3ZeJha4x+apy8rAM jcGHppIrciyfH38+LdV1FVi6sCx8sRKX++ypQc3fa6O7d7mKLr6uy16xS9U7zauLu1FYLy2U N/F1c4F+bOlPMndxEzNc/XqMOM9JZu1XLluqbi2C6JWGy0IYfoyirddKpwzEtKIwiDBI08JJ Cv4jtTWKeX8pjTmstay0yWbe0sTINPh+iDw+ybMwgXhr4A/jZ1wcKmPCFOpb7U3JYC+ysD6m 6+O/eOs21wVag/LnnMuOKHZa2oNsi6Zl0Cs6C7Vve87jtj+3xgeZ8NLvYyWrQhIHRu1tUeuf T8qdexDphTguMGJbA8iOrncHXjpxWhMWykIyN4TYrNwnyhqP9UgqRPLwJt5qB1FVfjfAlaPV sfsxuOEwvuIt19B/3pAP0nbevNymR3QpMPRl4m3zXCy+KPaSSQARAQABtC1RdWVudGluIE1v bm5ldCA8cXVlbnRpbi5tb25uZXRAbmV0cm9ub21lLmNvbT6JAj0EEwEIACcFAlnqRlsCGyMF CQlmAYAFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQNvcEyYwwfB7tChAAqFWG30+DG3Sx B7lfPaqs47oW98s5tTMprA+0QMqUX2lzHX7xWb5v8qCpuujdiII6RU0ZhwNKh/SMJ7rbYlxK qCOw54kMI+IU7UtWCej+Ps3LKyG54L5HkBpbdM8BLJJXZvnMqfNWx9tMISHkd/LwogvCMZrP TAFkPf286tZCIz0EtGY/v6YANpEXXrCzboWEiIccXRmbgBF4VK/frSveuS7OHKCu66VVbK7h kyTgBsbfyQi7R0Z6w6sgy+boe7E71DmCnBn57py5OocViHEXRgO/SR7uUK3lZZ5zy3+rWpX5 nCCo0C1qZFxp65TWU6s8Xt0Jq+Fs7Kg/drI7b5/Z+TqJiZVrTfwTflqPRmiuJ8lPd+dvuflY JH0ftAWmN3sT7cTYH54+HBIo1vm5UDvKWatTNBmkwPh6d3cZGALZvwL6lo0KQHXZhCVdljdQ rwWdE25aCQkhKyaCFFuxr3moFR0KKLQxNykrVTJIRuBS8sCyxvWcZYB8tA5gQ/DqNKBdDrT8 F9z2QvNE5LGhWDGddEU4nynm2bZXHYVs2uZfbdZpSY31cwVS/Arz13Dq+McMdeqC9J2wVcyL DJPLwAg18Dr5bwA8SXgILp0QcYWtdTVPl+0s82h+ckfYPOmkOLMgRmkbtqPhAD95vRD7wMnm ilTVmCi6+ND98YblbzL64YG5Ag0EWepGWwEQAM45/7CeXSDAnk5UMXPVqIxF8yCRzVe+UE0R QQsdNwBIVdpXvLxkVwmeu1I4aVvNt3Hp2eiZJjVndIzKtVEoyi5nMvgwMVs8ZKCgWuwYwBzU Vs9eKABnT0WilzH3gA5t9LuumekaZS7z8IfeBlZkGXEiaugnSAESkytBvHRRlQ8b1qnXha3g XtxyEqobKO2+dI0hq0CyUnGXT40Pe2woVPm50qD4HYZKzF5ltkl/PgRNHo4gfGq9D7dW2OlL 5I9qp+zNYj1G1e/ytPWuFzYJVT30MvaKwaNdurBiLc9VlWXbp53R95elThbrhEfUqWbAZH7b ALWfAotD07AN1msGFCES7Zes2AfAHESI8UhVPfJcwLPlz/Rz7/K6zj5U6WvH6aj4OddQFvN/ icvzlXna5HljDZ+kRkVtn+9zrTMEmgay8SDtWliyR8i7fvnHTLny5tRnE5lMNPRxO7wBwIWX TVCoBnnI62tnFdTDnZ6C3rOxVF6FxUJUAcn+cImb7Vs7M5uv8GufnXNUlsvsNS6kFTO8eOjh 4fe5IYLzvX9uHeYkkjCNVeUH5NUsk4NGOhAeCS6gkLRA/3u507UqCPFvVXJYLSjifnr92irt 0hXm89Ms5fyYeXppnO3l+UMKLkFUTu6T1BrDbZSiHXQoqrvU9b1mWF0CBM6aAYFGeDdIVe4x ABEBAAGJAiUEGAEIAA8FAlnqRlsCGwwFCQlmAYAACgkQNvcEyYwwfB4QwhAAqBTOgI9k8MoM gVA9SZj92vYet9gWOVa2Inj/HEjz37tztnywYVKRCRfCTG5VNRv1LOiCP1kIl/+crVHm8g78 iYc5GgBKj9O9RvDm43NTDrH2uzz3n66SRJhXOHgcvaNE5ViOMABU+/pzlg34L/m4LA8SfwUG ducP39DPbF4J0OqpDmmAWNYyHh/aWf/hRBFkyM2VuizN9cOS641jrhTO/HlfTlYjIb4Ccu9Y S24xLj3kkhbFVnOUZh8celJ31T9GwCK69DXNwlDZdri4Bh0N8DtRfrhkHj9JRBAun5mdwF4m yLTMSs4Jwa7MaIwwb1h3d75Ws7oAmv7y0+RgZXbAk2XN32VM7emkKoPgOx6Q5o8giPRX8mpc PiYojrO4B4vaeKAmsmVer/Sb5y9EoD7+D7WygJu2bDrqOm7U7vOQybzZPBLqXYxl/F5vOobC 5rQZgudR5bI8uQM0DpYb+Pwk3bMEUZQ4t497aq2vyMLRi483eqT0eG1QBE4O8dFNYdK5XUIz oHhplrRgXwPBSOkMMlLKu+FJsmYVFeLAJ81sfmFuTTliRb3Fl2Q27cEr7kNKlsz/t6vLSEN2 j8x+tWD8x53SEOSn94g2AyJA9Txh2xBhWGuZ9CpBuXjtPrnRSd8xdrw36AL53goTt/NiLHUd RHhSHGnKaQ6MfrTge5Q0h5A= Message-ID: <04154e60-a5d6-5ce5-2fbe-89437108fdc6@netronome.com> Date: Thu, 28 Nov 2019 17:30:53 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20191128160712.1048793-1-toke@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 2019-11-28 17:07 UTC+0100 ~ Toke Høiland-Jørgensen > From: Jiri Olsa > > Currently we support only static linking with kernel's libbpf > (tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable > that triggers libbpf detection and bpf dynamic linking: > > $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1 > > If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with: > > $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1 > Auto-detecting system features: > ... libbfd: [ on ] > ... disassembler-four-args: [ on ] > ... zlib: [ on ] > ... libbpf: [ OFF ] > > Makefile:102: *** Error: No libbpf devel library found, please install libbpf-devel or libbpf-dev. > > Adding LIBBPF_DIR compile variable to allow linking with > libbpf installed into specific directory: > > $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers > $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/ > > It might be needed to clean build tree first because features > framework does not detect the change properly: > > $ make -C tools/build/feature clean > $ make -C tools/bpf/bpftool/ clean > > Since bpftool uses bits of libbpf that are not exported as public API in > the .so version, we also pass in libbpf.a to the linker, which allows it to > pick up the private functions from the static library without having to > expose them as ABI. > > Signed-off-by: Jiri Olsa > Signed-off-by: Toke Høiland-Jørgensen > --- > v3: > - Keep $(LIBBPF) in $LIBS, and just add -lbpf on top > - Fix typo in error message > v2: > - Pass .a file to linker when dynamically linking, so bpftool can use > private functions from libbpf without exposing them as API. Thanks for the changes! Reviewed-by: Quentin Monnet