[net-next,3/4] samples/bpf: add a README file to get users started
diff mbox

Message ID 20160426110927.20716.89620.stgit@firesoul
State New
Headers show

Commit Message

Jesper Dangaard Brouer April 26, 2016, 11:09 a.m. UTC
Getting started with using examples in samples/bpf/ is not
straightforward.  There are several dependencies, and specific
versions of these dependencies.

Just compiling the example tool is also slightly obscure, e.g. one
need to call make like:

 make samples/bpf/

Do notice the "/" slash after the directory name.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 samples/bpf/README.rst |   67 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 samples/bpf/README.rst


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Comments

Daniel Borkmann April 26, 2016, 11:44 a.m. UTC | #1
On 04/26/2016 01:09 PM, Jesper Dangaard Brouer wrote:
> Getting started with using examples in samples/bpf/ is not
> straightforward.  There are several dependencies, and specific
> versions of these dependencies.
>
> Just compiling the example tool is also slightly obscure, e.g. one
> need to call make like:
>
>   make samples/bpf/
>
> Do notice the "/" slash after the directory name.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---
>   samples/bpf/README.rst |   67 ++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 67 insertions(+)
>   create mode 100644 samples/bpf/README.rst
>
> diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
> new file mode 100644
> index 000000000000..3e1ac05d8e7c
> --- /dev/null
> +++ b/samples/bpf/README.rst
> @@ -0,0 +1,67 @@
> +eBPF sample programs
> +====================
> +
> +This kernel samples/bpf directory contains a mini eBPF library, test
> +stubs, verifier test-suite and examples for using eBPF.
> +
> +Build dependencies
> +==================
> +
> +Compiling requires having installed:
> + * clang
> + * llvm >= version 3.7.0
> +
> +Note that LLVM's tool 'llc' must support target 'bpf', list with command::
> +
> + $ llc --version
> + LLVM (http://llvm.org/):
> +  LLVM version 3.x.y
> +  [...]
> +  Host CPU: xxx
> +
> +  Registered Targets:
> +    [...]
> +    bpf        - BPF (host endian)
> +    bpfeb      - BPF (big endian)
> +    bpfel      - BPF (little endian)
> +    [...]
> +
> +Kernel headers
> +--------------
> +
> +There are usually dependencies to header files of the current kernel.
> +To avoid installing devel kernel headers system wide, as a normal
> +user, simply call::
> +
> + make headers_install
> +
> +This will creates a local "usr/include" directory in the git/build top
> +level directory, that the make system automatically pickup first.
> +
> +Compiling
> +=========
> +
> +For compiling goto kernel top level build directory and run make like::
> +
> + make samples/bpf/
> +
> +Do notice the "/" slash after the directory name.
> +
> +Manually compiling LLVM with 'bpf' support
> +------------------------------------------
> +
> +In some LLVM versions the BPF target were marked experimental.  To
> +compile LLVM manually and enable BPF target run (build dependencies
> +are cmake and gcc-c++)::
> +
> + $ git clone http://llvm.org/git/llvm.git
> + $ cd llvm
> + $ mkdir build; cd build
> + $ cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF
> + $ make

That's perhaps a bit misleading in the sense that when you clone the
tree from git, you'd nowadays invoke cmake normally with LLVM_TARGETS_TO_BUILD
instead of LLVM_EXPERIMENTAL_TARGETS_TO_BUILD for BPF, as BPF is not an
experimental target anymore. It's probably also recommended to clone
clang into tools/ dir as well under your llvm/ repo when you compile
from scratch anyways.

> +It is also possible to point make to the newly compile 'llc' command
> +via redefining LLC on the make command line::
> +
> + make samples/bpf/ LLC=~/git/llvm/build/bin/llc
> +
>

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Jesper Dangaard Brouer April 26, 2016, 11:56 a.m. UTC | #2
On Tue, 26 Apr 2016 13:44:06 +0200
Daniel Borkmann <daniel@iogearbox.net> wrote:

> On 04/26/2016 01:09 PM, Jesper Dangaard Brouer wrote:
> > Getting started with using examples in samples/bpf/ is not
> > straightforward.  There are several dependencies, and specific
> > versions of these dependencies.
> >
> > Just compiling the example tool is also slightly obscure, e.g. one
> > need to call make like:
> >
> >   make samples/bpf/
> >
> > Do notice the "/" slash after the directory name.
> >
> > Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> > ---
> >   samples/bpf/README.rst |   67 ++++++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 67 insertions(+)
> >   create mode 100644 samples/bpf/README.rst
> >
> > diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
> > new file mode 100644
> > index 000000000000..3e1ac05d8e7c
> > --- /dev/null
> > +++ b/samples/bpf/README.rst
> > @@ -0,0 +1,67 @@
> > +eBPF sample programs
> > +====================
> > +
> > +This kernel samples/bpf directory contains a mini eBPF library, test
> > +stubs, verifier test-suite and examples for using eBPF.
> > +
> > +Build dependencies
> > +==================
> > +
> > +Compiling requires having installed:
> > + * clang
> > + * llvm >= version 3.7.0
> > +
> > +Note that LLVM's tool 'llc' must support target 'bpf', list with command::
> > +
> > + $ llc --version
> > + LLVM (http://llvm.org/):
> > +  LLVM version 3.x.y
> > +  [...]
> > +  Host CPU: xxx
> > +
> > +  Registered Targets:
> > +    [...]
> > +    bpf        - BPF (host endian)
> > +    bpfeb      - BPF (big endian)
> > +    bpfel      - BPF (little endian)
> > +    [...]
> > +
> > +Kernel headers
> > +--------------
> > +
> > +There are usually dependencies to header files of the current kernel.
> > +To avoid installing devel kernel headers system wide, as a normal
> > +user, simply call::
> > +
> > + make headers_install
> > +
> > +This will creates a local "usr/include" directory in the git/build top
> > +level directory, that the make system automatically pickup first.
> > +
> > +Compiling
> > +=========
> > +
> > +For compiling goto kernel top level build directory and run make like::
> > +
> > + make samples/bpf/
> > +
> > +Do notice the "/" slash after the directory name.
> > +
> > +Manually compiling LLVM with 'bpf' support
> > +------------------------------------------
> > +
> > +In some LLVM versions the BPF target were marked experimental.  To
> > +compile LLVM manually and enable BPF target run (build dependencies
> > +are cmake and gcc-c++)::
> > +
> > + $ git clone http://llvm.org/git/llvm.git
> > + $ cd llvm
> > + $ mkdir build; cd build
> > + $ cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF
> > + $ make  
> 
> That's perhaps a bit misleading in the sense that when you clone the
> tree from git, you'd nowadays invoke cmake normally with LLVM_TARGETS_TO_BUILD
> instead of LLVM_EXPERIMENTAL_TARGETS_TO_BUILD for BPF, as BPF is not an
> experimental target anymore. It's probably also recommended to clone
> clang into tools/ dir as well under your llvm/ repo when you compile
> from scratch anyways.

Can you come up with a formulation/desc I can use instead then?
Daniel Borkmann April 26, 2016, 12:40 p.m. UTC | #3
On 04/26/2016 01:56 PM, Jesper Dangaard Brouer wrote:
> On Tue, 26 Apr 2016 13:44:06 +0200
> Daniel Borkmann <daniel@iogearbox.net> wrote:
>
>> On 04/26/2016 01:09 PM, Jesper Dangaard Brouer wrote:
>>> Getting started with using examples in samples/bpf/ is not
>>> straightforward.  There are several dependencies, and specific
>>> versions of these dependencies.
>>>
>>> Just compiling the example tool is also slightly obscure, e.g. one
>>> need to call make like:
>>>
>>>    make samples/bpf/
>>>
>>> Do notice the "/" slash after the directory name.
>>>
>>> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
>>> ---
>>>    samples/bpf/README.rst |   67 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>    1 file changed, 67 insertions(+)
>>>    create mode 100644 samples/bpf/README.rst
>>>
>>> diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
>>> new file mode 100644
>>> index 000000000000..3e1ac05d8e7c
>>> --- /dev/null
>>> +++ b/samples/bpf/README.rst
>>> @@ -0,0 +1,67 @@
>>> +eBPF sample programs
>>> +====================
>>> +
>>> +This kernel samples/bpf directory contains a mini eBPF library, test
>>> +stubs, verifier test-suite and examples for using eBPF.
>>> +
>>> +Build dependencies
>>> +==================
>>> +
>>> +Compiling requires having installed:
>>> + * clang
>>> + * llvm >= version 3.7.0
>>> +
>>> +Note that LLVM's tool 'llc' must support target 'bpf', list with command::
>>> +
>>> + $ llc --version
>>> + LLVM (http://llvm.org/):
>>> +  LLVM version 3.x.y
>>> +  [...]
>>> +  Host CPU: xxx
>>> +
>>> +  Registered Targets:
>>> +    [...]
>>> +    bpf        - BPF (host endian)
>>> +    bpfeb      - BPF (big endian)
>>> +    bpfel      - BPF (little endian)
>>> +    [...]
>>> +
>>> +Kernel headers
>>> +--------------
>>> +
>>> +There are usually dependencies to header files of the current kernel.
>>> +To avoid installing devel kernel headers system wide, as a normal
>>> +user, simply call::
>>> +
>>> + make headers_install
>>> +
>>> +This will creates a local "usr/include" directory in the git/build top
>>> +level directory, that the make system automatically pickup first.
>>> +
>>> +Compiling
>>> +=========
>>> +
>>> +For compiling goto kernel top level build directory and run make like::
>>> +
>>> + make samples/bpf/
>>> +
>>> +Do notice the "/" slash after the directory name.
>>> +
>>> +Manually compiling LLVM with 'bpf' support
>>> +------------------------------------------
>>> +
>>> +In some LLVM versions the BPF target were marked experimental.  To
>>> +compile LLVM manually and enable BPF target run (build dependencies
>>> +are cmake and gcc-c++)::
>>> +
>>> + $ git clone http://llvm.org/git/llvm.git
>>> + $ cd llvm
>>> + $ mkdir build; cd build
>>> + $ cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF
>>> + $ make
>>
>> That's perhaps a bit misleading in the sense that when you clone the
>> tree from git, you'd nowadays invoke cmake normally with LLVM_TARGETS_TO_BUILD
>> instead of LLVM_EXPERIMENTAL_TARGETS_TO_BUILD for BPF, as BPF is not an
>> experimental target anymore. It's probably also recommended to clone
>> clang into tools/ dir as well under your llvm/ repo when you compile
>> from scratch anyways.
>
> Can you come up with a formulation/desc I can use instead then?

You mean how to build with clang? There are various docs/snippets out
there, for example, see the 'Build LLVM and Clang development libs'
part of [1], that you can tweak for your README with.

   [1] https://gist.github.com/brendangregg/cfa482acb71aa577789c
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Alexei Starovoitov April 26, 2016, 2:34 p.m. UTC | #4
On Tue, Apr 26, 2016 at 02:40:54PM +0200, Daniel Borkmann wrote:
> On 04/26/2016 01:56 PM, Jesper Dangaard Brouer wrote:
> >>>+Compiling requires having installed:
> >>>+ * clang
> >>>+ * llvm >= version 3.7.0

please change it to 3.7.1, since 3.7.0 had several bugs.
They're rare, but better to avoid the issue.

> >>>+
> >>>+Note that LLVM's tool 'llc' must support target 'bpf', list with command::
> >>>+
> >>>+ $ llc --version
> >>>+ LLVM (http://llvm.org/):
> >>>+  LLVM version 3.x.y
> >>>+  [...]
> >>>+  Host CPU: xxx
> >>>+
> >>>+  Registered Targets:
> >>>+    [...]
> >>>+    bpf        - BPF (host endian)
> >>>+    bpfeb      - BPF (big endian)
> >>>+    bpfel      - BPF (little endian)

there always be 3 targets for bpf, since some folks need to cross-compile.

> >>>+Manually compiling LLVM with 'bpf' support
> >>>+------------------------------------------
> >>>+
> >>>+In some LLVM versions the BPF target were marked experimental.  To
> >>>+compile LLVM manually and enable BPF target run (build dependencies
> >>>+are cmake and gcc-c++)::
> >>>+
> >>>+ $ git clone http://llvm.org/git/llvm.git
> >>>+ $ cd llvm
> >>>+ $ mkdir build; cd build
> >>>+ $ cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF
> >>>+ $ make
> >>
> >>That's perhaps a bit misleading in the sense that when you clone the
> >>tree from git, you'd nowadays invoke cmake normally with LLVM_TARGETS_TO_BUILD
> >>instead of LLVM_EXPERIMENTAL_TARGETS_TO_BUILD for BPF, as BPF is not an
> >>experimental target anymore. It's probably also recommended to clone
> >>clang into tools/ dir as well under your llvm/ repo when you compile
> >>from scratch anyways.

yes. LLVM_EXPERIMENTAL_TARGETS_TO_BUILD is the thing of the past
when bpf was just merged into llvm < 3.7
By default llvm will build all non-experimental backends including bpf.
If you need to make llc binary smaller you can use:
-DLLVM_TARGETS_TO_BUILD="BPF;X86"

Also fedora and ubuntu ship with llvm that has bpf support.

> >Can you come up with a formulation/desc I can use instead then?
> 
> You mean how to build with clang? There are various docs/snippets out
> there, for example, see the 'Build LLVM and Clang development libs'
> part of [1], that you can tweak for your README with.
> 
>   [1] https://gist.github.com/brendangregg/cfa482acb71aa577789c

yep. +1 for the link.

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Patch
diff mbox

diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
new file mode 100644
index 000000000000..3e1ac05d8e7c
--- /dev/null
+++ b/samples/bpf/README.rst
@@ -0,0 +1,67 @@ 
+eBPF sample programs
+====================
+
+This kernel samples/bpf directory contains a mini eBPF library, test
+stubs, verifier test-suite and examples for using eBPF.
+
+Build dependencies
+==================
+
+Compiling requires having installed:
+ * clang
+ * llvm >= version 3.7.0
+
+Note that LLVM's tool 'llc' must support target 'bpf', list with command::
+
+ $ llc --version
+ LLVM (http://llvm.org/):
+  LLVM version 3.x.y
+  [...]
+  Host CPU: xxx
+
+  Registered Targets:
+    [...]
+    bpf        - BPF (host endian)
+    bpfeb      - BPF (big endian)
+    bpfel      - BPF (little endian)
+    [...]
+
+Kernel headers
+--------------
+
+There are usually dependencies to header files of the current kernel.
+To avoid installing devel kernel headers system wide, as a normal
+user, simply call::
+
+ make headers_install
+
+This will creates a local "usr/include" directory in the git/build top
+level directory, that the make system automatically pickup first.
+
+Compiling
+=========
+
+For compiling goto kernel top level build directory and run make like::
+
+ make samples/bpf/
+
+Do notice the "/" slash after the directory name.
+
+Manually compiling LLVM with 'bpf' support
+------------------------------------------
+
+In some LLVM versions the BPF target were marked experimental.  To
+compile LLVM manually and enable BPF target run (build dependencies
+are cmake and gcc-c++)::
+
+ $ git clone http://llvm.org/git/llvm.git
+ $ cd llvm
+ $ mkdir build; cd build
+ $ cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF
+ $ make
+
+It is also possible to point make to the newly compile 'llc' command
+via redefining LLC on the make command line::
+
+ make samples/bpf/ LLC=~/git/llvm/build/bin/llc
+