[net-next,V3,3/5] samples/bpf: add a README file to get users started
diff mbox

Message ID 20160427073023.29959.17816.stgit@firesoul
State New
Headers show

Commit Message

Jesper Dangaard Brouer April 27, 2016, 7:30 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 |   75 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 samples/bpf/README.rst


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Comments

Naveen N. Rao April 27, 2016, 8:35 a.m. UTC | #1
On 2016/04/27 09:30AM, 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 |   75 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 75 insertions(+)
>  create mode 100644 samples/bpf/README.rst

Thanks for adding this! A few nits...

> 
> diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
> new file mode 100644
> index 000000000000..1fa157db905b
> --- /dev/null
> +++ b/samples/bpf/README.rst
> @@ -0,0 +1,75 @@
> +eBPF sample programs
> +====================
> +
> +This kernel samples/bpf directory contains a mini eBPF library, test
	^^^^^^^^^^^^^^^^^^
'This directory contains' should suffice.

> +stubs, verifier test-suite and examples for using eBPF.
> +
> +Build dependencies
> +==================
> +
> +Compiling requires having installed:
> + * clang >= version 3.4.0
> + * llvm >= version 3.7.1
> +
> +Note that LLVM's tool 'llc' must support target 'bpf', list with command::
> +
> + $ llc --version

'llc --version | grep bpf' is probably simpler?

> + 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::

For building the BPF samples, issue the below command from the kernel 
root directory:

> +
> + make samples/bpf/
> +
> +Do notice the "/" slash after the directory name.
> +
> +Manually compiling LLVM with 'bpf' support
> +------------------------------------------
> +
> +Since version 3.7.0, LLVM adds a proper LLVM backend target for the
> +BPF bytecode architecture.
> +
> +By default llvm will build all non-experimental backends including bpf.
> +To generate a smaller llc binary one can use::
> +
> + -DLLVM_TARGETS_TO_BUILD="BPF;X86"

Is the X86 target really needed?

> +
> +Quick sniplet for manually compiling LLVM and clang
> +(build dependencies are 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"
					    ^^^
Here too.

- Naveen

> + $ make -j $(getconf _NPROCESSORS_ONLN)
> +
> +It is also possible to point make to the newly compiled '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 27, 2016, 9:16 a.m. UTC | #2
On Wed, 27 Apr 2016 14:05:22 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:

> On 2016/04/27 09:30AM, 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 |   75 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 75 insertions(+)
> >  create mode 100644 samples/bpf/README.rst  
> 
> Thanks for adding this! A few nits...

I would prefer if we could apply this patchset and you could followup
with a patch with your nits...

> > 
> > diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
> > new file mode 100644
> > index 000000000000..1fa157db905b
> > --- /dev/null
> > +++ b/samples/bpf/README.rst
> > @@ -0,0 +1,75 @@
> > +eBPF sample programs
> > +====================
> > +
> > +This kernel samples/bpf directory contains a mini eBPF library, test  
> 	^^^^^^^^^^^^^^^^^^
> 'This directory contains' should suffice.

The reason I formulated it like this, was that people will often hit
this kind of documentation when searching google.


> > +stubs, verifier test-suite and examples for using eBPF.
> > +
> > +Build dependencies
> > +==================
> > +
> > +Compiling requires having installed:
> > + * clang >= version 3.4.0
> > + * llvm >= version 3.7.1
> > +
> > +Note that LLVM's tool 'llc' must support target 'bpf', list with command::
> > +
> > + $ llc --version  
> 
> 'llc --version | grep bpf' is probably simpler?

I wanted to give people the impression of how the output looks like.
 
> > + 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::  
> 
> For building the BPF samples, issue the below command from the kernel 
> root directory:

I like your formulation better, but it it worth a respin of the entire
patchset? 

Notice you need the extra "::" ending of the paragraph, to make this
document format nicely with RST (ReStructuredText).

The a README with a .rst suffix will be picked up by github and
displayed as the doc for the directory. Thus I also made sure it
"compiles" with the rst tools. E.g see how samples/pktgen gets auto
documented and nicely formatted via github (scroll down):
 https://github.com/torvalds/linux/tree/master/samples/pktgen

> > +
> > + make samples/bpf/
> > +
> > +Do notice the "/" slash after the directory name.
> > +
> > +Manually compiling LLVM with 'bpf' support
> > +------------------------------------------
> > +
> > +Since version 3.7.0, LLVM adds a proper LLVM backend target for the
> > +BPF bytecode architecture.
> > +
> > +By default llvm will build all non-experimental backends including bpf.
> > +To generate a smaller llc binary one can use::
> > +
> > + -DLLVM_TARGETS_TO_BUILD="BPF;X86"  
> 
> Is the X86 target really needed?

I'm not sure, but if you want to use clang/llc for something else it is
useful, and the example usage of the ";" separator syntax makes it
worth including as an example.

> > +
> > +Quick sniplet for manually compiling LLVM and clang
> > +(build dependencies are 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"  
> 					    ^^^
> Here too.
> 
> - Naveen
> 
> > + $ make -j $(getconf _NPROCESSORS_ONLN)
> > +
> > +It is also possible to point make to the newly compiled 'llc' command
> > +via redefining LLC on the make command line::
> > +
> > + make samples/bpf/ LLC=~/git/llvm/build/bin/llc
> > +
> >   
>
Naveen N. Rao April 27, 2016, 11 a.m. UTC | #3
On 2016/04/27 11:16AM, Jesper Dangaard Brouer wrote:
> On Wed, 27 Apr 2016 14:05:22 +0530
> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
> 
> > On 2016/04/27 09:30AM, 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 |   75 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 75 insertions(+)
> > >  create mode 100644 samples/bpf/README.rst  
> > 
> > Thanks for adding this! A few nits...
> 
> I would prefer if we could apply this patchset and you could followup
> with a patch with your nits...

... and have another patch just for that?
Regardless, I thought the reason we review is so the patch that goes in 
is already in a good shape.

> 
> > > 
> > > diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
> > > new file mode 100644
> > > index 000000000000..1fa157db905b
> > > --- /dev/null
> > > +++ b/samples/bpf/README.rst
> > > @@ -0,0 +1,75 @@
> > > +eBPF sample programs
> > > +====================
> > > +
> > > +This kernel samples/bpf directory contains a mini eBPF library, test  
> > 	^^^^^^^^^^^^^^^^^^
> > 'This directory contains' should suffice.
> 
> The reason I formulated it like this, was that people will often hit
> this kind of documentation when searching google.

That doesn't make sense - shouldn't they be looking at a README file in 
the local samples/bpf directory first before going to google?

> 
> 
> > > +stubs, verifier test-suite and examples for using eBPF.
> > > +
> > > +Build dependencies
> > > +==================
> > > +
> > > +Compiling requires having installed:
> > > + * clang >= version 3.4.0
> > > + * llvm >= version 3.7.1
> > > +
> > > +Note that LLVM's tool 'llc' must support target 'bpf', list with command::
> > > +
> > > + $ llc --version  
> > 
> > 'llc --version | grep bpf' is probably simpler?
> 
> I wanted to give people the impression of how the output looks like.

But, that won't help someone trying to check if their installed llc has 
bpf support or not.
> 
> > > + LLVM (http://llvm.org/):
> > > +  LLVM version 3.x.y
> > > +  [...]
> > > +  Host CPU: xxx

For instance, is the above output something the user needs to see to 
ensure BPF support for llc?

> > > +
> > > +  Registered Targets:
> > > +    [...]
> > > +    bpf        - BPF (host endian)
> > > +    bpfeb      - BPF (big endian)
> > > +    bpfel      - BPF (little endian)

The above is what really matters. Adding 'grep bpf' makes it explicit on 
what the user needs to look for.

> > > +    [...]
> > > +
> > > +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::  
> > 
> > For building the BPF samples, issue the below command from the kernel 
> > root directory:
> 
> I like your formulation better, but it it worth a respin of the entire
> patchset? 
> 
> Notice you need the extra "::" ending of the paragraph, to make this
> document format nicely with RST (ReStructuredText).
> 
> The a README with a .rst suffix will be picked up by github and
> displayed as the doc for the directory. Thus I also made sure it
> "compiles" with the rst tools. E.g see how samples/pktgen gets auto
> documented and nicely formatted via github (scroll down):
>  https://github.com/torvalds/linux/tree/master/samples/pktgen

Looks nice, though I wasn't aware we had any text in the kernel tree 
adhering to this formatting.

> 
> > > +
> > > + make samples/bpf/
> > > +
> > > +Do notice the "/" slash after the directory name.
> > > +
> > > +Manually compiling LLVM with 'bpf' support
> > > +------------------------------------------
> > > +
> > > +Since version 3.7.0, LLVM adds a proper LLVM backend target for the
> > > +BPF bytecode architecture.
> > > +
> > > +By default llvm will build all non-experimental backends including bpf.
> > > +To generate a smaller llc binary one can use::
> > > +
> > > + -DLLVM_TARGETS_TO_BUILD="BPF;X86"  
> > 
> > Is the X86 target really needed?
> 
> I'm not sure, but if you want to use clang/llc for something else it is
> useful, and the example usage of the ";" separator syntax makes it
> worth including as an example.

Ok. The reason I asked is if users need to include the appropriate arch 
target depending on where they build this. It doesn't look like X86 or 
other architecture targets are necessary though.

- Naveen

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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..1fa157db905b
--- /dev/null
+++ b/samples/bpf/README.rst
@@ -0,0 +1,75 @@ 
+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 >= version 3.4.0
+ * llvm >= version 3.7.1
+
+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
+------------------------------------------
+
+Since version 3.7.0, LLVM adds a proper LLVM backend target for the
+BPF bytecode architecture.
+
+By default llvm will build all non-experimental backends including bpf.
+To generate a smaller llc binary one can use::
+
+ -DLLVM_TARGETS_TO_BUILD="BPF;X86"
+
+Quick sniplet for manually compiling LLVM and clang
+(build dependencies are 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)
+
+It is also possible to point make to the newly compiled 'llc' command
+via redefining LLC on the make command line::
+
+ make samples/bpf/ LLC=~/git/llvm/build/bin/llc
+