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Date: Mon, 3 Aug 2020 19:34:07 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>,
davem@...emloft.net
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH v5 bpf-next 3/4] bpf: Add kernel module with user mode
driver that populates bpffs.
On 8/3/20 7:15 PM, Daniel Borkmann wrote:
> On 8/3/20 12:29 AM, Alexei Starovoitov wrote:
>> From: Alexei Starovoitov <ast@...nel.org>
>>
>> Add kernel module with user mode driver that populates bpffs with
>> BPF iterators.
>>
>> $ mount bpffs /my/bpffs/ -t bpf
>> $ ls -la /my/bpffs/
>> total 4
>> drwxrwxrwt 2 root root 0 Jul 2 00:27 .
>> drwxr-xr-x 19 root root 4096 Jul 2 00:09 ..
>> -rw------- 1 root root 0 Jul 2 00:27 maps.debug
>> -rw------- 1 root root 0 Jul 2 00:27 progs.debug
>>
>> The user mode driver will load BPF Type Formats, create BPF maps, populate BPF
>> maps, load two BPF programs, attach them to BPF iterators, and finally send two
>> bpf_link IDs back to the kernel.
>> The kernel will pin two bpf_links into newly mounted bpffs instance under
>> names "progs.debug" and "maps.debug". These two files become human readable.
>>
>> $ cat /my/bpffs/progs.debug
>> id name attached
>> 11 dump_bpf_map bpf_iter_bpf_map
>> 12 dump_bpf_prog bpf_iter_bpf_prog
>> 27 test_pkt_access
>> 32 test_main test_pkt_access test_pkt_access
>> 33 test_subprog1 test_pkt_access_subprog1 test_pkt_access
>> 34 test_subprog2 test_pkt_access_subprog2 test_pkt_access
>> 35 test_subprog3 test_pkt_access_subprog3 test_pkt_access
>> 36 new_get_skb_len get_skb_len test_pkt_access
>> 37 new_get_skb_ifindex get_skb_ifindex test_pkt_access
>> 38 new_get_constant get_constant test_pkt_access
>>
>> The BPF program dump_bpf_prog() in iterators.bpf.c is printing this data about
>> all BPF programs currently loaded in the system. This information is unstable
>> and will change from kernel to kernel as ".debug" suffix conveys.
>>
>> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> [...]
>> diff --git a/kernel/bpf/preload/Kconfig b/kernel/bpf/preload/Kconfig
>> new file mode 100644
>> index 000000000000..b8ba5a9398ed
>> --- /dev/null
>> +++ b/kernel/bpf/preload/Kconfig
>> @@ -0,0 +1,18 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +menuconfig BPF_PRELOAD
>> + bool "Preload BPF file system with kernel specific program and map iterators"
>> + depends on BPF
>> + help
>> + This builds kernel module with several embedded BPF programs that are
>> + pinned into BPF FS mount point as human readable files that are
>> + useful in debugging and introspection of BPF programs and maps.
>> +
>> +if BPF_PRELOAD
>> +config BPF_PRELOAD_UMD
>> + tristate "bpf_preload kernel module with user mode driver"
>> + depends on CC_CAN_LINK
>> + depends on m || CC_CAN_LINK_STATIC
>> + default m
>> + help
>> + This builds bpf_preload kernel module with embedded user mode driver.
>> +endif
> [...]
> When I applied this set locally to run build & selftests I noticed that the above
> kconfig will appear in the top-level menuconfig. This is how it looks in menuconfig:
>
> │ ┌────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐ │
> │ │ General setup ---> │ │
> │ │ [*] 64-bit kernel │ │
> │ │ Processor type and features ---> │ │
> │ │ Power management and ACPI options ---> │ │
> │ │ Bus options (PCI etc.) ---> │ │
> │ │ Binary Emulations ---> │ │
> │ │ Firmware Drivers ---> │ │
> │ │ [*] Virtualization ---> │ │
> │ │ General architecture-dependent options ---> │ │
> │ │ [*] Enable loadable module support ---> │ │
> │ │ -*- Enable the block layer ---> │ │
> │ │ IO Schedulers ---> │ │
> │ │ [ ] Preload BPF file system with kernel specific program and map iterators ---- │ │
> │ │ Executable file formats ---> │ │
> │ │ Memory Management options ---> │ │
> │ │ [*] Networking support ---> │ │
> │ │ Device Drivers ---> │ │
> │ │ File systems ---> │ │
> │ │ Security options ---> │ │
> [...]
>
> I assume the original intention was to have it under 'general setup' on a similar level for
> the JIT settings, or is this intentional to have it at this high level next to 'networking
> support' and others?
Hm, my config has:
CONFIG_BPF_PRELOAD=y
CONFIG_BPF_PRELOAD_UMD=y
I'm getting the following 3 warnings and build error below:
root@...k:~/bpf-next# make -j8 > /dev/null
arch/x86/hyperv/hv_apic.c: In function ‘hv_send_ipi_mask_allbutself’:
arch/x86/hyperv/hv_apic.c:236:1: warning: the frame size of 1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
}
^
make[3]: *** No rule to make target 'kernel/bpf/preload/./../../tools/lib/bpf/bpf.c', needed by 'kernel/bpf/preload/./../../tools/lib/bpf/bpf.o'. Stop.
make[3]: *** Waiting for unfinished jobs....
kernel/bpf/preload/iterators/iterators.c: In function ‘main’:
kernel/bpf/preload/iterators/iterators.c:50:2: warning: ignoring return value of ‘dup’, declared with attribute warn_unused_result [-Wunused-result]
dup(debug_fd);
^~~~~~~~~~~~~
kernel/bpf/preload/iterators/iterators.c:53:2: warning: ignoring return value of ‘read’, declared with attribute warn_unused_result [-Wunused-result]
read(from_kernel, &magic, sizeof(magic));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/preload/iterators/iterators.c:85:2: warning: ignoring return value of ‘read’, declared with attribute warn_unused_result [-Wunused-result]
read(from_kernel, &magic, sizeof(magic));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make[2]: *** [kernel/bpf/preload] Error 2
make[1]: *** [kernel/bpf] Error 2
make: *** [kernel] Error 2
make: *** Waiting for unfinished jobs....
[...]
Have you seen the target error before, what am I missing?
Thanks,
Daniel
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