From: Daniel Borkmann <daniel@iogearbox.net>
To: Alexei Starovoitov <ast@fb.com>, David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH net-next 6/9] bpf: fix stack_depth usage by test_bpf.ko
Date: Tue, 06 Jun 2017 12:19:39 +0200 [thread overview]
Message-ID: <593681BB.5080306@iogearbox.net> (raw)
In-Reply-To: <f79ef874-55a1-cd58-a0e4-9859401a9249@fb.com>
On 05/31/2017 08:45 PM, Alexei Starovoitov wrote:
> On 5/31/17 11:43 AM, David Miller wrote:
>> From: Alexei Starovoitov <ast@fb.com>
>> Date: Wed, 31 May 2017 11:39:37 -0700
>>
>>> On 5/31/17 11:15 AM, David Miller wrote:
>>>> From: Alexei Starovoitov <ast@fb.com>
>>>> Date: Tue, 30 May 2017 13:31:32 -0700
>>>>
>>>>> test_bpf.ko doesn't call verifier before selecting interpreter or
>>>>> JITing,
>>>>> hence the tests need to manually specify the amount of stack they
>>>>> consume.
>>>>>
>>>>> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>>>>> Acked-by: Daniel Borkmann <daniel@iogearbox.net>
>>>>
>>>> I do not like this and the previous patch, it seems so error prone.
>>>
>>> in what sense 'error prone' ?
>>
>> In the sense that a human computes these numbers, and nothing checks
>> if it is correct or not until program perhaps crashes if the value is
>> wrong.
>
> right. that's how all these tests are.
> See bpf_fill_ld_abs_vlan_push_pop() for example.
> If that codegen has a bug, it will crash the kernel.
> That's why it's done from kernel module to do things
> that user space cannot do.
Would probably have been easier to just default the tests to use
MAX_BPF_STACK if nothing further is specified, but I think it may
still be useful to test JIT implementations supporting this for
the non-default cases.
next prev parent reply other threads:[~2017-06-06 10:19 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-30 20:31 [PATCH net-next 0/9] bpf: stack depth tracking Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 1/9] bpf: free up BPF_JMP | BPF_CALL | BPF_X opcode Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 2/9] bpf: split bpf core interpreter Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 3/9] bpf: teach verifier to track stack depth Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 4/9] bpf: reconcile bpf_tail_call and stack_depth Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 5/9] bpf: track stack depth of classic bpf programs Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 6/9] bpf: fix stack_depth usage by test_bpf.ko Alexei Starovoitov
2017-05-31 18:15 ` David Miller
2017-05-31 18:39 ` Alexei Starovoitov
2017-05-31 18:43 ` David Miller
2017-05-31 18:45 ` Alexei Starovoitov
2017-05-31 22:41 ` Alexei Starovoitov
2017-05-31 23:30 ` David Miller
2017-06-06 10:19 ` Daniel Borkmann [this message]
2017-05-30 20:31 ` [PATCH net-next 7/9] bpf: use different interpreter depending on required stack size Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 8/9] bpf: change x86 JITed program stack layout Alexei Starovoitov
2017-05-30 20:31 ` [PATCH net-next 9/9] bpf: take advantage of stack_depth tracking in x64 JIT Alexei Starovoitov
2017-05-31 23:30 ` [PATCH net-next 0/9] bpf: stack depth tracking David Miller
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