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BPF: A New Type of Software

brendangregg.com

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Re: BPF: A New Type of Software

#81

Post by manyworlds »

nicoburns wrote: post #78
manyworlds wrote: post #69

Earlier quoted context omitted.

Doubtful. Webassembly is Turing complete, BPF isn’t. Running untrusted unbounded code in the kernel is not smart. BPF was invented with kernel constraints in mind, webassembly was invented with browser constraints in mind. Completely different use cases

> Running untrusted unbounded code in the kernel is not smart. Well currently we run code (e.g. drivers) as trusted full-permission code. Surely, web-assembly would be better than this from a security perspective.

Generally kernel code is also written to specific constraints. Out-of-tree drivers are usually bad at conforming and hypothetical out-of-tree webassembly drivers would be bad for similar reasons. Memory safety isn’t enough, using kernel interfaces safely requires conformance that webassembly can’t statically guarantee like BPF can

Basic examples: code that takes a lock and never releases it, code that loops forever, code that leaks kernel resources.

Re: BPF: A New Type of Software

#82

Post by eigenvalue »

phkamp wrote: post #35

The Lost Generation discovers IBM Mainframe Channel Programs? Want to bet if they are going to make all the same mistakes themselves, or if they are willing to learn from history?

Seems like they only resemble Channel Programs in spirit since they don't use any specialized hardware. If it all runs on commodity hardware and is completely generic/customizable in software then it seems a lot more useful and economical than anything for a mainframe.

Re: BPF: A New Type of Software

#83

Post by monocasa »

smartmic wrote: post #77

I do not know much about kernels and OS architecture. But I am wondering how this relates to the idea of GNU Hurd. Wasn't its concept also about microkernel-based design?

This is pretty different, Hurd ran all of this stuff in user space.

It's really close to exokernels though. XOK had three different, but similar VMs for running user code in kernel space. Like their version of futex was a filter program that got run to see if the program should be woke up.

Re: BPF: A New Type of Software

#84

Post by thinkmassive »

GrayShade wrote: post #3

Brendan has a lot of great content that gets posted here regularly: http://www.brendangregg.com/ (I'm still trying find the time to get through it though). There's also https://github.com/iovisor/bcc#tools as an easy way to get started using BPF.

He also has a book coming out this month, BPF Performance Tools http://www.brendangregg.com/bpf-performance-tools-book.html

Re: BPF: A New Type of Software

#86

Post by nikanj »

hackworks wrote: post #79

eBPF can be viewed as a mechanism to safely run user code in kernel since it uses a DSL and a compiler before the byte code is executed in kernel. This opens up doors for running performance critical functionality in kernel without having to bundle it with the kernel or very tightly coupled with the kernel version. Optimizing FUSE is an example: https://extfuse.github.io/ I expect custom security auditing software, r…

Bytecode + compiler was also how both Flash and Java Applets worked. Have we forgotten how secure those were?

Re: BPF: A New Type of Software

#87

Post by zippie »

arminiusreturns wrote: post #28
jokoon wrote: post #16

I have a hard time understanding what you would use it for. I could understand a use-case, but I fail to understand why it would be that much useful. I have a sense it allows much better performance for horizontal scaling, but I'm not sure...

The main use case for me as a linux admin is two fold. One, to augment iptables/nftables for increased speed and observability gains in them. It's possible to do BPF only netfilter (some firewall/IDS tools are likely to use it heavily) but I think it works better just helping the other tools, and you can lookup some benchmarks that show it. Two, as a better tool for general observability and problem tracing. For exam…

Not sure if you were hinting at it already, just in case, you may be interested in the ongoing work with bpfilter [0] which uses ebpf underneath existing xfilter rule interfaces.

[0] https://lwn.net/Articles/747551/

Re: BPF: A New Type of Software

#88

Post by boomlinde »

nicoburns wrote: post #78
manyworlds wrote: post #69

Earlier quoted context omitted.

Doubtful. Webassembly is Turing complete, BPF isn’t. Running untrusted unbounded code in the kernel is not smart. BPF was invented with kernel constraints in mind, webassembly was invented with browser constraints in mind. Completely different use cases

> Running untrusted unbounded code in the kernel is not smart. Well currently we run code (e.g. drivers) as trusted full-permission code. Surely, web-assembly would be better than this from a security perspective.

What use case do you envision?

Re: BPF: A New Type of Software

#89

Post by riyakhanna1983 »

hackworks wrote: post #79

eBPF can be viewed as a mechanism to safely run user code in kernel since it uses a DSL and a compiler before the byte code is executed in kernel. This opens up doors for running performance critical functionality in kernel without having to bundle it with the kernel or very tightly coupled with the kernel version. Optimizing FUSE is an example: https://extfuse.github.io/ I expect custom security auditing software, r…

Another example is a sandboxing file system https://lwn.net/Articles/803890/

Re: BPF: A New Type of Software

#90

Post by meithecatte »

nikanj wrote: post #86
hackworks wrote: post #79

eBPF can be viewed as a mechanism to safely run user code in kernel since it uses a DSL and a compiler before the byte code is executed in kernel. This opens up doors for running performance critical functionality in kernel without having to bundle it with the kernel or very tightly coupled with the kernel version. Optimizing FUSE is an example: https://extfuse.github.io/ I expect custom security auditing software, r…

Bytecode + compiler was also how both Flash and Java Applets worked. Have we forgotten how secure those were?

It's also how wasm works, and in some sense -- JavaScript. Somehow, these introduce much less security problems.
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