Missing syscalls required for dynamic allocation about ckb-vm HOT 2 CLOSED

Hi,

Actually, you don't need brk to implement malloc, we do have an example contract running mruby, which involves a lot of malloc, https://github.com/nervosnetwork/mruby-contracts and runs perfectly fine. The trick to this is to use a modified version of libc which works in userspace without needing brk: nervosnetwork/riscv-newlib@dbc4aa7

To answer your question more directly: we thought a lot about whether we want brk, in fact, at some earlier stage of this project, we do implement a MMU which can enable brk, but later we decided to remove it completely. The reason behind this, is that we believe CKB VM should be as simple as possible, while an MMU might help developing a contract, in production you really want the maximum performance, and the minimal attack surface. Plus, any MMU we implement here will only be nice to one kind of application, but might bring obstacles to applications with different memory usage patterns.

As a result, we decide to go without MMU nor brk in the official CKB spec, and defer to modifications in libc to implement malloc and free.

BTW: we do speak both English and Chinese but let's keep using English here for broader audience :)

from ckb-vm.

Thank you so much for getting back to me so quickly. Reading through, I better understand that decision -- that makes sense. I'll play around with that newlib implementation you shared. Thank you!

（好的 😊 在这里我会只用英语）

from ckb-vm.