4 ms·

Is it dangerous to perform some IO bypassing the kernel ? I suppose not regarding this commit, but the kernel isn't there to check calls of the application ?

• int0x80 8y ago
  The kernel handles the IO. You just don't need to enter the kernel (syscall) to issue it, it is done via a kernel<->user memory mapped ring buffer. Roughly, I don't really know the details well. See https://lwn.net/Articles/743714/ https://lwn.net/Articles/743714/
  • k__ 8y ago
    So you don't "ask" the kernel, but pump your data inside a special memory space where the kernel will perform IO with it?
    • tinus_hn 8y ago
      I think the kernel provides results in a special memory space where you can read it without using system calls. Performing operations in the kernel on a memory area writeable by user space sounds really dangerous.
      • int0x80 8y ago
        It is possible. As you say, not completely problem free and indeed has raised some discussions regarding security implications. AFAICT documentation is scarce (non-existent). Here is a previous patch prepping for this one, with sample code to both submit/reap events: https://patchwork.kernel.org/patch/10712819/ https://patchwork.kernel.org/patch/10712819/