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Asked: 2024-09-27T10:36:18+05:30 In: ,

How can I resolve the issue of BPF Type Format (BTF) generation failing on Ubuntu 21.04 due to the absence of the vmlinux file?

I’ve been diving deep into some kernel development on my Ubuntu 21.04 setup, and I’ve hit a pretty annoying roadblock related to BPF Type Format (BTF) generation. So, here’s the deal: I’m trying to work with BPF for a project, and everything was going smoothly until I realized that the BTF generation is failing because it can’t find the `vmlinux` file. I’ve read that the `vmlinux` file is essential for generating the BPF Type Format, but I’m not entirely sure how to get this file in the first place.

I’ve done some digging online and come across multiple discussions about this issue, but nothing has seemed to work for me yet. I’ve tried installing the Linux headers using `apt-get`, but even after that, I can’t locate the `vmlinux` file anywhere in my machine. I’ve made sure I have the right kernel version installed – you know, the one that matches the headers – but it’s still a no-go.

I guess my main questions are: how can I generate or obtain the `vmlinux` file needed for BTF? Should I compile the kernel myself just to get this file (and is that even a good idea?), or is there a simpler way to get it without going through the hassle of a complete rebuild? If anyone has been in this situation or has any tips or commands that could help me generate or find this elusive `vmlinux` file, I’d really appreciate your input. It’s kind of frustrating because I feel like I’m so close to having everything set up correctly for my project, but this little file is holding me back.

Any help, insights, or guidance would be awesome! Also, if it helps to know, I’m working on this within a development environment, and I have some knowledge of dealing with Linux builds, but the kernel compilation process is still a bit new to me. Thanks in advance!

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    2 Answers


    1. Getting the vmlinux File for BPF Type Format (BTF) Generation

      It sounds like you’re really diving into some interesting stuff with kernel development! I get how frustrating it can be to hit a roadblock, especially when it feels like you’re close to getting everything working.

      So, about that vmlinux file you’re looking for. You’re correct that it’s essential for BPF Type Format generation. Normally, you would find it in the kernel build directory if you’ve compiled the kernel from source. But since you mentioned that you’ve tried installing the Linux headers without finding it, let’s go through a couple of options.

      Options to Get vmlinux

      1. Install the Full Kernel Source

      You might want to install the full kernel source code, which includes vmlinux. You can do this by running:

      sudo apt-get install linux-source

      This should download a compressed archive of the kernel source. You can find it in /usr/src and extract it. After that, you can build the kernel and generate the vmlinux file.

      2. Compile the Kernel

      Yes, this might seem daunting, but compiling the kernel can be a good learning experience! If you want to go down this route:

      1. Navigate to the kernel source directory (where you extracted the source).
      2. Run the following command to configure the kernel (use make oldconfig if you already have a working config):
        3. make menuconfig
      3. Then compile the kernel with:
        4. make

      This process will generate the vmlinux file, which will be located in the source directory once the build is complete.

      3. Check Installed Kernel Packages

      Alternatively, you can check if the vmlinux file was included in any installed kernel packages. Sometimes it’s included with the package:

      dpkg -L linux-image-$(uname -r)

      Keep it Simple

      If you’re looking to avoid the hassle of compiling the entire kernel, you might want to check if there are pre-built packages for your kernel version that include the vmlinux file. For example, searching your package manager or kernel PPA (if you added one) might help.

      Ultimately, compiling the kernel does come with its complexities, so if you want to take it step by step and learn along the way, go for it! But if time is of the essence, check for the pre-built options first.

      I hope this helps you get closer to what you need for your project. Good luck with your kernel development and BPF endeavors!


    2. To obtain the `vmlinux` file needed for BPF Type Format (BTF) generation, you have a couple of options. If you have installed the Linux headers using `apt-get` and the `vmlinux` file is still missing, it may be that the Ubuntu package does not include the `vmlinux` binary in the installation by default. One common approach to get the `vmlinux` file is to download the corresponding kernel source package and compile it yourself, but if you’re not ready for a full kernel compilation just yet, you can check if a precompiled `vmlinux` is available for your specific kernel version. You can try searching for packages using commands like `apt-cache search linux-image` to see if any appropriate packages are available to install that might contain the `vmlinux` binary.

      Should you decide to compile the kernel yourself, you can follow these general steps: first, install the necessary packages for kernel compilation with `sudo apt-get build-dep linux` and familiarize yourself with the kernel configuration tools using `make menuconfig` or similar commands. Make sure to set the appropriate options to include BPF support and generate the `vmlinux` file. After configuring, run `make` to compile the kernel; this process might take some time, but once completed, the `vmlinux` file will typically be found in the root of the kernel source directory. Keep in mind that maintaining your own kernel could introduce complexities, so if you require stability, make sure to back up your current kernel and understand the implications of any changes.

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