fbos/README.md, branch main

Write down the requirement for the Zaamo extension

2024-12-03T13:56:17Z

Since 2eead36f97fa ("Run a hart lottery on SMP") the kernel is making use of the 'amoadd.w' instruction, which requires the Zaamo extension (included in the base A extension). This is notable and is worth a mention on the list of requirements. Signed-off-by: Miquel Sabaté Solà

Simplify the qemu target by removing QEMU_BIOS

2024-11-30T20:16:54Z

The QEMU_BIOS parameter was meant to help on old QEMU installations which did not support the proper fw_dynamic workflow. That being said, old QEMU versions might also not implement the proper SBI specification, or it may have other unexpected issues. Hence, just remove the option and force people to have a sufficiently recent QEMU version. Finally, I have updated the SVG showing off a QEMU run. Signed-off-by: Miquel Sabaté Solà

Organize the credits better

2024-11-29T21:56:51Z

Signed-off-by: Miquel Sabaté Solà

Allow the kernel to run as a Linux image

2024-11-29T21:17:13Z

In order to run on real hardware, it's actually easier to re-use workflows from existing bootloaders than loading things in memory manually. In order to achieve this two things had to be settled: 1. The image has to have a Linux header as defined in the RISC-V port. This header will be taken into consideration by bootloaders in order to know where to jump, the image offset, the endianness of the image, etc. 2. The image cannot just be an ELF executable. Rather, we must translate it into binary form via `objcopy`. With all of this at hand, I was able to make the kernel run on a Starfive VisionFive 2 board, and I have recorded an example so it's available as documentation. Signed-off-by: Miquel Sabaté Solà

Add a video example running on QEMU

2024-11-25T10:40:22Z

Signed-off-by: Miquel Sabaté Solà

Add a note on requirement a little-endian system

2024-11-20T11:03:25Z

The dt parsing algorithm assumes that a little-endian system is in place and hence most numbers on the DTB blob have to be converted from big-endian to little-endian. I am not planning on changing that any time soon, so let's add this as a requirement. Signed-off-by: Miquel Sabaté Solà

Setup the stack for an init task

2024-11-19T14:05:59Z

Bootstrap an init task which holds at least the initial stack that is to be used when setting up the registers (such as `sp` and `tp`). In order to guarantee that the stack and the rest of the registers are set up correctly, this commit also provides a raw implementation of a `printk` function. Moreover, this commit also adds an argument that must be passed to `start_kernel`, which is the pointer to the embedded `fdt` blob. This argument will be used by later work so to fetch, at least, the base address for the initial ram disk. This was also used to test that the stack was working as expected. Signed-off-by: Miquel Sabaté Solà

usr: Bootstrap the initramfs for the kernel

2024-11-18T14:56:37Z

Introduce a sample `foo` program which already calls the `write_and_block` system call which is yet to be implemented by this kernel. Moreover, the same CPIO format is used for the initramfs as with Linux, so we can pass it with QEMU without worries. Signed-off-by: Miquel Sabaté Solà

Load debug symbols on the gdb target

2024-09-24T20:45:00Z

Load the debug symbols into the gdb session by simply passing the executable file into gdb directly. Moreover, allow users of the gdb target to provide an extra variable so to pass extra flags to gdb. Moreover, this commit comes with other small cleanups on the Makefile, like a proper ABI specifier, Signed-off-by: Miquel Sabaté Solà

Add CI job

2024-09-24T20:40:31Z

This will ensure that the code style is preserved and that commits being pushed at least build successfully. Signed-off-by: Miquel Sabaté Solà