fbos/Makefile, branch main

Run a hart lottery on SMP

2024-12-03T13:34:43Z

On systems with SMP multiple harts will try to run the kernel, and they will appear at random. But in this kernel, in order to keep things simple, we want to make sure that *only one* hart is running the show, as it greatly simplifies things on these kinds of systems. The solution is similar to what Linux does, which is to allow the first hart to initialize things, but then (and different to what Linux does), it will infinitely stall all the other harts that arrive at a random later point in time. In order to make this more apparent, I have also added a print message showing which hart is being used to run the whole thing. Signed-off-by: Miquel Sabaté Solà

Ensure the right optimitzation level on DEBUG

2024-12-02T19:49:00Z

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

Fix gdb target by not removing ELF executable

2024-11-29T21:43:56Z

GDB actually needs the ELF executable to run a session with symbols loaded in. Hence, do not remove the `fbos.elf` file after calling `objcopy`. 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

Use mktemp when generating the archive

2024-11-27T15:30:00Z

Instead of manually making a temporary directory, do it through 'mktemp', which feels cleaner. Moreover, the base directory will now by named 'fbos' instead of the cryptic 'tmp' one. This is quite relevant when you uncompress the archive into another machine. Signed-off-by: Miquel Sabaté Solà

Move initrd.c into lib

2024-11-26T21:44:45Z

Even if it's tightly coupled with the kernel (e.g. identifying specific tasks from the kernel), in the end it's a library and so it should be placed accordingly. Signed-off-by: Miquel Sabaté Solà

Move string.S to the lib directory

2024-11-26T21:38:35Z

It was weird enough to have it in the 'kernel' directory, as it's way more fitting to have it on 'lib'. Signed-off-by: Miquel Sabaté Solà

Add a make target for producing a release archive

2024-11-25T20:21:17Z

Signed-off-by: Miquel Sabaté Solà

tests: Only test initrd addresses on debug

2024-11-25T06:45:26Z

In initrd tests, and in general, we only need to check that the function did something. As in, that it set the entry addresses somewhere and did not leave them NULL. This is going to be performed from now on on CI and regular tests. And, just if you want to go the extra mile, we will run specific tests that check on memory addresses but that are not guaranteed to work. This is to be replaced in the future by having some proper debugging output. As in, having a message at kernel boot time specifying the addresses being used among other info. This needs a more complex printk utility, of course. Signed-off-by: Miquel Sabaté Solà