fbos, branch main

Update links to git.mssola.com

2026-07-22T15:01:16Z

Signed-off-by: Miquel Sabaté Solà

Update changelog file

2024-12-05T13:03:09Z

Signed-off-by: Miquel Sabaté Solà

Add a note on HSM

2024-12-05T13:03:09Z

The hart lottery that we do on initialization is a bit rigged. Write a note on that in the documentation of the 'hart_lottery' variable. Signed-off-by: Miquel Sabaté Solà

Pass the hart ID on start_kernel instead

2024-12-04T16:23:57Z

Instead of storing the hard ID as given by the bootloader into a C variable, pass it directly into the 'start_kernel' function since we don't need to tamper the value as originally laid out on the 'a0' register. Signed-off-by: Miquel Sabaté Solà

Re-use the halting loop also for the main hart

2024-12-04T13:35:50Z

The halting in secondary harts should not be treated too differently as with the (unlikely) scenario that the main function quits. Hence, merge the code in both cases. Moreover, we do not really need to to initialize the values of most registers, as they will be explicitely set when needed anyways. Signed-off-by: Miquel Sabaté Solà

Move documentation to the proper places

2024-12-04T13:23:44Z

Code documentation was scattered between header and source files. Since the norm was already to have this documentation into header files, move some comments from source files to their header counterparts. This hopefully makes things more consistent. Signed-off-by: Miquel Sabaté Solà

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

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

test: Remove asserts on specific entry addrs

2024-12-03T07:00:53Z

These asserts where needed when I was iterating on the initrd handling code, but they are admittedly too specific and prone to errors. Hence, get rid off them. Signed-off-by: Miquel Sabaté Solà

Remove stack pointer for each process

2024-12-03T06:59:01Z

Since 6132623dbf30 ("Share the same stack everywhere") the same stack is used everywhere. Hence, it's rather pointless for each task to have a pointer to a stack which is the same and that is never read. Signed-off-by: Miquel Sabaté Solà