fbos/kernel/printk.c, branch main

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

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

Prepend the name of the task on debug

2024-12-02T19:47:19Z

On 'printk' and 'sys_write' calls, prepend the name of the task that is being executed for each message. This is an easy way to show off that we are doing the right thing with the 'tp' register, even if we don't do much with it. Signed-off-by: Miquel Sabaté Solà

Enable exception handling from user mode

2024-11-22T22:00:46Z

This allows us to actually catch system calls and start to run user space programs. That being said, the whole thing is still pretty brittle, and the scheduler is not quite there yet. Signed-off-by: Miquel Sabaté Solà

Check the return value from SBI ecalls

2024-11-19T14:22:35Z

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