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* Add a 'wfi' instruction on the main loopMiquel Sabaté Solà2024-11-221-2/+5
| | | | | | | The actual work is done somewhere else, there is no need to constantly run the main thread. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Enable the timer from the SBI interfaceMiquel Sabaté Solà2024-11-223-8/+135
| | | | | | | | A basic interrupt handler has been implemented which tracks the seconds that have been elapsing along the way. Depending on the value of these seconds, then a task has to be called. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Add basic parsing for underlying ELF executablesMiquel Sabaté Solà2024-11-223-9/+50
| | | | | | | | | | | | | The given initrd is a CPIO archive of multiple ELF executables. We are already able to parse the CPIO archive to detect where each file is located, this commit adds the mapping for each ELF executable to the corresponding task_struct. Note that this is still heavily under construction, since we cannot simply jump into the entry point of an executable as we have not yet setup the proper layout from performing context switches. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Initial parsing of the provided initrd fileMiquel Sabaté Solà2024-11-213-2/+164
| | | | | | | | | | | | We expect a CPIO archive with the 'newc' format for the initrd. Parse this archive from the given initrd address and fetch the address for each ELF executable while also pairing which task correspond to which ELF. This commit leaves to do the actual parsing of the ELF file for each task, while also leaving some string utilities to be refined. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* string: Cleanup leading tabsMiquel Sabaté Solà2024-11-201-3/+3
| | | | Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Fetch the initrd address from the DTB blobMiquel Sabaté Solà2024-11-204-30/+49
| | | | | | | | | | The kernel entry has a pointer to the DTB blob as a parameter. From this pointer we can parse the the DTB blob to find the properties "chosen->linux,initrd-start" and "chosen->linux,initrd-start". These properties are guaranteed to have 64-bit addresses which point where the initrd is in memory, which we need to fetch the binaries to be loaded. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Check the return value from SBI ecallsMiquel Sabaté Solà2024-11-191-1/+4
| | | | Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Setup the stack for an init taskMiquel Sabaté Solà2024-11-197-9/+156
| | | | | | | | | | | | | | | | | 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 <mikisabate@gmail.com>
* Bootstrap the projectMiquel Sabaté Solà2024-08-243-0/+70
For now the base layout has been defined and we have a binary that is properly reached through openSBI. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>