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* Add a video example running on QEMUMiquel Sabaté Solà2024-11-252-0/+3
| | | | Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* tests: Only test initrd addresses on debugMiquel Sabaté Solà2024-11-253-6/+13
| | | | | | | | | | | | | | | | 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 <mikisabate@gmail.com>
* test: Fix test on initrdMiquel Sabaté Solà2024-11-241-6/+9
| | | | | | | | | | | | This was broken since I first introduced the test on initrd on 40ffc517e20c ("Initial parsing of the provided initrd file") but it always was as a work in progress test. Now that the initrd parsing has separation of concerns with the global 'tasks' variable since f4986dab75fa ("Accept tasks as a parameter on initrd extraction"), we can have a proper test written for this. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Accept tasks as a parameter on initrd extractionMiquel Sabaté Solà2024-11-244-13/+21
| | | | | | This allows this functionality to be properly extracted for unit tests. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* kernel: Remove old code from initrd.cMiquel Sabaté Solà2024-11-241-36/+15
| | | | | | | And for the first time I saw this whole thing working with optimizations on :) Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Simplify the entry address computationMiquel Sabaté Solà2024-11-243-22/+25
| | | | | | | We actually don't need to preserve the initially computed base address for each binary, but we can just preserve the final entry address. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Simplify scheduling by introducing an init processMiquel Sabaté Solà2024-11-246-30/+26
| | | | | | | | | | | | | | | | Scheduling is easier if there is an init process which does nothing. This way we don't have to perform hacks in order to idle in S privilege mode while touching special registers in weird ways. For now this process is kind of costly since 'wfi' is not accepted in this context, but this can be further tuned down in the future by setting TW=1 on 'mstatus', or by handling the exception and allowing it if it comes from the proper process. All of that being said, there is still work to be done as things fail when optimitzations are on. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Enable exception handling from user modeMiquel Sabaté Solà2024-11-229-11/+85
| | | | | | | | 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 <mikisabate@gmail.com>
* Fix initrd parsing because of a path changeMiquel Sabaté Solà2024-11-223-14/+14
| | | | | | | | | | In commit 573a8c6b490a ("usr: Rename foo/bar to fizz/buzz") the path of the user-space binaries have changed. The `initrd` parsing code makes some decisions based on that naming, and so it needed to be updated as well. Fixes: 573a8c6b490a ("usr: Rename foo/bar to fizz/buzz") Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* 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>
* usr: Rename foo/bar to fizz/buzzMiquel Sabaté Solà2024-11-224-10/+10
| | | | | | | | | | | | When creating the user space binaries I forgot about their proper names, which is funny on its own. Anyways, let's get them the name they were intended. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com> alksjdlkajd Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Enable the timer from the SBI interfaceMiquel Sabaté Solà2024-11-226-8/+153
| | | | | | | | 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 Solà2024-11-2210-21/+79
| | | | | | | | | | | | | 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 Solà2024-11-2111-11/+244
| | | | | | | | | | | | 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>
* ci: Make the build work for Ubuntu 24.04Miquel Sabaté Solà2024-11-201-2/+2
| | | | | | | | | The binutils used in Ubuntu 24.04 has a crash when trying to link the end binary, which is avoided when passing `-fno-PIE`. Since this is a good idea anyways for the kernel in general, let's pass this flag always and kill two birds with one stone. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Add a note on requirement a little-endian systemMiquel Sabaté Solà2024-11-201-0/+2
| | | | | | | | | 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 <mikisabate@gmail.com>
* string: Cleanup leading tabsMiquel Sabaté Solà2024-11-201-3/+3
| | | | Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Ensure the environment is clean on QEMU launchMiquel Sabaté Solà2024-11-201-4/+4
| | | | | | | | | Since the library code can now be exchanged between tests and the actual kernel, there might be a missmatch when launching QEMU after calling `make all`. Ensure that this cannot happen by calling `clean` on the `qemu` target. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Fetch the initrd address from the DTB blobMiquel Sabaté Solà2024-11-2014-52/+285
| | | | | | | | | | 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 Solà2024-11-193-12/+29
| | | | Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Setup the stack for an init taskMiquel Sabaté Solà2024-11-1917-24/+281
| | | | | | | | | | | | | | | | | 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>
* usr: Make sure usr/bin/ existsRicardo B. Marliere2024-11-191-0/+1
| | | | | | | | | Fix the following build error on a clean repository: riscv64-suse-linux-ld: cannot open output file usr/bin/foo: No such file or directory Fixes: d79436a1170e ("usr: Bootstrap the initramfs for the kernel") Signed-off-by: Ricardo B. Marliere <rbm@suse.com>
* usr: Bootstrap the initramfs for the kernelMiquel Sabaté Solà2024-11-184-12/+57
| | | | | | | | | 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 <mikisabate@gmail.com>
* Load debug symbols on the gdb targetMiquel Sabaté Solà2024-09-242-20/+41
| | | | | | | | | | | 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 <mikisabate@gmail.com>
* Add CI jobMiquel Sabaté Solà2024-09-243-4/+37
| | | | | | | This will ensure that the code style is preserved and that commits being pushed at least build successfully. Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
* Bootstrap the projectMiquel Sabaté Solà2024-08-2413-0/+1095
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>