Not sure if you've come up against that
Ah no I also have a libc but it's almost empty
I don't intend to have my syscall interface readily accessible from C, so routing it though libc seemed like a waste of time
our situation is somewhat similar since all our syscalls are really async and all libc system calls goes through a posix userspace driver
ah right
that is interesting though
i think i'll probably do the classic 'draft up a blog post on my experiences and start a discussion' at some point
hm yeah that would be interesting if you do, I have been thinking of trying to push forwards with it but don't have the bandwidth
what's your degree?
you?
medicine, hence the OS on the back burner
tbh i should have just done maths instead, the cs part is pretty boring for the most part imo (especially first year)
and I'm nowhere near good enough at maths for a degree in it ;)
Hm, is there a good pattern for 'global drivers'? In the blog (V 0.9), all stuff is done with lazy static, however you can't init a lazy static with function arguments it seems, needed for V 0.10's boot_info. For now I resorted to a
static mut I only mutably set during init, then ever after access through a helper as an immutable reference, but I was hoping there was a safer/smarter way to do this that I'm just missing
Have reached up to interrupts, stuck on trying to get breakpoint working (Also tried double-fault, in case it was the specific interrupt that was the problem). I'm definitely calling load, but all interrupts are still double-faulting. The
lidt instruction is appearing in the resultant binary, so I have no clue what is wrong.
@ivkin25 probably that’s all the books you need for an entry level of OS knowledge. If you want to know further, I think course materials of Advanced Operating System from all Universities are the best way to start with, then you probably need to read papers or read source code. If you need some detailed info about OS like Linux or Windows, there are a lot of books too, but they are more specific to an implementation intead of general ideas.
Actually I only thoroughly read the Modern Operating Systems as a textbook back in colledge. I think I only had a glance of Three Easy Pieces. Either one is great book. They basically covering the same topics, but with organized in a different way. Modern Operating Systems is more traditionaly textbook style and you may need to read with a course slides. Three Easy Pieces is easier to read.
@ivkin25 honestly something like the xv6 textbook (https://pdos.csail.mit.edu/6.828/2012/xv6/book-rev7.pdf) is a really great introduction to how operating systems work, taking you through a real functioning system and it's only about 100 pages. It doesn't talk so much about the theory and alternate designs but it covers most of the topics that you need to care about for osdev in a good level of detail
is there a way for gdb to break when my os in qumu write a certain value to memory? I found my user space app’s memory is randomly overwritten by somebody (kernel or parent process I’m not sure). The overwrittent location is random, but the value it writes to is the same. I’m wondering if there is a way to break when the OS writes the value to memory.
*os in qemu
Have reached up to interrupts, stuck on trying to get breakpoint working (Also tried double-fault, in case it was the specific interrupt that was the problem). I'm definitely calling load, but all interrupts are still double-faulting. The
lidtinstruction is appearing in the resultant binary, so I have no clue what is wrong.
With QEMU -d int, I've determined that it is loading the IDT, but when it hits int3, it immediately page faults, then page faults, then the double fault also page faults, even when there is no code at all in the handlers. Stack misalignment, maybe???
@CraftSpider: You could try to look at the CR2 register and the error code when the page fault occurs (both are printed with QEMU's
-d int) to see at which memory access causes the page fault. Maybe it's really a stack overflow.
CR2 says location is
0x866B, corresponding to... an offset of 8 from the current GDT, which would be GDT::next_free. Error code is 0, which I gather means caused by a read to an unmapped page. This happens when I don't set a GDT myself, so... The GDT the bootloader is setting is in an unmapped location? Unless the bootloader just expects you to always set a GDT yourself, or I'm misunderstanding something :P
(Also, thank you so much for your help and patience so far)
Oh, that's fun. After getting all the way through allocation, went back and tried to make my framebuffer double-buffered, and play around with speeding it up. Just found out that
&mut self.local_buffer is very slow if local_buffer is a Vec<u8>, but very fast if it's a Box<[u8]>. Like, by a very noticeable amount. My jury-rigged profiling via the time interrupt and counting the IP location at each interrupt says most of the time for the Vec was spent in from_raw_parts_mut, interestingly.