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+ Seems to improve code quality a little bit
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+ ipc_kick() does a forward and a tail at the same time
The idea with ipc_tail() is to allow 'trusted' calls, so for example a
process is not allowed to willy-nilly open a file, as it has to go via
init(), making the eid 1. This way the receiver can know that the
request has gone through init() and can open up a new connection
(file, whatever) after which requests from that pid/tid are allowed
without init() intervention
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+ Can be used to build fast hashmaps to speed up ipc
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+ Current setup will likely not last long, just a stopgap until I figure
out how I want to build each testcase etc.
Probably dir based, but I'll probably add some scripts that generate
the build rules for each test case (or binary?). Also, should probably
put ouput files in a build directory and keep the source clean, but
again, good enough for now.
Will have to start implementing more extensive tests, and probably
come up with some way to compare textual output etc.
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+ User has to 'free' the 0 page before it becomes accessible to mapping.
Probably worth noting that this is likely VERY niche and mainly
concerns stuff like certain kinds of emulators that I'm still
eons from implementing, but still.
Unbacked pages can also be useful for some kinds of notifications,
like 'if someone writes to this page, please report it to me with this
ID' or whatever, I remember seeing some discussion about it somewhere
but that's also not really relevant for the moment.
Most significantly, at least with the current design,
after the null page is freed it becomes available for use to regular req_mem()
calls, so users should probably using locks around memory requests.
That's probably a good idea anyway as internally the kernal has to
lock the virtual memory, and without a scheduler it might cause
threads to spin for a while in the kernel which is rather bad.
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+ Anything extern is right out as LLVM doesn't produce correct code for
them. Maybe if I added some extra attributes but I'm skeptical.
Replaced with static variables and getters/setters.
+ Inline ASM is apparently a bit buggy, so use an assembly stub when jumping to init.
+ Minimize work done in main() to minimize chance of LLVM doing something silly.
Still not 100% certain that I shouldn't just write the main() as an assembly stub
in arch/riscv64 to be absolutely sure everything works as intended.
+ Make .kernel.start section SHF_ALLOC, otherwise lld complains about
pc-relative addressing
Probably some other stuff as well that I'm forgetting right now. But at least with
LLVM14 LTO seems to work, which is pretty cool?
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+ Can be used to pass contiguous memory regions to things like virtio
block devices for implementing disk drivers etc.
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+ Effectively means that all executables can be called into, but if an
exe doesn't want to deal with anyone else it should just set a flag
like `not_really_a_server` or whatever
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+ Slightly more overhead but will help track down possible memory leaks
in the future. Could also add in a flag for turning off/on but I don't
think the difference in performance is that significant.
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+ The system is now a bit simpler and hopefully easier to understand, while also
extending the shared memory to be 1:N, where there is one owner who
may become a zombie while waiting for the N to die.
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+ Start out using big kernel lock, apparently seL4 thinks its good
enough. I might have a go at using a more fair lock, and possibly
moving to more fine-grained locks if I really feel the need to get
scalability up.
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+ Compiling for size emits memcpy() calls after they've already been
removed by LTO, so add __used attribute to counteract this.
Newer versions of GCC seem to prefer `-flto=auto` to just `-flto`, so
use that.
printf format %d -> %ld
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+ Allow threads to make themselves become orphants
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+ Should write this down somewhere but the idea is that when a process
gets killed, it frees all the memory it can, making all threads within
that process orphans. Orphaned threads are assigned to the init
process, which will generally call exit() on each one. Zombie threads
are threads that own some bit of shared data, and whose reference
count is above zero. They may not be swapped to or called, even though
they take up space in thread map and reserve their thread ID.
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+ Also swap checks if thread is running
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+ Still largely untested, should really try to come up with a proper
testsuite, at the moment it's mostly me trying things out in the (as
of yet unreleased) kmx repo
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+ Terminology is still a bit poor, and will still have to write
documentation + implement ipis properly
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+ Sets the current core to sleep
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+ I keep starting to type src and wondering why autocomplete won't work,
I guess src is just uncounciously a better name
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