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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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+ 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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+ Align kernel to 2MiB boundary in u-boot
+ Optimize alignment functions a little bit, should still have to check
on real hardware but 'feels' more clean
+ Add early boot debugging
+ Put extra cores we aren't ready to account for to sleep if/when they
boot.
+ Make BASE_PAGE_SIZE constant on riscv64/32, helps the compiler with
some alignment checks among other things.
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+ No real point having multiple different levels of assertions, just say
you assert something and be done with it
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+ Had some minor issues with a wraparound of size_t that effectively
meant that some regions were allocated twice. Also, booting should be
a bit more reliable now, turned out that the previous iteration of the
booting was just accidentally working due to the kernel being placed
'close enough' in RAM to where it was linked to. Fixed by allocating a
vmem of O1 that maps the kernel to a 2MiB boundary at boot, pretty
nifty.
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+ dbg_fdt() is apparently broken, possibly due to UB or something, but
it causes some issues with optimizations enabled. Remove it
temporarily
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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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+ Took some fairly significant changes, for one the kernel is no longer
relocated at the start of a boot, instead it sits wherever the user
decides the kernel should sit. Similarly, the initial kernel stack and
page table are stored within the binary, slightly bloating the size
but making it much safer to boot since there's really no chance of us
overwriting the fdt or initrd in memory.
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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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+ 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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+ Gives a very slight improvement to RPC speeds, but mostly cleans up
code a little bit.
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+ Fairly considerable speedup, as we don't have to look up the rpc pte
every time separately, instead cacheing them. Adds an architecture
specific limitation to total rpc stack size, though.
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+ Only occur with my version of riscv64-linux-gnu-gcc. Funny, that.
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+ Found it in newlib. This allows the compiler to more effectively
optimize away unnecessary register operations. Applied to both kernel
and init.c for a slight speed increase.
I really should move init.c to some other repository though, the
binary files are starting to get annoying
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+ Make 8250 serial driver more generic
+ Still TODO: write a tutorial on how to boot on the visionfive2
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+ Not bootable quite yet. Among other things, I couldn't
get the current starfive u-boot fork to boot, so
try adding support for booting with precompiled u-boot
via the `go` command. Initial testing with qemu shows that
this should be possible, and if it works, might be useful
in the (far) future with other slightly janky SBCs.
Also, NS16550 is 8250-based, and I'm really only using the base
8250, so rename and add visionfive 2 uart to list of compatibles.
Visionfive 2 is still completely untested.
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+ CSR_STVEC requires four byte alignment
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+ RELEASE=1 doesn't work for some reason, though
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+ Both kind of go hand in hand, made sense to do both at the same time.
Some parts feel slightly hacky, the loader works by placing everything
on the stack and avoiding global values. Still, seems to work?
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