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This patch introduces a helpful copy_string_from_user() function
that takes a bounded null-terminated string from userspace memory
and copies it into a String object.
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Supervisor Mode Access Prevention (SMAP) is an x86 CPU feature that
prevents the kernel from accessing userspace memory. With SMAP enabled,
trying to read/write a userspace memory address while in the kernel
will now generate a page fault.
Since it's sometimes necessary to read/write userspace memory, there
are two new instructions that quickly switch the protection on/off:
STAC (disables protection) and CLAC (enables protection.)
These are exposed in kernel code via the stac() and clac() helpers.
There's also a SmapDisabler RAII object that can be used to ensure
that you don't forget to re-enable protection before returning to
userspace code.
THis patch also adds copy_to_user(), copy_from_user() and memset_user()
which are the "correct" way of doing things. These functions allow us
to briefly disable protection for a specific purpose, and then turn it
back on immediately after it's done. Going forward all kernel code
should be moved to using these and all uses of SmapDisabler are to be
considered FIXME's.
Note that we're not realizing the full potential of this feature since
I've used SmapDisabler quite liberally in this initial bring-up patch.
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ACPI subsystem includes 3 types of parsers that are created during
runtime, each one capable of parsing ACPI tables at different level.
ACPIParser is the most basic parser which is essentialy a parser that
can't parse anything useful, due to a user request to disable ACPI
support in a kernel boot parameter.
ACPIStaticParser is a derived class from ACPIParser, which is able to
parse only static data (e.g. FADT, HPET, MCFG and other tables), thus
making it not able to parse AML (ACPI Machine Language) nor to support
handling of hardware events and power management. This type of parser
can be created with a kernel boot parameter.
ACPIDynamicParser is a derived class from ACPIStaticParser, which
includes all the capabilities of the latter, but *should* implement an
AML interpretation, (by building the ACPI AML namespace) and handling
power & hardware events. Currently the methods to support AML
interpretation are not implemented.
This type of parser is created automatically during runtime if the user
didn't specify a boot parameter related to ACPI initialization.
Also, adding strncmp function definition in StdLib.h, to be able to use
it in ACPIStaticParser class.
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These types can be picked up by including <AK/Types.h>:
* u8, u16, u32, u64 (unsigned)
* i8, i16, i32, i64 (signed)
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Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
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The scheduler now operates on threads, rather than on processes.
Each process has a main thread, and can have any number of additional
threads. The process exits when the main thread exits.
This patch doesn't actually spawn any additional threads, it merely
does all the plumbing needed to make it possible. :^)
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This is all pretty rickety but we can now respond to "arping" from the host
while running inside QEMU. Very cool. :^)
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It still requires an ELF compiler and linker, but at least it builds.
I need to get rid of the "Unix" namespace. This does a lot of that.
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This is really neat. :^)
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It's a bit faster than g++ and seems to generate perfectly fine code.
The kernel is also roughly 10% smaller(!)
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sys$fork() now clones all writable regions with per-page COW bits.
The pages are then mapped read-only and we handle a PF by COWing the pages.
This is quite delightful. Obviously there's lots of work to do still,
and it needs better data structures, but the general concept works.
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I also added a generator cache to FileHandle. This way, multiple
reads to a generated file (i.e in a synthfs) can transparently
handle multiple calls to read() without the contents changing
between calls.
The cache is discarded at EOF (or when the FileHandle is destroyed.)
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It's a lot crappier than I remembered it. It's gonna need a lot of work.
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