This implements a simple bootloader that is capable of loading ELF64
kernel images. It does this by using QEMU/GRUB to load the kernel image
from disk and pass it to our bootloader as a Multiboot module.
The bootloader then parses the ELF image and sets it up appropriately.
The kernel's entry point is a C++ function with architecture-native
code.
Co-authored-by: Liav A <liavalb@gmail.com>
This is a much more ergonomic option than getting a
`VERIFY_NOT_REACHED()` failure at run-time. I encountered this issue
with Clang, where sized deallocation is not the default due to ABI
breakage concerns.
Note that we can't simply just not declare these functions, because the
C++ standard states:
> If this function with size parameter is defined, the program shall
> also define the version without the size parameter.
This commit makes use of the conditionally trivial special member
functions introduced in C++20. Basically, `Optional` and `Variant`
inherits whether its wrapped type is trivially copy constructible,
trivially copy assignable or trivially destructible. This lets the
compiler optimize optimize a large number of their use cases.
The constraints have been applied to `Optional`'s converting
constructors too in order to make the API more explicit.
This feature is not supported by Clang yet, so we use conditional
compilation so that Lagom can be built on macOS. Once Clang has P0848R3
support, these can be removed.
This attribute tells compilers that the pointer returned by a function
is never null, which lets it optimize away null checks in some places.
This seems like a nice addition to `NonnullOwnPtr` and `NonnullRefPtr`.
Using this attribute causes extra UBSan checks to be emitted. To offset
its performance loss, some additional methods were marked ALWAYS_INLINE,
which lets the compiler optimize duplicate checks
Clang enforces the ordering that attributes specified with the
`[[attr_name]]` syntax must comes before those defines as
`__attribute__((attr_name))`. We don't want to deal with that, so we
should stick to a single syntax (for functions, at least).
This commit favors the latter, as it's used more widely in the code
(for declaring more "exotic" options), and changing those would be a
larger effort than modifying this single file.
The ASAN_[UN]POISON_MEMORY_REGION macros can be used to manually notify
the AddressSanitizer runtime about the reachability of instrumented code
accessing a memory region. This is most useful for manually managed
heaps and arenas that do not go directly to malloc or alligned_alloc.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
I overlooked a corner case where we might call the built-in ctz() on zero.
Furthermore, the calculation of the shift was wrong and the results were often
unusable.
Both issue were caused by a forgotten 36daeee34f.
This time I made sure to look at bmpsuite_files first, and now they look good.
Found by OSS-Fuzz:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28985
This API was a mostly gratuitous deviation from POSIX that gave up some
portability in exchange for avoiding the occasional strlen().
I don't think that was actually achieving anything valuable, so let's
just chill out and have the same open() API as everyone else. :^)
The coarse clocks in time.h are a linux extension that we've adopted.
MacOS and the BSDs don't have it, so we need an alias in a platform
header for Lagom builds.
clang-format seems to barf on these attributes, to make it easier to
use these attributes and have clang-format not mangle the following code
we can hide them behind a macro so clang-format doesn't have to handle it.
This stopped working quite some time ago due to Clang losing track of
typestates for some reason and everything becoming "unknown".
Since we're primarily using GCC anyway, it doesn't seem worth it to try
and maintain this non-working experiment for a secondary compiler.
Also it doesn't look like the Clang team is actively maintaining this
flag anyway. So good-bye, -Wconsumed. :/
Clang keeps whining that NonnullFooPtrs are in "unknown" state and I'm
not sure how to resolve that right now. Disable the checking until we
can figure it out.
AK::Bitmap is extended with find_next_range_of_unset_bits().
The function is implemented using count_trailing_zeroes_32(), which is
optimized on many platforms, that gives a huge performance boost.
Functions find_longest_range_of_unset_bits() and find_first_fit() are
implemented with find_next_range_of_unset_bits(). According to
benchmarks, they are 60-100% faster.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
Clang loses the typestate when passing NonnullRefPtr's via lambda captures.
This is unfortunate, but not much we can do about it. Allowing ptr() makes
it possible to use captured NonnullRefPtrs as you'd expect.
You can currently use this to detect the CPU architecture like so:
#if ARCH(I386)
...
#elif ARCH(X86_64)
...
#else
...
#endif
This will be helpful for separating out architecture-specific code blocks.
