This is important for dmidecode because it does an fstat on the DMI
blobs, trying to figure out their size. Because we already know the size
of the blobs when creating the SysFS components, there's no performance
penalty whatsoever, and this allows dmidecode to not use the /dev/mem
device as a fallback.
Function-local `static constexpr` variables can be `constexpr`. This
can reduce memory consumption, binary size, and offer additional
compiler optimizations.
These changes result in a stripped x86_64 kernel binary size reduction
of 592 bytes.
This mostly just moved the problem, as a lot of the callers are not
capable of propagating the errors themselves, but it's a step in the
right direction.
The first byte of the EBDA structure contains the size of the EBDA
in 1 KiB units. We were incorrectly using the word at offset 0x413
of the BDA which specifies the number of KiB before the EBDA structure.
Using the phrase "create" doesn't give information on whether the object
must be allocated or a failure to do so can be handled gracefully.
Therefore, we must use better phrase for such purpose, so "must_create"
for the allocate-and-construct static methods is definitely good choice.
Instead, allocate before constructing the object and pass NonnullOwnPtr
of KString to the object if needed. Some classes can determine their
names as they have a known attribute to look for or have a static name.
This option is already enabled when building Lagom, so let's enable it
for the main build too. We will no longer be surprised by Lagom Clang
CI builds failing while everything compiles locally.
Furthermore, the stronger `-Wsuggest-override` warning is enabled in
this commit, which enforces the use of the `override` keyword in all
classes, not just those which already have some methods marked as
`override`. This works with both GCC and Clang.
We now use AK::Error and AK::ErrorOr<T> in both kernel and userspace!
This was a slightly tedious refactoring that took a long time, so it's
not unlikely that some bugs crept in.
Nevertheless, it does pass basic functionality testing, and it's just
real nice to finally see the same pattern in all contexts. :^)
These are constants, they don't need to be dynamically allocated.
Another minor step towards removing `AK::String` from the Kernel
and improving OOM safety.
Normally, trying to truncate a SysFSInode should result in EPERM error.
However, as suggested by Ali (@alimpfard), we can allow the PowerState
node to be "truncated" so one can open that file with O_TRUNC option.
Likewise, we also need to provide a way to set modified time on SysFS
inodes. For most inodes, we should return ENOTIMPL error, but for the
power state switch, we ignore the modified time setting and just return
KSuccess.
These fixes allow to do "echo -n 1 > /sys/firmware/power_state" in Shell
after gaining root permissions, to switch the power state.
Previously there was a mix of returning plain strings and returning
explicit string views using `operator ""sv`. This change switches them
all to standardized on `operator ""sv` as it avoids a call to strlen.
This change removes the halt and reboot syscalls, and create a new
mechanism to change the power state of the machine.
Instead of how power state was changed until now, put a SysFS node as
writable only for the superuser, that with a defined value, can result
in either reboot or poweroff.
In the future, a power group can be assigned to this node (which will be
the GroupID responsible for power management).
This opens an opportunity to permit to shutdown/reboot without superuser
permissions, so in the future, a userspace daemon can take control of
this node to perform power management operations without superuser
permissions, if we enforce different UserID/GroupID on that node.
Both should reside in the SysFS firmware directory which is normally
located in /sys/firmware.
Also, apply some OOM-safety patterns when creating the BIOS and ACPI
directories.
This will somwhat help unify them also under the same SysFS directory in
the commit.
Also, it feels much more like this change reflects the reality that both
ACPI and the BIOS are part of the firmware on x86 computers.
