Right now, NE2000 NICs don't work because the link is down by default
and this will never change. Of all the NE2000 documentation I looked
at I could not find a link status indicator, so just assume the link
is up.
next_packet_page points to a page, but was being compared to a byte
offset rather than a page offset when adjusting the BOUNDARY register
when the ring buffer wraps around.
Fixes#8327.
This bug manifests it self when the caller to sys$pledge() passes valid
promises, but invalid execpromises. The code would apply the promises
and then return an error for the execpromises. This leaves the user in
a confusing state, as the promises were silently applied, but we return
an error suggesting the operation has failed.
Avoid this situation by tweaking the implementation to only apply the
promises / execpromises after all validation has occurred.
GCC-11 added a new option `-fzero-call-used-regs` which causes the
compiler to zero function arguments before return of a function. The
goal being to reduce the possible attack surface by disarming ROP
gadgets that might be potentially useful to attackers, and reducing
the risk of information leaks via stale register data. You can find
the GCC commit below[0].
This is a mitigation I noticed on the Linux KSPP issue tracker[1] and
thought it would be useful mitigation for the SerenityOS Kernel.
The reduction in ROP gadgets is observable using the ropgadget utility:
$ ROPgadget --nosys --nojop --binary Kernel | tail -n1
Unique gadgets found: 42754
$ ROPgadget --nosys --nojop --binary Kernel.RegZeroing | tail -n1
Unique gadgets found: 41238
The size difference for the i686 Kernel binary is negligible:
$ size Kernel Kernel.RegZerogin
text data bss dec hex filename
13253648 7729637 6302360 27285645 1a0588d Kernel
13277504 7729637 6302360 27309501 1a0b5bd Kernel.RegZeroing
We don't have any great workloads to measure regressions in Kernel
performance, but Kees Cook mentioned he measured only around %1
performance regression with this enabled on his Linux kernel build.[2]
References:
[0] d10f3e900b
[1] https://github.com/KSPP/linux/issues/84
[2] https://lore.kernel.org/lkml/20210714220129.844345-1-keescook@chromium.org/
This patch greatly simplifies VMObject locking by doing two things:
1. Giving VMObject an IntrusiveList of all its mapping Region objects.
2. Removing VMObject::m_paging_lock in favor of VMObject::m_lock
Before (1), VMObject::for_each_region() was forced to acquire the
global MM lock (since it worked by walking MemoryManager's list of
all regions and checking for regions that pointed to itself.)
With each VMObject having its own list of Regions, VMObject's own
m_lock is all we need.
Before (2), page fault handlers used a separate mutex for preventing
overlapping work. This design required multiple temporary unlocks
and was generally extremely hard to reason about.
Instead, page fault handlers now use VMObject's own m_lock as well.
Despite what the declaration would have us believe these are not "u8*".
If they were we wouldn't have to use the & operator to get the address
of them and then cast them to "u8*"/FlatPtr afterwards.
Since we're taking from the committed set of pages, there should never
be a reason for this call to fail.
Also add a Badge to disallow taking committed pages from anywhere but
the Region class.
We don't need to have a dedicated API for creating a VMObject with a
single page, the multi-page API option works in all cases.
Also make the API take a Span<NonnullRefPtr<PhysicalPage>> instead of
a NonnullRefPtrVector<PhysicalPage>.
Depending on the values it might be difficult to figure out whether a
value is decimal or hexadecimal. So let's make this more obvious. Also
this allows copying and pasting those numbers into GNOME calculator and
probably also other apps which auto-detect the base.
KBufferBuilder is always allowed to expand if it wants to. This
restriction was added a long time ago when it was unsafe to allocate
VM while generating ProcFS contents.
Use a Mutex instead of a SpinLock to protect the per-FileDescription
generated data cache. This allows processes to go to sleep while
waiting their turn.
Also don't try to be clever by reusing existing cache buffers.
Just allocate KBuffers as needed (and make sure to surface failures.)
KBufferBuilder exists for code that wants to build a KBuffer instead
of a String. KBuffer is backed by anonymous VM, while String is backed
by a kernel heap allocation.
Advisory locks don't actually prevent other processes from writing to
the file, but they do prevent other processes looking to acquire and
advisory lock on the file.
This implementation currently only adds non-blocking locks, which are
all I need for now.
