Lazily committed shared memory was not working in situations where one
process would write to the memory and another would only read from it.
Since the reading process would never cause a write fault in the shared
region, we'd never notice that the writing process had added real
physical pages to the VMObject. This happened because the lazily
committed pages were marked "present" in the page table.
This patch solves the issue by always allocating shared memory up front
and not trying to be clever about it.
Before this change, we would sometimes map a region into the address
space with !is_shared(), and then moments later call set_shared(true).
I found this very confusing while debugging, so this patch makes us pass
the initial shared flag to the Region constructor, ensuring that it's in
the correct state by the time we first map the region.
We were jumping through some pretty wasteful hoops in the resize event
handler of OOPWV by first creating a bitmap and then immediately
creating a new (shareable) clone of that bitmap. Now we go straight
to the shareable bitmap instead.
Previously we had a static stack check cookie value for LibC.
Now we randomize the cookie value on LibC initialization, this should
help make the stack check more difficult to attack (still possible just
a bigger pain). This should also help to catch more bugs.
Insert stack canaries to find stack corruptions in the kernel.
It looks like this was enabled in the past (842716a) but appears to have been
lost during the CMake conversion.
The `-fstack-protector-strong` variant was chosen because it catches more issues
than `-fstack-protector`, but doesn't have substantial performance impact like
`-fstack-protector-all`.
This fixes a kernel crash that occured when calling ptrace with PT_PEEK
on non paged-in memory.
The crash occurred because we were holding the scheduler lock while
trying to read from the disk's block device, which we do not allow.
Fixes#4740
This makes it a bit more useful, as the user doesn't have to explicitly
ask for completion, it just provides completions, and tries really hard
to avoid suggesting things where they're not expected, for instance:
(cursor positions denoted as pipes)
```
@G | {|
foo: bar |
foo |
}
```
The user does not expect any suggestions in any of those cursor positions,
so provide no suggestions for such cases. This prevents the automatic autocomplete
getting in the way of the user, esp. when they try to press return fully
expecting to go to a new line.
This aims to be a "smart" autocomplete that tries to present the user
with useful suggestions without being in the way (too much).
Here is its current configuration:
- Show suggestions 800ms after something is inserted in the editor
- if something else is inserted in that period, reset it back to 800ms
to allow the user to type uninterrupted
- cancel any shown autocomplete (and the timer) on external changes
(paste, cut, etc)
We need to allocate all pages for the profiler right away so that
we don't trigger page faults in the timer interrupt handler to
allocate them.
Fixes#4734
Modify the user mode runtime to insert stack canaries to find stack corruptions.
The `-fstack-protector-strong` variant was chosen because it catches more
issues than vanilla `-fstack-protector`, but doesn't have substantial
performance impact like `-fstack-protector-all`.
Details:
-fstack-protector enables stack protection for vulnerable functions that contain:
* A character array larger than 8 bytes.
* An 8-bit integer array larger than 8 bytes.
* A call to alloca() with either a variable size or a constant size bigger than 8 bytes.
-fstack-protector-strong enables stack protection for vulnerable functions that contain:
* An array of any size and type.
* A call to alloca().
* A local variable that has its address taken.
Example of it catching corrupting in the `stack-smash` test:
```
courage ~ $ ./user/Tests/LibC/stack-smash
[+] Starting the stack smash ...
Error: Stack protector failure, stack smashing detected!
Shell: Job 1 (/usr/Tests/LibC/stack-smash) Aborted
```
Empty boxes should be fully collapsed, but a box with border and/or
padding is not empty.
This fixes an issue where <hr> elements were getting weirdly collapsed
since they have zero content height (but some border height.)
There's no spatial navigation here, Left/Up moves to the previous
sibling in the tab order, while Right/Down moves to the next.
The arrow keys keep focus within the same parent widget, unlike the tab
key which cycles through all focusable widgets in the window.
This makes GUI::MessageBox feel a bit nicer since you can now arrow
between the Yes/No/Cancel buttons. :^)
We need to free the regions before reverting the paging scope to the
original one when rolling back changes due to an error. This fixes
silent memory corruption.
Now that we commit memory, we need a lot more physical memory. Physical
memory requirements can be reduced again once we have memory swapping,
which allows the swap area/file to be counted against memory that can
be committed.
By designating a committed page pool we can guarantee to have physical
pages available for lazy allocation in mappings. However, when forking
we will overcommit. The assumption is that worst-case it's better for
the fork to die due to insufficient physical memory on COW access than
the parent that created the region. If a fork wants to ensure that all
memory is available (trigger a commit) then it can use madvise.
This also means that fork now can gracefully fail if we don't have
enough physical pages available.
This brings mmap more in line with other operating systems. Prior to
this, it was impossible to request memory that was definitely committed,
instead MAP_PURGEABLE would provide a region that was not actually
purgeable, but also not fully committed, which meant that using such memory
still could cause crashes when the underlying pages could no longer be
allocated.
This fixes some random crashes in low-memory situations where non-volatile
memory is mapped (e.g. malloc, tls, Gfx::Bitmap, etc) but when a page in
these regions is first accessed, there is insufficient physical memory
available to commit a new page.
