I ran into a need for this when running stress-ng against the system.
This change implements the full functionality of scandir, where it
accepts a selection callback, as well as a comparison callback.
These can be used to trim and sort the entries from the directory
that we are being asked to enumerate. A test was also included to
validate the new functionality.
While adding new functionality which used the d_reclen member
to copy a dirent, I realized that the value being populated
was incorrect. sys_ent::total_size() function calculates the
size of the sys_ent structure, but dirent is larger than sys_ent.
This causes the malloc to be too small and you end up missing
the end of the copy, which can miss the null terminator
resulting in corrupt dirent names.
Since we don't actually use the variable length member nature
of dirent on other platforms we can just use the full size of
the struct ad the d_reclen value.
Also replace the custom strcpy with the standard version.
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 *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
This achieves two things:
- Programs can now intentionally perform arbitrary syscalls by calling
syscall(). This allows us to work on things like syscall fuzzing.
- It restricts the ability of userspace to make syscalls to a single
4KB page of code. In order to call the kernel directly, an attacker
must now locate this page and call through it.
